Cosmology 2025 @ Elba Island

7 Sept 2025, 15:00 → 13 Sept 2025, 12:10 Europe/Rome

Hermitage Hotel, Isola D'Elba

Info for the Shuttle from Portoferraio to Biodola: call #+393485118616 when boarding in Piombino to ensure the presence of the shuttle at the piers in Portoferraio. A meeting point is in the bus station just facing the piers.

Cosmology offers today one of the most important frontiers of physics. The mystery of dark matter and the puzzle of dark energy are still outstanding.  On the observational side, there is an exponential growth of accurate and important data, which will help in establishing the new needed theories.

In this conference we plan to bring together researchers from the observational, computer simulation and theoretical sides working in cosmology, astrophysics, astroparticle and particle physics, to discuss the current situation as well as  prospects for the future improvements.

All the topics will be discussed from different angles starting from the booming flow of observational data. The topics to be discussed will include:

1. The current Cosmological Model and its Tensions (Theory and observations)
2. Dark Matter (Its nature: Theory, Observations, Detection, Production at accelerators)
3. The Evolving Universe (Reionization, first galaxies and their SMBH, Quasars and AGN, the assembly of cosmological structures)
4. Probes of the Universe from (new incoming) measurements of the CMB and of Large Scale structure.
5. Multimessenger cosmology (Gravitational waves, Cosmic Gamma and X-rays, Neutrinos)
6. Black holes in the Universe over many orders of magnitude in mass
7. Fundamental aspects of Cosmology.

A number of invited talks from leading scientists as well as a number of  contributed ones from participants will be presented.

The conference will take place in the Hermitage hotel in La Biodola, Elba island, in a conductive atmosphere, appropriate for the dramatic paradigm shift that we may be witnessing in these days.  

The conference will begin on the morning of Monday and end before lunch on Saturday.

The organizer and sponsors will support a number of young invited speakers. We also aim to support the accommodation for a limited number of young researchers (master’s/PhD students or early post-docs) who are submitting an abstract to the conference.

DOWNLOAD THE POSTER!

 

Scientific Organizing Committee (SOC)  TBC Cristiano Alpigiani Carlo Baccigalupi Alessandro Bressan Peter Berczik Massimo Carpinelli Santi Cassisi Annalisa Celotti Mariafelicia De Laurentis Eleonora Di Valentino Nicolao Fornengo Katherine Freese Carlos Frenk Viviana Gammaldi Paolo Gondolo Amina Helmi Andrea Lapi Andrea V. Macciò Sabino Matarrese Francesca Matteucci Lina Necib Keith Olive Valeria Pettorino Annalisa Pillepich Gauri Sharma Mairi Sakellariadou Joseph Silk Nicola Vittorio Matthew Walker Hai-Bo Yu   Fabrizio Nesti, Paolo Salucci, Nicola Turini (chairs)

Local Organizing Committee (LOC) TBC Fabrizio Nesti Paolo Salucci Nicola Turini Maicol Di Giambattista Annalisa Feliziani Simone Masci Gauri Sharma Michele Bosi Florie Carralot Cecilia Sgalletta

 

COSMO25_poster_3_smaller.jpg

COSMO25_poster_4_a4_smaller.jpg

Linea 6 Pf-Biodola.pdf

SHUTTLE 3-1-3.pdf

Sunday 7 September

15:00 → 20:00 Registration

Monday 8 September

08:00 → 13:00 Opening and Morning Session 1

08:00 Registration

09:30 Opening

09:50 Mapping out the Dark Matter in the Milky Way with Stars

In this talk, I will explore the interfacing of simulations, observations, and machine learning techniques to construct a detailed map of Dark Matter in the Milky Way, focusing on the Galactic Center/Halo and dwarf galaxies. For the Galactic Halo, I will present a recent work that reveals a decline in the stellar circular velocity, inducing tensions with established estimates of the Milky Way's mass and Dark Matter content. I will discuss how the underestimated systematic errors in such a common methodology necessitates a revised approach that combines theory, observations, and machine learning. In dwarf galaxies, I will present a novel Graph Neural Network methodology that facilitates the accurate extraction of Dark Matter density profiles, validated against realistic simulations. I will conclude with a discussion on the future trajectory of astroparticle physics, emphasizing the need for the integration of astrophysical probes, particularly those of stellar dynamics, with our understanding of Dark Matter in the Galaxy and its connection with Dark Matter detection experiments.

Speaker: Lina Necib (MIT)

Cosmology_2025.pdf

Cosmology_2025.pptx

10:30 Coffee

11:00 DESI Peculiar Velocity Survey and the DR1 Fundamental Plane sample

The Dark Energy Spectroscopic Instrument (DESI) Peculiar Velocity Survey aims to provide measurements of the growth rate of structure and the Hubble constant in our local universe. To do so the survey, over the course of its 5 years of operations, aims to measure peculiar velocities for over 186,000 galaxies using both the Fundamental Plane and Tully Fisher relations. Additionally, these peculiar velocity catalogues will be used to build density reconstruction maps which can be used to study the galaxy velocity field and underlying dark matter distribution. In this talk I will present the work being conducted by the DESI Peculiar Velocity Survey with a particular focus on the Fundamental Plane sample and its uses in cosmology. With Data Release 1 the sample contains peculiar velocities for 98,000 early-type galaxies making it the largest existing sample of peculiar velocities and potentially resulting in the tightest constraints on the growth rate of structure at z<0.1, to date.

Speaker: Caitlin Ross (The University of Queensland)

Cosmology_2025_Caitlin_Ross.pdf

Cosmology_2025_Caitlin_Ross.pptx

11:40 Needlets and foreground removal for SKAO HI intensity maps

Intensity Mapping (IM) of the 21-cm line of the neutral hydrogen (HI) has become a compelling new technique to map the large-scale structure of the Universe. One of the main challenges is the presence of strong foreground emissions of several orders of magnitude larger than the HI signal. Here we implement a version of the Principal Component Analysis, a blind component-separation technique, based on a kind of spherical wavelets called needlets. These functions exploit double localization both in real and in harmonic space. We test the Need-PCA performances on a set of maps that simulate the SKA AA4 telescope. We compare our results with other component separation methods such as Generalised Morphological Component Analysis (GMCA) and Generalized Needlet Internal Linear Combination (GNILC). All the methods have comparable results. We also test our pipeline in the presence of systematics such as polarization leakage e we find similar results.

