23rd Meeting MULTIDARK

17 Jun 2026, 09:00 → 19 Jun 2026, 18:00 Europe/London

Welcome to the 23rd MultiDark Meeting, hosted by the Instituto de Astrofísica de Canarias on 17 - 19 June. Despite the remarkable success of the standar models of particle physics and cosmology, we still do not know what constitutes the substance thought to make up up to ~85% of the Universe’s matter. Determining the nature of dark matter remains one of the most pressing challenges in modern physics.

MultiDark is a Spanish Research Network bringing together theoretical and experimental groups of particle physicists, astrophysicists, and cosmologists from 15 Spanish universities and research institutes to tackle the dark-matter puzzle from a genuinely multidisciplinary perspective. Funded by the Spanish Research State Agency of the Ministry of Science and Innovation, the network has been actively working on multiple aspects of dark matter for 15 years, and remains committed to advancing this research in the years ahead:

www.multidark.es

This workshop brings together experts in astroparticle physics, high-energy physics, phenomenology, astrophysics, cosmology, experiments, and simulations to share recent results, strengthen collaborations, and spark new interdisciplinary approaches. The program consist of contributed talks highlighting the latest activities of the MultiDark network structured around five working groups:

• WG1: Direct Detection
• WG2: Indirect Detection - Gamma & Cosmic Rays
• WG3: Indirect Detection - Neutrinos
• WG4: Dark Matter Theory and Colliders
• WG5: Cosmology

This workshop represents a coordinated effort organized by the recently founded transversal line at the IAC "Dark matter: observations, models and detection"  and is partially supported by the MICINN through the grant “DarkMaps” PID2022-142142NB-I00.

The main website of the event is

 

https://meetings.iac.es/multidark/

 

The MultiDark 2026 Connections Game can be found here.

Wednesday 17 June

09:15 → 09:45 Welcome & Intro

MD_welcome_170626_masc.pdf

MULTIDARK2026.pdf

09:45 → 10:45 Indirect - gammas & cosmic rays: (I)

09:45 ALP signal from magnetosphere

We explore the potential signatures of axion-like particles (ALPs) originating from magnetar-like pulsars in the Fermi-LAT energy range, a largely unexplored regime. Magnetars in a quiescent state are notoriously difficult to detect above 100 MeV and are typically observable only during transient flare episodes. These objects are characterized by extremely strong magnetic fields, B, which play a crucial role in particle production and conversion processes. In the Third Fermi-LAT Pulsar Catalog, a small subset of pulsars is classified as magnetar-like, as they exhibit properties similar to those of magnetars, most notably their high magnetic fields. In this work, we investigate the primary ALP production mechanisms within neutron stars identified as magnetar-like pulsars, along with their subsequent conversion into photons. This conversion can occur either within the pulsar magnetosphere or, at larger scales, in the Galactic magnetic field. Additionally, we examine the role of inverse Compton scattering in boosting keV photons to energies detectable by Fermi-LAT. This study provides a foundational framework for future spectral analyses of magnetar-like pulsars and enables a systematic comparison with scenarios involving an ALP origin of the observed emission

Speaker: Federica Giacchino

alp in magnetosphere - multidark.pdf

10:05 Sensitivity of the Cherenkov Telescope Array Observatory to Dwarf Irregular Galaxies

Dwarf irregular galaxies (dIrrs) are rotationally supported galaxies located in the Local Volume, and are considered to host star-forming regions with a low star-forming rate. Their gamma-ray background signal is expected to be low, making them interesting targets for WIMP Dark Matter (DM) indirect searches. Following previous works on dIrrs, we present the best four dIrrs targets for the forthcoming Cherenkov Telescope Array Observatory (CTAO). Since dIrrs have not been detected yet in gamma rays, in this work, we first explore the detection prospects of dIrrs as astrophysical emitters. Secondly, because the cusp-core problem is important for these objects, we compute the sensitivity prospects to a DM annihilating signal adopting both profiles, including halo substructures. Finally, we show that our DM sensitivity results are competitive with benchmark targets such as galaxy clusters.

Speaker: Jaume Zuriaga-Puig

20260617102213_MultiDark2026_Jaume_ZuriagaPuig.pdf

10:25 A New Generation of All-Sky Galactic Dark Matter Templates for Gamma-Ray Searches

We present a new generation of all-sky dark matter (DM) maps for gamma-ray DM searches in the Milky Way, including the contribution from DM halo substructure. The maps are based on repopulated subhalo catalogs built upon selected runs from Auriga, a set of state-of-the-art zoom-in cosmological hydrodynamical simulations that model Galactic substructure in the presence of baryons. The repopulation procedure extends the subhalo population to much lower masses than those resolved by Auriga, under two subhalo survival scenarios, namely fragile and resilient. Using the CLUMPY public code, we calculate the DM signal of each subhalo and construct HEALPix all-sky templates. The pipeline combines the smooth Galactic halo and subhalo components, separates spatially extended from point-like objects, and applies halo-by-halo corrections for consistent map normalization. These templates will be made publicly available as inputs for gamma-ray DM analyses, enabling studies of Galactic DM signal morphology and its dependence on different subhalo survival assumptions with observatories such as Fermi-LAT and CTAO.

