1st BiCoQ Conference: from gravity to particles

15 Jun 2026, 13:00 → 19 Jun 2026, 13:00 Europe/Zurich

Rooms U3-01 (Plenary Sessions), U3-01, U3-03, U3-05 (Parallel Sessions) (Dipartimento di Fisica G. Occhialini, Università Degli Studi di Milano-Bicocca)

Overview

The "BiCoQ Conference: from gravity to particles" aims at bringing together a broad community of scientists working at the intersection of gravitational-wave astronomy, dark matter physics, and experimental cosmology.

This interdisciplinary workshop is organized by the Bicocca Centre for Quantitative Cosmology (BiCoQ), and it seeks to discuss and explore the latest advancements in the study of the nature of gravity and matter across disciplines and scales, including:

• astrophysical tests of dark matter on cosmological scales
• direct detections of dark matter candidates
• probes of gravity across a wide frequency domain.

 

Plenary sessions will review the state-of-the-art in our view of the fundamental constituents of the universe. Three focused parallel sessions will discuss ongoing efforts and the next steps in constraining dark matter and dark energy with astrophysical observations, the physics of gravitational waves from binary systems, and the search for new physics with detections of dark matter candidates beyond the standard model or ultra-high frequency gravitational waves. 

Current invited speakers for the conference include:

• N. Fornengo (Universita' di Torino, Italy)
• S. Vegetti (Max Planck Insitute for Astrophysics, Germany)
• S. Simon (Fermi National Accelerator Laboratory, USA)
• A. Newman (Carnegie Science, USA)
• U. Sperhake (University of Cambridge, UK)
• N. Aggarwal (UC Davis, USA)
• N. Luetzgendorf (ESA-ESTEC, Noordwijk, NL)
• S. Fairhurst (University of Cardiff, UK)

 

The conference will be held on the main campus of the University of Milano-Bicocca.

Participants are required to pay a registration fee of 150 EUR, which covers lunches, coffee breaks, and the Welcome reception on Monday 15/06.

Monday 15 June

13:00 → 14:00 Registration and Welcome

14:00 → 15:00 Plenary Session: Astro Dark Matter - Speaker: S. Vegetti (Max Planck Insitute for Astrophysics, Germany)

15:00 → 16:00 Plenary Session: Astro CMB - S. Simon (Fermi National Accelerator Laboratory, USA)

16:00 → 16:30 Coffee Break

16:30 → 18:00 Topical Session 1 - Astro

16:30 The AIDA-TNG project: new insights on alternative dark matter in simulations of galaxy formation

One of the foundations of the concordance cosmological model is that approximately 85 per cent of the matter content of the Universe is in the form of some yet unknown component that we can detect only through its gravitational effect: dark matter. While the standard Cold Dark Matter model is very successful at explaining the large scale structure distribution of the universe, it has been challenged by observations at the scale of galaxies and below, motivating the exploration of alternative scenarios such as Self-Interacting or Warm Dark Matter.
I will present the first results from the new AIDA-TNG project, where we simulate three cosmological volumes, including six dark matter scenarios together with galaxy formation. Resolving systems from 10^9 to 10^14.5 solar masses, the AIDA-TNG project offers crucial new data to understand the effect of alternative dark matter models on multiple scales and observables. I will present our results on the density profiles of dark matter halos and subhalos, stellar and halo shapes, as well as the effect of SIDM and WDM on the properties of the galaxy general population. Moreover, I will talk about our first insight on large-scale power spectra and the Lyman-alpha emission on large scales, demonstrating the promising potential of this sample.

Speaker: Giulia Despali (University of Bologna)

16:50 MOND: An alternative to particle dark matter

Milgromian dynamics (or Modified Newtonian Dynamics, MOND) is a major alternative to particle dark matter proposed in 1983 by Mordehai Milgrom. MOND modifies the non-relativistic laws of gravity and/or inertia at low accelerations, below a characteristic acceleration scale a0. In this proposed contribution, I will showcase the content of the first "MOND white paper", which results from the collaboration of more than 60 researchers across the globe working on different aspects of MOND. The MOND white paper covers fundamental theories, numerical simulations, and observational tests across all astronomical scales, from the Solar System to Cosmology. In particular, I will focus on the successful a-priori predictions that MOND made on galaxy scales, as well as the long-standing problems it faces in galaxy clusters. I will also mention recent relativistic extensions of MOND that allow reproducing the cosmic microwave background, the linear matter power spectrum, and the observed behavior of gravitational waves.

Speaker: Federico Lelli (INAF - Arcetri Astrophysical Observatory)

17:10 Mapping the Cosmic Web in Lyα emission

The existence of filaments connecting galaxies, within which galaxies form, has been a long-standing prediction of structure formation theories in a Universe dominated by cold dark matter. However, direct imaging of these filaments has remained elusive until the advent of large-format integral field spectrographs such as the Multi Unit Spectroscopic Explorer (MUSE) at the Very Large Telescope.
In this talk, I will present recent direct detections of cosmic web filaments in Lyα emission from an ultra-deep (142-hour) observation in the MUSE Ultra Deep Field. This unique dataset enables us to directly probe the morphology, surface brightness profiles, and the transition radius between the circumgalactic and the intergalactic medium of different extended emitting structures spanning 3-5 cMpc. These filaments are observed both between a pair of bright quasars at redshift z~3.22 and within various overdensities of Lyα emitters between redshifts ~2.8 and ~4. I will also compare these findings with predictions from numerical simulations.
These discoveries represent a significant step forward in the study of large-scale structures in emission, providing a powerful new method to trace the distribution of dark matter and gas dynamics within the cosmic web.

Speaker: Davide Tornotti

17:30 Hidden properties and dynamical evolution of a giant disc galaxy at z~3

Understanding galaxy formation and evolution within the ΛCDM framework remains one of the critical challenges in astrophysics. Recent JWST observations revealed the existance of a massive giant disc within a Cosmic Web node at z~3, namely the Big Wheel. Constraining its origin requires a detailed characterisation of its dark matter halo, whose properties are notoriously difficult to extract from observations alone. With the aim of reconstructing the mass profile of the galaxy, I perform a physically motivated dynamical model by integrating high-resolution ALMA kinematical data with priors from JWST photometry. I find a lower limit for the stellar-to-halo mass ratio, which is already significantly higher than predicted by standard empirical relations, possibly suggesting an exceptional efficiency in forming stars. To verify the physical plausibility of the model, I performed an idealized numerical simulation, demonstrating that the galaxy remains gravitationally stable over 2.5 Gyr of adiabatic evolution. While based on an individual system, these findings could provide constraints on the evolution of massive discs within high-density environments in the early Universe.

Speaker: Giada Quadri (University of Milano-Bicocca)

18:00 → 19:00 Welcome reception

Tuesday 16 June

09:00 → 10:00 Plenary Session: Dark Matter Theory - Speaker: N. Fornengo (Torino University & INFN, Italy)

10:00 → 11:00 Plenary Session: Astro Dark Matter - Speaker: A. Newman (Carnegie Science, USA)

11:00 → 11:30 Coffee Break

11:30 → 12:30 Topical Session 1 - Astro

11:30 Calibration of Small-Aperture Telescopes for Cosmic Microwave Background with the POLOCALC drone-based artificial source

We present the strategy and hardware development for the POLOCALC drone-deployed calibration system for Cosmic Microwave Background. Achieving the unprecedented precision required for next generation CMB experiments, whose goal is the measurement of the inflationary signal due to the primordial gravitational waves. We have developed and deployed artificial sources capable of emitting in multiple bands centered at 90, 150, 220, and 280 GHz, respectively.
Each calibration source emits a stable, monochromatic signal. This controlled signal is used to calibrate the frequency-dependent properties of the telescopes, such as the polarization angle of the detectors and the telescope beam. For the latter, we focus on modelling cross-polar patterns and the natural variation of the beams across the wide observing bands. The sources are mounted on a Unmanned Aerial Vehicle (UAV), or drone, in order to position them accurately in the far-field of the telescopes. This allows for a comprehensive characterization of the instrument’s response, which is crucial for controlling systematic errors in the polarization measurements.
We show results from the drone-borne calibration campaigns performed in the Atacama desert throughout 2025. We also outline the development path towards a dichroic source capable of simultaneously emitting at frequencies of both the 90- and 150-GHz frequency bands, which will further enhance calibration efficiency.

Speaker: Gabriele Coppi

11:50 Polarization Angle Calibration of CMB Telescopes: Strategies and Implications for Cosmological Probes of Dark Matter and Dark Energy

Accurate polarization angle calibration of Cosmic Microwave Background (CMB) telescopes constitutes a critical challenge in modern observational cosmology. A miscalibration of the polarization angle induces spurious leakage from E-modes into B-modes, which contaminates the primordial gravitational wave signal, biases the reconstruction of the CMB lensing potential, and introduces systematic uncertainties in the measurement of cosmic birefringence.

In this contribution, we present an overview of the current strategies employed to calibrate the polarization angle, including observations of known celestial polarized sources, data analysis techniques exploiting the predicted nulling of the EB cross-correlation in the standard cosmological model, and the deployment of dedicated hardware solutions, including sparse wire grids and artificial calibration sources. We discuss the limitations and complementarity of each approach in the context of the quest to constrain the nature of dark matter and dark energy through high-accuracy CMB polarization measurements.

