Dark matter and black holes

1 Dec 2025, 08:00 → 5 Dec 2025, 18:00 Asia/Tokyo

Lecture Hall (Kavli IPMU)

Dark matter and black holes

This workshop will bring together astronomers, cosmologists, and particle physicists to discuss the fascinating connections between black holes and dark matter.   What can be learned from the intertwined cosmological histories of dark matter and black holes?  What are the interactions and observational consequences of various dark matter candidates in the presence of black holes? Is dark matter composed of black holes?  Was the formation of supermassive black holes influenced by dark matter?  Can dark matter cause neutron stars to collapse into black holes?   Can black hole observations reveal the particle properties of dark matter?   We hope to shed light on these and other questions that surround the profound mysteries of black holes and dark matter.

Dates

1-5 December, 2025

Topics

• Microlensing search for primordial black holes (PBH)   

• Astronomical observations of supermassive black holes.  

• WIMPs and black holes.  

• Axions and black holes

• Formation of PBHs.  

• Interactions of PBHs with compact stars as means for their detection

Speaker List

Invited speaker list (alphabetical order; as of 24/March/2024):

• George Fuller - UCSD
• Shunsaku Horiuchi - Institute of Science Tokyo
• Kazunori Kohri - NAOJ
• Sachiko Kuroyanagi - IFT, Madrid
• Yifan Lu - UCLA
• Shigeki Matsumoto - Kavli IPMU
• Lucio Mayer - University of Zurich
• Smadar Naoz - UCLA
• Stefano Profumo - UCSC
• Sunao Sugiyama - University of Pennsylvania
• Surjeet Rajendran - JHU
• John Silverman - Kavli IPMU
• Masahiro Takada - Kavli IPMU
• Jonathan Tan - Chalmers University, Virginia
• Haibo Yu - University of California, Riverside
• Michael Zantedeschi -  INFN, Pisa

On-site Venue

The on-site workshop will take place at the Lecture Hall of Kavli IPMU, The University of Tokyo, Kashiwa Campus (5-1-5, Kashiwanoha, Kashiwa-shi, Chiba, 277-8584, Japan).

Online Venue

This symposium will be held in a hybrid format. 

Zoom information: https://u-tokyo-ac-jp.zoom.us/j/89334536331?pwd=RfAhHqx0oy9GQ5aVY5Nz3Hluaiiws2.1

Meeting ID: 893 3453 6331; Passcode: 678360

Registration Fee

free

Organizers

• Elisa G. M. Ferreira (Chair)
• Alexander Kusenko (Co-Chair)
• Shigeki Matsumoto
• Tom Melia
• Hitoshi Murayama
• Misao Sasaki
• Satoshi Shirai
• John Silverman
• Masahiro Takada
• Junichi Yokoyama

Contact

DM_BH_workshop2025@ipmu.jp

Sponsors

img KavliIPMU-logo_posi_short.png WPI_symbolmark.png

pdf FloorMap.pdf Posters.pdf

Monday 1 December

09:00 Registration

09:30 Coffee break/Discussion

Opening Remark

DM_BH_intro.pdf

Plenary 1-2: Surjeet Rajendran and Jonathan Tan

Convener: Chair: Tom Melia

1 Conservative Thoughts on Black Holes

Speaker: Surjeet Rajendran

PBH.pdf

2 The Origin of Supermassive Black Holes from Pop III.1 Seeds and Implications for Particle Physics and Cosmology

The origin of supermassive black holes (SMBHs) is a key open question for contemporary astrophysics and cosmology. Here we discuss the predictions of a model of SMBH formation from Pop III.1 protostars, i.e., metal-free stars forming in locally isolated dark matter minihalos, where dark matter annihilation has a chance to alter the structure of the star allowing growth to supermassive scales (Banik, Tan & Monaco 2019; Singh, Monaco & Tan 2023; Cammelli et al. 2025; Nandal et al. 2025; Sanati et al. 2025a,b; for a review see Tan et al. 2024 and this project page: http://cosmicorigins.space/smbh). The model predicts that all SMBHs form very early in the Universe (i.e., by z ~ 20) with a spatial distribution that is initially relatively unclustered. It also makes predictions for SMBH occupation fractions, host galaxy properties, frequency of binary SMBHs and the gravitational wave background. These predictions are compared to latest results from the Hubble Space Telescope, James Webb Spact Telescope and pulsar timing array observations. Another key prediction of the model is an early phase of “flash” ionization of the universe at z~20, which can help alleviate cosmological tensions (Hubble tension, dynamical dark energy, negative neutrino masses) (Tan 2025; Komatsu & Tan 2025). Finally, since the Pop III.1 mechanism relies on the process of WIMP dark matter self-annihilation, there are implication for the nature of the dark matter particle.