Speaker: Bianca De Caro (INAF-IASF Milano)

decaro_bianca_08_09_1st_session.pdf

12:20 Primordial Black Holes -- Positivist Perspective, Quantum Quiddity and Galaxy Genesis

Primordial black holes are black holes that may have formed in the early Universe. Their masses potentially span a range from as low as the Planck mass up to many orders of magnitude above the solar mass. This, in particular, includes those black holes recently discovered through gravitational waves, and (part of) these may conceivably be of primordial origin. After a general introduction on primordial black holes, I review the observational hints for their existence -- from a variety of lensing, dynamical, accretion and gravitational-wave effects. As I will show, all of these (over 20) may be explained by a single and simple unified model, naturally shaped by the thermal history of the Universe. If time permits, I discuss how recent advances in our understanding of quantum effects in black holes impact PBHs. On the one hand, this concerns deviations from Hawking radiation in the form of the memory-burden effect. On the other hand, I will discuss vorticity, which we recently conjectured to be a new characteristic of (near-extremally rotating) black holes. In the second part of my talk, I will present novel results on large-scale simulations of spatially-correlated random fields, being able to resolve events as rare as one in 10^13, and discuss their application to PBHs. Finally, I will elucidate on the role primordial black holes have on early galaxy and star formation.

Speaker: Florian Kühnel

13:00 → 16:00 Lunch Break

16:00 → 19:05 Afternoon session

16:00 Cosmoglobe: Planck-HFI and advanced dust modelling

The Cosmoglobe collaboration has conducted a groundbreaking joint analysis of the Planck-LFI, WMAP, and DIRBE data. Its unified, end-to-end, Bayesian approach provides improved control over systematic errors, leading to enhanced cosmological constraints and more accurate component maps and sky models. In this talk, I will provide an overview of the Cosmoglobe approach and highlight key results from the collaboration’s joint analysis to date. I will also present our currently ongoing reanalysis of the Planck-HFI data, which is already demonstrating areas of improvements. Additionally, I will introduce a new multi-component dust model based on the Planck-HFI NPIPE maps. This now includes a nearby dust template, a CII-correlated dust component, and an H-alpha–correlated dust component. By expanding the complexity of the dust model, we achieve a more realistic and physically motivated description of Galactic foregrounds—ultimately enabling a clearer view of the cosmic microwave background.

Speaker: Raelyn Sullivan (ITA, University of Oslo)

16:30 Disentangling Modified Gravity and Massive Neutrinos with Intrinsic Shape Alignments of Massive Halos

We present a new diagnostics based on the intrinsic shape alignments of group/cluster size dark matter halos to disentangle the effect of f(R) gravity from that of massive neutrinos. Using the snapshot data from a series of the DUSTGRAIN-pathfinder N-body simulations for the Planck ΛCDM cosmology and three f(R) gravity models with massive neutrinos, we first determine the probability density functions of the alignment angles between the shape orientations of massive halos and the minor principal axes of the local tidal fields. The numerically obtained results turn out to agree very well with the analytic formula derived under the assumption that the anisotropic merging along the cosmic web induces the halo shape alignments. The four cosmologies, which several standard diagnostics failed to discriminate, are found to yield significantly different best-fit values of the single parameter that characterizes the analytic formula.

Speaker: Jounghun Lee

JLEE_talk25_elba.pdf

17:00 Coffee

17:30 Void spin distribution as a powerful probe of $σ_{8}$

We present a numerical proof of the concept that the void spin distributions can provide a tight constraint on $\sigma_{8}$ without without being severely deteriorated by the degeneracies of $\sigma_{8}$ with $\Omega_{\rm cdm}h^{2}$, $M_{\nu}$ and $w$. Applying the Void-Finder algorithm to AbacusSummit N-body simulations of 15 different cosmological models, we identify the voids and measure the magnitudes of rescaled specific angular momenta of void halos as their spins. We determine the probability density distribution of void spins for each model and for the first time find it to be well approximated by the generalized Gamma distribution. It turns out that the best-fit values exhibit very sensitive dependence only on $\sigma_{8}$. This exclusive $\sigma_{8}$-dependence of the void spin distributions is confirmed to be robust against the variation of the mass and number cuts of void halos. We also test an observational feasibility of estimating the void spins from real data on the galaxy redshifts.

Speaker: GEONWOO KANG (Seoul National University)

cosmic void cosmology2025_distrib.pdf

18:00 Superfluid dark matter: from theory to observations

In this talk we will review the model of superfluid dark matter, based on the existence of sub-eV particles with repulsive self-interactions. These particles are able to generate a superfluid core in galaxies upon Bose-Einstein condensation and thermalisation. We will delve into the various phenomenological implications of the model, including the formation of vortices, the behaviour around black holes and dynamical friction, and discuss prospects of detectability through gravitational wave experiments.

Speaker: Valerio De Luca (University of Pennsylvania)

Elba-DeLuca.pdf

18:30 Theoretical Predictions for the Inner Dark Matter Distribution in the Milky Way Informed by Simulations

Understanding the distribution of dark matter (DM) within a few kpc of the Milky Way's center is critical for interpreting and projecting indirect detection signals. Some studies use the inner DM profile directly from hydrodynamic cosmological simulations; however, differences in baryonic physics prescriptions can significantly affect the resulting DM profiles. In this talk, I will quantify the impact of the various baryonic physics implementations by modeling the DM profile in FIRE-2, Auriga, Vintergatan, and Illustris TNG50 using the adiabatic contraction algorithm from Gnedin et al.2004. We find that FIRE-2's stellar feedback dominates over baryonic contraction, while the other simulations are well described by adiabatic contraction. Using models calibrated to simulations and the observed stellar profile in the Milky Way, we provide a theoretical bound on the inner DM distribution in our Galaxy, setting a new standard for DM direct detection analyses and a departure from the overuse of unphysical profiles.