Speaker: Noemi Mezzanzanica

12:10 COSMIC BIREFRINGENCE: SEARCHING FOR PARITY VIOLATION WITH CMB POLARIZATION

In this talk, I will give an overview of the cosmic birefringence effect, from its theoretical foundations to its imprint on the polarized Cosmic Microwave Background. Cosmic birefringence, the rotation of the linear polarization plane of photons as they travel across the universe, would be a direct manifestation of parity violation in the Universe. It arises naturally when a pseudoscalar field, such as an axion-like particle coupled to electromagnetism through a Chern-Simons term, evolves over cosmic time, and as such it provides a unique observational window onto physics beyond the standard model, including dark matter and dark energy candidates.
I will discuss how the rotation of the linear polarization plane of the CMB generates observable signatures, in particular non-zero TB and EB correlations, that are otherwise forbidden in a parity-conserving universe. I will also review the current observational status, including the intriguing hints of a non-zero isotropic birefringence angle at the 2.4–3.6σ level from Planck data, the latest results from more recent searches, and outline the prospects for a detection with current and planned experiments.

Speaker: Idil Ezgi Karaaslan (University of Milano-Bicocca)

11:30 → 12:30 Topical Session 2 - DM

11:30 The XENONnT Dark Matter experiment: results and prospects

XENONnT is the latest detector of the XENON program for the direct detection of dark matter, currently operating at the INFN Laboratori Nazionali del Gran Sasso. It employs a dual-phase liquid xenon time projection chamber with a 5.9-tonne active target, achieving extremely low background levels and a low energy threshold, making it highly sensitive to rare interactions.
In this talk, I will present an overview of the detector and its performance, followed by recent physics results. These include the first observation of coherent elastic neutrino–nucleus scattering (CEvNS) from solar $^8$B neutrinos, demonstrating sensitivity to low-energy nuclear recoils relevant for WIMP searches.
I will also report on the latest blinded WIMP search based on the first two science runs, corresponding to a total exposure of 3.1 tonne-years. No significant excess is observed, leading to new exclusion limits on the spin-independent WIMP–nucleon cross section, reaching $2.5 \times 10^{-48}\mathrm{cm}^2$ at a WIMP mass of $30\mathrm{GeV}/c^2$.
Finally, I will discuss recent results on light dark matter based on an ionization-only (S2-only) analysis, which extends sensitivity to lower recoil energies and allows XENONnT to probe a wider class of models, including axion-like particles and dark photons.

Speaker: VIRGINIA MAZZA (INFN Bologna)

11:50 Light dark matter searches with the NA64 experiment at CERN

The light dark matter (LDM) hypothesis provides a compelling framework in which dark matter consists of sub-GeV particles interacting with Standard Model states via a new feebly coupled mediator, such as a dark photon.

The NA64 experiment at CERN’s SPS is specifically designed to probe this scenario through a broad fixed-target program based on missing-energy and missing-momentum techniques.

In its primary electron-beam configuration (NA64-$e$), a 100 GeV electron beam impinges on an active electromagnetic calorimeter acting as a thick target. The experiment searches for events with significant missing energy arising from the production of invisible particles in electron–nucleus interactions. With about $10^{12}$ electrons-on-target (EOT) accumulated during 2016–2022, the absence of signal candidates has allowed NA64 to set some of the most stringent limits in the LDM parameter space. More recently, the program has been extended to positron beams, enhancing sensitivity in the $\sim$100 MeV mass region via resonant $e^+e^-$ annihilation.

A major extension of the program is the muon-beam configuration (NA64-$\mu$), which employs high-energy muons to probe mediators coupled to second-generation leptons. The setup features a high-precision tracking system upstream and downstream of the target, enabling a measurement of the beam missing momentum. A pilot run in 2022, with about $2\times10^{12}$ muons-on-target (MOT), demonstrated the feasibility of this approach.

Finally, the program is complemented by hadron-beam studies (NA64-$h$), aiming to search for hidden-sector particles produced in meson decays and other processes, thereby extending sensitivity to states coupled predominantly to quarks and gluons.

Together, these complementary approaches establish NA64 as a versatile platform for exploring light dark sectors beyond the Standard Model. In this talk, after a brief introduction to the LDM physics case, I will present the NA64 experiment, reviewing the latest results from its four complementary programs and discussing the experiment’s plans for the forthcoming CERN post-LS3 period.

Speaker: Andrea Celentano (INFN e Universita Genova (IT))

12:10 Excitations of Spacetime in a Quantized Field

We investigate the properties of a Proper-Time Oscillator—the temporal analog of the quantum harmonic oscillator. Such an oscillator exhibits the same properties consistent with those of a particle in both quantum theory and general relativity. To begin, we find that spacetime can be quantized at energies far above the Planck scale. The quanta of this spacetime–excitation field are proper-time oscillators. the field is characterized as bosonic, and each proper time oscillator possesses the properties of a boson. We further extends our results for a fermionic field. Next, we examine the spacetime geometry outside a stationary proper time oscillator, treating it as a classical object (i.e., neglecting quantum effects). The resulting geometry is Schwarzschild, corresponding to a rest mass in general relativity. Together, these results indicate that a particle's intrinsic proper-time oscillation provides the means for direct spacetime interaction and the generation of a gravitational field, assuming the particle is an excitation of its quantum field and the underlying spacetime. We also explore how such oscillations might affect neutrino arrival-time measurements. Our analysis indicates that spatial oscillations of a 1-TeV neutrino may not be entirely beyond observational reach in a laboratory, offering a potential signature of time-based fluctuations.

References
[1] Yau, H. Y.: Quantized field with excitations of spacetime. Sci Rep 15, 30844 (2025)
[2] Yau, H. Y.: Matter, spacetime and proper time oscillator. To appear in (2024) Marcel Grossman Conference Proceeding
[3] Yau, H. Y.: Proper time operator and its uncertainty relation. J. Phys, Commun. 105001 (2021)
[4] Yau, H. Y.: Schwarzschild field of a proper time oscillator. Symmetry 12(2), 312 (2020)
[5] Yau, H. Y.: Self-adjoint time operator in a quantum field. J. Quant. Info. 1941016 (2020)
[6] Yau, H. Y.: Thin shell with fictitious oscillations”, in Spacetime Physics1907 – 2017, Chapter 6 (Minkowski Institute Press, Montreal, 2019)

Speaker: Hou Yau (San Francisco State University)

12:30 → 14:00 Lunch Break

14:00 → 16:00 Topical Session 1 - Astro

14:00 A new era for galaxy clusters: testing gravity and the dark sector using mass profile reconstructions

Galaxy clusters are excellent natural laboratories to study the nature of gravity and test possible alternative to the Concordance Model, at the edge between cosmology and astrophysics. I present recent results obtained by using the updated version of MG-MAMPOSSt, a code that reconstructs the mass distribution of clusters with kinematics and lensing analyses in modified gravity/Dark Energy frameworks. I will show the constraints that can be placed on the parameter space of viable modifications of the LambdaCDM scenario, as well as on the distribution of dark matter down to the cluster core, using high quality imaging and spectroscopic data, highlighting the strength and limitations of the method as well as future lines of investigation.

Speaker: Lorenzo Pizzuti (Dipartimento di Fisica G. Occhialini, Università Milano Bicocca)

14:20 The interplay between self-interacting dark matter and baryons: the case of cosmological simulations

In this work I aim to characterize the interplay between self-interacting dark matter (SIDM) models with velocity-dependent cross-section and the baryonic component inside galaxy clusters, investigating their combined effects on 3D and projected halo profile shapes and their deviation from collisionless dark matter (CDM) predictions. To this end, I investigate the DIANOGA-SIDM simulations of galaxy clusters featuring SIDM models with rare and frequent self-interactions as a result of, respectively, larger and smaller scattering angles. In particular, I employ a newly developed profiling and analysis pipeline to perform fitting and stacking of mass, density and velocity profiles, in order to compute statistically robust estimators of the SIDM effects across various halo mass scales. In general, I find that SIDM can consistently lower the central mass and density of low-mass halos inside dark-matter-only simulations, especially for frequent SIDM. However, while the inclusion of baryons suppresses this effect due to their clustering at low radii, the deviations from standard in this case are actually greater because CDM profiles exhibit a stronger central enhancement from baryons than their SIDM counterparts. Additionally, SIDM tends to isotropize the central particle velocity distribution leading to a lower velocity anisotropy profile than CDM at small radii, with boosted negative deviations in the rare SIDM model when introducing baryons. I further study global halo properties such as the concentration-mass relation and inner density profile slopes, and compare my theoretical predictions with the profiles of real galaxy clusters. Overall, this study will provide key theoretical predictions for comparison to ongoing and upcoming galaxy survey data, in order to distinguish between models of dark matter beyond $\Lambda$CDM.

Speaker: Giovanni Ferron (Università di Milano Bicocca)

14:40 The Missing Mass Problem in Galaxy Clusters: A MOND Perspective

While Modified Newtonian Dynamics (MOND) successfully accounts for the observed dynamics of individual galaxies without invoking dark matter, galaxy clusters still require additional mass beyond the observed baryonic buget even in this framework.

I will present recent results on five galaxy clusters from the XCOP survey (A1795, A2029, A2142, A644, A2319) using X-ray data under the assumptions of hydrostatic equilibrium and spherical symmetry to try to investigate the nature of this residual missing mass.

The results obtained are broadly consistent with what shown in recent papers, corroborating the "dark mass follow gas" hypothesis, suggesting that the missing mass in galaxy clusters within MOND may be of baryonic origin, possibly in the form of cold gas clouds. Future work will focus on the outskirts of the clusters, where the influence of the large-scale cosmic environment may become non-negligible, due to the External Field Effect and/or the loss of hydrostatic equilibrium.

