PASCOS 2026

22 Jun 2026, 07:00 → 26 Jun 2026, 20:25 Europe/London

Richard Roberts Auditorium

Please complete the dinner form sent by email to the registered participants by the 31st of May. Unfortunately, submissions received after this date cannot be considered for the conference dinner arrangements.

PASCOS 2026, the 31st International Symposium on Particles, Strings, and Cosmology, will be held in Sheffield from June 22 to 26, 2026. The conference aims to highlight recent advances in particle physics, astroparticle physics, string theory, and cosmology, with a strong focus on the interplay between these fields.

The conference includes invited plenary talks and parallel sessions. We warmly encourage participation from early-career researchers, and submission of abstracts for contributed talks and posters.

Topics will include:
LHC physics, dark matter and dark energy, string theory, neutrino physics, precision measurements, non-accelerator probes of new physics, inflation, gravitational waves, cosmic tensions, and modified gravity.

Invited speakers:

• Tessa Baker
• Martin Bauer
• Francesco Benini
• Florian Beutler
• Robert Brandenberger
• Philippe Brax
• Miranda Cheng
• Djuna Croon
• Tamara Davis
• Francesca Di Lodovico
• John Ellis
• Diksha Jain
• Julien Lesgourgues
• David Mulryne
• Sara Pasquetti
• Hiranya Peiris
• Vivian Poulin
• Diego Redigolo
• Adam Riess
• Andreas Ringwald
• Sakura Schäfer-Nameki
• Stefan Soldner-Rembold
• Joel Swallow
• Sally Shaw
• Luigi Tizzano
• Alessandro Tomasiello
• Sebastian Trojanowski
• Iacopo Vivarelli
• Fergus Wilson

 

Monday 22 June

Registration

Welcome

Conveners: Carsten van de Bruck (University of Sheffield), Eleonora Di Valentino (University of Sheffield)

Particles

1 TBA

Speaker: Prof. John Ellis

2 Axion Physics and Detection

We review the motivation for the axion as a solution of the strong
CP puzzle. We discuss benchmark axion models and present their predictions concerning
(i) axion couplings to the Standard Model and (ii) axion dark matter abundance.
We give an overview on the discovery potential of current and planned
axion experiments, reaching from direct production and detection
of axions in the laboratory, over searches for solar axions,
to axion dark matter direct detection.

Speaker: Andreas Ringwald

3 X-ray Smoking Guns from Galactic Center Compact Stars: A New Probe of Inelastic Dark Matter

An inelastic structure is a classic feature of many dark matter (DM) models arising from symmetry breaking, and investigating transitions between states with small mass splittings allows for the identification of unique, detectable signatures. While such inelasticity is a characteristic hallmark of well-motivated scenarios like Higgsino DM, it leads to particularly striking phenomenology in light hidden sectors. In this talk, we present a novel probe of this paradigm utilizing the extreme environment of the Galactic center. We investigate the capture and upscattering of DM within compact stars as they traverse the central DM density spike. Accelerated DM becomes trapped and upscatters into excited states that, following geodesics, can escape the stellar volume to decay semi-visibly in the vacuum outside. We show that the resulting X-ray signals could provide a possible origin for observed Sgr A* flares, while carrying distinct "smoking-gun" features. Using an inelastic dipole portal as a benchmark model, we demonstrate that the sensitivity of this astrophysical channel is highly competitive with that of traditional accelerator based searches, offering a powerful new frontier for identifying dark matter.

Speaker: Sebastian Trojanowski

Coffee Break

Strings

4 Challenging the Standard Paradigm of Early Universe Cosmology

Cosmological inflation has become the standard paradigm of
early universe cosmology. I will argue that this scenario, at least
when described at the level of an effective field theory, suffers
from serious conceptual problems. In light of these problems, I will
discuss a new and more consistent approach to early universe scenario
based on a proposed non-perturbative definition of
superstring theory (the BFSS matrix model). I will indicate how
a continuous, infinite and spatially flat space can emerge from
this starting point, and discuss specific predictions for cosmological
observables.

Speaker: ROBERT Brandenberger (McGill University)

5 TBA

Speaker: Sara Pasquetti (Milan-Bicocca University)

Lunch

Cosmology

6 Galaxy Evolution Meets Cosmological Inference

Next-generation cosmological surveys — LSST, Euclid, Roman — will be limited not by statistical power but by systematic uncertainties rooted in our understanding of galaxy populations. Photometric redshift calibration, intrinsic alignments, and baryonic effects on the matter power spectrum are all manifestations of the same underlying problem: cosmological inference requires an accurate model of the galaxy population and its evolution. I will present pop-cosmos, a simulation-based inference framework that learns the joint distribution of galaxy properties — redshift, stellar mass, star formation history, dust, metallicity, and black hole activity — from deep multiwavelength photometric data. The resulting generative model simultaneously delivers calibrated redshift distributions for weak lensing tomography, enables physically-motivated sample selection that mitigates intrinsic alignment contamination and unlocks multi-tracer clustering analyses, and provides improved Type Ia supernova standardisation through host galaxy property inference. It also reveals the astrophysical processes — including black-hole-driven feedback and the cessation of star formation — that shape the very populations we use as cosmological tracers. I will show applications spanning the Kilo-Degree Survey, DESI, the Zwicky Transient Facility, and COSMOS-Web, illustrating how a unified model of galaxy evolution connects to the next generation of cosmological constraints.

Speaker: Hiranya Peiris

7 Physical, Viable and Predictive Models of Dark Energy

Recent combinations of BAO, supernovae and CMB data prefer cosmologies with an evolving dark energy equation of state, w(z), which crosses the phantom divide (w=-1). But parameterisations of w(z) are not, in themselves, complete physical models of dark energy.

In this talk we’ll ask: what kind of underlying modified gravity or dark energy models give rise to phantom-crossing behaviour? We’ll see that crossing the phantom divide can have strong consequences for other observables, particularly for ISW-galaxy cross-correlations and voids.

I’ll present a system to triage the large gravity model space down to a set of viable, predictive theories which can be verified or falsified with Stage IV galaxy surveys.

Speaker: Tessa Baker

8 Dark energy and screening

Recent surveys suggest that dark energy could be dynamical and cross the phantom divide. This can be easily reproduced in scalar-tensor theories where
matter couples to dark energy. This potentially leads to serious gravitational problems in the solar system which can be evaded thanks to screening. I will argue that
multi-field models could both reconcile phantom crossing and screening.

Speaker: philippe brax (CEA)

Coffee Break

Particles

9 Direct Detection of Dark Matter: Status and Prospects

Despite overwhelming astrophysical evidence that approximately 84% of the matter in the Universe is dark and fundamentally distinct from ordinary matter, terrestrial experiments searching for direct interactions of dark matter particles have yet to observe a convincing signal. Over the past two decades, dramatic gains in experimental sensitivity have been driven by the development of liquid noble-element detectors, and now specialised low-threshold searches and novel detector technologies are extending the search toward lighter dark matter candidates. In this talk, I will review the current status of direct detection experiments, highlight recent results, and discuss future prospects on the path toward discovery.

Speaker: Sally Shaw (University of Edinburgh)

10 Direct Searches for New Physics at the LHC: From Run 2 to the HL-LHC Era

This talk will review the status of direct searches for physics beyond the Standard Model at the LHC, from the mature Run 2 programme to the emerging Run 3 landscape and the prospects of the HL-LHC era. After a broad overview of established search programmes—including supersymmetry, dark matter, heavy resonances —the discussion will focus on what is genuinely new in Run 3: not simply increased centre-of-mass energy and integrated luminosity, but also improved detector performance, upgraded trigger capabilities, and new strategies. The talk will conclude with a forward-looking perspective on Run 4 and the HL-LHC, where both the opportunities and the challenges for direct BSM searches will become qualitatively different, requiring increasingly creative approaches to probe elusive new physics.

Speaker: Iacopo Vivarelli (Universita e INFN, Bologna (IT))

Welcome Drink + Poster Session

Tuesday 23 June

Strings

11 TBA

Speaker: Francesco Benini

12 TBA

Speaker: Alessandro Tomasiello

13 TBA

Speaker: Sakura Schafer-Nameki (University of Oxford)

Coffee Break

Cosmology

14 TBA

Speaker: Julien Lesgourgues (TTK, RWTH Aachen University)

15 Mapping Cosmic Expansion with DESI: Precision BAO and the Road Ahead

Spectroscopic surveys map the three‑dimensional large‑scale structure of the Universe, providing precise tests of cosmic expansion and the growth of structure. The Dark Energy Spectroscopic Instrument (DESI) is a Stage‑IV experiment on the 4‑m Mayall telescope, using 5000 robotically positioned fibres to obtain spectra for more than 40 million galaxies and quasars over ~14,000 deg². I will briefly outline DESI’s design and survey strategy, including its target classes (BGS, LRGs, ELGs, QSOs, and the Lyα forest), and the analysis methods that underpin robust distance measurements.
I will then summarise DESI’s first cosmology results, highlighting per cent-level baryon acoustic oscillation (BAO) constraints that deliver the most precise expansion history to date across a broad redshift range. I will discuss internal consistency tests, comparisons with previous surveys, and the cosmological interpretation of these measurements within ΛCDM and simple extensions. In particular, I will examine the current hint (still at modest significance) for departures from a constant dark‑energy equation of state.
Finally, I will preview what the expanding DESI dataset will enable: tighter BAO and redshift‑space distortion measurements, improved full‑shape analyses, and sharpened constraints on curvature, gravity, and the sum of neutrino masses.

Speaker: Florian Beutler

Lunch

Cosmology: Inflation

Conveners: Konstantinos Dimopoulos, Dr Laura Iacconi (Queen Mary University of London)

16 How Sensitive is Cosmic Inflation to Quantum Corrections?

In this talk, I will present a non-perturbative framework that allows to track the dynamics of slow-roll inflation while consistently incorporating quantum corrections, based on an alternative functional renormalisation group (RG) approach. I will guide you through the derivation of a set of coupled Friedmann-RG flow equations governing the joint evolution of spacetime, the inflaton field, and its effective potential. Applying this formalism to α-attractor E-models, I will show that the RG flow induces a dynamical destabilisation of the inflationary trajectory, leading to a premature termination of slow roll. Remarkably, the resulting predictions bring α-attractors into full agreement with the latest ACT data without introducing new physics beyond a consistent quantum-corrected treatment of the inflaton dynamics.

Speaker: Lucien Heurtier (King's College London)

17 A universal scaling for induced gravitational waves during inflation

We consider the gravitational wave (GW) background induced by arbitrary source fields that are amplified during inflation. We first conduct a very general analysis where the associated tensor spectral index $n_T$ is shown to be given, under minimal assumptions, by a simple and ready-to-use formula. Remarkably, we demonstrate that during slow-roll inflation $n_T$ becomes completely independent of the original spectrum of the source, exhibiting a universal near scale invariance. We then refine our study to the case of GWs induced by abelian gauge fields, covering the case of axion inflation. We analytically derive the amplitude of GWs and argue that they can overtake the standard inflationary GW background. We use this to constrain the values of gauge field couplings allowed by observations. This presentation is based on https://arxiv.org/abs/2510.00869 and https://arxiv.org/abs/2512.14670.

Speaker: Martin Teuscher (LPSC Grenoble, France)

18 Post-Inflationary Higgs Dynamics from Spacetime Curvature

The Standard Model Higgs field, when non-minimally coupled to gravity, can display rich dynamics after inflation. In cosmological setups that include a short kination stage, the fast variation of spacetime curvature can temporarily destabilize the electroweak vacuum through curvature-induced tachyonic effects. This process can trigger a gravitationally sourced phase transition, leading to the rapid growth of Higgs fluctuations, the development of transient inhomogeneous configurations, and an efficient conversion of vacuum energy into radiation. Within the Standard Model, this provides a minimal and self-consistent reheating mechanism.