Speaker: Julia Mamprim

A New Generation of All-Sky Galactic Dark Matter Templates for Gamma-Ray Searches-3.pdf

10:45 → 11:30 Coffee break

11:30 → 12:40 Indirect - gammas & cosmic rays: (II)

11:30 Unidentified Sources in the 4FGL-DR4 Fermi-LAT Catalog as Potential Dark Matter Subhalos

We explore the prospects for indirect dark matter (DM) detection through gamma-ray emission from the annihilation of weakly interacting massive particles (WIMPs). Within the ΛCDM cosmological framework, hierarchical structure formation predicts a large population of halos and subhalos that, below ~10⁷ M☉, are expected to be devoid of baryons. If DM consists of WIMPs, annihilation within these dark satellites would yield a gamma-ray signal potentially detectable by Fermi-LAT as unidentified sources (unIDs). We present a systematic search for dark satellite candidates among the 2428 unIDs of the 14-year 4FGL-DR4 Fermi-LAT catalog, applying successive filters on their expected spatial distribution, spectral shape, and multi-wavelength counterparts to isolate a final sample of 77 promising candidates. A dedicated likelihood analysis of these sources, assessed via the Akaike Information Criterion, reveals no statistically significant preference for a DM interpretation. We then derive constraints on the annihilation cross-section by comparing the number of surviving candidates with the predicted population of detectable subhalos from the repopulated VL-II zoom-in simulation. Our limits exclude thermal WIMPs below ~7 GeV in the conservative scenario, reaching ~100 GeV at the sensitivity reach of the method.

Speaker: Fernando Valenciano

FV_unIDs_MD26.pdf

11:50 Stellar streams as targets for indirect dark matter searches

In this talk, we summarize our research on stellar streams as a new and complementary target for dark matter (DM) searches with gamma rays.

Stellar streams whose progenitor is a dwarf galaxy (dG) are particularly interesting targets for DM searches, since dGs are thought to be highly DM-dominated systems. We expect these streams to have lost most of their DM content during the stretching process, yet a significant amount of DM should remain within their core. If the DM particles are Weakly Interacting Massive Particles (WIMPs), they could annihilate in the streams’ core, producing a detectable gamma-ray signal. In this work, we analyze data from the Large Area Telescope on board the NASA Fermi satellite (Fermi LAT) to look for a potential WIMP annihilation signal from the direction of an optimized sample of streams. In the absence of a signal, we place the first constraints on the WIMP parameter space obtained from these objects for several annihilation channels.

A key challenge in this analysis is the uncertainty in the DM density profile of the streams, which directly impacts the expected gamma-ray flux. To address this issue, we will also present our ongoing work in which we are using the Auriga suite of high-resolution hydrodynamical simulations to model the DM distribution within disrupted dG streams. These simulations provide a more robust framework for interpreting our results and refining future DM searches with stellar streams.

Speaker: Cristina Fernández Suárez

MD2026_Streams_CristinaFernandezSuarez.pdf

12:10 Gamma-ray dark matter searches circa 2026: status and future prospects

The nature of dark matter (DM) in the Universe remains one of the greatest mysteries of our time. Searches for annihilation or decay products of DM particle candidates such as WIMPs have already provided stringent constraints on their properties across a wide range of masses and interaction channels. In this review talk, I will summarize the current status of these ‘indirect’ DM searches in gamma rays. I will highlight key targets, current limitations, and the role of systematic uncertainties. I will then discuss future prospects for DM sensitivity with upcoming experiments as well as emerging opportunities for exploring DM signatures in gamma rays.

Speaker: Miguel Ángel Sánchez Conde

Gammas&DMstatus_masc_MD_170626.pdf

12:40 → 14:30 Lunch & Discussions

14:30 → 15:20 Indirect - gammas & cosmic rays: (III)

14:30 Light dark matter searches with space- and Moon-based radio telescopes

Ground-based radio telescopes are routinely used to search for light dark matter candidates such as axion-like particles or dark photons.
However, these instruments face inherent limitations in probing masses
below eV, due to the effect of the Earth's ionosphere. Current and planned space- or Moon-based radio telescopes can overcome this limitation and open a largely unexplored discovery space. In this talk, I will present a systematic sensitivity study of resonant dark-matter conversion into radio signals in three nearby astrophysical environments: the Sun, the Earth, and Jupiter. I will first discuss the intrinsic limitations set by environmental noise for space-based observations, and then derive sensitivity projections for the parameter space of the two candidates using existing and planned instruments. I will show that particularly strong prospects arise for dark-photon searches using the Sun as a target, and for axion-like particle conversion in Jupiter’s magnetosphere.