Speaker: Abd El Aziz Hussein (Massachusetts Institute of Technology)

Cosmology_2025.pdf

Tuesday 9 September

09:00 → 13:00 Morning Session 2

09:10 Formation of Nuclear Star Clusters and Supermassive Black Holes via First-Generation Globular Cluster Disruption.

The Nuclear Star Cluster (NSC) resides at the center of the Milky Way galaxy and represents an extremely dense stellar system. Most such systems are also known to harbor Supermassive Black Holes (SMBHs).

Several mechanisms have been proposed to explain the formation of NSC+SMBH structures, with two prevailing scenarios:

(i) the inward migration of gas toward the galactic center, followed by star formation from the accreted material, and

(ii) the inward migration and subsequent disruption or merger of Globular Clusters (GCs), resulting in the buildup of a common NSC.

In our study, we focus on the second scenario — the complete decay of GCs during their interaction with the central NSC+SMBH. We model the orbital dynamics and mass loss evolution of present-day GCs, assuming they formed approximately 10 billion years ago. To accomplish this, we employ time-varying Milky Way-like potentials, extracted from the Illustris TNG-100 cosmological simulation.

Speaker: Peter Berczik (Main Astronomical Observatory, National Academy of Sciences of Ukraine)

ber-elba.pdf

09:50 Searches for dark matter using LHC Run-2 and Run-3 data recorded by the ATLAS experiment

Dark matter constitutes about 85% of the matter content of the Universe, yet its microscopic nature remains unknown. While astrophysical and cosmological observations provide compelling evidence for its existence, they do not reveal how it interacts with Standard Model particles beyond gravity. Collider experiments such as the LHC provide a complementary avenue of investigation by directly searching for dark matter production at the highest available energies. This approach enables the exploration of a wide variety of final states, ranging from traditional WIMP searches to more complex and intriguing scenarios involving dark sectors and new mediator particles. Such searches are crucial for mapping out the possible connections between cosmological evidence and particle physics signatures.
The sensitivity achieved by ATLAS underscores the continued impact of collider-based searches in probing the particle nature of dark matter and in constraining theoretical models. In this contribution, we will present an overview of dark matter searches performed with ATLAS during Run 2, based on the full dataset corresponding to an integrated luminosity of 140 fb⁻¹, as well as highlight recent results from the ongoing Run 3 data-taking campaign. Together, these results provide an essential complement to direct and indirect detection experiments.

Speaker: Alvaro Lopez Solis (The Barcelona Institute of Science and Technology (BIST) (ES))

DarkMatterATLAS_AlvaroLopez_9Sept2025.pdf

10:30 Coffee

11:00 Dark matter searches in dwarf irregular galaxies with gamma-ray observatories.

I will review the state-of-the-art of dark matter (DM) searches in dwarf irregular galaxies (dIrrs). DIrrs have been proposed as new astrophysical targets of interest for DM searches in gamma rays, complementary to dwarf spheroidal galaxies, galaxy clusters and the Galactic center. DIrrs show high DM content (with respect to the luminous matter), relatively close distance and low gamma-ray background: all these characteristics make dIrrs interesting targets for DM searches. After the first proof-of-concept paper, dIrr galaxies have been studied by both satellite and ground-based observatories, such as Fermi-LAT, HAWC and HESS. I will review the main results obtained so far, as well as preliminary observational prospects for the upcoming Cherenkov Telescope Array Observatory.

Speaker: Viviana Gammaldi (San Pablo CEU, Madrid, Spain.)

dIrr_review_Cosmo_2025_v3.pdf

11:40 Scaling Relations between the Luminous and Dark Matter Density Parameters of Milky Way Dwarf Spheroidal Galaxies

We use surface brightness and velocity dispersion data to constrain the parameters of the luminous and dark matter densities for a sample of 10 Milky Way, dwarf spheroidal galaxies (MW dSphs). We model the luminous matter density with a generalized Plummer profile, of inner slope $\gamma_*$, and the dark matter (DM) density with a Zhao-type model, of inner slope $\gamma$. The specific DM density model we use has the advantage of an analytic mass integral, facilitating particularly simple DM density and mass profile fits for any $0 \leq \gamma \leq 1$. We find that the best-fit values of $\gamma_*$ and $\gamma$ are correlated with each other, as well as with other parameters, such as the effective radii, $R_{\rm eff}$, and the stellar-to-total mass ratios of the dSphs in our sample. Additionally, we find that the best-fit DM scale radii and scale density parameters are also correlated with $R_{\rm eff}$.

Speaker: Casey Watson (Millikin University)

Watson Cosmology 2025 in Elba lecture final.pdf

12:20 Cosmology with Ultralight Dark Matter

The presence of ultralight dark matter in the early Universe suppresses small-scale structure formation. Moreover, if it couples to the Standard Model, it can induce a variation of fundamental constants. In this talk, I will discuss the cosmological impact of an ultralight dark matter field with an effective quadratic coupling to the Standard Model, such that the fine structure constant and the mass of the electron have time-dependent, oscillatory variations. I will present CMB constraints on this scenario for a wide range of dark matter masses, associated with the oscillations occurring around BBN and the formation of the CMB.