I will outline the theoretical framework underlying this dynamics and discuss its cosmological implications. The interplay between curvature, vacuum stability, and non-perturbative evolution yields a predictive scenario that connects electroweak-scale physics with potentially observable stochastic gravitational-wave backgrounds.

Speaker: Dr JAVIER RUBIO (Universidad Complutense de Madrid)

19 Discovering New Particles with Cosmic Microwave Background

Cosmological collider signals of primordial non-Gaussianity arise at tree level when a particle has Hubble mass during inflation. We critically review the formalism finding that a large class of inflationary theories, based on Planck-scale physics, predict a scalar bi-spectrum around the gravitational floor level. This mild signal arises for example in R2 gravity, in the regime where its gravitational scalar has Hubble-scale mass. Signals much above the gravitational floor arise in theories where scalars undergo multiple turns during inflation, thanks to sub-Planckian physics.

Speaker: Anish Ghoshal (University of Warsaw, Poland)

20 Primordial Black Hole Formation from Inflationary Higgs Instability

Metastability of the Standard Model Higgs during inflation raises the possibility that stochastic fluctuations push the field beyond the instability barrier and into a region of negative energy vacuum. Whether such excursions are fatal to our Universe depends on their fully nonlinear gravitational evolution. We revisit this problem using numerical simulations of a spherically symmetric gravity-scalar-fluid system. We consider an intially radiation dominated Friedmann–Lemaître–Robertson–Walker background with superhorizon fluctuations in the field, which are generated during inflation. We find that once an unstable patch enters classical collapse, it first forms a primordial black hole hiding the crunching true vacuum core within. The late time evolution is controlled by the ratio of the barrier size to its self-gravity $R_w/\ell_\sigma$. For subcritical configurations, the remaining true vacuum region is gradually swallowed by the original black hole. For supercritical configurations, the barrier briefly drives the spacetime into a wormhole-like phase with a second trapped surface and a bifurcating horizon, allowing a transient baby-universe interpretation. In all cases we study, the entire region with field values beyond the potential barrier eventually becomes hidden behind horizons, and the late time exterior is that of an ordinary primordial black hole embedded in an FLRW universe. Our results therefore suggest that field excursions beyond an instability scale are not necessarily catastrophic for the compatibility of inflation with our observed Universe. More broadly, this mechanism is not unique to the Higgs, but is expected to apply quite generally to spectator scalar fields with metastable potentials containing a negative true vacuum.

Speaker: Ethan Milligan (QMUL)

21 Coffee Break

22 Observational prospects of axion inflation

Axions are well-motivated pseudoscalar fields that arise in many extensions of the Standard Model and can drive inflation. In scenarios where an axion couples to a gauge sector during inflation, the rolling field can lead to exponential amplification of gauge-field fluctuations, with important implications for particle production, reheating dynamics, primordial gravitational wave signatures, and primordial magnetic fields.
In this talk, I will review recent progress in axion inflation with Abelian and non-Abelian gauge fields, emphasizing the resulting signatures in the primordial gravitational wave background and their correlation with primordial magnetic fields. I will further discuss how the emergence of a primordial plasma via the Schwinger effect modifies early universe dynamics, impacting reheating, the gravitational wave signal, and primordial magnetic field predictions.

Speaker: Oksana Iarygina (Nordita)

23 Primordial Power Spectrum from a deformed Bouncing background

We present the formalism of Deformed Commutation Relations, consisting in a modification of the standard Heisenberg commutator (or of the Poisson brackets in the semiclassical limit) inspired by the Generalised Uncertainty Principle representation, and its implementation to the cosmological Friedmann-Lemaitre-Robertson-Walker isotropic model. One specific form had previously been shown to yield the same exact dynamics of effective Loop Quantum Cosmology, removing the cosmological singularities and replacing them with a Bounce. Here we use this modified background to compute the evolution of perturbations during the Inflationary expansion. We obtain a modified time-dependent mass term for the Mukhanov-Sasaki equation and compare the resulting Power Spectrum with those obtained in Loop Quantum Cosmology, such as with the Hybrid or the Dressed Metric approaches.

Speaker: Gabriele Barca (University of the Basque Country)

24 Optimized numerical evolution of perturbations across sharp background trajectory turns in multifield inflation

Features in the primordial power spectrum require numerical methods that are both accurate and scalable across the wide class of multifield inflationary models that produce them. Sharp turns in the background trajectories, induced by either potential or geometric effects, render these computations particularly challenging. In this work, we introduce an efficient method for evolving primordial scalar fluctuations, requiring timesteps comparable to those used for the background evolution. We demonstrate that the method accurately tracks perturbations through rapidly turning trajectories in arbitrary field-space geometries, enabling systematic exploration of spectral features across diverse multifield scenarios. Our approach scales robustly to large numbers of degrees of freedom, providing a reliable computational framework for probing regimes that significantly depart from slow-roll dynamics.

Speaker: Guillermo Fernando Quispe Peña (Simon Fraser University)

25 Large Primordial Fluctuations: Stochastic vs. Classical $\delta N$ approaches

The classical evolution of fields during a period of accelerated expansion in the very early universe ("inflation") can establish an idealised homogeneous and isotropic cosmology. However, quantum fluctuations inevitably generate inhomogeneities and anisotropies on all observable scales and beyond. The $\delta N$ formalism provides a powerful framework to describe the nonlinear curvature perturbation in terms of fluctuations in the duration of inflation, $N$. In its standard implementation, $\delta N$ is calculated using the classical trajectory to find the number of e-folds of inflation from a given field value to the end of inflation. In contrast, the stochastic $\delta N$ formalism incorporates quantum fluctuations as stochastic noise along the trajectory, enabling a non-perturbative treatment of inflationary dynamics that can be crucial for rare, large fluctuations. In this work, we compare the classical and stochastic approaches to study the statistics of large curvature perturbations when coarse-grained at a given length scale. This is particularly relevant for calculations of primordial black hole formation. Using the numerical code PyFPT, we compute the distribution of curvature perturbations from slow-roll inflation driven by a quadratic potential, and perform a detailed comparison with the classical $\delta N$ formalism, identifying regimes where quantum diffusion significantly impacts the probability distribution of large fluctuations.

Speaker: Parth Bhargava (ICG, Portsmouth)

Cosmology: Joint MG&DE

Conveners: Alessandra Silvestri, Laura Herold, Matteo Martinelli (INAF - OAR), Supriya Pan

26 Theoretical implications of DESI BAO: the case for Nonminimal Coupling

The recent baryon acoustic oscillation (BAO) measurements from the DESI collaboration have revealed a first hint towards a deviation from a cosmological constant, signaling a preference for dynamical dark energy. In this talk, we explore the deep theoretical implications of these observations for dark energy and gravitational physics. Utilizing a model-agnostic, non-parametric reconstruction approach, we constrain the behaviour of the dark energy equation of state. Our analysis demonstrates that the combined DESI, CMB, and Type Ia Supernovae datasets favor a crossing of the phantom divide, a behavior that structurally rules out standard canonical scalar field models like quintessence due to ghost instabilities.
To interpret this result, we survey the wider scalar-tensor landscape via the Effective Field Theory of Dark Energy, within the Horndeski class of gravity theories. We identify the non-minimal coupling of gravity as the unique operator capable of stabilizing this phantom crossing, establishing the DESI results as a potential observational hint of modified gravity.

Speaker: Matteo Martinelli (INAF - OAR)

27 A Lapse in the Cosmological Constant Problem

We present a new mechanism for addressing the cosmological constant problem based on global constraints arising from a lapse function in a higher-dimensional gravitational theory. Inspired by Horava-Lifshitz gravity, we consider a 5d spacetime with anisotropic scaling along a compact extra dimension, while preserving Lorentz invariance in four dimensions. In the deep infrared limit, variation with respect to the lapse generates a global constraint on the 4d geometry, closely analogous to that of vacuum energy sequestering. Although the resulting effective gravitational equations differ from standard sequestering, radiative contributions to the Standard Model vacuum energy are nevertheless cancelled at all orders.

Speaker: Benjamin Muntz (University of Nottingham)

28 Late time behavior in f(R,Lm) gravity through Gaussian reconstruction and dynamical stability

In this paper, we explore modified gravity in the framework of $f(R, \mathcal{L}_m)$ theory by reconstructing the function $G(\mathcal{L}_m)$, where $\mathcal{L}_m = \rho$ be the matter Lagrangian, under the assumption of a pressureless, matter-dominated Universe. Using a non-parametric Gaussian process reconstruction technique applied to Hubble data, we present two cosmological models with the form of $G(\mathcal{L}_m)$ such as (i) a power-law model, $G_1(\mathcal{L}_m) = \alpha \mathcal{L}_m^{b_1}$ with $b_1 \in [0.018, 0.025]$ and (ii) an exponential model, $G_2(\mathcal{L}_m) = \alpha \mathcal{L}_{m0} \left(1 - e^{-b_2 \sqrt{\mathcal{L}_m/\mathcal{L}_{m0}}} \right)$ with $b_2 \in [2.3, 3.0]$. We then fix the parameter values within these reconstructed ranges and analyze the corresponding dynamical systems within the matter-dominated epoch by constructing autonomous equations. Phase-space analysis reveals the presence of stable critical points in both models, suggesting viable cosmic evolution within their domains of validity. Both the models exhibit stable attractor solution at late time, reinforcing their viability in explaining the late time cosmic acceleration without explicitly invoking a cosmological constant. Our results indicate that $f(R, \mathcal{L}_m)$ gravity with data-driven matter-sector modifications can offer a compelling alternative description of cosmic dynamics during the matter-dominated era.

Speaker: Yengkhom Kalpana Devi (Bits Pilani Hyderabad Campus)

29 Reconstructing Sign-Changing Dark Energy Density: From Data to Fundamental Theory

Recent cosmological observations continue to challenge the standard $\Lambda$CDM paradigm through persistent tensions in the Hubble constant $H_0$, the clustering amplitude $S_8$, and possible hints of nontrivial late-time dark-energy dynamics. In this talk, we discuss two complementary studies showing how sign transitions in the effective vacuum sector may arise naturally from modified gravity and higher-dimensional geometry. We first present new solution branches in teleparallel $f(T)$ gravity, focusing on the exponential infrared model $f(T)=T e^{T_*/T}$, where $\beta=T_*/T_0$ controls deviations from $\Lambda$CDM. While the positive-$\beta$ branch has been widely explored, the previously overlooked negative-$\beta$ branch exhibits rich and viable cosmological behavior. It predicts an effective dark-energy density that changes sign at a data-driven transition redshift, emerging around $z_\dagger\sim1.5$, rather than being imposed by hand, while remaining consistent with CMB and local gravity constraints through an effective screening mechanism [1]. Interestingly, cosmic acceleration can begin while the effective dark-energy density is still negative, highlighting the nontrivial role of modified gravitational dynamics. Adding a cosmological constant further enlarges the viable parameter space and may allow moderated or transient late-time acceleration. We then discuss, this time within unmodified general relativity, a purely geometric realization of $\Lambda_{\rm s}$CDM using a $(1+3+n)$-dimensional Kaluza--Klein framework with compact extra dimensions of constant intrinsic curvature. For a stabilized internal manifold of radius $s_*$, the internal curvature contributes $\tilde{\chi}=-n(n-1)k_{\rm int}/(2s_*^2)$, which combines with $\tilde{\Lambda}$ to define an effective vacuum term $\tilde{\gamma}=\tilde{\Lambda}+\tilde{\chi}$, yielding a background expansion degenerate with $\Lambda$CDM. A rapid transition $s_{\rm p}\rightarrow s_0$ can shift $\tilde{\gamma}$ abruptly and change its sign. Since $G_{\rm 4D}\propto s^{-n}$, the same event induces a correlated step in gravity strength, providing a key observational discriminator[2]. Together, these results show that sign-changing dark-energy density may emerge from theoretically well-established frameworks, suggesting new insight into cosmic acceleration and current cosmological tensions.