Speaker: Valeria Broccolato (Università degli Studi di Torino)

15:00 Halo structure and lensing signatures of a polytropic dark matter fluid

We investigate whether a minimal effective pressure in the dark matter sector can generate observable deviations from standard cold dark matter ($\Lambda$CDM) predictions at nonlinear scales. We model dark matter as a polytropic fluid with equation of state $P = K \rho^{3/2}$, interpreted as an effective coarse-grained closure of the collisionless Jeans hierarchy in virialized halos.

For this choice, equilibrium configurations correspond to the $n = 2$ Lane--Emden solution, producing finite-density cores with mass-dependent scaling. Embedding these solutions within $\Lambda$CDM halo populations, we obtain kiloparsec-scale core radii with weak mass dependence across dwarf-to-galaxy scales, while preserving the background expansion history and linear perturbation growth.

We compute projected surface densities and weak-lensing convergence profiles for mass-matched halos. Relative to Navarro--Frenk--White profiles, the model predicts a systematic suppression of central convergence within $R \lesssim \mathrm{few}\, R_c$, with deviations confined to nonlinear scales. The convergence power spectrum exhibits scale-dependent suppression at high multipoles, providing a potential observational signature for upcoming high-resolution weak-lensing surveys.

This framework introduces a single phenomenological parameter governing nonlinear pressure support and continuously reduces to collisionless cold dark matter in the limit $K \to 0$. It therefore provides a minimal and testable extension of $\Lambda$CDM linking halo core structure to observable lensing signatures.

Speaker: Marriam Naeem

15:20 Numerical polology: next-generation model-building for precision cosmology

Particle dark matter, along with many ultraviolet scenarios, suggest that additional low-energy degrees of freedom remain to be discovered. Theories of new physics may be understood as statistical models, for which the Lagrangian couplings are model parameters. The net worth of a theory is determined by its Bayesian evidence: the likelihood of precision cosmology data is multiplied by the prior probability of the couplings, and integrated over the coupling-space. Precision cosmology has made great advances both in the collection of data and the efficient computation of likelihoods. But whilst the complementary programme of manufacturing candidate models is very active, it is far less systematic, and priors are seldom specified.

We present a framework for massively automating the construction of new physics models, designed to scale with the ever-increasing volume of data. Numerical polology uses nested sampling to identify unitary and technically natural regions in coupling-space. Such models form self-consistent effective field theories, which is essential since the predictivity of a model (the ability to compute a likelihood) is endowed by the systematics of QFT alone. The framework is adapted to bosonic theories of the dark sector: the phenomenological implications of arbitrary field content (field number, rank and index-symmetry) can be systematically explored with recourse to tools such as GetDist and Cobaya. The framework is inspired by the SOFTSUSY/SARAH tools for supersymmetric model-building, and builds directly on the PSALTer software for modified gravity. The latter is computer algebra software, which scales badly with complexity: numerical polology overcomes this technical hurdle and facilitates data-driven model-building.

We illustrate numerical polology with a Stueckelberg extension of massive gravity, and derive simple posterior reweightings from black hole superradiance, large scale structure, pulsar timing data and gravitational wave dispersion. We also discuss realistic prospects for more sophisticated likelihood plugins. We then perform a high-resolution survey of the coupling-space of symmetric rank-two fields, using high-performance computing. We discuss numerical challenges, and the benefits of migrating the present Julia implementation to JAX.

Speaker: Dr Will Barker (Central European Institute for Cosmology and Fundamental Physics, Institute of Physics of the Czech Academy of Sciences)

15:40 Dark Energy Stars: Structural Properties and Stability in Rastall Gravity Framework

This work explores a novel singularity-free relativistic solution to the Einstein field equations, focusing on dark energy stars within the framework of Rastall gravity. The Low-Mass X-ray Binary (LMXB) 4U 1608-52, characterized by a mass of 1.74 $M_{\odot}$ and a radius of 9.3 Km (T. G\"uver et al., Astrophys. J. {\bf 712}, 964 (2010)), is considered as a potential candidate for dark energy star. The analysis begins with the equation of state for dark energy, where its density is linearly related to an isotropic perfect fluid distribution via a coupling parameter $\alpha$. To address the unknown constants within the model, the induced metric and extrinsic curvature tensors are computed at the stellar surface. A detailed investigation is conducted to examine how the physical properties of the model depend on the Rastall parameter $\xi$. Notably, the results reveal the possibility of a phase transition from a dark energy-dominated regime to a baryonic matter profile, influenced by both $\alpha$ and $\xi$. Additionally, the model evaluates the percentage of dark energy present by varying $\xi$, demonstrating that for a fixed $\xi$, the dark energy fraction is sensitive to the mass and radius of the star. The model satisfies the energy conditions and causality requirements, affirming its physical viability. Stability analysis further supports the stability of the stellar configuration. The graphical representations of physical parameters, alongside the theoretical results, indicate that the proposed model is non-singular and provides a realistic description of a stable stellar structure composed of both dark energy and baryonic matter.

Speaker: Mr DEBADRI BHATTACHARJEE (COOCH BEHAR PANCHANAN BARMA UNIVERSITY)

14:00 → 16:00 Topical Session 2 - DM

14:00 Status of the PADME X17 Search

The PADME experiment at the Frascati National Laboratory of INFN has performed a
search for the hypothetical X17 particle, by observing the product of the collisions
of the positron beam from the BTF facility of LNF on a diamond fixed target.
The beam energy has been varied in the range
265–300 MeV, corresponding to values of √s between 16.4 and 17.5 MeV,
completely covering the CoM region identified by the
ATOMKI collaboration as significant for observing the postulated X17 particle.
The result of the analysis shows an about 2-sigma excess corresponding to the mass indicated by
the ATOMKI experiment. A new data taking campaign, with an improved detector
has been carried out during the summer and fall of 2025, with the aim of pushing forward the
sensitivity of the search.

Speaker: Chiara Arcangeletti (Istituto Nazionale di Fisica Nucleare)

14:20 Direct Dark Matter search with the CRESST experiment

The Cryogenic Rare Event Search with Superconducting Thermometers (CRESST) is a direct dark matter detection experiment, located at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy.

It employs cryogenic calorimeters instrumented with Transition Edge Sensors (TESs) and operates at millikelvin temperatures (~15 mK). This technology enables CRESST to achieve outstanding nuclear recoil energy thresholds of O(10 eV), reaching high sensitivity to dark matter particles in the sub-GeV mass range.

However, its low-mass sensitivity is currently limited by an unexpected excess of events at low energies (below ~200eV), known as the Low Energy Excess (LEE), whose origin remains unclear. Understanding and mitigating the LEE is one of the primary objectives of the CRESST collaboration.

This talk provides an overview of the CRESST experiment, covering the working principles of its detectors, recent efforts to characterise and mitigate the LEE, and the latest dark matter search results.

Speaker: Eleonora Rebecca Cipelli (Max Planck Society (DE))

14:40 DAREDEVIL

The DAREDEVIL (DARk-mattEr-DEVIces-for-Low-energy-detection) is a new project aiming
to develop a novel class of detectors to study Dark Matter candidates with mass below 1
GeV/c²
. The detection channel is DM-electron scattering, where the excitation energies of
the electrons should be matched to the transferred momenta. The only materials with energy
gaps of eV or below are special semiconductors, Dirac Semimetals, Weyl Semimetals, and
Scintillators. Such materials, already explored from a theoretical point of view, will be
implemented in a detector as planned by the DAREDEVIL project. The first phase of the
project aims at designing a novel class of gram-scale detectors with meV threshold suitable
for light DM-electron scattering detection. In order to achieve the high performances needed
for detecting such small energy depositions, we will use these crystals as absorbers in
low-temperature calorimeters with dual phonon and IR-photon readout. In this contribution,
we present the very first results of a low-temperature calorimeter based on GaAs as the
target crystal, operated at 15 mK, coupled to a Neutron Transmutation Doped thermistor for
the phonon readout. Furthermore, we have conducted the first tests of the double readout
technique with a germanium light detector utilizing the Luke effect, and in the future, we
aim to test CdTeHg-based photon detector tuned to detect its IR scintillation light.

Speaker: Andrea Melchiorre (LNGS-INFN)

15:00 DELight: Direct Search Experiment for Light Dark Matter with Superfluid Helium-4

The low-mass region of the dark matter (DM) parameter space remains largely unexplored, as detecting Light Dark Matter (LDM) requires both nuclear recoil thresholds below 100 eV and an approach capable of increasing exposures. The Direct search Experiment for Light dark matter (DELight) aims to address this challenge by using superfluid helium-4 as a target material, exploiting its low nuclear mass, intrinsic radiopurity, as well as its dual photon and quasiparticle signal channels. Detection will be performed using Large-Area Cryogenic Microcalorimeters (LAMCALs). The latter are athermal detectors based on Magnetic Microcalorimeter (MMC) technology which offer excellent energy resolution and detection thresholds of a few eV. With an initial exposure of just 1 kg·day, DELight will already probe new regions of the parameter space, achieving sensitivities below 10⁻³⁹cm²at a LDM mass of 200 MeV/c². This serves as a starting point for a long range plan for DELight with increasing exposures and further improvements on design parameters such as the threshold and background level.
We will present the working principle of the DELight experiment and an overview of the latest progress towards its realization, including recent results from a dedicated R&D cell studying MMC operation in superfluid helium.