Speaker: Jonathan Tan

Coffee break

Contributed talks

Convener: Chair: Yannis Georis

3 Searches for dark sector particles at Belle and Belle II

I will give an update on important and recent results on dark sector particle searches at Belle and Belle II

Speaker: Sourav Dey

4 Finding Macroscopic Dark Matter

Speaker: Zachary Picker

5 Fermionic freeze-in from flavon portal

We investigate the phenomenology of a non-thermal dark matter (DM) candidate in the context of flavor models that explain the hierarchy in the masses and mixings of quarks and leptons via the Froggatt-Nielsen (FN) mechanism. A flavor-dependent U(1)FN symmetry explains the fermion mass and mixing hierarchy, and also provides a mechanism for suppressed interactions of the DM, assumed to be a Majorana fermion, with the Standard Model (SM) particles, resulting in its FIMP (feebly interacting massive particle) character. Such feeble interactions are mediated by a flavon field through higher dimensional operators governed by the U(1)FN charges. We point out a natural stabilizing mechanism for the DM within this framework with the choice of half-integer U(1)FN charge n for the DM fermion, along with integer charges for the SM fermions and the flavon field. In this flavon portal scenario, the DM is non-thermally produced from the decay of the flavon in the early universe which becomes a relic through the freeze-in mechanism. We explore the allowed parameter space for this DM candidate from relic abundance by solving the relevant Boltzmann equations. We find that reproducing the correct relic density requires the DM mass to be in the range (100−300) keV for n=7.5 and (3−10) MeV for n=8.5 where n is the U(1)FN charge of the DM fermion.

Speaker: Nandini Das

12:20 Lunch

Plenaries 3: Kazunori Kohri

Convener: Chair: Misao Sasaki

6 Verifying primordial black holes as dark matter by mergers, evaporation, and occasionally the memory burden effect

I will discuss methods for verifying primordial black holes to be dark
matter in terms of mergers, evaporation, and occasionally the memory
burden effect

Speaker: Kazunori Kohri

15:00 Coffee break

Contributed talks

Convener: Chair: Satoshi Shirai

7 Bosonic dark matter dynamics in neutron stars

Excessive dark matter (DM) capture in neutron star (NS) via DM-nucleon scattering, leads to transmutation of NS into solar mass black hole. The formation of such black hole depends on the thermal properties of captured DM particles, particularly if DM particles are bosons. In this work, we study the capture of bosonic particle and subsequent dynamics inside the star, taking the NS temperature evolution into account. In particular, formation of Bose-Einstein condensate (BEC) out of DM particles have been studied along with its consequence on the subsequent black hole formation. We have shown distinct upper bounds on the DM-nucleon cross-section for both BEC and non-BEC scenarios from the existence of old NS. From our dynamical analysis, we find that the DM-nucleon cross-section for DM masses at the electroweak scale is unbounded from NS observations, thereby the direct detection experiments remain important at this regime.
Ref : K. Dutta, D. Ghosh, B. Mukhopadhyaya, JCAP 12 (2024) 053, arxiv: 2408.16091

Speaker: Deep Ghosh

8 A Dark Matter Probe in Accreting Pulsar–Black Hole Binaries

The accretion of dark matter (DM) into astrophysical black holes slowly increases their mass. The rate of this mass accretion depends on the DM model and the model parameters. If this mass accretion effect can be measured accurately enough, it is possible to rule out some DM models, and, with the sufficient technology and the help of other DM constraints, possibly confirm one model. We propose a DM probe based on accreting pulsar-black hole binaries, which provide a high-precision measurement on binary orbital phase shifts induced by DM accretion into black holes, and can help rule out DM models and study the nature of DM.