Speaker: Ruben Zatini

MultiDark_presentation.pdf

14:50 Cosmic Rays in the search for Dark Matter

Dark matter constitutes most of the matter content of the Universe, yet its particle nature remains unknown. Charged cosmic rays provide a powerful avenue to search for possible dark matter signatures through anomalous contributions to the observed fluxes of antimatter. In this talk, I will discuss the status of indirect dark matter searches across multiple cosmic-ray channels. After reviewing the main theoretical framework and relevant astrophysical backgrounds, I will present current observational constraints from cosmic-ray measurements and discuss the main associated uncertainties. Finally, I will highlight the potential of cosmic rays to probe dark matter models beyond standard WIMP scenarios.

Speaker: Pedro De la Torre Luque (Institute of theoretical physics (IFT-UAM))

Multidark_DMCRs.pdf

15:20 → 16:10 Indirect - neutrinos: (I)

15:20 Recent results from the KM3NeT neutrino telescope

Speaker: Sergio Navas (Universidad de Granada (ES))

Multidark2026_KM3NeT_SergioNavas_2026-06-17_INDICO.pdf

15:50 WIMP Dark Matter Searches from the Galactic Centre with KM3NeT/ORCA

Speaker: Adriana Bariego-Quintana (IFIC, Valencia.)

MultiDark 2026.pdf

16:10 → 16:55 Coffee break

16:55 → 17:55 Indirect - neutrinos: (II)

16:55 The usual suspect: has a heavy dark matter particle decayed to KM3-230213A?

Speaker: Sara Rebecca Gozzini

Event_display_KM3NeT.mov

MultiDark2026.pdf

17:15 Constrains to sub-GeV dark matter interactions with galactic neutrino observations

Speaker: Pedro De la Torre Luque (Institute of theoretical physics (IFT-UAM))

CRDM-nu_Multidark2026.pdf

17:35 Gamma rays as leptonic portals to energetic neutrinos: a new Monte Carlo approach

Speaker: Gaetano Di Marco

18:00 → 19:30 MD steering committee

Closed meeting, only for node PIs.

Thursday 18 June

09:15 → 10:45 DM theory and Colliders

09:15 Mass-unspecific classifiers for mass-dependent searches (for DM at the LHC)

Searches for new particles often span a wide range of mass scales, where the shape of potential signals and the SM background varies significantly. We make use of a multivariate method that fully exploits the correlation between signal and background features and the explored mass scale, and is trained on a sample that is balanced across the entire mass range. The classifiers, either a neural network or a boosted decision tree, produce a continuous output across the full mass range and, at a given mass, achieve nearly the same performance as a classifier specifically trained for that mass. The performance of the classifiers is better than the one obtained with parameterised neural networks and similar methods. The application for DM searches at the LHC is briefly discussed.

Speaker: Juan Antonio Aguilar Saavedra (Consejo Superior de Investigaciones Científicas (ES))

JAAS.pdf

09:45 Looking for fermionic scotogenic dark matter at the LHC

Weakly interacting massive particles (WIMPs) constitute a paradigm in the search for particle dark matter. In contrast to supersymmetry (SUSY), we explore the possibility that WIMP dark matter acts as mediator of neutrino mass generation. We examine in detail the phenomenology of fermionic dark matter in the revamped (or singlet-triplet) scotogenic model and study its collider implications. Unlike SUSY WIMP dark matter, collider searches for the lightest scotogenic particle at LHC/LHC-HL are strongly complementary to charged lepton flavor violation probes and dark matter studies.

Speaker: Victor Martin Lozano (IFIC/UV)

23MD_vmlozano.pdf

10:15 SUSY DM production at the LHC: GUT based solutions

ATLAS and CMS have observed consistent excesses in the search $pp \to \tilde{\chi}_2^0 \tilde{\chi}_1^\pm \to \tilde{\chi}_1^0 Z^* \, \tilde{\chi}_1^0 W^{\pm *}$. The favored mass ranges are $m_{\tilde{\chi}_2^0} \sim m_{\tilde{\chi}_1^\pm} \ge 200$ GeV and $\Delta m := m_{\tilde{\chi}_2^0} - m_{\tilde{\chi}_1^0} \approx 15-20$ GeV. We interpret these excesses in GUT based scenarios within the NMSSM with the $\tilde{\chi}_1^0$ as dark matter (DM) candidate. We demonstrate that this model can describe the excesses well, while being in agreement with all current experimental constraints, in particular with the DM relic density and the DM direct detection (DD) limits. We briefly analyze the prospects for future DD experiments.