Speaker: Anna Bertolini (Heidelberg University (DE))

15:20 Multiplexed read out for low threshold detectors in astroparticle physics

Cryogenic detectors have demonstrated sub-keV sensitivity to both electron and nuclear recoils, enabling the exploration of dark matter candidates—such as sub-GeV particles and ALPs—that are otherwise hardly accessible to conventional solid-state detectors. Despite significant advancements in cryogenic technology and detector performance, scalability remains a primary challenge, largely due to readout limitations. Transition Edge Sensors (TESs) offer an unparalleled Signal-to-Noise ratio, making them the preferred choice for low-threshold detection. However, their readout relies on DC-SQUIDs, which provide extremely low noise at the cost of complex control electronics that limit the total channel count per installation. In this contribution, we discuss the implementation of microwave multiplexing for sizeable cryogenic calorimeters, addressing the technological challenges and the resulting impact on the sensitivity of high-granularity, TES-based experiments.

Speaker: Nahuel Ferreiro Iachellini

15:40 Vacuum energy density and strong gravity with running gravitational constant

A static geometry with applications in microphysics is studied in this paper. The source of curvature is given by an anisotropic stress tensor and the spacetime is a traversible wormhole. The null and timelike radial geodesics are investigated and found to represent hyperbolae, but with different accelerations. Due to the very high acceleration, close to the maximum one given by Caianiello, a massless particle reach very quickly the velocity $c$. That is related to the Zeldovich vacuum energy density $\epsilon$ which, using the strong gravitational constant $G_{s} = c\hbar/m_{p}^{2}$ instead of Newton’s constant $G_{N}$, appears as $\epsilon_{vac} = m_{p}^{4}c^{5}/\hbar^{3}$, i.e. proportional to $m_{p}^{4}$, where $m_{p}$ is the proton mass. A similar dependence has recently been obtained by LeClair.
Some numerical examples are given, emphasizing the strong curvatures near $r =1/a$. The source of curvatures corresponds to a massless scalar field with negative kinetic energy (ghost field).

Speaker: Culetu

16:00 → 16:30 Coffee Break

16:30 → 17:55 Topical Session 1 - Astro

16:30 New robust constraints on Dark Photon Dark Matter from the intergalactic medium

The ultralight dark photon is a well-motivated, hypothetical dark matter candidate. In a dilute plasma, they can resonantly convert into photons and heat up the intergalactic medium between galaxies. In this talk, we explore the dark photon dark matter parameter space by comparing synthetic Lyman-α forest data from cosmological hydrodynamical simulations to observational data from VLT/UVES of the quasar HE0940-1050 (z = 3.09). We use a novel flux normalisation technique that targets under-dense gas, reshaping the flux probability distribution. Not only do we place robust constraints on the kinetic mixing parameter of dark photon dark matter, but notably, our findings suggest that this model can still reconcile simulated and observed Doppler parameter distributions of z ∼ 0 Lyman-α lines, as seen by HST/COS. This work opens new pathways for the use of the Lyman-α forest to explore new physics, and can be extended to other scenarios such as primordial black hole evaporation, dark matter decay, and annihilation

Speaker: Andrea Trost

16:50 The morphology of fluorescent emission from the intergalactic medium as a probe of dark matter properties

While the existence of dark matter is well established, its precise properties remain a pivotal question of modern cosmology. In this talk, I will present a new probe to constrain dark matter properties: fluorescent emission from the intergalactic medium around UV-bright quasars in the young universe (z~3). The gas in the intergalactic medium is an optimal tracer of the underlying dark matter, but its low surface brightness makes it challenging to observe. UV-bright quasars represent a particularly favorable environment as they can ionize their surrounding gas which can then be observed through its recombination emission, particularly at the Lyman-alpha frequency. In the recent years, new, more sensitive instruments, such as MUSE on the VLT, have delivered for the first time observations of this emission extending several Mpc from the central objects. I will first introduce our new suite of hydrodynamical simulations used to create mock observations in different dark matter scenarios. I will then show that the morphology of the Lyman-alpha emission is impacted by dark matter properties, and that the differences happen at surface brightness levels observable by current instruments with moderate to deep exposure times. These results constitute the first steps towards new constraints on the nature of dark matter complementary to, and competitive with existing ones.

Speaker: Titouan Lazeyras (University of Milano-Bicocca)

17:10 Testing gravity theories with gravitational redshift in galaxy clusters

Galaxy clusters are privileged astrophysical laboratories, tracing the most massive dark matter haloes in the Universe and allowing for accurate studies about their gravitational potential. The high masses (>10^14 Msun) of galaxy clusters make them ideal objects to probe new gravity models through gravitational redshift (GRS), which is recently established among the most important probes to detect deviations from general relativity (GR). Traditional GRS detection methods require to stack a high (~10^5) number of spectroscopically confirmed cluster members, analysing the mean rest-frame velocity shift from 0 km/s in a set of radial bins. In my talk, I will present a new method to reduce the necessary number of cluster members to detect GRS, which analyses the overall GRS-induced distortion of a galaxy cluster projected phase-space (PPS). This new method, coded in the Gravitational Redshift in GAlaxy clusters Software (GRAGAS), allows detecting GRS signal in massive galaxy clusters (virial mass M_200c ~10^15 Msun). It is designed to deliver a full dynamical analysis through a Bayesian fit of the PPS, and it has proven to be capable of recovering the original parameters of a mock galaxy clusters validation set. GRAGAS key feature is the flexible likelihood, that allows for an easy inclusion of different gravity models. Moreover, I will show that for massive clusters, although GRS effects are small (≲50 km/s) compared to their velocity dispersion (~1000 km/s), neglecting GRS in dynamical models can lead to an incorrect measurement of velocity anisotropy or to a ~5% overestimate of M_200c values, depending on the sampling algorithm. The GRAGAS method offers a crucial benchmark to test new gravity models even with few cluster members, and a key solution to avoid biases when measuring virial masses of clusters.

Speaker: Enrico Maraboli (Università degli Studi di Milano)

17:30 High-resolution RHD simulations at cosmological scales with the GPU-accelerated QUOKKA code

The high-resolution study of the large-scale structures (LSS) of the universe is one of the most intriguing frontiers in computational astrophysics and represents a crucial tool to support recent advancements in observations, especially in emission. In this context, we present the currently ongoing project of implementing cosmology on QUOKKA, a state-
of-the-art, GPU-optimized radiation-hydrodynamics (RHD) code built on the AMReX library, which handles adaptive mesh management. QUOKKA combines the piecewise parabolic method (PPM) in a method-of-lines formulation for the hydrodynamic solver with the variable Eddington tensor (VET) approach in the explicit-in-time evolution of the radiation moment equations, leveraging the reduced speed-of-light approximation. Many simulations have already taken advantage of the exquisite resolution and efficient scaling of the GPUs in this code, such as a series of studies on the multiphase galactic outflows. Despite the remarkable features and achievements of QUOKKA, a cosmological implementation is still missing; therefore, our ongoing work aims to robustly integrate it. Following the
preexisting modular philosophy, we developed a dedicated module that integrates directly with the solvers and time-step calculations. We accounted for the cosmic expansion on the comoving coordinates and we introduced Hubble drag for momentum and adiabatic cooling for internal energy as additional sources. Validation is currently underway; specifically, a Zel’dovich pancake test was introduced and cross-checked with the well-established ENZO analogous problem, showing good compatibility. Building upon these encouraging milestones, we plan to refine and fully harmonize this module, in view of a merging into the official public release of QUOKKA. This will open the path to observationally-motivated high-precision simulations of cosmic web filaments. By resolving the thermal and ionization states of these structures, we finally hope to provide a new tool to investigate the mysterious nature of dark matter and its influence on the earliest stages of structure formation.

Speaker: Michele Fulghieri

16:30 → 17:30 Topical Session 2 - DM

16:30 Investigating the keV Energy Frontier with CUORE: Axion and Rare-Event Searches

The Cryogenic Underground Observatory for Rare Events (CUORE) is the first tonne-scale experiment using cryogenic calorimeters. The detector is located underground at the Laboratori Nazionali del Gran Sasso and consists of 988 TeO2 crystals operated in a dilution refrigerator at a base temperature of about 10 mK. Thanks to the large exposure, sharp energy resolution, segmented structure and radio-pure environment, CUORE provided the most sensitive exclusion limit of the neutrinoless double beta decay of 130Te. The same features offer a unique opportunity to search for the interaction of dark matter candidates in the CUORE crystals. By applying specialized data selection and noise rejection techniques to over 2 tonne·yr TeO2 exposure, we demonstrate effective event reconstruction at the keV-scale. We quantify the detector performance across the array, exploring how cryogenic conditions, vibrational isolation, and sensor properties influence sensitivity at low energies. These findings validate the use of ton-scale cryogenic calorimeters as broad-range rare event detectors, spanning from the keV to the MeV scale. In this contribution, we present recently published and new results on CUORE's potential for keV-scale energy physics—including searches for axion and WIMP interactions and rare nuclear decays.

Speaker: Elena Ferri

16:50 Axion searches with a RES-NOVA prototype cryogenic detector

Axions and axion-like particles (ALPs) are well-motivated dark matter candidates. We present the potential of the RES-NOVA experiment, originally designed for astrophysical neutrino detection via CEνNS, to probe axion interactions using ultra-low background cryogenic detectors based on archaeological Pb. RES-NOVA employs PbWO4 crystals grown from ultra-radiopure archaeological Pb and operated as cryogenic calorimeters at mK temperatures. The high atomic number of Pb enhances sensitivity to axion-induced processes such as the axio-electric effect, while the low energy threshold enables searches for rare absorption signals. As a direct detection experiment based on absorption, RES-NOVA is largely insensitive to the axion mass over a broad range, probing couplings rather than resonant conversions. This makes the experiment sensitive not only to electron couplings but also to photon couplings g_a-gamma. Although not optimized for resonant enhancement, this approach provides a more universal probe that naturally covers QCD axion models. We report the performance achieved in prototype runs and outline projected sensitivities for future large-scale deployment.