[1]Ö.Akarsu, B.Bulduk, A.De Felice, N.Katırcı and N.M.Uzun,``Unexplored regions in teleparallel $f(T)$ gravity: Sign-changing dark energy density,'' Phys. Rev. D 112 (2025), 083532, arXiv:2410.23068

[2] Ö.Akarsu, B.Bulduk, N.Katırcı, E.Özülker and L.Perivolaropoulos,``Constructing $\Lambda_{\rm s}$CDM via compact, curved extra dimensions: Coupled transitions in the effective $\Lambda_{\rm 4D}$ and $G_{\rm 4D}$,'' in preparation.

Speaker: Prof. Nihan Katırcı (Dogus University)

30 Asymptotically Cubic Galileon Gravity: Late-Time Departures for Viable Dark Energy

In this talk, we introduce Asymptotically Cubic Galileon gravity: a luminal Horndeski theory designed to remain close to the cubic Galileon over most of cosmic history, whilst allowing late-time departures that are be broadly consistent with current observations including the recent DESI results. These departures are generated by promoting the coefficients of the Galileon terms to functions of the scalar field. We show that, once this explicit field dependence is introduced, the closed theory space is fully characterised, modulo scalar-field redefinitions, by two invariant functions. Working in a convenient field parametrisation, we identify the functional behaviour these invariants must exhibit in order to lift the theory away from the cubic Galileon’s eternally phantom regime and allow a crossing of the phantom divide. We then use the ISW effect and the modified force in cosmic voids to identify phenomenologically viable regions of the theory space, before confronting these regions with DESI, Planck, and supernova data through an MCMC analysis. For the models studied, the data-favoured regions can overlap the phenomenologically viable sector, although the void modified-force condition remains the limiting constraint.

Speaker: James Hallam (Institute of Cosmology and Gravitation - University of Portsmouth)

31 Coffee Break

32 Modified gravity & friends vs current CMB data.

In this talk we will look at the evidence of the effects induced by seemingly different extensions to the standard cosmological model in the cosmic microwave background (CMB) primary and secondary anisotropies: modified gravity (through the growth index - '$\gamma$', a modification of the growth of linear perturbations in the standard model, and the '$\mu-\Sigma$' framework, a modification of the Poisson and lensing perturbation equations), massive neutrinos and non-vanishing spatial curvature. By looking at their correlations and the differences in the impact they have on cosmological observables, such as the CMB lensing spectrum, we assess whether such additions can be told apart and identify the common root to their detection: the lensing anomaly.

Speaker: Enrico Specogna (University of Sheffield)

33 A Holographic Dark Energy Model in Light of Recent Data

The latest data release of the DESI collaboration shows an increasing preference for time-depending dark energy models compared to the $\Lambda$CDM model.
In our work, we construct a holographic dark energy model motivated by the work of Cohen, Kaplan and Nelson (CKN) which proposed to use the Hubble horizon as an IR cutoff and connect it to the UV cutoff of the theory.
We take the resulting dark energy model that is proportional to $H(z)^2$ and compare it to different data sets in both, the late-universe and early-universe. Depending on the data set used, we find a preference of up to $2.6\,\sigma$ over the $\Lambda$CDM model and discuss several extensions of this model to improve the stability and sensitivity to early-universe data.

Speaker: Patrick Adolf

Particles: Dark Matter

Conveners: Adam Brown (University of Sheffield), Christopher McCabe (King's College London)

Particles: Neutrino Physics

Conveners: IVAN MARTINEZ SOLER (Durham University and IPPP), Pasquale Di Bari

34 Status of three-flavor neutrino oscillations and the lessons from the first JUNO results

35 JUNO

36 HYPER-K

37 Towards the final analysis of the KATRIN data

The KATRIN experiment aims at direct kinematic measurement of the neutrino mass with the expected sensitivity below 300 meV (90% CL), performing a high-resolution, high-statistics spectroscopy of tritium beta-decay. To reach such sensitivity, the systematic effects, modifying the measured electron spectrum shape have to be modeled and controlled by dedicated calibration measurements.
KATRIN obtained the world-leading direct constraint on the effective mass of the electron antineutrino of 0.45 eV (90% CL) using only 16% of the data. The final dataset of KATRIN contains 1000 days of tritium spectra recorded by the end of 2025 and therefore increases the statistics by a factor of 6 compared to previous results.
In this talk after introducing the framework of the analysis, the challenges and steps towards the analysis of the full KATRIN dataset are presented.

Speaker: Karo Erhardt (KIT)

38 Search for keV Sterile Neutrinos with the KATRIN Experiment

The KATRIN experiment is designed to measure the mass of the electron anti-neutrino by studying the high energy end of the tritium β decay spectrum. In addition, KATRIN is also a well suited instrument to explore the sterile neutrino hypothesis. The existence of sterile neutrinos would cause a kink-like distortion in the spectrum.
Using the same datasets as for the active neutrino mass, KATRIN has previously presented results on the search for sterile neutrinos at the eV scale, complementing the reactor and radioactive source experiments. With an endpoint of 18.6 keV, KATRIN also offers a high potential for the search of sterile neutrinos in the keV range. With data acquired during the
2018 commissioning campaign, KATRIN reported results from a search for keV-scale neutrinos in the restricted mass range of 0.01 to 1.6 keV. No keV-sterile neutrino signal was observed and KATRIN reported exclusion limits competitive with other laboratory-based searches. The current KATRIN detector is not designed to handle the higher count rate that occurs with a wider mass range. Equipped with the TRISTAN detector KATRIN
aims to search for keV sterile neutrinos across the full tritium beta decay spectrum. This detector is currently in production and is scheduled to be operational in KATRIN in 2026.
In this talk, I will present the latest results from KATRIN on the search for keV sterile neutrinos, as well as the ongoing efforts to conduct a high sensitive search with the TRISTAN detector.

Speaker: Leo Laschinger (MPIK, TUM)

39 KATRIN++: Towards a next-generation neutrino mass experiment using tritium beta decay

After completing 1000 days of data taking at the KATRIN experiment, the collaboration expects to reach a final sensitivity on the effective anti-electron neutrino mass below 300 meV. However, neutrino oscillation observations allow the value to be as low as 50 meV or 9 meV, depending on the neutrino mass ordering. Taking the next step in direct neutrino-mass searches includes probing the region of inverted mass hierarchy and therefore requires to achieve substantial improvements in statistics, energy resolution, and background suppression.

Within the framework of KATRIN++, several novel experimental concepts are being explored to extend the sensitivity of such a next-generation experiment. Two particularly promising strategies are:
(1) the implementation of differential detection techniques with sub-eV energy resolution and
(2) the commissioning of a large-volume atomic tritium source, enabling significantly increased signal statistics. The combination of these approaches would allow for high statistics to be acquired quickly and with ultra-high energy resolution. The goal of KATRIN++ is to identify and develop the hardware technologies needed to reach the required precision. We have formed several working groups within KATRIN++ to tackle the challenges of developing new source and detector concepts. On the source side we are looking into reliable ways to produce, cool and trap tritium atoms. For the differential detection method, we are currently investigating the applicability of quantum sensor based detectors, such as metallic microcalorimeters (MMCs), as well as a Time-of-Flight based technology coupled with a Transverse Energy Compensator (TEC). Our aim is to investigate these different approaches and develop scalable technologies by mid-2030s.

In this talk, we will summarize the technological requirements and fundamental physics limitations to confine the achievable sensitivity on the neutrino mass for several experimental configurations, and present the ongoing efforts towards realising the hardware technologies inside a future experiment.

Speaker: Svenja Heyns (Karlsruhe Institute of Technology)

40 The ICARUS experiment at the Short-Baseline Neutrino program and the search for sterile neutrinos

The ICARUS T600 LAr-TPC detector (760 t of ultrapure liquid argon) was successfully operated for three-years at the underground LNGS laboratory, carrying out a sensitive search for LSND-like anomalous appearance in the CERN Neutrinos to Gran Sasso beam. The LSND anomaly has been the subject of numerous experimental investigations over the past 25 years, suggesting the possible existence of a fourth, so-called “sterile” neutrino state, though no definitive conclusion has yet been reached.
Following a major overhaul at CERN, ICARUS was installed at Fermilab and began operations in 2020, recording neutrinos from the Booster Neutrino Beam (BNB) and from the off-axis Neutrinos at the Main Injector (NuMI) beam. In late 2025, ICARUS celebrated five continuous years of data taking, collecting about half a million of neutrino interactions, marking an important milestone for large-scale LAr-TPC technology supporting future projects such as DUNE.
This talk will highlight the ICARUS detector, its experimental program on sterile neutrino search, and recent results, with particular emphasis on the first ICARUS search for muon-neutrino disappearance in the BNB. Data are compared with simulation-based expectations and interpreted, for the first time, within a two-neutrino approximation of the 3+1 sterile-neutrino model, including all systematic uncertainties. In addition to oscillation searches, neutrino events recorded by ICARUS with the NuMI beam enable key measurements of neutrino cross sections and searches for physics beyond the Standard Model, whose first results will also be summarized in this contribution.

Speaker: Alessandro Menegolli

41 Global Extraction of the Nuclear Electromagnetic Response Functions of C-12, Ca-40 and Fe-56 and Comparisons to the Predictions of the SuSAv2 Superscaling Formalism for Electron and Neutrino Scattering

We perform a global extraction of the ${\rm ^{12}C}$, ${\rm ^{40}Ca}$ and ${\rm ^{56}Fe}$ longitudinal (${\cal R}_L$) and transverse (${\cal R}_T$) nuclear electromagnetic response functions from an analysis of all available electron scattering data on carbon. The response functions are extracted for energy transfer $\nu$, spanning the nuclear excitation, quasielastic (QE), resonance and inelastic continuum over a large range of the square of the four-momentum transfer, $Q^2.$ In addition, we perform a universal fit to all electron scattering data on these nuclear targets which also provides parmeterizations of ${\cal R}_L$ and ${\cal R}_T$ over a larger kinematic range. Given the nuclear physics common to both electron and neutrino scattering from nuclei, extracted response functions from electron scattering spanning a large range of $Q^2$ and $\nu$ also provide a powerful tool for validation and tuning of neutrino Monte Carlo (MC) generators. In particular, the predictions of the SuSAv2 formalism (which is implemented in the GENIE electron and neutrino scattering generator) are in disagreement with the electron scattering data. We extract $Q^2$ dependent correction factors to the SuSAv2-QE and SuSAv2-MEC-2p2h predictions for ${\cal R}_T$ and ${\cal R}_T$ to the theory for better agreement with electron scattering data.

Speaker: Arie Bodek (University of Rochester (US))

42 Coffee Break

43 A possible solution to the gallium anomaly moving beyond the leptonic wave function factorization

For over three decades, the gallium anomaly, a persistent discrepancy exceeding 5σ between measured and predicted neutrino capture rates on gallium-71 in the GALLEX, SAGE, and BEST experiments, has challenged the particle physics community. While frequently interpreted as evidence for short-baseline sterile neutrino oscillations, this scenario is increasingly in tension with recent bounds from reactor, solar, and accelerator experiments, including KATRIN and MicroBooNE. In this contribution, we revisit the theoretical evaluation of the cross-section for neutrino capture on gallium-71. We move beyond the standard detailed-balance framework by abandoning both the conventional leading-order approximation and the strict factorization of leptonic wave functions from the nuclear matrix element. Instead, we calculate exact Dirac-Hartree-Fock-Slater wave functions for bound and continuum electron states and integrate them directly with phenomenologically constrained Gamow-Teller transition densities. By ensuring these densities accurately reproduce the precisely measured germanium-71 half-life, we are able to evaluate the full, non-factorized transition amplitude. We demonstrate that this approach yields a substantial reduction of approximately 20% in the predicted charge-current neutrino capture cross-section. Ultimately, this reduction offers a viable solution to the gallium anomaly, effectively eliminating the need to invoke physics beyond the Standard Model.