Speaker: Sven Heinemeyer (CSIC (Madrid, ES))

sven.pdf

10:45 → 11:30 Coffee break

11:30 → 12:50 Direct Detection: (I)

11:30 Latest Results from ANAIS-112: Testing DAMA/LIBRA and Constraining WIMP Parameter Space

The ANAIS-112 experiment operated 112.5 kg of
NaI(Tl) detectors at the Canfranc Underground Laboratory (LSC) from August
2017 to January 2026, with the primary goal of performing a modelindependent
test of the annual modulation signal reported by the DAMA/
LIBRA experiment. In addition to the modulation search, the ANAIS-112
dataset is also sensitive to Weakly Interacting Massive Particles (WIMPs)
through model-dependent analyses of the measured energy spectra. In this
talk, we report the latest results of the ANAIS-112 annual modulation
analysis and discuss their implications for the interpretation of the DAMA/
LIBRA result. In addition, we present the exclusion limits in the WIMP mass–
cross-section parameter space, derived using an improved background
model and quenching factors for sodium and iodine obtained from dedicated
onsite neutron calibrations. To assess the impact of the quenching factors,
we also provide results obtained using those adopted by DAMA/LIBRA,
assuming experiment-independent values.

Speaker: Carmen Seoane (CAPA-UZ)

ANAIS_Multidark_CSeoane.pdf

11:50 ANAIS+ status: exploring NaI/CsI scintillating crystals with SiPM readout for dark matter searches at cryogenic temperatures

Scintillation detectors have been widely used in
particle physics. Among them, scintillating crystals are a suitable choice for
dark matter searches thanks to their high light yield, compact detector
design, allowing for large mass experiments with a modular approach, and
interesting combination of different target nuclei. However, they cannot
discriminate nuclear recoils from electron recoils and do not have interaction
position reconstruction capability. In addition, the use of PMTs to read the
scintillation signal introduces significant background contributions and
makes it difficult to lower the energy threshold below 1 keVee, limiting their
sensitivity. ANAIS+ is a project built as a collaboration between University of
Zaragoza, LNGS and CIEMAT which aims to reduce the energy threshold in
NaI and CsI detectors, while improving the radiopurity of the crystals and
using an active veto for background rejection. This would allow to increase
the sensitivity and make ANAIS+ competitive in the searches for light mass
WIMPs with spin-dependent interactions, but it could also enable other
applications, as the study of neutrino-nucleus coherent scattering, for
instance. The experimental approach relies on the replacement of the
classically used PMTs by SiPMs to read the scintillation light. These new
devices have the advantage of a higher quantum efficiency which, combined
with the low dark current level at cryogenic temperatures around 100 K and
the increased light yield of pure crystals at these conditions, could lead to a
significant reduction in the energy threshold. Furthermore, operating the
detector inside a LAr cryostat would serve as a thermal bath and as an
active 4π veto. In this talk we will review the evolution of the different
prototypes and the status of the latest set-up tested at the Underground
Laboratory of Canfranc inside LAr.

Speaker: Jaime Apilluelo Allué

ANAIS+ MultiDark 2026 JaimeAA.pdf

12:10 Probing Freeze-In Dark Matter with Direct Detection

Freeze-in offers a well-motivated production
mechanism for dark matter that interacts very weakly with the Standard
Model. We study MeV-scale fermionic dark matter coupled through vector
portal mediators, including kinetically mixed dark photons and anomaly-free
gauge extensions such as $U(1)_{L_i-L_j}$ and $U(1)_{B-L}$. We explore
the impact of low reheating temperatures on the relic abundance and
identify viable regions of parameter space consistent with current
experimental constraints. We construct benchmark scenarios that illustrate
how upcoming direct detection experiments can probe these models through
both electron and nuclear recoil signals. In particular, for dark matter masses
in the range of 50–500 MeV, large regions of parameter space become
accessible if freeze-in occurs at low reheating temperatures. Furthermore,
enhanced coherent elastic nuclear scattering of solar neutrinos can provide
an additional signature of the new interactions involved. These results
demonstrate that next-generation direct detection experiments can test
freeze-in dark matter scenarios and provide a complementary probe of light
vector mediators connected to dark matter and the neutrino sector.