Speaker: Ali Akil

9 Dark matter spikes with strongly self-interacting particles

An unavoidable prediction of scenarios with Dark Matter (DM) self-interactions is the existence of number changing processes that convert $n$ initial DM particles into $m$ final ones ($n\to m$ processes), possibly accompanied by Standard Model particles. We argue that the $n\rightarrow m$ processes could be probed in DM spikes at the center of galaxies, where the high density may allow sizable rates. We systematically study the implications of the $n \to m$ processes in DM spikes, including other possible interactions involving DM, such as annihilation and self-scattering. We find that for $n\geq3$, the spike is significantly depleted for $n\to m$ cross-sections favored by DM production via thermal freeze-out. On the other hand, the semi-annihilation of two DM particles into one DM particle and one Standard Model particle preserves in general the structure of the spike. Such density modifications significantly affect phenomenological studies of both astrophysics and particle DM processes around DM spikes.

Speaker: Takashi Toma

Tuesday 2 December

09:30 Coffee break/Discussion

Plenaries 4-5:George Fuller and Yifan Lu

Convener: Chair: Elisa Ferreira

10 Supermassive Stars: evading (temporarily!) the inevitable with Dark Matter

Speaker: George Fuller

IPMU-Fuller.pdf

11 Dark Matter and the Formation of Direct Collapse Supermassive Black Holes

The surprising abundance and properties of supermassive black holes (SMBHs) observed at high redshifts have opened a new window into the interplay between cosmology and dark matter physics. While explaining how SMBHs are assembled within the first few hundred million years after the Big Bang remains a major challenge, an attractive route is the direct collapse of pristine, metal-free gas clouds, provided that catastrophic cooling and fragmentation of the cloud are effectively suppressed. In this talk, I will present several mechanisms through which the dark sector can give rise to the conditions necessary for direct collapse. Energy injection from evaporating primordial black holes or photon emission from decaying relic particles, such as axion-like particles or Majorons, can sustain the monolithic collapse of protogalaxies, suggesting a potential link between the origin of early SMBHs and the underlying physics of the dark sector.

Speaker: Yifan Lu

IPMU 2025.pdf

Coffee break

Contributed talks

Convener: Chair: Elisa Ferreira

12 20 GeV halo-like gamma-ray excess: dark matter annihilation?

Fifteen years of the Fermi Large Area Telescope (LAT) data in the halo region of the Milky Way (MW) are analyzed to search for gamma rays from dark matter annihilation. Gamma-ray maps within the region of interest (|l| < 60 deg, 10 < |b| < 60 deg) are modeled using point sources, the GALPROP models of cosmic-ray interactions, isotropic background, and templates of Loop I and the Fermi bubbles, and then the presence of a halo-like component is further examined. A statistically significant halo-like excess is found with a sharp peak around 20 GeV, while its flux is consistent with zero below 2 GeV and above 200 GeV. Examination of the fit residual maps indicates that a spherically symmetric halo component fits the map data well. The radial profile agrees with annihilation by the smooth NFW density profile, and may be slightly shallower than this, especially in the central region. Various systematic uncertainties are investigated, but the 20 GeV peak remains significant. In particular, the halo excess with a similar spectrum is detected even relative to the LAT standard background model, which does not depend on GALPROP or other model templates. The halo excess can be fitted by the annihilation spectrum with a mass m_χ∼ 0.5-0.8 TeV and annihilation cross section <sigma v> ∼ (5-8)×10^{-25} cm^3 s^{-1} for the bb¯ channel. This cross section is larger than the upper limits from dwarf galaxies and the canonical thermal relic value, but considering various uncertainties, especially the density profile of the MW halo, the dark matter interpretation of the 20 GeV ``Fermi halo'' remains feasible. The prospects for verification through future observations are briefly discussed. (preprint: arXiv:2507.07209, JCAP in press)

Speaker: Tomonori Totani

13 Vacuum relics in ultra-slow-roll inflation

We study the formation of vacuum bubbles in ultra-slow-roll inflation. Our results show that these bubbles play a significant role in the dynamics of the system and provide an important contribution to the primordial black hole population, potentially accounting for a substantial fraction of dark matter.

Speaker: Albert Escrivà

12:20 Lunch

Plenaries 6-7: Sachiko Kuroyanagi and Stefano Profumo

Convener: Chair: Alex Kusenko

14 LVK O4a Constraints on Primordial Black Holes

I will review various methods for constraining primordial black holes through gravitational wave observations and discuss the latest results from the O4a run of the LIGO-Virgo-KAGRA collaboration.

Speaker: Sachiko Kuroyanagi

Kuroyanagi.pdf

15 Planck relics as dark matter

I will survey scenarios that produce Planck-mass relics and assess whether they can stably carry electric, magnetic, or dark charge. I’ll examine charge retention and neutralization in the late Universe (including Schwinger discharge and plasma capture), and highlight quantum-gravity effects near extremality—especially for magnetically charged and near-extremal black holes. Finally, I’ll outline concrete detection avenues.