Speaker: Luca Ferro (INFN Cagliari, University of Cagliari)

44 Non-Adiabatic Mixing in Density Matrix Formalism

Description of quantum coupling is a universal problem appearing in many different fields (NMR, quantum computing, molecular and atomic physics,...). In particle physics, it applies to particle mixing, underlying neutrino oscillations and resonant particle production (applicable beyond these two) in different environments, of great importance in many BSM scenarios. I will discuss non-adiabatic transitions in the simplest two-state coupled quantum system. An analytical description is traditionally provided by the Landau-Zener-Stuckelberg-Majorana (LZSM) approximation. However, in many applications, such as various cosmological problems, a time dependent mixing and interactions with the environment, where thermal effects and decoherence play an important role, have to be considered, requiring an extension of the LZSM approach. I will show how a density matrix formalism provides a powerful tool for treating such a problem. I will show some general analytic results that reproduce LZSM approximation in the appropriate limit but also generalise it when a time-dependent mixing is considered (decoherence can also be included, I will show results in the absence of decoherence for simplicity). I will finally comment on a comparison with existing numerical results.

Speaker: Shreya Girishkumar Pandit (University of Southampton)

45 From CUORE to CUPID: Toward a Next Generation Search for Neutrinoless Double Beta Decay

The search for neutrinoless double beta decay (0νββ) is fundamental for investigating lepton-number violation, probing new physics beyond the Standard Model, and determining whether neutrinos are Majorana particles. CUORE, a cryogenic calorimetric experiment at LNGS, studies 0νββ in $^{130}$Te using 988 TeO₂ crystals, reaching a tonne-scale mass and operating below 15 mK. Since 2017, CUORE has accumulated close to 3.0 tonne-years of exposure, constraining 0νββ in $^{130}$Te and achieving one of the most precise two-neutrino double beta decay (2νββ) half-life measurements and a detailed background reconstruction across a broad energy range. The next generation of experiments aims to probe half-lives greater than $10^{27}$ years, reaching the sensitivity required to explore the Inverted-Ordering region of the neutrino mass spectrum. CUPID (CUORE Upgrade with Particle IDentification) will search for the 0νββ decay of $^{100}$Mo, leveraging the existing cryogenic infrastructure and expertise gained from CUORE. CUPID will utilize scintillating Li₂MoO₄ crystals enriched in $^{100}$Mo, coupled with light detectors featuring Neganov-Trofimov-Luke amplification. With a total isotope mass of 240 kg, CUPID is designed to achieve a background index of 10⁻⁴ counts/keV/kg/year and a FWHM energy resolution of 5 keV. This performance will allow for a 3σ discovery sensitivity of 1.0 × 10$^{27}$ years after 10 years of life-time, corresponding to an effective Majorana neutrino mass sensitivity in the range of 12–21 meV. This work presents the latest CUORE results, recent findings from the CUPID demonstrator, and outlines the forthcoming milestones toward the realization of the CUPID experiment.

Speaker: Elena Ferri

46 Search for the Majorana Nature of Neutrino with the LEGEND Experiment

Search for the Majorana Nature of Neutrino with the LEGEND Experiment

A. Biondi on behalf of the LEGEND Collaboration

Observation of the neutrinoless double beta (0$\nu\beta\beta$) decay would establish that neutrinos are Majorana particles and demonstrate violation of lepton number, providing a key ingredient for understanding the origin of neutrino masses and the matter-antimatter asymmetry in the Universe. As one of the most sensitive probes of physics beyond the Standard Model, the search for the $0\nu\beta\beta$ decay plays a central role in modern neutrino physics.

The Large Enriched Germanium Experiment for Neutrinoless $\beta\beta$ Decay (LEGEND) is a phased program devoted to search for the $0\nu\beta\beta$ decay in the $^{76}$Ge isotope using enriched high-purity germanium detectors operated in a low-background environment. The first phase, LEGEND-200, is taking data at the Laboratori Nazionali del Gran Sasso (LNGS) since March 2023. Following the latest upgrade, the experiment is operating 138 kg of enriched detectors, and it will employ up to 200 kg of $^{enr}$Ge in its final design. LEGEND-200 has reported its first physics results based on 61 $kg \cdot yr$ of exposure, demonstrating excellent energy resolution and very low background levels. From the collective analysis of data from GERDA, MAJORANA DEMONSTRATOR and LEGEND-200, the LEGEND Collaboration has set one of the best limits in the field on the half-life of $0\nu\beta\beta$ decay, namely $T^{0\nu}_{1/2} > 1.9 \times 10^{26}~yr$ at the 90% confidence level. It corresponds to a limit on the effective Majorana mass of $m_{\beta\beta} < 70 - 200$ meV, depending from the chosen nuclear matrix element.

The next phase, LEGEND-1000, will scale the detector mass to 1000 kg of enriched germanium while further reducing the background by an order of magnitude. With an exposure of about 10 $t\cdot yr$, it is expected to operate in a quasi background-free regime and reach a discovery sensitivity for half-lives beyond $10^{28}~yr$, covering the inverted neutrino mass ordering region.

In this talk I will provide an overview of the LEGEND program, present the latest results from LEGEND-200, and discuss the design and projected sensitivity of LEGEND-1000.

Speaker: Alex Biondi (Jagiellonian University in Krakow)

47 Universal Seesaw: Leptogenesis, Strong CP and Dark Radiation

We study the implications for leptogenesis in a class of left-right symmetric model, where all fermion masses are induced through the Universal Seesaw mechanism. Unlike conventional analyses, we do not use the decays of the neutrino embedded in the right-chiral lepton doublet, but rather those of the gauge-singlet mediators required for neutrino mass generation in the canonical Type-I seesaw. This model features a generalized parity symmetry, which is motivated by the solution to the strong $CP$ problem. Since this discrete symmetry doubles the fermionic degrees of freedom in this model, we can generate the required $CP$ violation in the heavy fermion decays with only a single generation of mediators. One of the distinct features of our scenario is that the bounds from thermalization or washout via gauge interactions typically encountered in the canonical left-right symmetric models do not apply here. Moreover, the heavy mediators can decay to both the left and the right-chiral neutrinos, leading to a cancellation in the resulting baryon asymmetry for decays above the left-right symmetry breaking scale. We discuss ways to avoid this cancellation and show that low scale left-right symmetry breaking above the current collider limits $v_R >18$ TeV is viable. The right chiral neutrinos also obtain their masses from the seesaw mechanism, and the lightest one turns out to have a sub-eV scale mass. We find that its abundance is consistent with standard cosmology, and it acts as potentially observable dark radiation.

Speaker: Drona Vatsyayan (Carleton University)

48 Implications of Modular $A_4$ Group on Left-Right Symmetric Inverse Seesaw Model

In this work, we have incorporated $A_4$ modular symmetry into the left-right symmetric inverse seesaw model. By restricting the proliferation of flavon fields, such modular symmetry can improve the predictability of the model. In this scenario, two right-handed neutrinos and three sterile fermions are added to the standard model, resulting in three light active neutrino states and a light sterile state with a mass in the keV range. The scalar sector consists of Higgs doublets and bidoublets. Here, we numerically investigate different Yukawa coupling coefficients, neutrino masses, and mixing parameters. The predictions of the model are consistent with the current neutrino oscillation data at the $3\sigma$ range. We have also studied the non-unitarity of the mixing matrix for the lepton flavor violation and the baryon asymmetry of the universe through leptogenesis.

Speaker: Raktima Kalita

49 Beyond the Standard Model investigations at CONUS+

The detection of coherent elastic neutrino-nucleus scattering (CEνNS) opens up new opportunities for neutrino physics within and beyond the standard model (BSM) of elementary particles. The first detection of CEνNS at nuclear reactors by the CONUS+ experiment allows very valuable tests of BSM scenarios in a low momentum transfer regime. Among them, Non Standard Interactions (NSIs), light mediators (scalar and vector couplings) and electromagnetic properties were tested, setting very competitive limits in both the nuclear scattering interaction channel as well as the electron scattering channel. In particular, for vector NSIs, a sensitivity to new physics of up to 145 GeV was achieved. Whereas, for the light mediators, couplings down to $4 \cdot 10^{−7}$ were probed. Further, the Weinberg angle was constrained and found in good agreement with the Standard Model.

Speaker: Dario Piani (Max-Planck-Institut für Kernphysik)

50 The NUCLEUS experiment for Coherent Elastic Neutrino-Nucleus Scattering

Coherent elastic neutrino-nucleus scattering (CE$\nu$NS) offers a broad range of physical and technological applications. First predicted in 1974 and remained undetected until 2017, the process is currently entering the era of precision measurements. For this purpose, low energy neutrinos from nuclear reactors represent an ideal source, enabling the investigation of CE$\nu$NS in the fully coherent regime of low momentum transfer. Additionally, extremely sensitive experiments with low energy threshold and low environmental background are needed to probe the small nuclear recoil signature.

In this context, the NUCLEUS experiment is designed to detect CE$\nu$NS with antineutrinos from the Chooz nuclear power plant in France, using CaWO$_4$ cryogenic calorimeters read out by transition-edge sensors. With a demonstrated energy threshold below 20 eV and several layers of active and passive shielding, NUCLEUS aims to measure the CE$\nu$NS cross section with $\sim$20% precision during its upcoming first phase. After a successful commissioning at the Technical University of Munich (TUM), the experiment is currently being relocated to the Chooz experimental site, where a first technical run is scheduled to test a minimal version of the system. We present the milestones achieved so far and the future plans of the experiment.

Speaker: Matteo Cappelli (Sapienza Università di Roma e INFN, Roma I (IT))

Strings: Generalized symmetries & Mathematical structures in string theory and QFT

Conveners: Joseph Enea Davighi, Piotr Sułkowski (University of Warsaw)

Wednesday 24 June

Cosmology

51 TBA

Speaker: Adam Riess

52 TBA

Speaker: Dr Vivian Poulin (LUPM, CNRS & U. de Montpellier, France)

53 Dark Energy: hints of time variation?

Based on 6 years of observations and ~1,500 new high-redshift supernovae, the Dark Energy Survey (DES) team presented tentative evidence in 2024 that dark energy may be changing with time. A few months later the Dark Energy Spectroscopic Instrument (DESI) team also presented hints of time-varying dark energy, by mapping the distribution of galaxies. This talk will review the current state of evidence for the nature of dark energy, including recent updates, and discuss the implications time-dependent dark energy would have for fundamental physics and the fate of the Universe.

Speaker: Tamara Davis

Coffee Break

Particles

54 TBA

Speaker: Francesca Di Lodovico (University of London (GB))

55 MicroBooNE

Speaker: Stefan Soldner-Rembold

Group Photo

Lunch

Kelham Island Museum and Conference Dinner

Thursday 25 June

Cosmology: Neutrinos in Cosmology

Conveners: Olga Mena, Willem Elbers (Durham University)

56 Probing neutrino dark matter interactions at neutrino detectors

We study the possibility that dark matter primarily interacts with the SM through neutrinos, and the prospects for detection in neutrino detectors. In particular, we analyze the DSNB searches at Super-Kamiokande in terms of such a neutrino-dark matter interaction.

Speaker: Salvador ROSAURO-ALCARAZ (LPCA - CNRS)

57 Neutrino flavour conversion in the early universe

Neutrinos play a pivotal role in the early Universe, as their evolution and decoupling set the conditions for Big Bang Nucleosynthesis (BBN) and influence subsequent cosmological epochs. In this talk, I will focus on the effects of neutrino flavour conversion before and during the decoupling epoch, and their implications across different contexts.