Speaker: Patrick Foldenauer (Instituto de Física Teórica UAM/CSIC Madrid)

MD_PF.pdf

12:30 Phenomenological implications of CEvNS in dark matter experiments

The recent detection of coherent elastic neutrinonucleus
scattering (CE$\nu$NS) induced by solar $^8$B neutrinos in dark
matter direct-detection experiments signals the onset of the so-called
neutrino fog era and reinforces the role of these detectors as precision lowenergy
neutrino observatories. The latest results from XENONnT, PandaX-4T,
and LUX-ZEPLIN provide new avenues to probe Standard Model physics and
search for possible new interactions, in complementarity with dedicated
neutrino facilities. In this talk, I will discuss the phenomenological
implications of these measurements, including determinations of the weak
mixing angle at low momentum transfer and constraints on heavy and light
mediators beyond the Standard Model. I will also address the consequences
for dark matter direct detection, focusing on the characterization of the
neutrino fog and its implications for future discovery sensitivities.

Speaker: Valentina De Romeri (IFIC CSIC/UV (Valencia, Spain))

De_Romeri_MD_Tenerife26.pdf

12:50 → 14:50 Lunch & Discussions

14:50 → 16:00 Direct Detection: (II)

14:50 Direct Detection of Dark Matter: Highlights from IDM 2026

Despite overwhelming gravitational evidence for dark matter, its particle nature remains unknown. In this review, I will summarize the current status of direct dark matter searches, highlighting the main results and trends discussed at IDM 2026. I will present the present experimental landscape across a broad range of dark matter candidates, from WIMPs to light dark matter and axions, as well as the main technological challenges and future prospects of the field.

Speaker: Maria Martinez

MD26_MMartinez.pdf

15:20 Probing New Neutrino Physics at Dark Matter Detectors: The Impact of CP phase in Solar NSI

As Dark Matter Direct Detection experiments reach
unprecedented sensitivities, they are entering a regime where solar
neutrinos become a prominent and unavoidable signal. While traditionally
viewed as a background, these actually provides a unique opportunity to test
new physics beyond the Standard Model. Traditionally, solar neutrino
oscillations are analyzed using standard matter effects. In this talk, I will
explore a more complex scenario: how Non-Standard Interactions (NSI)
between neutrinos and solar matter could alter the signals we expect to see
in dark matter detectors. Specifically, I investigate the physical effects of
introducing the CP-violating phase, and the interplay between this phase and
the complex NSI terms necessitates the introduction of a new complex phase
into the neutrino mixing matrix. This addition makes the evolution of
neutrinos through the Sun's varying density profile significantly more
intricate. I will present a general framework for tracking this journey,
highlighting a careful analysis to prove that the neutrino propagation
remains smoothly adiabatic. Understanding how these non-standard effects
modify the final flavor composition of the neutrinos reaching our detectors is
crucial, as it directly impacts the expected coherent scattering rates, turning
direct detection experiments into powerful observatories for new neutrino
physics.

Speaker: Valeria Costa (IFT-UAM-CSIC)

NSI_MultiDark_CostaValeria.pdf

15:40 Optimising ultra-light dark matter searches with ground-based interferometers

Ultra-light dark matter fields can induce nearly monochromatic signals in gravitational-wave detectors through their coupling to the Standard Model. In this talk, I will discuss the distinctive spectral features produced by sidereal modulation which, at frequencies below ∼30 Hz, enable discrimination between spin-1 and spin-2 fields. In the context of Earth-based gravitational-wave detector search techniques, we show that current excess-power and cross-correlation methods are not implemented in their optimal configuration. Projected updates to existing constraints indicate improvements of up to ∼36% at low frequencies. Additionally, we propose an optimized implementation of the cross-correlation statistic within the Band-Sampled-Data framework, enhancing the sensitivity of cross-correlation analyses across nearly the entire frequency range, with gains reaching up to ∼42% at low frequencies and ∼35% at high frequencies.

Speaker: Dr Ornella Juliana Piccinni (IFAE)

ULDM_Multidark.pdf

16:00 → 16:40 Coffee break

16:40 → 17:40 Cosmology: (I)

16:40 Environment-conditioned subhalo boosts: reducing systematics in indirect dark-matter forecasts

Indirect searches for dark matter rely on accurate astrophysical modelling of the annihilation (or decay) signal, where unresolved subhaloes are commonly summarized by a subhalo “boost factor”. Current boost prescriptions are typically calibrated as functions of host halo mass and internal structure, while ignoring the large-scale environment that shapes halo assembly, accretion geometry, and tidal histories.

I will show results from N-body simulations demonstrating that the boost factor is systematically modulated by cosmic-web environment. At fixed host mass, haloes in filaments and knots exhibit distinct subhalo abundances and radial distributions relative to haloes in sheets and voids, producing environment-dependent changes in the predicted annihilation luminosity. These effects naturally arise from anisotropic infall and different merger and stripping histories in the web. The resulting scatter and bias can propagate into targets of interest for gamma-ray searches (clusters, groups, Milky-Way analogs), and can mimic changes usually attributed to concentration scatter or subhalo disruption modelling.