Speaker: Stefano Profumo

Profumo_2025102_IPMU.pdf

15:00 Coffee break

Contributed talks

Convener: Chair: Xinpeng Wang

16 Exotic defect dynamics in axion cosmology

We investigate an early history in which topological defects are dynamical within an axion cosmology post-inflation, motivated by the increasing popularity of models predicting primordial black holes formed of defects contributing to present-day dark matter content. We highlight the capabilities of the axionic context, and identify unique features pertaining to the interactions between defects coexisting at an early time, such as monopole-domain wall systems. In particular, our work aims to emphasise non-standard scenarios supported by well-motivated theories, with which we may probe fundamental physics both observationally and analytically.

Speaker: Yu Komiya

17 PBHs and Dark Matter Regurgitation from First Order Phase Transitions

First order phase transitions can create a large mass gap between the false and true vacua for dark sector particles, effectively trapping them in false vacuum pockets. After an initial contraction phase, these particles coalesce into semi-stable compact objects, thermal balls and Fermi balls. Further cooling of these objects leads to a final collapse into primordial black holes. We show how this formation mechanism leads to two interesting possibilites: late-forming PBHs which could evade CMB bounds and regurgitated dark matter which form the PBHs from which they are re-emitted as Hawking radiation.

Speaker: Philip Lu

18 BSM-enhanced PBH Dark Matter

In this talk I will give an overview of several beyond Standard model theories predicting a large number of additional degrees of freedom. The corresponding softening in equations of state can be significant. I will show that, within these models, it is then possible to achieve a large enhancement in PBH abundance on scales relevant for PBHDM; namely, the asteroid mass and memory burden windows.

Speaker: Xavier Pritchard

Poster presentation

Koustav Mukherjee - Electroweak Phase Transition in Two Scalar Singlet Model with pNGB Dark Matter
Jie Sheng - Torsion Balance Experiments Enable Direct Detection of Light Dark Matter
Koki Tokeshi - Coloured Noises and Primordial Black Holes
Subaru FUJISAWA - TBA
Zachary Picker - Dark Matter Hail

Conveners: Jie Sheng, Koki Tokeshi, Koustav Mukherjee, Subaru FUJISAWA, Zachary Picker

Wednesday 3 December

Discussions and collaborative work

12:00 Lunch break

15:00 IPMU tea time

Thursday 4 December

09:30 Coffee break/Discussion

Plenaries 8-9: Lucio Mayer and John Silverman

19 The role of dark matter in the origin and dynamical evolution of massive black binaries towards the LISA band

The typical binaries of massive black holes that the LISA gravitational wave detector will observe
are in the range 10^4-10^6 solar masses. In the low redshift Universe, observations of active
galactic nuclei and other types of sources suggest that such black holes preferentially reside
in dwarf galaxies. Dwarf galaxies are notoriously dark matter dominated down to their cores. I will
show how the process of pairing and binary formation of massive black holes inside dwarf galaxies
is heavily affected by the dark matter density profile. This, in turn, carries information on the nature
of dark matter, with the caveat that baryonic physics effects might also play a role in shaping the
evolution of dwarf galaxies' dark matter profiles. In particular, successful formation of a binary of massive black holes seems to be disfavoured in cored dark matter profiles, which are predicted in
some dark matter models alternative to Cold Dark Matter. The rate of LISA sources as a function
of redshift might thus carry precious information on the nature of the host dark matter halos.
I will conclude with a digression on another important aspect, also relevant to GW astronomy,
namely how dark matter might have influenced, directly or indirectly, the formation of the seeds
of massive black holes at high redshift.

Speaker: Lucio Mayer

20 TBA

Speaker: John Silverman

Coffee break

Contributed talks

Convener: Chair: Nivedita Ghosh

21 Primordial Black Hole formation from power spectrum with finite width

Primordial black holes (PBHs) can form from gravitational collapse of large over-
densities in the early Universe, giving rise to rich phenomena in astrophysics and cosmology. We develop a novel, general, and systematic method based on theory of density contrast peaks to calculate the abundance of PBHs for a broad power spectrum of curvature perturbations with Gaussian statistics. We introduce a window function to account for the relevant perturbation scales associated with PBHs of different masses, along with a filter function that removes unphysical contributions from super-horizon-scale overdensities. While some uncertainties remain due to the limited understanding of the nonlinear collapse process, our approach substantially reduces the discrepancy previously observed between peaks theory and the Press–Schechter formalism.