While flavour oscillations have only minor effects in the standard scenario with small differences between neutrino flavours, they can become crucial in the presence of, e.g., significant lepton asymmetries. Recent developments in the treatment of neutrino quantum kinetics have enabled a more refined description of the evolution of these asymmetries, leading to new constraints and renewed interest in oscillation-driven sterile neutrino dark matter production scenarios, namely the Shi–Fuller mechanism.

Speaker: Julien Froustey (IFIC (CSIC-UV))

58 Neutrino decays in light of the neutrino mass tension

A new tension is starting to emerge between the tight cosmological upper bounds on the total neutrino mass and the lower limits from oscillation data, with potentially far-reaching implications for cosmology and particle physics. Invisible neutrino decays provide a compelling particle physics scenario to understand such measurements. In this talk, I will present updated limits on a framework where neutrinos decay non-relativistically into dark radiation, showing that the mass bound from Planck 2018+DESI BAO DR2 is relaxed to 0.23 eV, in full agreement with oscillation data. I will also report the first late-time cosmological analysis of neutrino decays into lighter neutrinos in a manner consistent with the measured measured mass splittings, showing that this scenario marginally alleviates - or even tightens - the neutrino mass bounds. These results were possible thanks to new neural network emulators, which are ~200 times faster than the full Boltzmann solutions. Based on arXiv:2601.04312.

Speaker: Dr Guillermo Franco Abellán (IFIC, CSIC - University of Valencia)

59 Limits on total lepton number and lepton flavour asymmetries from BBN and the CMB

In this talk, I will discuss the impact of lepton flavour asymmetries on BBN and the CMB. I will show that solving the momentum averaged quantum kinetic equations describing neutrino oscillations and interactions is an accurate approximation to the full momentum-dependent system. Our formalism allow us to study the scenario of total vanishing lepton number, revealing a rich flavour structure in stark contradiction to the assumption of simple flavour equilibration. We then achieve a limit on the maximal primordial total lepton number L, while specific flavour directions can be even more constrained. I will also present the publicly available COFLASY code based on our momentum-averaged formalism, which is orders of magnitude faster than similar codes which solve the full-momentum dependent system.

Speaker: Mario Fernandez Navarro (University of Zurich)

60 Origin of cosmological neutrino mass bounds: background versus perturbations

In this talk, I will address the emerging anomaly between cosmological and oscillation constraints on the sum of neutrino masses. I will review the main implications of neutrino masses at both the background and perturbations levels, discussing the primary neutrino effects to which CMB data is sensitive, and finding valuable hints to evade cosmological bounds. Our findings show that the CMB neutrino-mass bound is mostly a background measurement, i.e., how the neutrino energy density evolves with time.

Speaker: Rasmi Hajjar (CCAPP - Ohio State University)

61 Coffee Break

62 Low-Energy Neutrino Predictions from SO(10)-Inspired Leptogenesis

We discuss neutrino mass generation and Leptogenesis in GUT-motivated type-I seesaw models, focusing on the connection between matter-antimatter asymmetry and measurable low-energy neutrino parameters. Building on our study of flavour coupling, we show that spectator-induced effects can significantly reshape the viable regions in the space of the lightest neutrino mass, the Dirac CP phase, the atmospheric mixing angle, and the effective mass probed by neutrino-less double beta decay. We then present progress on an extended SO(10)-inspired framework with hierarchical Dirac neutrino masses linked to the up-quark sector. Using current neutrino data and excluding highly fine-tuned crossing-level solutions, we find that these models generically predict a strongly hierarchical right-handed neutrino spectrum and naturally realise successful N2-leptogenesis when the Dirac masses are close to the up-quark masses. This provides a unified framework linking GUT-scale neutrino physics, the cosmic matter-antimatter asymmetry, and upcoming neutrino experiments.

Speaker: Xubin Hu (University of Southampton)

63 Probing the neutrino chemical potential with cosmological observations

The electron neutrino degeneracy parameter, $\xi_{\nu_\mathrm{e}} = \mu_{\nu_\mathrm{e}} / T$, is tightly constrained by Big Bang Nucleosynthesis (BBN), while the degeneracy parameters of the other neutrino species, $\xi_{\nu_\mathrm{x}}$, remain weakly constrained by cosmological observations alone. In this talk, we present constraints on $\xi_{\nu_\mathrm{e}}$ and $\xi_{\nu_\mathrm{x}}$ using two complementary approaches: a constant free-parameter treatment to obtain physical bounds, and a model-independent reconstruction based on the Piecewise Cubic Hermite Interpolating Polynomial (PCHIP) formalism, allowing $\xi_{\nu}$ to vary with redshift and probing the origin of these bounds. We also consider two scenarios for neutrinos, specifically three degenerate neutrinos ($\xi_{\nu_\mathrm{e}}$ = $\xi_{\nu_\mathrm{x}}$) and the case in which we actually differentiate between $\xi_{\nu_\mathrm{e}}$ and $\xi_{\nu_\mathrm{x}}$. We perform a cosmological analysis combining CMB data from Planck, SPT, and ACT with BAO measurements from DESI, and reassess the results after including BBN observables from either EMPRESS, which allows for a non-zero chemical potential, or LBT, which is compatible with the standard $\xi_\nu$ = 0 prediction.

Speaker: Pietro Ghedini (IFIC, CSIC - UV)

64 Beyond thermal approximations: Precise cosmological bounds on Axion-Like Particles

We derive updated cosmological constraints on light axion-like particles (ALPs) coupled to leptons and photons using a full phase-space treatment of their production in the primordial plasma. The resulting non-thermal phase-space distributions are consistently propagated into calculations of cosmological observables, allowing a precise determination of their impact on $\Delta N_{\rm eff}$. Combining latest available CMB data with BBN measurements, we obtain $95\%$ credible limits of $f_a > 1.63 \times 10^6\,\mathrm{GeV}$, $9.41 \times 10^6\,\mathrm{GeV}$, and $8.06 \times 10^4\,\mathrm{GeV}$ for couplings to electrons, muons, and taus, respectively, and $g_{a\gamma} < 1.98 \times 10^{-8}\,\mathrm{GeV}^{-1}$ for photon couplings. Compared to astrophysical and laboratory limits, these cosmological bounds are particularly competitive for the ALP couplings to $\mu$ and $\tau$. Inclusion of baryon acoustic oscillation data mildly relaxes these bounds. We also present forecasts for future CMB experiments, discussing the importance of an exact phase-space treatment for robust constraints on ALP interactions.

Speaker: Nicola Barbieri (IFIC (CSIC-UV))

65 Listening for Right-Handed Neutrinos in Gravitational-Wave Backgrounds

I will show that spectral features of a gravitational-wave background can probe type-I seesaw parameters, independently of the gravitational-wave production mechanism. Long-lived Right-Handed Neutrinos generically induce a temporary period of early matter domination in the thermal history of the Universe, which imprints a feature in any primordial gravitational-wave background, characterised by two frequencies corresponding to the onset and end of this epoch. These frequencies are determined by the initial abundance, mass, and decay rate of the dominating species. I will explore how this mechanism is realised through non-thermal production of right-handed neutrinos in the minimal type-I seesaw, and separately the gauged $U(1)_{B-L}$ model.

Speaker: Angus Spalding (Univeristy of Southampton)

Cosmology: Cosmic Tensions

Conveners: Elsa Teixeira (Laboratoire Univers et Particules de Montpellier, University of Montpellier), William Giarè

66 From Distance Ladder to Network: Methods, Code, and Results from H0DN

The H0 Distance Network (H0DN) combines multiple distance indicators (Cepheids, TRGB, SNe Ia, SBF, megamasers, and others) into a single covariance-aware linear system to determine the Hubble constant. The baseline analysis yields H0 = 73.50 +/- 0.81 km/s/Mpc (1.09% precision, 7.1-sigma tension with early universe based inferences that assume LCDM) and demonstrates robust stability across more than 30 systematic variants. This talk will focus on the methodology: outlining the linear system of equations and covariance matrix structure underlying the generalized least-squares fit.

Speaker: Emre Ozulker

67 Dark Energy Survey Year 6: Cosmological Results and Lensing Ratios

Increasingly precise observations are beginning to expose potential cracks in the standard cosmological model, from the Hubble constant tension to emerging hints of evolving dark energy. Resolving whether these point to new physics, and uncovering the nature of dark matter and dark energy, requires precise measurements of cosmic geometry and the growth of structure. The Dark Energy Survey (DES) was designed precisely to address these questions.

In this talk, I will present the final cosmological results from DES Year 6, covering $\sim 5000 \text{ deg}^2$ with 140 million source galaxies and 9 million lens galaxies. Through the combination of cosmic shear, galaxy clustering, and galaxy–galaxy lensing ($3\times2$pt), DES Y6 yields constraints on the amplitude of matter fluctuations $S_8$ with a factor of two improvement over DES Y3. For the first time, we combine all four DES dark energy probes - $3\times2$pt, Type Ia supernovae, baryon acoustic oscillations (BAO), and galaxy clusters - into a single coherent analysis, presenting constraints in both $\Lambda$CDM and wCDM.

I will then discuss lensing ratios, an exciting geometric probe for weak-lensing cosmology. By comparing galaxy-galaxy lensing signals around the same lens sample but different source samples, the dependence on the lens mass distribution cancels, leaving a signal governed by angular diameter distances. This makes lensing ratios a clean probe of cosmic geometry and expansion history, while providing an internal validation of redshift and shear calibrations. I will show how this has already been realised in DES Y6, where lensing ratios have been used to validate photometric redshift and multiplicative shear calibrations.

Stage-IV surveys such as Euclid, Rubin/LSST, Roman and Simons Observatory, will dramatically increase statistical power, making calibration systematics ever more critical while simultaneously unlocking the full potential of lensing ratios. I will close by showing how their geometric sensitivity on small angular scales positions lensing ratios as both a precision calibration tool and a cosmological probe in their own right.

Speaker: Gisela Cristina Camacho Ciurana (ICE-CSIC)

68 How safe is supernovae data?

The tantalising hint of evidence for dark energy evolution depends on the interplay of data from the cosmic microwave background, baryon acoustic oscillations and Type Ia supernovae. Two recent supernovae data releases, DES-Dovekie and Union3.1, have reduced the preference for evolution compared to previous versions. What has changed? And can the data be trusted?

Speaker: Paul Shah (UCL)

69 Coffee Break

70 Disentangling cosmic distance tensions with early and late dark energy

Recent cosmological data reveal tension between parameters inferred from measurements of the cosmic microwave background (CMB), baryon acoustic oscillations (BAO), and supernovae (SN) under $\Lambda$CDM. Typical dynamical dark energy parameterizations (such as $w_0w_a$) that seek to jointly resolve these tensions have an equation of state parameter that crosses into the phantom regime, leading to potential instabilities for physical models. We show that the BAO (early-time) and SN (late-time) sides of the tension can instead be treated independently. Early dark energy (EDE) can reduce the tension between CMB-BAO data by changing the calibration of the sound horizon at the drag epoch $r_d$, with a $\Delta\chi^2 = -9.4$ relative to $\Lambda$CDM, raising $H_0$ to 70.87 $\mathrm{km \ s^{-1}Mpc^{-1}}$. EDE alone cannot bring consistency between CMB, BAO, and SN data, but combining with a thawing-quintessence component of dark energy reduces tensions between the three datasets, with $\Delta\chi^2=-12.6$ relative to $\Lambda$CDM without
a phantom component, vs.\ $\Delta\chi^2=-15.8$ for $w_0 w_a$ with one. We consider different SN datasets, using the most recent DES Dovekie catalog as our default while assessing differences with the original DESY5 and Pantheon+ catalogs. While the significance of adding thawing quintessence changes, the EDE solution to the CMB-BAO tension remains nearly unaffected. Moreover, though we do not include direct Hubble constant measurements in these $\Delta\chi^2$ values, the EDE solution reduces the Hubble tension with the Local Distance Network value from $7\sigma$ in $\Lambda$CDM to $2-3\sigma$ depending on the SN dataset, nominally the equivalent of an extra $\Delta\chi^2 \sim -40$ or more.