Finally, I will outline a compact prescription for “environment-conditioned” boost factors and show how it can be folded into existing indirect-detection forecasts with minimal overhead, enabling more realistic uncertainty budgets and sharper target ranking.

Speaker: Dr Wojciech Hellwing (Center for Theoretical Physics of PAS)

Boost factor CWEB.pdf

17:00 Modelling the Non-linear regime of Angular Redshift Fluctuations

Angular redshift fluctuations (ARF) are a recently introduced cosmological observable (Hernández-Monteagudo, Chaves-Montero, & Angulo, MNRAS, 2021) shown to exhibit several significant properties: complementarity with spatial clustering in two dimensions; sensitivity to parameters such as galaxy bias, cosmological growth rate and inflationary local non-gaussianity; and robustness against both multiplicative and additive systematics. Up until now, the entirety of the theoretical description of ARF has been limited to the first order of cosmological perturbation theory, where only linear terms in the density contrast of matter or halos, as well as in the peculiar velocities and gravitational potentials, are considered. This linear approximation imposes a restriction to large scales, hence discarding valuable cosmological information contained in shorter-wavelength matter modes below the non-linear scale 1/k_NL ∼ 60 Mpc/h, which is expected to be highly significant.

Given that the sensitivity to cosmological parameters provided by ARF on scales larger than 60 Mpc/h is already comparable to that achieved by other analyses using different standard statistics, where notoriously smaller scales, down to 25 Mpc/h, are included, it is promising to extend the theoretical modeling of ARF into the moderately non-linear regime.

In this work, we present a physically-motivated parametric model for the non-linear regime of ARF, also applicable to galaxy clustering or angular density fluctuations (ADF), as well as to both dark matter and galaxy populations. By fitting this model to N-body simulations using Markov Chain Monte Carlo (MCMC) algorithms, we infer the parameter values that best reproduce the angular power spectrum coefficients extracted from the simulations across different redshifts and Gaussian shell widths, taking into account the tomographic nature of these cosmological observables. Our results show that the implementation of this model significantly improves the agreement between theoretical predictions and simulation measurements of ADF and ARF, thus enabling the use of ARF as a cosmological probe on smaller scales.

Speaker: Alba Crespo Pérez

Talk Slides Multidark Alba Crespo.pdf

17:20 Differentiable Forward Modeling for Field-Level Inference of the Cosmic Web

Extracting maximal cosmological information and reconstructing the underlying dark matter distribution from galaxy redshift surveys requires differentiable forward models that couple dark matter structure formation with an accurate tracer bias prescription. We present a framework, implemented in JAX, that combines fast LPT-based approximate gravity solvers with the hierarchical cosmic-web galaxy bias model HICOBIAN—a nonlinear, nonlocal, and stochastic bias prescription that connects observable tracers to distinct dark matter environments classified by the local tidal field. We extend this framework to include cosmology-dependent initial power spectrum generation, enabling the joint gradient-based inference of the primordial initial conditions, bias parameters, and cosmological parameters via Hamiltonian Monte Carlo sampling. We present preliminary results from our application to N-body dark matter halo catalogues, discussing challenges in parameter degeneracies and the role of the approximate gravity solver in accurately capturing the nonlinear dark matter cosmic web.

Speaker: Pere Roselló (IAC/ULL)

Multidark Slides Pere Rossello Final.pdf

20:00 → 23:00 Social dinner (El Drago)

Please be at 19:45 at
https://maps.app.goo.gl/6grbnz2mYFPa5dtPA
Bus will leave at 20:00 sharp!
Bus will return to the same spot at 23:30 approximately

Friday 19 June

09:45 → 11:25 Cosmology: (II)

09:45 Local Group dwarf galaxies as dark matter probes

Astrophysical observations are crucial probes of the fundamental nature of dark matter. In fact, to date, the most compelling inferences for the existence of dark matter comes from astrophysical and cosmological observations. Local Group dwarf galaxies are widely considered among the most crucial gravitational probes of dark matter, since, for instance, they sit at the low mass end of the galaxy mass function, where the LambdaCDM paradigm is put more severely under test. In this talk, I propose to give an overview of our group's activities, which range from dark matter inferences in Local Group dwarf galaxies from dynamical modeling, to investigating various effects that can affect those inferences and assembling/dealing with the necessary observational data.

Speaker: Dr Giuseppina Battaglia (IAC)

MULTIDARK2026_battaglia.pdf

10:05 Hunting for dark matter and black holes with GravSphere2

We introduce GravSphere2, an improved, state-of-the-art Jeans modeling framework designed for dynamical inferences of dark matter and black holes in stellar systems. We show examples of how this can be applied to infer the dark matter distribution of nearby dwarf galaxies and show a recent case for the detection of an ellusive intermediate-mass black hole in a globular cluster.