Speaker: Ms Laura Trombetta (Università degli Studi di Milano-Bicocca)

17:10 Novel BSM framework could leave unique signature on the SGWB (Stochastic Graviational Wave Background)

Several attempts have been made over the decades to integrate gravity into the Standard Model of the elementary particles, the most notable being the AdS/CFT gauge-gravity scenarios. However, none of these attempts have yielded satisfactory results. In this work, a novel BSM (Beyond Standard Model) theoretical framework is introduced to describe a possible integration of gravity into the standard model. In this framework, the constant of universal gravitation, and the vacuum energy are significantly higher at the start of the universe, up to the end of the quark-gluon phase. Once quarks get confined into hadrons, the high gravitational and vacuum energy effects become trapped inside the strongly interacting particles and no longer have any influence on spacetime. This scenario is shown to shed new light on the dark energy problem, as well as on the ‘cosmological constant’ discrepancy. Further, gravitational waves produced during the early expansion phase in our model are shown to have a unique signature and may be detectable as part of the primordial Stochastic Gravitational Wave Background using pulsar timing arrays.

Speaker: Usha Raut (Milwaukee School of Engineering)

Wednesday 17 June

09:00 → 10:00 Plenary Session: Gravitational Waves Exp. 1 - Speaker: S. Fairhurst (University of Cardiff, UK)

10:00 → 11:00 Plenary Session: High Frequency Gravitational Waves Exp - Speaker: N. Aggarwal (UC Davis, USA)

11:00 → 11:30 Coffee Break

11:30 → 12:30 Topical Session 3 - HFGW

11:30 Tabletop Efforts Toward kHz Gravitational Wave Detection at QUAX

Gravitational waves in the kHz regime are of particular interest because they may offer a window into astrophysical processes beyond the reach of current detection technologies. Within the framework of the QUest for AXion collaboration, tabletop-scale approaches to kHz gravitational-wave detection are being pursued by leveraging expertise in quantum sensing, quantum-limited detection, cryogenics, and high-field magnets. This talk presents a detection concept based on a superconducting LC circuit operated in a strong magnetic field and read out with SQUID amplifiers, together with the current status of the experiment, possible upgrades, and new experimental ideas for improving sensitivity.

Speaker: Danho Ahn (INFN-Padova)

11:50 The MAGO cavity and prospects for high-frequency GW searches

In a joint effort between DESY/U. Hamburg and Fermilab, we are advancing the R&D program originally initiated by the MAGO collaboration (led by INFN Genoa) to search for high-frequency gravitational waves using superconducting radio-frequency (SRF) cavities. We are using a MAGO prototype cavity, fabricated nearly two decades ago but never previously tested. Following a detailed mechanical survey, we performed plastic tuning to correct geometric deviations, and carried out extensive measurements and simulations of its mechanical resonances and electromagnetic properties, which are key factors for evaluating its GW coupling potential. Ongoing cryogenic tests focus on noise characterization and the development of cavity control and signal readout systems. This effort lays the foundation for a first GW search with the existing cavity and informs the design of next-generation cavities.

Speaker: Krisztian Peters (Deutsches Elektronen-Synchrotron (DE))

12:10 Megahertz gravitational waves from neutron star mergers

Neutron star mergers provide a unique laboratory for the study of strong-field gravity coupled to QCD in extreme conditions. Simulations to date show that potential first-order phase transitions in the phase diagram of quantum chromodynamics may be accessed during the merger. In this talk I will argue that a phase transition would result in the emission of high frequency gravitational waves from bubble collisions, and I will provide with a rough estimate of the peak frequency and strain amplitude. Additionally, I will report on ongoing work in the study of bubble dynamics in QCD-like phase transitions, required for a better characterization of the emission from first-order phase transition during neutron star mergers.

Speaker: Mikel Sanchez Garitaonandia (University College Dublin)

11:30 → 12:30 Topical Session 4 - GW

11:30 Pinpointing PTA Single Sources: Sequential SBI for Sky Localization

Accurate localisation of continuous gravitational waves (CGWs) from supermassive black hole binaries (SMBHBs) remains one of the key challenges in Pulsar Timing Array (PTA) data analysis. Traditional searches based on the $\mathcal{F}_e$ statistic provide a robust analytic framework, but the resulting sky maps are strongly affected by the PTA antenna pattern, which redistributes signal power across the sky and generates secondary peaks that complicate the identification of the true source position. This degeneracy motivates the development of alternative approaches capable of disentangling instrumental artefacts from true localisation information.

In this work, we investigate whether Sequential Simulation-Based Inference (SBI) can improve CGW sky localisation by learning the mapping between $\mathcal{F}_e$ maps and true source positions. Using a suite of simulated PTA datasets, we demonstrate that our SBI pipeline effectively marginalises over antenna pattern search artefacts, providing reliable posterior distributions for the source coordinates. A key advantage of this framework is its extreme computational efficiency: our pipeline can generate $10^5$ $\mathcal{F}_e$ statistic maps in approximately 3 minutes, with the subsequent network training completed in under 2 hours on a single GPU. This enables both the rapid generation of large training sets and near-instantaneous source characterisation. Our results show
that the angular resolution ($\Delta\Omega$) achieved via SBI is consistent with the theoretical lower bounds predicted by the Fisher Information Matrix.

Speaker: Ludovica Carbone (University of Milano-Bicocca)

11:50 Investigating the role of inter-source correlations in LISA data analysis

We investigate how overlapping signals from massive black hole binaries can bias gravitational wave measurements in future missions like LISA. We demonstrate that ignoring these inter-source correlations during individual analysis leads to systematic errors in the recovered physical parameters. These biases are a fundamental risk for any frequency-domain data-reduction technique that disrupts signal interference—including Clenshaw-Curtis quadrature, relative binning, or heterodyning—rather than being limited to a single specific method.

Speaker: Rachele Rosso (University of Trento - University of Pisa)

12:10 Gravitational wave astronomy without waveform approximants

Gravitational wave astronomy relies on waveform approximants for both detection and parameter estimation. However, these models inherit uncertainties that grow increasingly relevant as detectors sensitivity improves. Notably, GW231123 revealed discrepancies between different waveform models. In this work we explore the possibility to perform parameter estimation directly from numerical relativity waveform using simulation-based inference. This approach avoids approximant calibration errors, even with the limited coverage of existing NR catalogs. I will present ongoing studies, highlighting both the advantages and current challenges of this "approximant-free" pathway.

Speaker: Matteo Boschini (University of Milano-Bicocca)

12:30 → 14:00 Lunch Break

14:00 → 16:00 Topical Session 3 - HFGW

14:00 Coherent network of haloscopes for dark matter and HFGWs: GravNet

We present GravNet, a distributed array of quantum-enhanced haloscopes aimed at the detection of light dark matter and high-frequency gravitational waves (HFGWs) in the GHz frequency range. The experiment is based on microwave cavities permeated by strong static magnetic fields, enabling resonant conversion of axions, dark photons and light dark matter particles. In addition, the same apparatus provides sensitivity to HFGWs via the Gertsenshtein effect, whereby gravitational waves are converted into electromagnetic excitations within the cavity volume.

GravNet is designed as a network of cavities distributed across three geographically separated European sites. A key feature of the experiment is the coherent combination of the cavity outputs, achieved through time-synchronization protocols. For the HFGWs analysis, this approach enables a scaling of the detection significance as $N$, the number of detectors, surpassing the $\sqrt{N}$ scaling characteristic of incoherent averaging.

To increase the signal-to-noise ratio in each detector, the collaboration will exploit the quantum technologies currently under development, i.e. single photon detection through superconducting qubits dispersively coupled to 3D cavities. Thus, with an optimal setup, the experiment could reach strain sensitivities of $h\sim 10^{-20}$, testing the existence of primordial black hole mergers of $\sim 10^{-13}$ solar masses.

GravNet thus defines a scalable distributed haloscope network, opening a novel parameter space for light dark matter searches and high frequency gravitational waves.

Speaker: Alessio Rettaroli (INFN - LNF)

14:20 MAGE: a multimode acoustic detector for high-frequency gravitational waves and an Australian node for GravNet

The search for high-frequency gravitational waves opens a complementary observational window on the early Universe and on compact objects far below the mass range accessible to kilometre-scale interferometers. We present the Multi-mode Acoustic Gravitational-wave Experiment (MAGE) [1], a cryogenic resonant-mass detector based on ultra-high-Q quartz bulk acoustic wave resonators with SQUID readout [2,3]. MAGE operates two near-identical detectors simultaneously, with multiple overtone modes monitored in parallel, enabling sensitivity in several narrow bands in the MHz regime while providing strong rejection of local backgrounds through coincidence analysis [1-4]. We summarise the detector concept, calibration strategy, and matched-filter analysis used to search for short-duration impulsive signals that excite the acoustic modes [4]. Recent observing runs have demonstrated stable multimode operation and placed new constraints on transient signals in the 5–15 MHz region, including limits on planetary-mass primordial black hole mergers [4].