Speaker: Kimberly Boddy (University of Texas at Austin)

kboddy-Cosmology2025.pdf

13:00 → 16:00 Lunch Break

16:00 → 19:30 Afternoon session

16:00 Cosmography through the ages of low-redshit early-type galaxies

Using Early Type Galaxies (ETGs) ages as cosmic chronometers has been recently revisited as a model independent way to determine the Hubble parameter, through the inspection of their Lick indices. We present a cosmographic analysis of the ages of SDSS Legacy ETGs, aiming at a novel continuous fit of the Hubble parameter along the redshift range of the data.
We introduce a robust stacking procedure to enhance the signal-to-noise ratio of the spectra, rendering the estimated ages much more reliable. Stellar ages are subsequently derived using two independent SPS models, which are then fit with a second order Taylor expansion in $y$-redshift $y = z/(1+z)$ of the Hubble parameter $H(z; H_0, q_0, j_0)$. We obtain estimations for the Hubble constant $H_0$, deceleration $q_0$ and jerk $j_0$ parameters. Notably we find $H_0 = 69.5^{+4.3}_{-7.4}$, and the overall sampling of $H(z)$ is competitive wrt to punctual estimations from the literature.

Following these results, higher-$z$ work with (e)BOSS data is ongoing.

Speaker: Carlos Alonso Álvarez (SISSA)

Cosmology_2025_Carlos_Alonso_Alvarez.pdf

16:30 Trace Anomaly, Condensates and Cosmological Constant

We explore the origin of the cosmological constant. One salient and intriguing property of the cosmological constant is that the associated pressure is the negative of its energy density. By analyzing the energy-momentum tensor form factors of hadrons, we find that the QCD trace anomaly balances the pressure from quarks and gluons, thereby playing a key role in hadron confinement. This anomaly originates from the gluon and quark condensates in the vacuum and exhibits the same pressure-energy density relation as the cosmological constant. A similar phenomenon is observed in type II superconductors, where the same pressure-energy density relation arises from the unpairing of Cooper pairs in the vortex core. In view of these analogies, it is suggested that the cosmological constant could arise from the trace anomaly of a vacuum condensate resulting from the spontaneous breaking conformal symmetry in quantity gravity. The presence of a condensate could resolve the issue of energy conservation.

Speaker: Kehfei Liu

Cosmological constant and condensates.pdf

17:00 Coffee

17:30 Microlensing of Microlensing: Resolving Time-Delay Bias with Multi-Plane Quasar Lensing

When a luminous source is gravitationally lensed, its images arrive at different times. These time delays can be measured in lensed quasars to constrain $H_0$, offering a possible resolution to the Hubble tension. A quasar’s point-like nature, however, makes it sensitive to microlensing: deflections caused by compact objects within lensing galaxies that introduce small additional delays. If unaccounted for, microlensing-induced delays can bias time-delay measurements, and estimates of $H_0$.
We use the Python library JAX to build an inverse ray-tracing pipeline, simulating light propagation through multiple lens planes. Applying this to the newly observed lensed quasar J1721+8842, with an intermediate lensing plane, we construct realistic microlensing maps and light curves. These reveal a distinctive signature due to a novel microlensing of microlensing effect. Our forthcoming analysis aims to quantify the resulting bias on $H_0$, providing new insight into systematics affecting cosmology with strong lensing.

Speaker: nada salama (The University of Sydney)

elba talk.pdf

18:00 Nonextensive Entropies as Holographic Dark Energy in Cosmology

A plethora of various entropic forms have been presented in the literature recently starting with famous Tsallis q-entropic statistics [1]. Like the Bekenstein-Hawking (horizon) entropy, which is nonextensive due to its scaling with the area and not with the volume, they go beyond the standard extensive and additive Boltzmann-Gibbs formulation of thermodynamics. However, they fit perfectly to gravity due to taking into account long-range interactions between subsystems.

During my talk, I will briefly present the properties of the selected nonextensive entropies (Tsallis, Tsallis-Cirto, Barrow, Renyi, Tsallis-Jensen, Sharma-Mittal, Kaniadakis) and show their application for the explanation of the dark energy phenomenon in the universe (known as Holographic Dark Energy (HDE) models) making statistical comparison against LCDM using the Bayesian evidence criterion [2]. Interestingly, Barrow and Tsallis-Cirto entropies have the property of ‘’near-extensivity’'which agrees with our previous result [3].

Speaker: Mariusz Dabrowski (University of Szczecin)

Cosmology2025_Elba_09_2025_2.pdf

18:30 Dark Matter in extra-dimensional scenarios

The Nature of Dark Matter is, still, a widely open question that allows for very different anwers. One option is represented by particles that do interact gravitationally (as hinted by experiments), albeit with a coupling with gravity enhanced by an underlying extra-dimensional space-time. Several options have been proposed, either within a WIMPy or FIMPy approach, with different possibility for the geometry of the 5D space-time. I will shortly review these options and their experimental constraints, focusing eventually in a recent proposal of a Randall-Sundrum 5D setup with three branes that avoid most of the collider bounds while still producing the required amount of DM relic abundance.

Speaker: Andrea Donini

DMin3b.pdf

Wednesday 10 September

09:10 → 13:00 Morning Session 3

09:10 Tests of LCDM on small scales

The LCDM model has the virtue of having strong predictive power in so
far as the properties of the dark matter are concerned. For example,
the mass function of dark matter halos is known to high precision,
from the mass scale of the Earth to that of rich clusters. The
predictive power is weakened when baryons are considered because of
the complex astrophysical processes to which they can give rise. This
shortcoming can be mitigated with detailed modelling which has become
increasing sophisticated over the years. Neglecting such processes is
dangerous and this has led to the often voiced view that LCDM suffers
from a ``small-scale crisis'', that is that it disagrees with data on
the scales of galaxies and below. I will discuss this perceived crisis
and focus on claims that the abundance and properties of the galaxies
recently discovered at very high redshift by the JWST are inconsistent
with LCDM.