Speaker: Andres Bañares Hernandez (Instituto de Astrofísica de Canarias)

MULTIDARK_GS2_Presentation_ABanares.pdf

MULTIDARK_GS2_Presentation_ABanares.pptx

10:25 The search for gravitational wave emission from ultra-light boson clouds around rotating black holes.

Ultra-light bosons can extract angular momentum from rotating black holes through a superradiance process, forming macroscopic ``clouds’’. Once the black hole angular momentum decreases below a threshold, the superradiance stops and the cloud depletes over time mainly through the annihilation of bosons into gravitons, generating long-duration periodic gravitational waves. For boson masses in the range 1E-14 — 1E-11 eV, and stellar mass black holes, the emitted signals have frequency in the sensitivity band of Earth-bound interferometric gravitational wave detectors. In this talk I will present an overview of recent results obtained in the search of such kind of signals in LIGO-Virgo-KAGRA data. Some important open issues and prospects for the future will be also discussed.

Speaker: Cristiano Palomba

gw_boson_clouds.pdf

10:45 A new halo boundary: the accretion radius

Subhalos are typically considered as such once they have first crossed the virial radius of the host halo. However, in most cases, they have already undergone tidal stripping before reaching that point. This means that subhalos do not exhibit an NFW density profile when accretion is assumed. In this work, we explore the typical distance at which subhalos are accreted in a Milky Way-like galaxy, from now on the accretion radius, defining accretion time as the first time when the subhalo has been impacted by the host.

To do this, we employ the Auriga simulations, a suite of state-of-the-art hydrodynamical zoom-in simulations of Milky Way-like systems, and investigate the effect of the host on dark matter subhalos. We study different parameters, including the maximum subhalo mass, the mass loss, and the tidal radius.

Although it is still a work in progress, the first results show that the accretion radius found is systematically larger than the virial radius, which in turn implies that the accretion redshift is earlier than is usually assumed. This would have an impact on indirect dark matter searches, since subhalos would be more stripped and thus more concentrated than expected.

Speaker: ALEJANDRA AGUIRRE-SANTAELLA (Institute for Computational Cosmology, Durham University)

Subhalo accretion jun 2026 MD.pdf

11:05 Ultra-deep astronomical imaging to probe the dark matter properties

Over the last 20 years, our ability to scrutinize the faintest objects in the night sky has improved a hundredfold. Thanks to this progress, structures that were previously invisible can now be systematically studied. In this talk, I will explain the new scientific possibilities they offer. In particular, I will discuss the new galaxies being discovered and their relevance to understanding the nature of dark matter.

Speaker: Dr Ignacio Trujillo Cabrera (IAC)

TrujilloMultidark2026.pdf

11:25 → 11:55 Coffee break

11:55 → 13:15 Cosmology: (III)

11:55 Constraining the ARCADE-2 excess with QUIJOTE and WMAP data

The ARCADE-2 experiment detected in 2011 an amount of radio flux at the Gigahertz range that lies about 4 or 5 times above expectations for the extra-galactic radio source population. Likewise, that excess seems incompatible with standard Galactic radio mechanisms like synchrotron or free-free emission, and consequently controversy has arosen in the last decade about the origin of this radio signal and its possible link to dark matter. By using the difference of QUIJOTE sky temperature maps obtained at 11 and 13 GHz we attempt to (1) remove the CMB contribution, (2) identify and isolate high Galactic radio emission regions, and (3) build a map of steep extra-galactic radio emission. We cross correlate this map with extra-galactic surveys, finding significant correlation to maps built upon the NVSS radio catalogue, the eBOSS QSO catalogue, and the Planck CMB lensing convergence. This correlation not only allows us constraining the redshift and the clustered amplitude of this extra-galactic radio background, but also, under the assumption of a typical synchrotron spectral index of ~-2.65, its contribution to the radio monopole measured by ARCADE-2. Our results suggest that the this extra-galactic radio background contributes to the 20-30% of the ARCADE-2 excess, thus discarding an origin for this signal that is fully traced by the large scale structure sampled by our surveys. This allows us concluding that the ARCADE-2 excess is either of Galactic origin, or extra-galactic but of (quasi-)isotropic character.