MAGE also forms part of Australia’s contribution to the emerging international GravNET effort, providing a Southern Hemisphere platform for correlated searches for ultra-high-frequency gravitational waves and other wave-like signals from new physics. In this broader context, MAGE is complemented by the Australian ORGAN and ORGAN-Q infrastructure, which has demonstrated near-quantum-limited microwave detection, rapid-response capability for targeted searches for axion and dark-photon dark matter, and complementary sensitivity to high-frequency gravitational-wave signals [5–7]. As a quantum-enabled cryogenic resonator platform with precision timing, low-noise readout, and coincidence capability, ORGAN-Q can also participate as a node within the GravNET network, extending Australia’s capacity for distributed searches for correlated transient and persistent signals. Together, MAGE and ORGAN-Q show how compact Australian experiments can probe otherwise unexplored frequency bands while contributing to a global quantum sensor network. These efforts position Australia as an important Southern Hemisphere node in GravNET, strengthening international searches for high-frequency gravitational waves and other signatures of new physics.
References
[1] W. Campbell, M. Goryachev, and M. E. Tobar, “The Multi-mode Acoustic Gravitational Wave Experiment: MAGE,” Sci. Rep. 13, 10638 (2023).
[2] M. Goryachev and M. E. Tobar, “Gravitational wave detection with high frequency phonon trapping acoustic cavities,” Phys. Rev. D 90, 102005 (2014); Erratum Phys. Rev. D 108, 129901 (2023).
[3] M. Goryachev, W. M. Campbell, I. S. Heng, S. Galliou, E. N. Ivanov, and M. E. Tobar, “Rare events detected with a bulk acoustic wave high frequency gravitational wave antenna,” Phys. Rev. Lett. 127, 071102 (2021).
[4] WM Campbell, L Mariani, ME Tobar, M Goryachev, Experimental Exclusion of Planetary Mass Primordial Black Hole Mergers, Phys. Rev. Lett., vol. 135, 251402, 2025.
[5] M. E. Tobar, C. A. Thomson, W. M. Campbell, A. Quiskamp, J. F. Bourhill, B. T. McAllister, E. N. Ivanov, and M. Goryachev, “Comparing Instrument Spectral Sensitivity of Dissimilar Electromagnetic Haloscopes to Axion Dark Matter and High Frequency Gravitational Waves,” Symmetry 14(10), 2165 (2022).
[6] A. P. Quiskamp, G. R. Flower, S. Samuels, B. T. McAllister, P. Altin, E. N. Ivanov, M. Goryachev, and M. E. Tobar, “Near-quantum-limited axion dark matter search with the ORGAN experiment around 26 μeV,” Phys. Rev. D 111, 095007 (2025).
[7] A. P. Quiskamp, G. R. Flower, M. Goryachev, M. E. Tobar, and B. T. McAllister, “Follow-up Search for a Tentative Dark Photon Signal Near 19.5 μeV using ORGAN-Q infrastructure,” Phys. Rev. D 113, 012007 (2026).

Speaker: Michael Tobar (The University of Western Australia)

14:40 A Magnetized Dielectric Haloscope for Axion Searches and High-Frequency Gravitational Waves

We investigate a magnetized optical dielectric haloscope as a platform for high-frequency gravitational-wave detection. This approach is motivated by the close connection between proposed high-frequency gravitational-wave detectors and technologies originally developed for axion searches. Our setup consists of a multilayer silicon nitride and silicon oxide stack with optical focusing and single-photon readout, building on an optical haloscope setup currently in data-taking for axion searches targeting $m_a \sim 1\text{--}1.5\,\mathrm{eV}$. In its gravitational-wave configuration, the same setup is sensitive to frequencies of roughly $250\text{--}360\,\mathrm{THz}$. In this framework, the same externally applied magnetic field that mediates axion--photon conversion can also enable gravitational-wave-induced electromagnetic signal generation via the inverse Gertsenshtein effect. We emphasize that the gravitational-wave case is not a trivial extension of the axion one. In particular, we focus on the main differences between the two, including the possibility of conversion in vacuum, the phase and directional structure inherited from the incoming gravitational wave and the resulting implications for resonant, broadband and hybrid operating modes. We also present our approach to sensitivity estimation in the optical regime, taking into account the detector architecture, response and single-photon readout. Our study highlights the potential of dielectric haloscope technology as a cost-effective option for ultra-high-frequency gravitational-wave detection.

Speaker: Alia Zino

15:00 Status and perspectives of the QUAX-LNL 10 GHz axion haloscope

We present the latest results from the QUAX haloscope experiment at LNL, which searches for post‑inflationary QCD axions around 10.2 GHz. Compared to earlier QUAX runs, a quasi‑automatic tuning protocol now allows adjustment of the cavity frequency without significantly degrading the detector’s performance.

The haloscope uses a TM$_{030}$ Bragg resonator made of a copper cylindrical cavity housing a sapphire tube, providing a five-fold increase in effective volume relative to an empty‑cavity TM$_{010}$​ mode at the same frequency. A clamshell mechanism enables tuning from 10.212 GHz to 10.126 GHz with minimal impact on the TM$_{030}$​ mode quality factor.

Axion‑to‑photon conversion is driven by an 8 T NbTi magnet. The first amplification stage employs a near–quantum‑limited TWPA, achieving sensitivity to post‑inflationary QCD axions at the $10^{-14}\,\mathrm{GeV}^{-1}$ level with one hour of data.

We demonstrate that, after manual calibration, the TWPA can track cavity tuning over several MHz automatically. Combined with an improved mechanical tuning system, this enables automated data taking for one to several days, advancing the development of a cosmological QCD axion haloscope observatory in the 9–11 GHz range.

Finally, we outline the improvements scheduled for the apparatus for the next years, including implementation of a Single Microwave Photon Detector.

Speaker: Raffaele Di Vora (INFN)

15:20 An array of acoustic resonators for the detection of high-frequency gravitational waves

We present a multi-mode resonant-mass strain antenna for the exploration of Gravitational Wave (GW) sources in the uncharted frequency band from around 100 kHz to 10 MHz. This region may host signals from non-standard sources, such as post-merger emission from sub-solar-mass binaries or dark matter candidates. Following an approach originally proposed by Tobar and Goryachev, the experimental technique adopts Bulk Acoustic Wave (BAW) resonators made of piezoelectric quartz crystals to convert the strain of an impinging GW into an electric signal. Cryogenic operation enhances sensitivity by improving mechanical quality factors and reducing thermal noise, while enabling the use of Superconducting QUantum Interference Devices (SQUIDs) as low-noise amplifiers. FPGA-based acquisition allows for digital lock-in amplification and the concurrent monitoring of multiple overtones and vibration modes from the same crystal. In this presentation, after an introduction of the science case and the operating principle, we report on the project status, including the measured sensitivity of $10^{-21}$ strain / $\sqrt{\text{Hz}}$, achieved with commodity GPS resonators at 5 MHz and prospects for widening the frequency coverage with an array of multiple resonators.

Speaker: Leonardo Mariani (Bicocca)

15:40 Gravitational waves from high-power twisted beams of light

Recent advances in high-energy and high-peak-power laser systems have opened up new possibilities for fundamental physics research. In this presentation, I will focus on gravitational waves signals emitted by high-intensity (twisted) beams and show how the properties of the generated gravitational waves 
are controllable by the laser pulse parameters and optical arrangements. Notably, the possibility to use intense beams of light to create a generation/detection setup of has recently been discussed. Is a setup like this truly achievable in the coming decades? How close are we, exactly? In this talk I will provide an overview of where things currently stand on this question.

Speaker: Killian Martineau (LPSC - CNRS)

14:00 → 16:00 Topical Session 4 - GW

14:00 Gravitational waves lensing, a new opportunity for investigating gravity and dark matter ?

Gravitational lensing, i.e. the deflection of propagating signals by spacetime curvature is one key prediction of General Relativity. Besides this intrinsic interest as a fundamental prediction, this effect has become one crucial probe used by the cosmology community to identify and map dark matter.
Relying on the idea that the propagation of both electromagnetic and gravitational waves (GW) signals is analogous, it is tempting to think that these two types of signals obey the same type of gravitational lensing. However, I will argue why this idea is insufficient when wave-optics effects are taken into account. I will illustrate how GW lensing differs from the usual lensing formalism and discuss its relevance, challenges and opportunities for cosmology with GW.

Speaker: Martin Pijnenburg

14:20 Eccentricity in binary black hole event from the third gravitational wave transient catalog

The first detection of gravitational waves in 2015 opened a new window into the universe, offering a unique probe of the properties and evolution of binaries of compact objects (black holes and neutron starts). There are several proposed channels through which these binaries form and merge, and one of the key challenges in gravitational wave astrophysics it to unambiguously pinpoint them through gravitational wave data.
Eccentricity in the orbital motion is smoking gun evidence of a non-isolated formation channel, since stellar-mass eccentric binaries can form in dense stellar environments such as globular clusters or active galactic nuclei, or from triple stellar systems in the Galactic field. However, confidently measuring eccentricity is challenging — short signals from high-mass eccentric mergers can mimic spin-induced precession, making the two effects hard to disentangle. This degeneracy weakens considerably for longer-duration signals. Here, GW200208_222617 provides a rare opportunity. Originating from a relatively low-mass binary, its gravitational-wave signal spanned several inspiral orbital cycles in band, with no indication of data quality issues. Previous analyses strongly favor the eccentric hypothesis, but without ever fully disentangling the spin-precessing - eccentricity ambiguity.
The goal of my work is to re-analyize this event in a way that confidently flags the presence of eccentricity, providing further constraints on its formation channel. In particular, this is done through the use of an inspiral-only waveform model that describes, resorting to post newtonian expansions, spin precession and eccentricity simultaneously.

Speaker: Matilde Garcia (Universitá degli Studi Milano Bicocca)

14:40 Measuring binary black hole time-delay distribution with GWxLSS

Gravitational wave observatories offers a unique view into the physics of compact object binary systems. However, the richness of astrophysical models is partially lost due to our ability of measuring a limited number of parameters from individual GW events, thus limiting our ability to break degeneracies between different models. It then becomes crucial to find alternatives ways to extract information from these datasets. The anisotropic clustering of GWs can provide such way forward. In this talk, I will discuss how by cross-correlating the spatial distribution of galaxies and BBH detected by ET/CE we can breaks such degeneracies. In particular, I will show how it is possible to constrain the time delay distribution thanks to the GW bias parameter acting as a "second clock" of the BBH population, on top of the usual "clock" given by the binary merger rate.