Speaker: Carlos Frenk (Durham ICC)

elba_25_clean.pdf

09:50 Cosmology with prompt cusps

Every dark matter halo forms with a ρ ∝ r^−1.5 density cusp at its center. This prompt cusp has a mass comparable to the cutoff scale in the spectrum of initial density perturbations. For warm and interacting dark matter models, prompt cusps significantly influence the structures of low-mass halos, so they are an important consideration for efforts to use satellite galaxies, strong lensing, and stellar streams to constrain the dark matter mass and interaction properties. For annihilating dark matter, prompt cusps amplify the annihilation rate an order of magnitude above previous predictions. I will present the basis for prompt cusps in simulations and theory, including new results showing how each halo's central cusp depends on the dark matter model. I will also discuss two observational tests of dark matter that prompt cusps enable: the measured kinematics of dwarf galaxies can strongly constrain warm dark matter, while gamma rays from galaxy clusters strongly constrain annihilating dark matter.

Speaker: Dr Sten Delos (Carnegie Observatories)

delos.pdf

10:30 Coffee

11:00 Modelling high redshift structure formation and reionization in the JWST era

The study of primitive stars and galaxies is an exciting new frontier in astrophysics and cosmology. They form within the first gigayear after the Big Bang and significantly impact their surroundings by emitting a lot of high-energy radiation that transforms the surrounding cold neutral gas into a hot and ionized medium. They also form an important evolutionary link between the smooth matter distribution at early times and the highly complex structures seen today. Fortunately, a whole slew of instruments that have been specifically designed to study the high-redshift Universe (JWST, ALMA, Roman Space Telescope, HERA, SKA, CCAT-p, SPHEREx), have started providing valuable insights into high redshift structure formation and reionization. Therefore, theoretical/numerical models must achieve sufficient accuracy and physical fidelity to meaningfully interpret this new data. In this talk, I will introduce the THESAN simulation framework that is designed to efficiently leverage current and upcoming high redshift observations to constrain the physics of early galaxy formation and reionization. The multi-scale nature of these processes is tackled by coupling large volume (~100s Mpc) simulations designed to study the large-scale statistical properties of the galaxies, with high-resolution (~ 10 pc) simulations that zoom-in on single galaxies which are ideal for predicting their resolved properties. I will discuss applications from the first set of papers, including predictions for high redshift galaxy properties, the galaxy-IGM connection and the back reaction of reionization on galaxy formation. I will finish by highlighting recent improvements to the model and proposed future work.

Speaker: Rahul Kannan

Cosmology2025.pdf

11:40 Astrophysical Signatures of Gravothermal Collapse in Dark Matter Halos

I will present recent high-resolution N-body simulations of self-interacting dark matter (SIDM) and discuss their implications across a broad range of astrophysical observations. In particular, I will highlight novel signatures arising from gravothermal collapse in dark matter halos. I will then explore the prospects for detecting these signatures in strong gravitational lensing systems, stellar streams, dwarf galaxies, and the formation of supermassive black holes. Together, these studies open promising new avenues for probing the fundamental nature of dark matter.

Speaker: Hai-Bo Yu (University of California Riverside)

2025ElbaHAIBOYU.pdf

12:20 How our Nuclear Star Cluster formed and grew due to first generation globular clusters disruption

The Nuclear Star Cluster (NSC) is at the centre of the Galaxy, an extremely dense star system. Several mechanisms are exists to explain how NSCs form, including gas migrating or GCs merging to the NSC.

Based on the second idea, we will present the processes involved in the complete decay of GCs during their interaction with the NSC of our Galaxy.

We have generated 'theoretical' GCs in a time-varying potential as these likely formed 10 Gyr ago. Initial positions for the GCs were randomly generated in the total angular momentum energy phase space, taking into account various orbital parameters. For the GCs N-body simulations, we employed a high-order, dynamical N-body code with updated stellar prescription and time-variable external potential.

In total, we integrated 150 GC models from -10 to -5 Gyr interval. Consequently, we will present the total mass and stellar accretion rates to the NSC from our GC models. We will also analyse the parameters of cluster orbits where star accretion is more prevalent.

Speaker: Maryna Ishchenko (Main Astronomical Observatory of National Academy of Sciences of Ukraine)

Ishchenko_elba.pdf

13:00 → 15:00 Lunch Break

15:00 → 20:05 Free Afternoon + Tour

Thursday 11 September

09:10 → 13:00 Morning session 4

09:10 DArk Matter Particle Explorer: 9 years in Space

The Dark Matter Particle Explorer (DAMPE) is a pioneering calorimetric space experiment that has been successfully operating since December 2015. Its primary scientific objectives include measuring the spectra of both primary and secondary cosmic-ray species, searching for potential indirect signatures of dark matter in cosmic rays, and gamma-ray physics. For electrons and gamma rays, DAMPE covers an energy range from a few GeV up to around 10 TeV, achieving an exceptional energy resolution of nearly 1%. For hadronic cosmic rays, its measurements reach several hundred TeV in kinetic energy.

In this talk, we will begin with an overview of the DAMPE mission and its current operational status in orbit. We will then highlight key scientific achievements, including recent measurements of the BCNO group, iron nuclei, the extended light element spectra beyond 100 TeV, and other significant results.

Speaker: Andrii Tykhonov (Universite de Geneve (CH))

Cosmology2025_DAMPE_Tykhonov____.pdf

09:50 Learning about the early Universe with the cosmic 21-cm signal

The 21-cm hyperfine line of HI is set to revolutionize studies of the first billion years, spanning the cosmic dawn of the first stars and eventual reionization of our Universe. I will discuss the potential of this probe in learning about the unknown astrophysics of the first galaxies as well as physical cosmology. Preliminary claims of a detection of the mean (sky-averaged) 21cm signal showcased its potential in constraining exotic dark matter-baryon interactions in the early Universe, although recent robust interpretation points against new physics. The true potential of the cosmic 21cm signal is in mapping out the first half of our observable Universe through HI fluctuations. Current upper limits on the 21-cm power spectrum already provide new insights into the heating of the intergalactic medium, likely caused by a new population of high mass X-ray binaries. Future detections will allow us to set the strongest available constraints on exotic heating mechanisms through dark matter decay and annihilation.