Speaker: Carlos Hernandez Monteagudo

chm_extragalRadio.pdf

12:15 Mapping Dark Matter Through Stellar Wakes

Stellar wakes generated by massive satellites moving through the Milky Way’s halo offer a promising avenue to infer the properties of their dark matter haloes. Extracting such information, however, requires accurate theoretical descriptions of the wake structure. We investigate the formation of wakes using windtunnel simulations in which a perturber, mimicking the dark matter halo of the Large Magellanic Cloud, moves through a collisionless background medium. We compare the time evolution of the background response with predictions from linear perturbation theory based on analytical steady-state solutions of the collisionless Boltzmann equation and find clear differences between the two. As a consequence, applying steady-state analytical wake models to evolving systems can bias inferences of satellite properties. Our results highlight the need for improved prescriptions of wakes if they are to be used as robust dynamical probes of dark matter substructure in our Galaxy.

Speaker: María Benito Castaño

mariabenito-multidark-June26.pdf

mariabenito-multidark-June26.pptx

12:35 The Energy Minimization Principle for Dark Matter Haloes

Inferring abundance, position and size of cosmic structures  from the initial conditions is a long standing effort in theoretical cosmology. It allows (semi-)analytical predictions of mass function, bias and correlation
functions of dark matter haloes, and an intuitive understanding of the
formation of the cosmic web, a complementary tool to numerical simulations.
Standard methods assume that dark matter haloes  originates from critically high peaks of the initial matter density  field, which act as seeds for the structure formation process. Although simpe and intuitive, this approach suffers from numerical and  conceptual inconsistencies. I will review the standard analytical methods, highlighting their  advantages and shortcomings.
I will then show how many difficulties can be  overcome by focusing on the initial energy of the protohalo patch, rather  than its mean density. This approach improves substantially the results of protohalo abundance  and mass, and provides a first-principles prediction for protohalo shapes.

Speaker: Prof. Marcello Musso (Universidad Salamanca)

MultiDark-Musso.pdf

12:55 ELGxLRG distribution through dark matter halo dynamics

Upcoming and ongoing spectroscopic surveys, such as DESI, Euclid or PFS, are delivering high-precision measurements of galaxy clustering across multiple tracers, pushing theoretical models to accurately capture both large-scale bias and small-scale galaxy–halo physics. In this talk, I will present a comprehensive analysis of the clustering of DESI Y1 emission-line galaxies (ELGs) and luminous red galaxies (LRGs) at redshift 0.8 < z < 1.1, including their cross-correlation, using a new hybrid Halo Occupation framework designed for multi-tracer populations: HOMe.

In particular, HOMe combines physically motivated prescriptions for intra-halo dynamics, halo exclusion, and quenching, and bridges insights from hydrodynamical simulations, traditional HODs, abundance matching, and semi-analytic models. By leveraging full phase-space information from the Uchuu N-body simulation and populating halos with satellites from dark-matter particle positions, the model reproduces the anisotropic galaxy clustering down to 200h-1kpc scales with unprecedented accuracy.

I will show how a two-level Bayesian inference pipeline allows us to constrain all model parameters using only two-point statistics, yielding high-fidelity ELG, LRG, and cross-tracer reference catalogs. The analysis reveals that satellite ELGs exhibit incoherent orbital motions that dominate the anisotropic clustering below 4h-1Mpc, while the ELG×LRG signal on intermediate scales is shaped by central–central pairs and halo exclusion effects. The inferred halo occupation highlights distinct central and satellite populations and a non-trivial role for orphan galaxies.

These results demonstrate the power of physically grounded multi-tracer modeling to interpret small-scale clustering, control systematics, and open new avenues to probe the dynamical nature of dark matter and test gravity with next-generation surveys.

Speaker: Dr Ginevra Favole (ULL/IAC)

GFavole_MIRACLE_MultiDark.pdf

13:15 → 14:15 Lunch

17:00 → 18:00 Charla pública MCC: Rayos gamma para descifrar el enigma de la materia oscura en el Universo

Los enormes avances producidos en la astrofísica de altas energías a lo largo de los últimos años han desvelado un inesperado y furioso ‘bestiario’ cósmico lleno de sorpresas: insaciables agujeros negros súper masivos morando en el centro de casi todas las galaxias, colosales explosiones de estrellas con decenas de veces la masa de nuestro Sol, estrellas de neutrones actuando como viudas negras en sistemas estelares dobles… Esta revolución ha sido posibles gracias a potentes telescopios de rayos gamma situados tanto en órbita como en tierra, por ejemplo Fermi-LAT y MAGIC. Por si fuera poco, los rayos gamma pueden ser la clave para descifrar uno de los mayores desafíos de la ciencia contemporánea: la naturaleza de la enigmática materia oscura, que se cree compone más del 80% del contenido de materia en el Universo y de la que sin embargo aún desconocemos casi todo. En esta charla, nos asomaremos al Universo para asombrarnos con su cara más violenta, más oscura y menos conocida a la luz de los rayos gamma.

Speaker: Miguel Ángel Sánchez Conde