Speaker: Tanisha Jhaveri (University of Chicago)

71 TBA

Speaker: Laura Herold

72 Axion-dilaton interactions in the dark sector

Axion-dilaton models constitute a well-motivated and minimal class of theories that emerge in extra-dimensional completions of high-energy physics. These models naturally feature kinetic couplings between multiple scalar fields, which can have significant consequences in late-time cosmology. I will present the cosmological implications of these interactions when prescribing an axion and a dilaton field to describe dark matter and dark energy, respectively, including the predicted effects on the CMB, late time structure growth, and particle mass evolution. I will show that these effects allow a resolution of the Hubble tension and the model to fake a phantom cross, fitting the recent DESI data as well as the phenomenological parameterisations, in a single minimal framework.

Speaker: Adam Smith (University of Sheffield)

73 Viable interactions in the dark sector

Extensions of $\Lambda$CDM with interactions between dark matter and dark energy are a promising route to address the current cosmic tensions. In this talk, I will discuss interacting dark sector models with entropy couplings, which give rise to pure-momentum transfer in cosmology. While the background evolution is unchanged, the models are characterised by distinct observational signatures at the level of cosmological perturbations. I show that the couplings lead to a late-time suppression of structure growth while remaining compatible with CMB measurements, which is especially relevant for addressing the $S_8$ tension. I will then discuss the theoretical viability of these types of interactions and observational constraints from current survey data.

Speaker: Erik Jensko (University College London)

Cosmology: Modified Gravity

Conveners: Alessandra Silvestri, Matteo Martinelli (INAF - OAR)

74 Gauge invariant perturbations of F(T,T_G) Cosmology

The Gauss-Bonnet invariant connects foundational aspects of geometry with physical phenomena in a variety of ways. Teleparallel gravity offers a novel direction in which to use the Gauss-Bonnet invariant to go beyond standard cosmology. In this work, we explore the cosmological perturbations of teleparallel gravity generalized through the Gauss-Bonnet invariant. This is crucial in understanding the viability of these models beyond background analyses. We do this by taking a gauge invariant approach, which is followed by popular gauge choice examples. It is important to take this approach to understand the stability and healthiness of the underlying theory. We determine the equations of motion for all perturbative modes and offer a physical interpretation for the new contributions for each of the modes.

Speaker: Prof. Bivudutta Mishra (BITS-Pilani, Hyderabad Campus)

75 General relativity as diffusive equilibrium of scalar-tensor gravity

Scalar-tensor theories of gravity are known to generically admit an effective imperfect fluid description, which leads to a natural interpretation of GR as a state of thermal equilibrium. In particular, it is possible to assign a temperature to nonminimally coupled fields, which increases as the theory deviates from GR. However, this temperature is conformally dependent, and can be arbitrarily tuned, threatening its interpretation as an intrinsic property of a scalar-tensor theory (as opposed to a representation-dependent property). To remedy this, we employ the frame-invariant formulation of scalar-tensor gravity, in which all quantities are manifestly independent of the choice of conformal frame. We then find that all scalar-tensor theories, not just minimal ones, feature an identically vanishing temperature. As a result, the deviation from GR is a diffusive (rather than thermodynamical) process, controlled by the frame-invariant chemical potential, and so GR emerges as the state of diffusive equilibrium in the class of scalar-tensor theories (minimal or nonminimal).

Speaker: Sotirios Karamitsos (University of Tartu)

76 A Master Equation for Screening in Luminal Horndeski Gravity

Determining the active screening mechanism from a general scalar-tensor Lagrangian remains a significant challenge when testing modified gravity models against cosmological observations. In this talk, I will present a new diagnostic framework based on a systematic study of nonlinear cosmological perturbations in luminal Horndeski theories. I will outline the derivation of a master equation for screening and demonstrate how it recovers established mechanisms, such as Vainshtein and Chameleon, directly from fundamental theory. Furthermore, this framework reveals a completely new regime we term "Phaedrus" screening, characterised by a screening radius that grows linearly with the mass of the source object. For each mechanism, I will present analytical and numerical solutions, clarifying the conditions under which they activate. Finally, I will introduce the new open-source software tools that enable this work.

Speaker: Sergi Sirera (Institute of Cosmology and Gravitation)

77 Alleviating Hubble tension with Torsion Condensation (TorC)

Persistent cosmological tensions, including the Hubble and curvature tensions, together with the theoretical challenge of unifying General Relativity (GR) with the other fundamental forces in particle theory, motivate the exploration of extensions to the $\Lambda$CDM model.
We investigate the Torsion Condensation (TorC) model, a framework derived from Poincare Gauge Theory that introduces two parameters in addition to $\Lambda$CDM. The resulting modifications can be redefined as evolving dark energy components, i.e. as a standard extension to $\Lambda$CDM model. Implementing TorC in the CAMB Boltzmann code, we perform Bayesian inference using nested sampling with PolyChord and Cobaya to compare TorC against $\Lambda$CDM. Notably, the TorC field equations are insensitive to spatial curvature. We therefore examine the implications of this "k-screening" mechanism and compare it to k$\Lambda$CDM.
We present constraints on TorC from cosmological data and assess its performance relative to $\Lambda$CDM in terms of Bayesian evidence and tension metrics, evaluating its potential to alleviate current observational discrepancies. Our results highlight the importance of exploring well-motivated extensions to GR, and of applying robust statistical frameworks when assessing their viability against precision cosmological data.

Speaker: Sinah Legner (University of Cambridge)

78 Coffee Break

79 Non-Gaussian statistics to break degeneracies in modified gravity

The characterization of the statistical properties of the cosmological density field represents a central topic in today's cosmology. Understanding the distribution of matter in the Universe provides a powerful means of testing the standard cosmological model and identifying possible deviations. Among the available probes to characterize the statistical properties of the cosmological density field, weak gravitational lensing (WL) has proven particularly effective for constraining departures from General Relativity (GR), being sensitive to the enhanced clustering of matter predicted by modified gravity (MG) theories while being largely unaffected by the uncertainties associated with galaxy bias on small scales.

Traditionally, cosmological information from the Large-Scale Structure (LSS) has been extracted through two-point statistics, such as the two-point correlation function (2PCF) and the power spectrum. However, these estimators are insensitive to non-Gaussianities arising from non-linear gravitational evolution, precisely where MG screening mechanisms are expected to operate. This limitation is especially relevant in light of upcoming Stage IV surveys, such as the Dark Energy Spectroscopic Instrument (DESI) , the Legacy Survey of Space and Time (LSST), and \textit{Euclid}.

In this work, we studied the performance of different higher-order statistics (HOS) when applied to the Hu-Sawicky formulation of $f(R)$ gravity. These models have a widely known degeneracy with the total neutrino masses that counteract the enhancement in matter clustering form MG effects. We relied on convergence maps obtained from the DUSTGRAIN-\textit{pathfinder} N-body simulations. We used both distance metrics between distributions, as well as nonparametric hypothesis tests, to assess the statistical significance of the distance between the distributions of the HOS measured on $\Lambda$CDM and $f(R)$ simulations. A common results was the HOS outperforming the 2PCF in discriminating between cosmologies, even in the presence of shape noise, which is the main source of error in this kind of analysis.

Speaker: Alessandro Vadala (INAF - Astronomical Observatory of Rome)

80 Model-independent tests of gravity with the Weyl potential evolution

Cosmological observations are well described by the LCDM model, a universe with a cold dark matter component and a cosmological constant acting as dark energy. However, more and more cosmological tensions have emerged in the past decades, putting this simple model into question. A large amount of research has focused on the quest for an alternative model of modified gravity and dark energy, but no consensus has been reached. Model-independent tests of gravity can help us to identify viable models while keeping the computational cost of data analysis minimal. In this talk, I will focus on the Weyl potential evolution, a model-independent observable tracking the combined gravitational potential Ψ + Φ. I will present a measurement of this quantity obtained using galaxy-galaxy lensing and galaxy clustering data from the Dark Energy Survey. I will also highlight how, in combination with redshift-space distortions, this new observable can help us to disentangle different alternative models.

Speaker: Nastassia Grimm (University of Portsmouth)

81 Testing modified gravity with gravitational wave lensing

Gravitational waves propagating through the universe inevitably encounter massive objects, getting deflected and magnified. The presence of lenses such as galaxies, clusters, or stars breaks the symmetries of the FLRW metric, allowing for new interactions between different polarizations. These bear the signatures of modified gravity and imprint distinctive effects on the waveforms. I will present the potential of gravitational wave lensing as a testing ground for theories beyond GR, focusing on scalar-tensor theories with screening. These are particularly interesting since screened environments naturally modify GW propagation, while evading local gravity tests. I will focus on a formalism that goes beyond the geometric optics approximation, allowing for lens-induced dispersion, which can constrain any modified theory without the need for EM counterparts.

Speaker: Dr Serena Giardino (Imperial College London)

82 Closing in on the EFTofDE with combined probes

The EFT of Dark Energy (EFTofDE) is a theoretically well-motivated class of modified gravity models, able to explain observational hints for dynamical dark energy with further testable predictions for structure growth and lensing. I will discuss the merits and challenges of combining probes of linear perturbations and present state-of-the-art constraints on the EFTofDE by combining CMB, BAO, SNe, RSD, ISW, and 3x2pt datasets. I will show that these constraints are driven not just by the constraining power of probes but also by theoretical priors. I will finally discuss how considering observables on mildly nonlinear scales from higher order terms in the EFTofDE Lagrangian can help to strengthen constraints further.

Speaker: Neel Shah (University of Portsmouth)

Particles: joint BSM and Flavour & DM experiments

Conveners: Adam Brown (University of Sheffield), Christopher McCabe (King's College London), Sarah Williams, William Barter (University of Edinburgh)

Strings: Black Holes

Conveners: Arash Ardeali, Marina David

83 TBA

Speaker: Sam Dolan

84 Evaporating black holes: how the burden of their memory stabilizes them

The memory burden effect describes how an object's stored information resists its own decay. This mechanism is especially pronounced in saturons—systems that saturate unitarity bounds on entropy—with black holes providing the prime example. I will show how memory burden can halt Hawking evaporation and dynamically stabilize black holes against complete decay. Crucially, this phenomenon is not exclusive to gravity: it arises naturally in generic quantum many-body systems and renormalizable field theories, underscoring its broader theoretical relevance. I will then discuss the phenomenological consequences, focusing on potential signatures in the early Universe and today. In particular, memory-stabilized black holes can produce distinctive high-energy cosmic-ray signals and leave characteristic imprints on the CMB, offering correlated cosmological and astrophysical probes of this peculiar form of dark matter.

Speaker: Michael Zantedeschi

85 TBA

Speaker: Robie Hennigar

86 Numerical Relativity in effective field theories of gravity

I will discuss how Numerical Relativity can serve as a tool to study non-linear dynamics in effective field theories (EFTs) of gravity. I will first present our work on scalar-Gauss-Bonnet gravity, in which a change of gauge enables well-posed evolutions in black hole spacetimes, which reveal potential smoking gun signatures in gravitational-wave emission. I will then introduce a recently proposed well-posed formulation by Figueras, Held and Kovács that applies to all polynomial higher-derivative EFTs of gravity and show our initial progress in exploring dynamical Chern-Simons gravity.

Speaker: Llibert Aresté Saló

87 Coffee Break

88 Volume as Time: Boundary Dynamics Near Black Hole Horizons

Different notions of time arise from different choices of observer. In cosmological settings, a particularly natural choice is the spacetime volume, which is conjugate to the cosmological constant. This gives rise to unimodular time, deparametrizing the Wheeler–DeWitt equation into a Schrödinger-like evolution equation. I will first explain how this construction appears in arbitrary dimension, with particular emphasis on the four-dimensional case.