Speaker: Andrei Mesinger

Mesinger_Elba_2025.pdf

10:30 Coffee

11:00 Implications for Cosmic Birefringence from Recent Cosmological Observations

In this talk, I present implications for the cosmic birefringence from recent cosmological observables. We begin by showing constraints on cosmic birefringence induced by ALPs using the Planck $EB$ power spectrum. We find that cosmic birefringence signal is consistent with a constant rotation model and some specific ALP masses are excluded. Next, we show that cosmic birefringence can explain a higher optical depth $\tau\simeq0.09$ as a result of the DESI BAO measurements and CMB observations within the standard cosmological model. Specifically, we use the fact that the recent cosmic birefringence measurement, $\beta_0=0.34\,$deg, has the phase ambiguity, $\beta=\beta_0+180n\,$deg with $n\in\mathbb{Z}$). An ALP-induced birefringence model with a nonzero $n$ can suppress the reionization bump in the $EE$ spectrum while allowing for a large optical depth. We show a viable parameter region that simultaneously explain the large-scale CMB polarization, Planck $EB$ power spectrum, and an eleveted value of $\tau$.

Speaker: Toshiya Namikawa

2025-09_Cosmology-at-Elba_Namikawa.pdf

11:40 Evolution of Mass and Structure in Dark Matter Halos: Scaling Laws from Dwarfs to Galaxy Clusters

We investigate the mass evolution of dark matter subhalos in Milky Way–like galaxies using ultra-high-resolution N-body simulations (Kazuno et al. 2024). Subhalos undergo early accretion followed by tidal stripping, losing over 80% of their mass by z = 1. Their orbits closely resemble those of Milky Way satellites, as revealed by Gaia EDR3, reinforcing the CDM paradigm. In contrast, Kaneda et al. (2024) examine internal structure. The radius of maximum circular velocity emerges as a critical scale where observed surface densities align with CDM predictions from the concentration–mass (c–M) relation. This agreement reflects the universality of dark matter halo scaling relations, including the near-constant central surface density seen from dwarf galaxies to galaxy clusters. Remarkably, despite baryonic feedback, observational evidence from UFDs and SPARC rotation curves confirms that these relations persist down to halo masses below 10⁸ M☉, highlighting their robustness across a broad mass range.

Speaker: Masao Mori (University of Tsukuba)

250911_MasaoMori.pptx

12:20 Mapping Gravity with Extragalactic Streams and Citizen Science

Wide-field surveys like Euclid mark a new era of extragalactic stellar stream studies, with exciting applications in measuring baryon and dark matter distributions, and connecting galaxies to their cosmological context.
I present results from a pilot study combining Euclid imaging with Zooniverse classifications to detect and analyze streams. We use projected stream morphologies to constrain the shape and barycenter of each host galaxy’s potential, jointly probing baryonic and dark matter distributions. These inferences complement lensing, with sensitivity to halo geometry on tens of kpc scales. The method enables both stacked, population-level constraints on halo triaxiality and barycenters, and individual-halo inference on the same. Already, we find promising agreement with ΛCDM predictions. Our program will identify thousands of streams, enabling precise constraints on halo shapes and barycenters across large samples and redshifts, offering a new dynamical test of dark structures.

Speaker: Nathaniel Starkman (MIT Kavli Institute for Astrophysics and Space Research)

13:00 → 16:00 Lunch Break

16:00 → 19:05 Afternoon session

16:00 Unveiling small-scale dark matter structure with starless halos: Are mass and concentration estimates reliable?

RELHICs (REionization-Limited H I Clouds) are a population of gas-rich, starless dark matter halos predicted by the $\Lambda$CDM model. Being in hydrostatic equilibrium with the dark matter and the UV background, their gas distribution provides a unique opportunity to directly probe the structure of dark matter halos on small scales. These systems have recently become accessible to observations thanks to deep radio surveys as FAST. I will present results from high-resolution cosmological simulations from the EAGLE project, focusing on the performance of mass and concentration estimators applied to simulated RELHICs. Using a physically motivated model for the H I and gas profiles, we can infer halo properties directly from observable quantities. We find that mass estimates are unbiased on average, though systematic deviations appear in the most H I-rich systems due to environment pressure effects. This analysis provides guidance for current and future observational efforts with upcoming facilities such as SKA.

Speaker: Francesco Turini (Università degli studi Milano-Bicocca)

PresentazioneElba25F.Turini.pdf

16:30 Exploring keV-scale physics with CUORE: a new window for dark matter searches

Initially designed to search for neutrinoless double beta decay, the CUORE (Cryogenic Underground Observatory for Rare Events) experiment also offers a unique opportunity to explore potential dark matter signals at the keV-scale. Leveraging over 2 tonne·yr of TeO$_2$ exposure, we optimized data processing and event-selection techniques, achieving stable detector performance and effective event reconstruction down to thresholds as low as 3 keV. CUORE’s large exposure, segmented detector structure, ultra-low-background environment, and excellent energy resolution enable sensitive searches for cosmic axions originating from the galactic halo, solar axions, and WIMP-induced annual modulation signals. We present our advanced low-energy analysis methods, current status, and future prospects of these ongoing dark matter searches.

Speaker: Anastasiia Shaikina (Gran Sasso Science Institute, Istituto Nazionale di Fisica Nucleare)

Shaikina_Cosmology2025.pdf

17:00 Coffee

17:30 Addressing the Hubble tension and a proposal to increase the accuracy of cosmological observables

The Hubble tension denotes the discrepant values of $H_0$ obtained from direct measurements in the local Universe compared to those derived from the CMB. Observational programs often compare their data also with extensions to ΛCDM applying dynamical models of dark energy (DDE) with a time-dependent equation of state parameter w. They use the MCMC method to fit the ΛCDM extensions to their data, where they use the CPL model $w(a) = w_0 + w_a(1 − a)$ as the parametrization of the DDE model. We discovered a degeneracy in the MCMC method and propose a complementary computational procedure as an extension to the MCMC method that breaks the degeneracy, where our results reveal that the CPL model $w(a) = −0.9 + 0.1(1 − a)$ could provide a resolution to the Hubble tension problem. Moreover, we find that this approach can serve as a kind of consistency check for cosmological models and will increase the accuracy of inferred cosmological parameters significantly, in particular for ΛCDM extensions with DDE.