Speaker: Jianing Wang

22 When Tiny Halos Stir Spacetime: Gravitational Waves from the Fifth Forces

Dark matter fermions interacting via attractive fifth forces mediated by a light mediator can form dark matter halos in the very early Universe. Motivated by the scenario, we discovered that the bound systems composed of such halos, even very light, are capable of generating Gravitational Wave (GW) signals detectable today.
Due to the additional strong force that contributes to the acceleration of the orbit, such binaries can lead to strong gravitational waves with initially extremely high frequencies--and cosmological redshift shifts these signals into the observable frequency bands today, i.e., the PTA surveys.
The resulting gravitational wave from a single event can carry distinctive features in the waveform that enable future observations to distinguish them from conventional ones solely due to gravitational interaction, providing a new avenue to probe the macroscopic properties of dark matter through gravitational wave observations.

Speaker: Xinpeng Wang

23 Exploring Ultra-Slow-Roll Inflation in Composite Pseudo-Nambu–Goldstone Boson Models: Implications for Primordial Black Holes and Gravitational Waves

We study inflation driven by a scalar potential arising from composite-sector dynamics, inspired by generalized composite Higgs models. The introduction of a non-minimal coupling, possessing the same functional form as the potential, induces a flattening at large field values that enables successful inflation. We analyze the conditions for ultra-slow-roll inflation, which leads to enhanced curvature perturbations, by combining analytical criteria near the inflection point with comprehensive numerical scans of the parameter space. The region consistent with Cosmic Microwave Background constraints and yielding approximately $N_e \approx 55\text{--}60$ e-folds also predicts primordial black holes with masses in the range $10^3\text{--}10^5\,\mathrm{g}$. Although such ultra-light primordial black holes are typically expected to have evaporated, recent proposals invoking evaporation suppression via memory-burden effects could allow their survival as viable dark matter candidates. Under this assumption, the predicted gravitational wave signal lies in a frequency range currently inaccessible to any existing or proposed detectors. Although no experimental proposals presently reach this frequency band, our results provide strong motivation to push the frontiers of gravitational wave detection towards these unexplored high-frequency regimes.

Speaker: Marco Merchand Medina

12:20 Group photo

12:30 Lunch break

Plenaries 10-11: Michael Zantedeschi and Haibo Yu

Convener: Chair:

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

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

Speaker: Michael Zantedeschi

25 Seeding Supermassive Black Holes from the Dark Sector

I will present a novel mechanism for forming supermassive black holes through dark matter dynamics. In the self-interacting dark matter framework, halos can undergo gravothermal collapse, producing black hole seeds that subsequently grow via baryonic Eddington and dark Bondi accretion. This process can naturally account for the massive black holes observed at high redshift, including the JWST Little Red Dots. I will discuss the underlying dynamics, the connection to halo evolution across cosmic time, and potential observational signatures in strong lenses, stellar streams, and dwarf satellites.

Speaker: Haibo Yu

15:00 Coffee break

Contributed talks

Convener: Chair: Jianing Wang

26 Primordial black holes from inflation and their observational imprints (online)

Primordial black holes (PBH) have recently emerged as a very interesting candidate for the cold dark matter in the universe. We study their generation in a single field inflationary model with an inflection point potential and found that PBHs can be produced in our scenario in the asteroid-mass window with a nearly monochromatic mass fraction, accounting for the total dark matter in the universe. Further, we study the induced stochastic gravitational waves background (ISGWB) arising from the second order scalar perturbations. We found that the ISGWB in our scenario can be generated in the frequencies range from nanoHz to kHz that covers the observational scales corresponding to future space based GW observatories such as IPTA, LISA, DECIGO and ET as well as Advanced LIGO and BBO. Moreover, we also explore various observational imprints on ISGWB due to the Hawking evaporation of ultralight PBH and from the memory burden effect.