Speaker: Nicola Bellomo (University of Padova)

15:00 Tracing formation channels with spin–orbit misalignment in black-hole binaries

Understanding the formation channels of black hole binaries remains an open problem in gravitational-wave astronomy, made increasingly compelling by the growing catalog of detections from LIGO-Virgo-KAGRA. In this talk, I present a comparison between binaries formed through isolated (field) binary evolution and those assembled dynamically in dense environments, with particular focus on spin–orbit misalignment. For the dynamical scenario, I introduce a toy model in which black holes are paired through hierarchical interactions. In the isolated channel, I investigate how supernova kicks imparted during black hole formation can tilt the spins with respect to the orbital angular momentum. By comparing the resulting spin–orbit misalignment distributions from these two formation channels, I assess the extent to which spin orientations retain memory of their formation history and whether they can be used to distinguish between different formation pathways.

Speaker: Sofia Dossena

15:20 Tackling labelling-related uncertainties in the mass and spin distributions of compact objects in binary systems observed via Gravitational Waves

All Gravitational Wave signals detected so far were generated by the coalescence of black holes and/or neutron stars in binary systems. Correctly identifying the primary and secondary objects within said systems is crucial to obtain unbiased astrophysical information regarding their masses and spins; as of now, labels are assigned on a mass basis: the "primary" label is given to the more massive object, and vice versa.
This choice carries an inherent assumption that can result in unaccounted for labelling uncertainties, especially in cases where the masses of the two objects are comparable.
An alternative to this a priori labelling choice comes in the form of an a posteriori approach (Gerosa et al. 2025), through which posterior samples from a single GW signal are grouped by means of a clustering algorithm; the two objects thus identified are then labelled according to the median of the respective masses.
The aim of this work is to extend this novel approach to the analysis of populations of compact objects; specifically, the same a posteriori procedure is applied to samples that are representative of a population of compact objects and the resulting mass distributions (relative to the primary and secondary objects) are compared to those found in the existing literature. We make use of a variety of mass distribution models to generate the set of population samples, including a non-parametric one and two parametric models that are invariant under mass relabelling.

Speaker: Giulia Cuomo (University of Milano - Bicocca)

15:40 samsara: A Continuous-Time Markov Chain Monte Carlo Sampler for Trans-Dimensional Bayesian Analysis

Trans-dimensional Bayesian analysis requires determining the posterior distribution when the number of parameters is not fixed. In this talk, I will present an alternative approach to Reversible Jump Markov Chain Monte Carlo and Simulation-Based Inference. Our method relies on the evolution of the parameter space through birth-death and mutation processes in a continuous-time framework. More specifically, the state is evolved according to Poisson dynamics with rates associated with each process. Such rates are constructed to satisfy the detailed balance conditions, ensuring the asymptotic convergence of the chain to the posterior distribution. We show that birth-death processes allow the sampler to explore the trans-dimensional parameter space in a very efficient way, because the rates adapt to the current value of the posterior. I will then present the algorithm we developed in Pisa for continuous-time Markov Chain Monte Carlo sampling, samsara, and discuss a few test cases, including a preliminary application to the LISA Global Fit.

Speaker: Gabriele Astorino (University of Pisa)

16:00 → 16:30 Coffee Break

16:30 → 17:30 Topical Session 3 - HFGW

16:30 Ultra-stable optical cavities for the fundamental physics tests

Table-top-size ultra-stable Fabry-Perot optical cavities are one of the most precise measuring instruments and, together with optical atomic clocks, play a vital role in state-of-the-art metrology and fundamental physics tests. Here we present two applications for the cavity itself: detecting gravitational waves [1] and testing the hypothesis of space-time fluctuations [2].

The first gravitational-wave detection attempts were based on mechanical resonances in large aluminum bars triggered by a passing gravitational wave [3]. To date, none of the proposed resonant-mass bar detectors have provided evidence of gravitational-wave events through acoustic resonance, despite their extremely stable operation and excellent noise reduction. We propose a resonant detector based on existing and rapidly developing Fabry-Perot cavities. This "bar-like" detector can observe frequencies from a few kHz to tens of kHz, depending on its length and material, surpassing the range covered by previous resonant detectors. Ultra-stable optical cavities allow detection not only of predicted gravitational-wave signals such as binary neutron star mergers, post-mergers, subsolar-mass primordial black hole mergers, and collapsing stellar cores, but also of new physics beyond the Standard Model, including searches for ultralight bosons such as QCD axions and axion-like particles formed through black hole superradiance.

Beyond their potential as gravitational-wave detectors, ultra-stable optical cavities may offer a way to test fundamental limits of spacetime itself. Many unifying theories predict quantum fluctuations of spacetime at extremely small distances [4]. This fundamental fuzziness, often called space-time foam, may limit the precision of length measurements to the Planck length [5]. As a result, quantum-gravity-induced fluctuations may set the ultimate limit for distance measurements and as a result frequency stability of ultra-stable Fabry-Perot optical cavities [6]. Therefore, the noise budget of a set of independent ultra-stable cavities can be used to constrain the amplitude of such fluctuations.

[1] M. Narożnik, M. Bober, and M. Zawada, Phys. Lett. B 846, 138260 (2023).
[2] M. Narożnik, et al. in preparation.
[3] J. Weber, Phys. Rev. 117, 306 (1960).
[4] G. Amelino-Camelia, Living Reviews in Relativity 16, 5 (2013).
[5] G. Calcagni, M. Ronco, Nuclear Physics B 923, 144 (2017).
[6] G. Amelino-Camelia, Nature 398, 216 (1999).

Speaker: Mateusz Narożnik (Institute of Physics, Nicolaus Copernicus University in Toruń)

16:50 Gravitational Wave Measurement and wavelike axion searches with a Novel Mössbauer Spectrometer

Under the local gravitational field, perturbations from gravitational waves can cause a vertical shift of the Mossbauer resonance height. Considering a stationary scheme with the Ag-109 isotope, we demonstrate that the extremely high frequency precision in Mossbauer resonance allows for competitive gravitational wave sensitivity from KHz up to above MHz frequencies. Mossbauer resonance can offer a novel and small-sized alternative in the quest of multi-band gravitational wave searches, with potential to measure gravitational wave direction and polarization at high precision. Meanwhile, this setup is also sensitive to wavelike axion particle that can perturbate neuclon binding energy level.

Speaker: Huaqiao Zhang (Chinese Academy of Sciences (CN))

17:10 BULLKID-DM: direct detection of light WIMP dark matter with a monolithic arrays of cryogenic detectors

BULLKID-DM is a new experiment designed to search for low-mass WIMP-like dark matter particles (1~GeV/c$^2$ or below) with nucleon cross-sections below 10$^{-41}$~cm$^2$. The detector consists of an 800~g array of over 2000 silicon dice, each acting as a particle absorber instrumented with multiplexed Kinetic Inductance Detectors (KIDs). Background rejection is achieved through a fully active structure, enabling fiducialization and anticoincidence techniques.

A 20~g prototype, consisting of 60 voxels diced from a 3'' silicon wafer, demonstrated the feasibility of this approach. Following its success, we present the first operation, in a surface laboratory equipped with a lead and copper radiation shield, of a 60~g demonstrator with 180 dice. This setup closely replicates the final experimental configuration. The recorded backgrounds are compared to Geant4 simulations performed by the collaboration.

We also discuss ongoing R\&D activities, including low-radioactivity detector mounting, a cryogenic scintillating veto readout with KIDs, in situ calibration techniques, and detector upgrades such as KIDs with dedicated phonon-collecting structures and germanium substrates for multi-target capabilities.

Finally, we outline the deployment plan of the setup at the Gran Sasso underground laboratory (LNGS). The demonstrator will be installed at LNGS, in the cryo-platform, by late 2026. Following successful validation, the full experiment is expected to be commissioned in 2027.

Speaker: Camilla Bonomo (Sapienza University of Rome and INFN - Roma 1)

16:30 → 17:30 Topical Session 4 - GW

16:30 Probing Supermassive Black Hole Mergers with Pulsar Timing Arrays

By monitoring the times of arrival of radio pulses from millisecond pulsars, Pulsar Timing Arrays (PTAs) serve as unique gravitational wave (GW) laboratories in the nanohertz band.
To date, the primary astrophysical sources of GWs targeted in this frequency range have been inspiraling supermassive black hole binaries (SMBHBs) on circular or eccentric orbits.
In this work, we demonstrate that, thanks to the so-called pulsar term in the timing residual waveform of GW signals, PTAs can probe individual SMBHBs that merged before timing observations began.
We refer to the latter as zombie binaries.
Using SMBHB population models consistent with current PTA constraints, we find that while the probability of detecting such systems in existing PTA datasets remains low, the Square Kilometer Array observatory is expected to achieve sufficient sensitivity to have a few zombie binaries with a signal-to-noise ratio exceeding 3 in its data.
Although their confident identification might be challenging, this new class of PTA sources opens a novel window for studying the most massive SMBHBs in our local universe.