Speaker: Horst Foidl (Department of Astrophysics at the University of Vienna)

Cosmo2025-Hubble tension and a increasing the accuracy of cosmological observables-Foidl.pdf

18:00 Production, thermalisation and constraints on hidden sector dark matter from asymmetric reheating

The evolution of the early Universe may have been driven by a hot hidden sector, made of dark matter and possibly other companion particles. Such conditions can be achieved, for instance, by asymmetric reheating from inflaton decay, and open new regions in the parameter space. In this talk, using dark QED as a benchmark model for the dark sector, I will introduce asymmetric reheating and the conditions of thermalisation in the produced hidden sector. Next I will present the main classes of reheating scenarios in this framework and show the corresponding cosmological constraints in the parameter space, with a focus on the unitarity limit on the dark matter mass.

Speaker: Jean Kimus (Université Libre de Bruxelles)

Cosmo@Elba_Kimus.pdf

18:30 Characterization of Galaxy Cluster Gamma-Rays.

Barring a few potential exceptions, galaxy clusters (GC) are not confirmed gamma-ray sources despite theoretical expectations. We use 16 years of Fermi-LAT data to characterize the gamma-ray emission of a population of GC selected from the Planck Sunyaev-Zeldovich catalog. We employ a likelihood stacking technique to uncover the cumulative gamma-ray signal from this population. The stack of 207 target clusters significantly exceeds the cumulative likelihood of a large control field sample. Refitting our targets as extended sources consistently increases the likelihoods, indicative of large-scale GC emission rather than point source contamination. We also create a stacked spectral energy distribution (SED) and perform likelihood-based correlation analyses between the gamma-ray luminosities and X-ray data. We compare the SED to physical models to gauge the balance between hadronic and leptonic processes, gain insight into the role of cosmic rays in GC evolution, and the nature of cosmic ray acceleration in GC.

Speaker: Ms Thyra Eysselinck (CUNY Graduate Center, Simons foundation, AMNH)

Elba gamma-ray presentation final.pdf

20:30 → 22:30 Social Dinner

Friday 12 September

09:10 → 13:00 Morning session 5

09:10 Explaining the H0 Tension via the Local Hole and CMB Lensing

Observational evidence for a large local galaxy underdensity goes back to the 1990’s and, like the "Hubble tension", remains unexplained by standard 𝜦CDM. Wong et al (2022) show that this “Local Hole” covers >90% of the sky out to ~200Mpc with an ~20-30% underdensity, consistent with previous observations (e.g. Keenan, Barger and Cowie, 2014). We have speculated that this underdensity could explain the H0 tension but an even larger/more underdense “Hole” would be required, uncomfortable given that the current Local Hole is already a 4𝜎 deviation from 𝜦CDM. However, recall that we are only measuring galaxy density and biasing has to be taken into account. Crucially, Kaur et al (2025) find that galaxy-CMB lensing results from Planck+ACT give significantly higher amplitudes at 2-halo scales than predicted. These results argue for an anti-bias that increases the local mass underdensity to ~50% over 200Mpc, enough to explain the Hubble tension (eg Huterer 2023), although remaining in disagreement with 𝜦CDM.

Speaker: Tom Shanks (Durham University, UK)

Cosmo25_elba_TS_both.pdf

09:50 The Host Masses of Active Galactic Nuclei before Cosmic Noon with TNG-Cluster and other cosmological Simulations of Galaxies

We investigate the host dark matter halo masses of AGNs across various cosmological simulations of galaxies (Illustris, IllustrisTNG, TNG-Cluster, Simba and EAGLEs). In particular we examine the co-evolution of the luminosity of AGNs in relation to the mass of their host dark matter halo from z=7 to z=3. Despite differences in AGN feedback implementations and SMBH seeding prescriptions across simulations, we find that AGNs of a given luminosity can occupy a wide range of halo masses, exhibiting a significant scatter. We also find that in the TNG model, the median halo mass of "quasars" remains roughly constant with redshift which is consistent with quasar clustering measurements, implying that luminous quasars do not exclusively occupy the most massive halos, which increasingly host supermassive black holes depleted of their gas reserves near cosmic noon.

Speaker: Akanksha Kapahtia (Max Planck Institute for Astronomy Heidelberg)

10:30 Coffee

11:00 Data-driven galaxy-AGN co-evolution studies with eROSITA, Euclid and LSST

Galaxy evolution follows the tapestry set by cosmology, but is modulated by central supermassive black holes. Human lifetimes limit the study of the stochastic gas motion from halos to the event horizon. Nevertheless, the last few decades have revealed a probabilistic multidimensional link between AGN outflows, black hole mass, accretion, galaxy mass, star-formation, morphology, and obscuration. Degeneracies linger in the demographic evolution of black holes and their radiative processes, which are important to resolve if we want to precisely understand the cosmic mass outflow budget affecting galaxies and the intergalactic medium. The millions of AGN found by new surveys (eROSITA, Euclid, LSST, SphereX, SDSS-V, DESI, 4MOST) will be able to break these degeneracies if selection effects are addressed with scalable inference methods. First results with eROSITA include abundant over-massive black holes at odds with their interpretation as seed remnants and tight correlations in current simulations.

Speaker: Johannes Buchner (Max Planck for extraterrestrial Physics)

2025-cosmoelba25_buchner.pdf

11:40 Processing of gas in galaxies within the cosmic web.