As an explicit Holographic realisation, I will then focus on near-extremal black holes, whose low-energy throat dynamics is universally described by Jackiw–Teitelboim gravity. In this setting, promoting the vacuum cosmological constant to a dynamical top-form degree of freedom provides a bulk clock in the Henneaux–Teitelboim sense. Holographically, this modifies the usual Schwarzian boundary dynamics by coupling it to an additional U(1) phase mode, reproducing the universal low-energy structure familiar from complex SYK. Finally, I will show that the resulting boundary theory can be rewritten as a (0+1) dimensional observer action, making explicit the relation between the bulk volume clock and its holographic boundary counterpart.

Speaker: Farbod-Sayyed Rassouli (University of Nottingham)

89 Detecting black hole microstates

A step towards probing the black hole interior and its structure is being able to detect the black hole microstate. We demonstrate that the Euclidean two-point function of an appropriately chosen probe operator can detect the microstate of an asymptotically AdS black hole. This detection, which requires a tuned, state-dependent choice of probe, is the result of a new gravitational saddle, which dominates over the usual saddles. The gravitational result can be explicitly reproduced in the dual boundary CFT if we assume the eigenstate thermalization hypothesis. We also discuss a binary search protocol to detect the black hole microstate from a candidate list.

Speaker: William Chan (University of Pennsylvania)

90 Tidal Love Numbers of Black Holes Dressed by Dark Matter

Tidal Love numbers (TLNs) encode the deformability of compact objects under external tidal fields and leave observable imprints in gravitational wave signals. While black hole TLNs vanish in vacuum general relativity, the presence of surrounding matter can alter this picture. This talk presents a study of the axial (magnetic) TLNs of a Schwarzschild black hole embedded in a spherically symmetric dark matter distribution, modeled as an anisotropic fluid with three astrophysically motivated density profiles: Einasto, Hernquist, and NFW. Analytic closed-form expressions are derived via a small-compactness expansion and benchmarked against direct numerical integration of the perturbation equations. A key finding is that profiles without compact support generically produce logarithmic terms in the asymptotic expansion of the perturbation variable, obstructing the standard tidal matching procedure and pointing to the subtleties of defining tidal observables for black holes dressed by matter. The broader implications for gravitational wave detectability with next-generation detectors are discussed, highlighting dark matter environments around compact objects as a promising multi-messenger target.

Speaker: Simone D'Onofrio (ICE - CSIC)

91 TBA

Speaker: Marina David

Lunch

Particles

92 TBA

Speaker: Prof. MARTIN BAUER (IPPP Durham)

93 TBA

Speaker: Dr Joel Swallow (INFN - Laboratori Nazionali di Frascati)

94 Measurement of the ratios $R(D^{(*)}) = \mathcal{B}(B \to D^{(*)} \tau \nu) / \mathcal{B}(B \to D^{(*)} \ell \nu)$, using semileptonic tagging and leptonic $\tau$ decays with the $BABAR$ detector

Semileptonic decays of $B$ mesons involving $\tau$ leptons are sensitive probes for physics beyond the Standard Model. The relative rates of the branching fractions $R(D) = \mathcal{B}(B \to D \tau \nu) / \mathcal{B}(B \to D \ell \nu)$ and $R(D^*) = \mathcal{B}(B \to D^* \tau \nu) / \mathcal{B}(B \to D^* \ell \nu)$, where $(\ell=e,\mu)$ are independent of the CKM element $|V_{cb}|$ and many theoretical uncertainties. We report a measurement of ratios $R(D)$ and $R(D^{*})$ using semileptonic $B$-tagging and leptonic $\tau$ decays using the 433 fb$^{-1}$ data collected at the $\Upsilon(4S)$ resonance by the $BABAR$ detector at the PEP-II collider located at the SLAC National Accelerator Laboratory.

Speaker: Fergus Wilson (Science and Technology Facilities Council STFC (GB))

Coffee Break

Strings

95 Entropy of near-extremal and near-BPS black holes in AdS_3 supergravity.

In this talk, I will discuss the behaviour of the Euclidean path integral at low temperatures in the context of AdS_3 supergravity, highlighting the difference between near-extremal and near-bps limits. In our work, we analyzed quantum fluctuations in both the near-horizon and asymptotic regions and clarified various aspects of the bosonic fluctuations (namely, the rotational modes and gauge modes) that have been confusing in the literature. We highlight the role of boundary conditions in AdS_3, and show in particular that the gravitational path integral in the near-horizon region is inequivalent to that around the full BTZ solution at low temperature.

Speaker: Diksha Jain

96 TBA

Speaker: Luigi Tizzano

Public Talk

Convener: Adam Riess

Friday 26 June

Cosmology: Dark Matter in cosmology

Conveners: Clare Burrage (University of Nottingham), Laura Covi (Georg August Universitaet Goettingen (DE))

Particles: Beyond the Standard Model & Flavour Physics

Conveners: Sarah Louise Williams (University of Cambridge (GB)), William Barter (University of Edinburgh)

Particles: Higgs & Electroweak

Conveners: Chris Hays (University of Oxford (GB)), Peter Millington (University of Manchester)

97 Higgs boson production and decay rate measurements with the ATLAS experiment

With the Run 2 and Run 3 pp collision dataset collected by the ATLAS experiment at LHC, very precise measurements of Higgs boson production and decay rates can be performed, shedding light over the electroweak symmetry breaking mechanism. This talk presents the latest precise measurements of Higgs boson productions and decays, including fiducial, differential, as well as Simplified Template Cross-section (STXS) measurement results, from the ATLAS experiment.

Speaker: Ahmed MARKHOOS

98 Search for the rare Higgs boson decay H -> Z gamma

We present a search for the rare Higgs boson decay H→Zγ using proton–proton collision data recorded by the CMS experiment at the LHC at center-of-mass energies of 13 and 13.6 TeV, corresponding to a total integrated luminosity of 200 fb⁻¹. The analysis targets final states where the Z boson decays to an electron or muon pair. Sensitivity is enhanced through dedicated event categorization optimized for different production modes. The signal is extracted from a simultaneous fit to the three-body (lepton pair and photon) invariant-mass distributions across all categories. For a Higgs boson mass of 125.38 GeV, the measured signal strength relative to the Standard Model expectation is μ = 1.10 (+0.52/-0.61), with an observed (expected) significance of 1.9 (2.3) standard deviations. These results provide an important test of loop-induced Higgs couplings and no significant evidence of physics beyond the Standard Model is observed.

Speaker: Xingchen Fan (Cornell University (US))

99 V-associated production & vector boson fusion of Higgs bosons as an LHC signature of CP violation

Many well-motivated extensions of the Standard Model predict new, entirely bosonic sources of CP violation (CPV). In these scenarios, the simultaneous observation of carefully selected bosonic processes emerges as a simple yet powerful method to unambiguously reveal the presence of CPV. The present study, which establishes a promising framework of CPV searches for the upcoming HL-LHC era, showcases this method by exploring the detectability of such generic CPV signatures within the economical Complex Two-Higgs Doublet Model (C2HDM). Specifically, we assess the observation prospects for viable combinations of gluon fusion, vector boson fusion and V-associated production processes which unequivocally signal the existence of CP-violating couplings within the bosonic spectrum of the model. Finally, we discuss an ongoing extension of this work which completes the framework through the exclusive use of gluon fusion processes.

Speaker: Álvaro Lozano Onrubia (IFT UAM-CSIC & Universidad Autónoma de Madrid)

100 Natural Higgs mass from the power-law running

Unprotected by any symmetry, we show that the scalar mass squared runs by a power law.
It is O(M_GUT^2) at M_GUT^2 and O(m_W^2)at m_W^2, which follows from the standard on-shell renormalization of quantum field theory.
The 28 orders of discrepancy is naturally explained by the ``beta function coefficient'' of the Standard Model, dominated by the top quark Yukawa coupling.

Speaker: KAng-Sin Choi (Ewha Womans University)

101 Higgs Criticality: Electroweak Vacuum Metastability as a Window to Beyond the Standard Model Physics

This work proposes a direct link between the hierarchy problem and Weakly Interacting Massive Particles (WIMPs): we suggest that the small mass of the Higgs boson arises from being dynamically driven to the scale of the WIMP. Such a special electroweak vacuum is singled out by lying close to the critical boundary of a phase transition, as recently explored in a new class of cosmological solutions to the hierarchy problem. They generically predict the Higgs potential to be destabilised just above the weak scale. Intriguingly, the requirement for new physics to achieve this coincides with two independently well-motivated expectations: a split spectrum of light fermions and heavy bosons, as anticipated from naturalness, and the so-called "WIMP miracle". A WIMP with mass around the weak scale not only happens to have the correct thermal relic abundance to be the dark matter (DM), it can also give rise to the necessary critical boundary at the TeV scale through its Yukawa couplings to the Higgs. We use a higgsino-like singlet-doublet model to illustrate our Higgs-DM criticality scenario and show that if this WIMP DM mass is observed to be greater than ~1.2 TeV then it necessarily implies a strong bound on the Higgs mass and an upper bound on the scale of heavy new physics that restores vacuum stability. It can be thoroughly probed in direct detection experiments, astrophysical signals and future collider searches, further motivating a comprehensive exploration of the remaining heavy WIMP parameter space.

Speaker: Maximilian Detering (King's College London)

102 Toward a real-time theory of vacuum decay

False vacuum decay plays a pivotal role in many models of particle physics and the early Universe, from inflation to the electroweak vacuum. However, we lack a satisfying theoretical understanding of this process, with existing approaches working only in imaginary (Euclidean) time, and relying on assumptions that have yet to be empirically tested.
In this talk, I will describe ongoing efforts to develop a real-time theory of vacuum decay by combining two new empirical approaches: semiclassical numerical simulations on the lattice, and quantum analogue experiments in the laboratory.

Speaker: Alex Jenkins (University of Cambridge)

103 Coffee Break

104 Searches for New Physics in Effective Field Theory Approaches from ATLAS

We present two analyses searching for new physics in the context of effective field theory approaches from the ATLAS collaboration. The analyses use multiple experimental measurements across a range of processes in electroweak boson, top-quark and Higgs production to constrain dimension-6 operators. In addition multi-boson production measurements provide leading constraints on anomalous quartic gauge couplings.

Speaker: Oleksii KURDYSH

105 Characterizing LHC-Resonances in extended HEFT

In theories with extended scalar sectors, the lightest new scalar could be accessible at colliders. Instead of relying on simplified models, we describe such scenarios in a general and gauge-invariant way using an extended HEFT framework with a nonlinearly realized electroweak symmetry. The structure of the effective operators depends on the $SU(2)$ nature of the scalar in the UV, leading to different suppressions by the heavy scale. In this talk, we show how dimensional analysis allows us to identify hierarchies among Wilson coefficients that translate into correlations between LHC observables, providing a model-independent strategy to interpret a potential scalar signal and infer its UV origin without fixing its $S U(2)$ representation.

Speaker: David Cabo Almeida (University of Göttingen)

106 Precision Measurement of the Electroweak Mixing Angle in the Region of the Z pole

This contribution presents an overview of an improved extraction of the effective leptonic weak mixing angle, $\sin^2θ^ℓ_{eff}$, based on the published CMS measurement of the forward-backward asymmetry in Drell-Yan events at 13 TeV. While the original CMS analysis achieved a significant reduction in experimental uncertainties, its overall precision remains limited by residual uncertainties in the parton distribution functions (PDFs). This talk highlights the impact of incorporating complementary CMS measurements (W asymmetry and W/Z cross section ratio) that probe different combinations of parton densities, thereby providing additional PDF constraints beyond those obtained from the asymmetry measurement alone. The improved analysis leads to a substantially reduced total uncertainty, yielding $\sin^2θ^ℓ_{eff}$=0.23156±0.00024. This result is consistent with the Standard Model prediction and represents the most precise single determination of this parameter to date.