Speaker: Hippolyte Quelquejay (Università degli Studi di Milano-Bicocca)

16:50 Modeling the nHz gravitational wave background with t-process

Unveiling the nature of the nanoHz gravitational wave signal reported by Pulsar Timing Array collaborations is the next goal of low-frequency GW astronomy. The signal likely originates from the incoherent superposition of GWs emitted by a population of supermassive black hole binaries (SMBHBs). The discrete nature of the population, environmental effects and eccentricity are expected to produce significant deviations of the GWB power spectrum from the smooth powerlaw approximation.
In this talk I explore the possibility of modeling the GWB using a t-process power spectral density. This model also takes into account possible extra power in specific frequency bins, which may arise from single sources dominating the GWB. I will present results from testing the model on real PTA datasets and on simulations of realistic populations to evaluate the ability to detect a more complex PSD that deviates from the powerlaw. I will discuss current limitations and potential improvements of the model.

Speaker: Beatrice Eleonora Moreschi (University of Milano-Bicocca)

17:10 Spin-2 Boson Stars

The relevance of compact objects to both astrophysics and theoretical physics is well-established, as the extreme compactness of these systems provide an optimal environment to probe the strong-field gravity regimes. Within this framework, boson stars are considered to be viable models for ultralight dark matter, as well as black hole mimickers. While scalar boson stars offer simple, self-gravitating solutions to the minimally coupled gravity-matter system, they may represent a conceptual simplification of the universe’s matter content. On the other hand, the study of self-gravitating spin-2 fields is particularly compelling, as modern theories of modified gravity, such as ghost-free massive gravity and bimetric theory, rely on these fields to provide a consistent description of massive gravitons. I present a novel field ansatz, based on the ghost-free dRGT massive gravity action , for a possible bound tensor configuration. This framework is characterised by non-trivial matter–curvature couplings, yielding highly nonlinear equations, which we aim at investigating by means of a Physics-Informed Neural Network (PINN). I discuss the viability of the model and the robustness of the ansatz compared to scalar and vector solutions.

Speaker: Andrea Gobbo (Università degli Studi di Milano-Bicocca)

Thursday 18 June

09:00 → 10:00 Plenary Session: Gravitational Waves Theory - Speaker: U. Sperhake (University of Cambridge, UK)

10:00 → 11:00 Poster Session

11:00 → 11:30 Coffee Break

11:30 → 12:30 Plenary Session: Gravitational Waves Exp. 2 - Speaker: N. Luetzgendorf (ESA-ESTEC, Noordwijk, NL)

12:30 → 14:00 Lunch Break

14:00 → 16:00 Poster Session

14:00 → 16:00 Topical Session 4 - GW

14:00 Probing astrophysical environment of stellar mass black holes through the LISA stochastic signal

The LISA stochastic signal from stellar mass black holes may be detectable. In this talk, given such a detection, I will describe how the presence of an astrophysical environment can be inferred from the stochastic signal. Additionally, I will discuss how eccentricity affects the spectrum and can be used as an indirect probe of the astrophysical formation of such binaries. Finally, I will comment on the implications of this work for dark matter environments.

Speaker: Rohit Subbarayan Chandramouli (SISSA)

14:20 Photometric identification and spectroscopic confirmation of massive black hole binaries

Massive black hole binaries (MBHBs) are expected to be among the loudest gravitational wave sources to be detected by pulsar timing arrays and space-borne interferometers. If accreting, MBHBs at sub-parsec separations can be identified through periodic variability in their light curves. Current periodicity detection methods are largely optimised for quasi-sinusoidal signals, whereas the predicted lightcurves from MBHBs present a much richer phenomenology. In this talk, I will present a periodicity detection method based on Gaussian processes that flexibly models periodic variability independently of its specific shape. I will then introduce a spectroscopic test to distinguish photometrically selected MBHB candidates from single massive black holes with quasi-periodic continuum variability, using the response of the broad-line region.

Speaker: Lorenzo Bertassi (Università degli Studi di Milano-Bicocca)

14:40 Massive Black Holes formation and evolution in cosmological environments

Recent observations of high-redshift luminous QSOs and faint AGN candidates, as well as the upcoming space-based gravitational wave experiments, motivate the development of detailed theoretical models which focus on the formation and evolution of massive black holes (MBHs). This talk will present recent results obtained with the L-GalaxiesBH (LGBH) semi-analytic model about the formation, evolution and dynamical interaction of MBHs. I will showcase the state-of-the art capabilities of LGBH by presenting its predictions for standard observables related to the evolution of MBHs (e.g. AGN luminosity function and MBH-Mstar correlations) as well as for ongoing and upcoming gravitational wave experiments (e.g. PTA collaborations and the LISA mission). In addition, I will focus on showing how LGBH can be used to study the cosmological evolution of light, intermediate-mass and heavy MBH-seeds, from their formation down to z=0. This will provide insights about the occurrence of these BH-seeding scenarios over cosmological scales, as well as the fate of their MBH descendants.

Speaker: Mr Daniele Spinoso (Dipartimento di Fisica "G. Occhialini", Università degli Studi di Milano-Bicocca, Piazza dell'Ateneo Nuovo 1, 20126, Milano (IT))

15:00 Towards a comprehensive description of black hole binary inspiral from Newtonian to relativistic scales

The massive black hole binary (MBHB) path from formation on galactic scales down to their coalescence is extremely complex, and still poorly constrained, due to the huge dynamical range involved and the variety of physical processes at play on different scales. With the approval of the LISA mission, we are entering now a new era for MBHB astronomy, that requires a detailed theoretical understanding of the binary evolution. To date, studies have typically focused on different stages separately, often assuming idealized conditions and including different physical processes. I will first review the recent efforts made by the community to constrain the expected parameter space, of coalescing MBHBs, and discuss the typical limitations of current models. Then, I will present a recent ongoing effort aimed at following the binary inspiral from Newtonian scales down to the coalescence using detailed simulations of MBHBs surrounded by circum-binary discs. In particular, I will present a general-relativistic extension of the GIZMO code which will enable us to accurately track the pre-merger properties of MBHBs before the advent of LISA.

Speaker: Alessandro Lupi (Como Lake Centre for Astrophysics, University of Insubria)

15:20 Eccentricity distribution of extreme mass ratio inspirals

We present realistic eccentricity distributions for extreme mass ratio inspirals (EMRIs) forming via the two-body relaxation channel in nuclear star clusters, tracking their evolution up to the final plunge onto the central Schwarzschild massive black hole (MBH). We find that EMRIs can retain significant eccentricities at plunge, with a distribution peaking at $e_\mathrm{pl} \approx0.2$, and a considerable fraction reaching much higher values. In particular, up to $20\%$ of the forming EMRIs feature $e_\mathrm{pl} > 0.5$ for central MBH masses $M_\bullet$ in the range $10^5 \, \mathrm{M_\odot} \leq M_\bullet \leq 10^6 \, \mathrm{M_\odot}$, partially due to EMRIs forming at large semi-major axes and ''cliffhanger EMRI'', usually neglected in literature. This highlights the importance of accounting for eccentricity in waveform modeling and detection strategies for future space-based gravitational wave observatories such as the upcoming Laser Interferometer Space Antenna (LISA). Furthermore, we find that the numerical fluxes in energy and angular momentum currently implemented in the FastEMRIWaveforms (FEW) package may not adequately sample the full parameter space relevant to low-mass MBHs ($M_\bullet < 10^6 \, \mathrm{M_\odot}$), potentially limiting its predictive power in that regime. Specifically, for $M_\bullet=10^5 \, \mathrm{M_\odot}$ we find that about $75\%$ ($50 \%$) of EMRIs at 2 years (6 months) from plunge fall outside the currently available flux parameter space. Our findings motivate the development of extended flux grids and improved interpolation schemes to enable accurate modeling of EMRIs across a broader range of system parameters.

Speaker: Davide Mancieri (University of Trento / University of Milano-Bicocca)

15:40 Warped accretion discs and black-hole spins in gravitational-wave astronomy

Spin configuration of supermassive black-hole binaries affect gravitational waves at post-Newtonian level, making it observable by the future LISA space mission. Spin alignment is of significant relevance not only for black-hole recoils, whose kick magnitude increases with binary misalignment and can be greater than galaxies' escape velocity, but also as a possible discriminant between gas-poor and gas-rich binary environments. Gas-rich galaxies are able to provide an accretion channel thanks to the presence of a circumbinary disc, consequentially producing a massive circum-black-hole disc which drives alignment through the Bardeen-Petterson effect. In gas-poor environments, such a channel does not exist and the binary is therefore expected to merge in a misaligned configuration.

One-dimensional numerical integrations of the disc conservation equations have already attempted to reproduce the shape and evolution of the system in a gas-rich environment. However, such integrations assume an infinite disc, fixed at its outer boundary, an approximation which inherently prevents disc evolution. We propose a new non-local boundary-value problem formulation, in which we relax this assumption by globally constraining the disc total angular momentum instead of fixing its specific value at the outer boundary. Our approach is able to reproduce both massive discs and systems where the disc angular momentum is comparable to that of the black hole, while also incorporating non-linear viscosities. We investigate whether the Bardeen–Petterson effect is sufficient to drive alignment or counter-alignment in the latter regime, or whether the disc breaks before such a configuration is achieved. If such low-angular-momentum discs can exist, this could imply that binaries in gas-poor environments may also achieve aligned (or counter-aligned) configurations at merger. Although less detailed than full hydrodynamical simulations, our framework has the advantage of being significantly faster and cost-effective, allowing for an efficient exploration of the parameter space and quicker prediction of the end-state of the system.

Speaker: Lisa Merlo (University of Milano-Bicocca)

16:00 → 16:30 Coffee break

16:30 → 17:30 Poster Session

Friday 19 June

09:00 → 13:00 Free Day

Free day to explore the city of Milan. A guided visit to the Brera Astronomical Observatory and the Pinacoteca di Brera will be organized, depending on the number of participants expressing interest.