Galaxies are distributed in a complex filamentary network of matter called the cosmic web. It remains debated which is the overall impact of the cosmic web in processing cold gas of galaxies, as they move through large-scale filaments around the clusters down to the densest regions of the cluster cores. I will present the results of a large observational campaign, mainly exploiting IRAM millimeter facilities, with the goal of quantifying the processing of galaxies' gas in the cosmic web and with cosmic time. I will discuss the degree of such processing in a variety of dense megaparsec-scale environments. Finally, I will discuss the potential of such studies for next generation multi-wavelength facilities. Thousands of distant clusters and BCGs will be detected with Euclid, enabling an unprecedented leverage to constrain galaxy evolution in cluster.

Speaker: Gianluca Castignani (INAF OAS Bologna)

presentation_clusters_Elba_12sett2025_Castignani.pdf

12:20 Stellar Tracers of the Local Dark Matter Velocity Distribution Over a Range of Galaxy Simulations

Dark matter (DM) remains one of the central unresolved questions in modern physics. The majority of terrestrial direct detection experiments for DM rely on the assumption that the local DM velocity distribution conforms to the Standard Halo Model (SHM). However, perturbations arising from merger events can induce deviations from the SHM. Previous studies have suggested that the local stellar velocity distribution may serve as a tracer for DM populations originating from the same progenitor systems. In this talk, I discuss how we systematically investigate the impact of the merger history on the correlation between local stellar and DM velocity distributions across multiple halos from the FIRE latte suite. Additionally, we assess the influence of simulation resolution on these results. We find that DM accreted from lower-mass mergers at earlier times exhibits a stronger correlation with its stellar counterpart, highlighting the importance of merger history in interpreting local DM phase-space structure.

Speaker: Xiuyuan Zhang

13:00 → 16:00 Lunch Break

16:00 → 19:05 Afternoon session

16:00 The CMS PPS spectrometer searching for photon-DM interaction

The CMS Precise Proton Spectrometer (PPS) has opened a new window in the gamma-gamma interactions at TeV energies. A discussion on recent results and future searches will be presented focusing on the impact of photon-DM interaction at cosmological level

Speaker: Prof. Nicola Turini (INFN Sezione di Pisa, Universita' di Siena)

PPS-Cosmology.pdf

16:30 Probing Charm Baryon Dipole Moments at the LHC: the ALADDIN experiment

The magnetic and electric dipole moments (MDM and EDM) of charm baryons remain unmeasured and offer a unique window into physics beyond the Standard Model. In particular, a nonzero EDM would signal new sources of CP violation, potentially linked to the baryon asymmetry of the universe.

The proposed ALADDIN experiment at the LHC aims to perform the first direct measurement of these moments. By accessing the charm sector, ALADDIN explores a largely untested regime where non-perturbative QCD effects and new CP-violating mechanisms may emerge.

This talk will outline the physics motivations behind the measurement, its relevance to cosmology, and recent experimental progress toward realizing this program.

Speaker: Nicola Neri (Università degli Studi e INFN Milano (IT))

Neri_ALADDIN_Cosmology25.pdf

17:00 Coffee

17:30 The Characteristic Mass for Cusp–Core Transformation in Dark Matter Halos

Shinozaki et al. in prep. present an analytical model that embeds the cusp–core transition into the c–M relation of dark matter halos. The model accounts for deviations from scaling relations in galaxies, where central surface densities fall below c–M predictions. In contrast, UFDs retain high central densities consistent with CDM. Assuming supernova(SN) feedback drives the transition, the model predicts it operates within a characteristic halo mass range of 10⁸–10¹¹ M☉, defining a critical stellar mass and a “forbidden region” where core formation is ineffective. The framework is validated by analysis using SPARC and UFD data (Hayashi, Kaneda, Mori & Shinozaki in prep.). These data confirm that most galaxies lie outside this region and can undergo the transition, while groups, clusters, and UFDs remain trapped within it. The observed diversity in low-mass density profiles likely arises from variations in star formation efficiency and the coupling efficiency between SN feedback and the dark matter potential.

Speaker: Michi Shinozaki (University of Tsukuba)

Shinozaki_cosmo2025_elba.pdf

18:00 Probing GeV-Scale Dark Matter Annihilation with the JUNO Experiment

The Jiangmen Underground Neutrino Observatory (JUNO) is poised to make significant contributions to neutrino physics, including the indirect search for dark matter from the annihilation of WIMPs with masses in the GeV range, which can become gravitationally trapped within the solar core. While Pulse Shape Discrimination (PSD) is a standard technique for classifying events in JUNO , this work demonstrates that a substantial improvement in sensitivity can be achieved by applying dedicated machine learning (ML) and deep learning (DL) algorithms. This enhanced signal-to-background discrimination JUNO can become a leading instrument in the search for solar WIMPs, with a projected sensitivity that is comparable to current limits from major facilities like the IceCube Neutrino Observatory, particularly in the challenging low-mass WIMP range (3-20 GeV). This work highlights JUNO's strong potential to probe the existence of dark matter and its important role in the global multi-messenger effort.

Speaker: Utane Sawangwit (National Astronomical Research Institute of Thailand (NARIT))

JUNO_Cosmo2025_Utane.pdf

18:30 Stream Splitting as a New Signature of Dark Matter Subhaloes and Intermediate-Mass Black Holes in the Milky Way

The population of dark matter subhaloes in the Milky Way provides constraints on the dark matter particle mass. Previous studies suggest that stellar streams serve as probes of dark substructure through the dynamical signatures, such as gaps, imprinted by perturbations. With the advent of the Gaia satellite, several streams running nearly parallel to each other have been discovered. In this study, we report that a single stellar stream can split into two parallel streams following an encounter with a dark matter subhalo or an intermediate-mass black hole. This stream splitting occurs when the perturber approaches along the stream’s tidal axis. Our scenario is supported by analytical modelling and N-body simulations. Moreover, the morphology and kinematics of the resulting parallel streams have possibility to offer an estimation of the mass of the perturber. Our results highlight that not only gaps but also splits should be considered to estimate the true abundance of subhaloes.

Speaker: Yuka Kaneda (University of Tsukuba)

presentation_cosmology2025_yukakaneda.pdf

Saturday 13 September

09:10 → 12:10 Saturday's session and Farewell