Speaker: Arie Bodek (University of Rochester (US))

107 Quantum Entanglement Is Quantum: Insights from Diboson Systems at the LHC

Polarisation and spin correlations in diboson systems are powerful probes for precision tests of the Standard Model and searches for new physics. More recently, viewing these observables through the lens of quantum information, such as assessing whether diboson systems exhibit quantum entanglement, has opened a compelling new frontier in these investigations. They also provide a unique opportunity to test quantum information principles at the highest accessible energy scales. We analyze the angular coefficients for the $pp \to ZZ \to 4 \ell$ and Higgs decay to di-bosons $h \to WW$ and $h \to WW$, incorporating higher-order QCD and electroweak corrections. For Higgs decays, we consider both fully leptonic and semileptonic final states. Guided by the fundamental properties of the spin density matrix, we assess the stability of the two-qutrit interpretation under radiative effects. For the $pp \to ZZ \to 4 \ell$ process, NLO QCD corrections preserve the two-qutrit structure but weaken entanglement indicators, an effect that can be partially mitigated by jet binning. In contrast, EW introduce non-factorizable contributions that modify the quantum properties of the system. While these effects can be largely depleted by selecting events with a double-resonant $ZZ$ structure, such a kinematic handle is not available for Higgs decays. For $h \to ZZ$, channel, singly-resonant NLO electroweak corrections substantially distort the angular coefficients, challenging the description of these events as a two-qutrit system. These effects are milder for $h \to WW$ compared with $h \to ZZ$. For both processes, semileptonic final states exhibit greater stability than fully leptonic final states.

Speaker: AJAY Kaladharan

Cosmology: Dark Energy

Conveners: Laura Herold, Supriya Pan

108 Distinguishing dark sector interactions: from energy transfer to elastic and entropy couplings

Interactions in the dark sector can arise through a variety of physical
mechanisms, including energy exchange, momentum (elastic) transfer, and entropy
couplings. While these are often studied in isolation, their phenomenology can
overlap at the level of cosmological observables, leading to degeneracies in current
analyses. With the advent of Stage IV surveys, improving our ability to distinguish
between these scenarios has become increasingly important. In this contribution, I
discuss consistently incorporating different classes of couplings within a common
description of the dark sector. This approach allows for a systematic comparison of
their impact on both background evolution and linear perturbations, and highlights
the primary physical quantities controlling their observational signatures. I will
discuss how different classes of couplings leave distinct signatures on cosmological
observables, while also identifying regimes in which they can mimic each other, with
particular emphasis on the role of momentum transfer and its interplay with entropy
perturbations.

Speaker: Elsa Teixeira (Laboratoire Univers et Particules de Montpellier, University of Montpellier)

109 Reconstructing dark energy with few assumptions

Baryon acoustic oscillation (BAO) measurements from the Dark Energy Spectroscopic Instrument (DESI) strengthen the cosmological evidence for dark energy beyond the cosmological constant to the ~3σ level when combined with cosmic microwave background (CMB) and Type Ia supernovae (SNe Ia) observations. This evidence is obtained assuming a dark energy equation of state restricted to linear order in the scale factor, and an active area of research is determining how this restriction affects the data’s preferences. Dark energy “reconstructions” take a data-driven approach, describing dark energy’s properties with flexible functions that have fewer restrictions on the possible forms of evolution. We parametrize the dark energy equation of state and energy density using piecewise constant functions of redshift, effectively inferring these functions’ averages within seven redshift bins from $z=0$ to $z=4.2$. Across six different BAO and SNe Ia dataset combinations—with BAO from DESI and the Sloan Digital Sky Survey (SDSS) alongside the latest, recalibrated SNe Ia samples—we find local deviations from $\Lambda$CDM with significance up to ~3σ in the energy density and ~2σ in the equation of state. Our results are broadly consistent with linear evolution and indicate a tentative phantom crossing, most clearly manifesting as a local maximum in the dark energy density.

Speaker: Daniel A. Kessler (University of Sheffield)

110 Non-Linear Effects of the Interacting Dark Energy Model

We focused on a phenomenological interacting dark energy model (IDE) with energy-momentum transfer from dark matter to dark energy through a coupling $Q = ξ\mathcal{H}ρ_{DE}$. Following our previous work on constraining the parameters of the same IDE model using CMB and DESI data, we now present the N-body simulation results based on a modified version of RAMSES code. Compared with the fiducial LCDM results, the IDE model predicts an enhanced power on large scales but suppressed clustering on small scales (k ≥ 2 h/Mpc), consistent with the reduced dark matter density at late times.

Speaker: Yuejia Zhai (University of Sheffield)

111 Early- and Late-Time Dark Energy Dynamics after DESI

Speaker: William Giarè

112 Coffee Break

113 Unveiling the Dark Universe with the Sun

The sun is a powerful tool for investigating the dark universe. In the core of the sun light scalar particles can be produced via Primakoff process in the electric field of the ions and via the intense magnetic field. There can also be production vis the magnetic field in the tachocline. This allows for stringent constraints on new scalar particles which could play the role of dark energy. This will be discussed

Speaker: Anne Davis

114 Beyond LCDM: Dynamical Dark Energy and High-Redshift Reionization

This talk will explore deviations from the standard cosmological model across cosmic history. First, I will present data analysis results on dynamical dark energy using a novel pressure parametrization and four parameters parametrization testing by the latest datasets. Second, I will discuss model-independent reconstructions of the reionization history using Gaussian processes. We utilize these reconstructions to place robust bounds on exotic energy injections and decaying particle models.

Speaker: Hanyu Cheng

115 Cosmological signatures of a solidly unified dark sector

I will present a cosmological model with a unified solid dark sector that transits from a CDM phase at high redshift to a quasi-de Sitter phase at late times. Remarkably, this can be accomplished without generating strong acoustic oscillations, thus being compatible with observations of the matter power spectrum. The solid unified dark sector can reduce the rate of matter clustering in the late universe compared to the standard $\Lambda$CDM scenario, providing potential ways to alleviate the σ8 tension. A distinctive signature of the model is the generation of a non-trivial slip parameter that could be imprinted in weak lensing measurements. Additionally, gravitational waves acquire a nonvanishing mass term due to the shear distortions.

Speaker: María Pérez Garrote (Universidad de Salamanca)

116 A QCD vacuum motivated model of dynamical dark energy

The nature of dark energy has been a growing point of debate in recent years, particularly after the DESI measurements of the Baryon Acoustic Oscillations. While frequentist metrics appear to indicate a growing preference for a dynamical dark energy, some bayesian approaches indicate otherwise. Beyond this, there also lies the question of whether there exists a physical motivation behind any phenomenological parametrisation of dynamical dark energy.
The model described in this talk is motivated from computations of the non-perturbative QCD vacuum, which we parametrise into a dynamic, non-local contribution to the energy density, described by two additional cosmological parameters. I will describe how this model compares against both CPL and ΛCDM on the latest cosmological datasets, employing both frequentist χ² statistics and Bayesian model comparison. For the latter, the evidence is estimated from MCMC chains via the learnt harmonic mean estimator method which bypasses the need for the computationally expensive, nested sampling to obtain estimates of the evidence.

Speaker: Dong Ha Lee (University of Sheffield)

Strings: String phenomenology/cosmology

Conveners: Ivonne Zavala, Susha Louise Parameswaran (University of Liverpool)

117 TBA

Speaker: Ivonne Zavala

118 TBA

Speaker: Prof. Lilia Anguelova (INRNE, Bulgarian Academy of Sciences)

119 Modular quintessence and de-Sitter in heterotic orbifolds

Recent results from DESI indicate that the accelerated expansion of the Universe may not be fully explained by a simple cosmological constant and instead may point toward a dynamical form of dark energy. At the same time, modular symmetries are emerging as important ingredients in string theory, as modular invariance is naturally built into many string compactifications. In this work, we explore a possible connection between these ideas by focusing on scalar potentials arising in heterotic orbifolds, where the underlying geometry simultaneously shapes the flavor structure and the dynamics of the moduli. An interesting feature is that the dynamics of these modular fields can give rise to multifield hilltop quintessence, compatible with recent observations and consistent with the Swampland conjectures.

Speaker: Hansel Gordillo Ruiz (UNAM, Mexico)

120 Coffee Break

121 Generalised anomalies, QCD, and holography

During the last decade, the notion of an 't Hooft anomaly has
been generalised to the case of discrete symmetries. An interesting
instance, discussed by Tanizaki, is the mixed anomaly between the
discrete axial symmetry and the flavour and baryonic symmetries in
massless QCD. The goal of this talk is to provide a derivation of this
anomaly from a top-down holographic dual of QCD. I will show that the
topological couplings in the bulk supergravity dual of the D4-D8 system
encode Tanizaki's anomaly, once fluctuations around the bulk gauge
fields are turned on. A technical challenge for this computation is the
difficulty in maintaining gauge invariance of supergravity theories in
the presence of D-branes. To overcome this issue, a compact formulation
of the flux sector of (massive) type IIA supergravity in the presence of
D8 branes is presented.

Speaker: Mohammad Akhond

122 SUSY and non-SUSY analysis of truly confining gauge theories

We classify 4D N=1 truly confining supersymmetric gauge theories, in which no center charges can be screened. This property guarantees that Wilson loops in the fundamental representation exhibit an area law. We systematically identify all such theories for simple Lie groups and determine the allowed matter content. In each theory, we find condensing magnetic operators, which are expected to explain confinement via the dual Meissner effect. We also analyze the non-SUSY versions of truly confining gauge theories and identify stable vacua that indicate confinement via the dual Meissner effect.

Speaker: Shota Saito (Kavli IPMU)

123 Brane-Cosmology

Holography(AdS/CFT correspondence) has proved to be quite useful in under-
standing field theory at the boundary from the information in the bulk and vice-
versa, the goal is to see if such a prescription can help us understand our universe

and provide a mapping between cosmology and a CFT defined on a manifold with

boundary(BCFT). The bulk geometry is taken to be AdS with an additional End-
Of-the-World (EOW) brane along with the asymptotic AdS boundary such that the

boundary in the dual BCFT theory corresponds to EOW brane on gravity. The ad-
vantage of this construction is that although the bulk geometry is taken to be AdS,

the space-time on the brane could be dS and thus could pave a way to study dS/CFT
by embedding in higher dimensional AdS/CFT.
First AdS3/BCFT2 is considered and matter fields (complex scalar) on the brane
are coupled to the gravitational dynamics of the AdS bulk, thus serving as potent
tools for cosmology. Then the analysis is extended to AdS5, to draw some conclusions
about our real world cosmology from branes with some big-bang like solutions.

Speaker: Lakshita Bageja (IISER,B)

124 TBA

Speaker: Susha Louise Parameswaran (University of Liverpool)

Lunch

Strings

125 TBA

Speaker: Salvatore Bottaro

126 TBA

Speaker: Miranda Cheng

127 TBA

Speaker: Albrecht Klemm

Coffee Break

Cosmology

128 TBA

Speaker: Dr Djuna Croon (IPPP Durham)

129 Taylor expansion methods for loops during inflation and the decoupling of scales

Taylor expansion methods based on the separate universe approximation, or more general approaches that do not rely on this approximation, can provide insight into the debate on the strength of loop corrections in inflationary models with a large peak. Such a peak is needed for the production of primordial black holes and scalar-induced gravitational waves. In particular, these methods can clearly show how the peak scales decouple from predictions on CMB scales. These methods are also extremely useful for numerical simulations. After reviewing Taylor expansion methods, the codes that implement them, and the debate around loop corrections, I’ll highlight our recent results on the decoupling of scales.

Speaker: David Mulryne (Queen Mary University of London)