Speaker: Rajeev Kumar Jain

27 The trichotomy of PBH initial conditions

We show that the threshold to form a black hole, in an asymptotically flat and radiation dominated Friedman-Robertson-Walker (FRW) Universe, is not solely (mainly) determined by the behaviour of the compaction function at its maximum, as earlier thought, but also by the three-dimensional curvature at smaller (but super-horizon) scales, which we call "the core". We find three classes of initial conditions characterized by an open (O), closed (C), or flat (F) FRW core surrounded by a shell with higher three-dimensional curvature. In the C case, the core helps the collapse so that the black hole formation threshold is there the lowest among all cases. Type-II black holes might only be generated by Type-O or F (each of those with different thresholds, with O being the highest) or by a Type-C with an effective F core.

Speaker: Laia Montellà

28 Primordial black hole formation from the merger of oscillons

We show that the merger of oscillons results in a broad spectrum of the oscillon mass. A huge number of oscillon samples obtained from numerical lattice simulations reveal that the oscillon mass distribution has an exponential tail in a heavy-mass region. This enables us to infer the fractional abundance of heavy oscillons. Using the criterion for the primordial black hole (PBH) formation from the oscillon collapse obtained in previous studies, we estimate the abundance of PBHs and conclude that a sizable number of PBHs can be produced from oscillons. It can be an alternative PBH formation mechanism without employing the tuning of the inflaton potential to enhance the small-scale density fluctuations in the conventional PBH formation scenario.

Speaker: Naoya Kitajima

Friday 5 December

09:30 Coffee break / Discussion

Plenaries 12-13: Masahiro Takada and Sunao Sugiyama

Convener: Chair: Shigeki Matsumoto

29 Observational search of PBH

Gravitational microlensing is a powerful probe of PBHs, and I will give a review of the microlensing searches for PBHs.Gravitational microlensing is a powerful probe of PBHs, and I will give a review on the microlensing search of PBH

Speakers: Masahiro Takada, Sunao Sugiyama

11:00 Coffee break

Contributed talks

Convener: Chair:

30 Discovery of a Little Red Dot candidate at z ~ 10

Deep IR observations by JWST have discovered a new population of high-redshift compact objects known as "little red dots" (LRDs) with a characteristic V-shape SED. Based on the detection of broad Balmer emission lines, previous studies suggested that LRDs are low-luminosity AGNs, possibly linked to super-Eddington accretion shortly after seed BH formation. In this study, we propose a new color selection technique for identifying LRDs at z~10, utilizing both NIRCam and MIRI photometry to extend the redshift frontier of LRD studies. Applying this method to COSMOS-Web, the largest NIRCam-MIRI joint survey, we find one solid candidate with a compact morphology, a clear F115W dropout, and a V-shape SED. This candidate with the photometric redshift of ~10.5 may represent one of the most distant SMBH so far, potentially representing the era just after seed BH formation. In the talk, we will present the first constraints on the luminosity function of LRDs at z~10 and discuss the implications of this discovery for our understanding of SMBH evolution in the early Universe.

Speaker: Takumi Tanaka

31 Neutrino signals from Dark Stars seeding SMBHs

Dark Stars (DS), powered by dark matter annihilation may form in the place of Pop. III stars. They can grow to $\gtrsim 10^5~M_\odot$ and collapse to black holes making them excellent candidates to seed supermassive black holes. We establish first constraints on DSs as SMBH progenitors based on DM annihilations using data from Super-Kamiokande and IceCube neutrino experiments, while remaining consistent with James Webb Space Telescope observations. Upcoming experiments such as Hyper-Kamiokande, DUNE, and JUNO will be able to explore DS properties with enhanced sensitivity.

Speaker: Thomas Schwemberger

32 Revisiting the merger rate of primordial black holes

The merger rate of binary black holes inferred by the LIGO-Virgo-KAGRA (LVK) collaboration is potentially compatible with primordial black holes (PBHs). Reexamining the latest merger rate calculations for Poisson-distributed PBHs, we find that they did not fully implement the binary formation conditions required for PBH pairs to decouple from the Hubble flow. Once these conditions are properly taken into account, the predicted merger rate becomes comparable to, or even inconsistent with, current observational constraints from the cosmic microwave background (CMB). Motivated by this, we revisit the binary formation criteria in a more realistic framework and extend the calculation to scenarios with primordial clustering. With these improvements, we show that PBHs can still account for the LVK merger rate.

Speaker: Shunsuke Neda

12:20 Lunch

Plenary 14-15: Shigeki Matsumoto and Shunsaku Horigome

Convener: Chair:

33 Sub-GeV dark matter detection around SMBH.

Speaker: Shigeki Matsumoto

34 TBA

Speaker: Shunsaku Horiuchi

Closing remarks

15:05 IPMU tea time