Conveners
Parallel 2: Inflation / reheating / CMB
- Jerome Quintin (University of Waterloo and Perimeter Institute)
Parallel 2: Gravitational and inflationary DM production
- Seyda Ipek
Parallel 2: Black holes / remnants
- Andrey Shkerin
Parallel 2: DM models II
- Aaron Vincent (Queen's University)
Parallel 2: DM mechanisms
- Tracy Slatyer
Parallel 2: Sub-GeV and ultralight DM I
- Walter Tangarife (Loyola University Chicago)
Parallel 2: Heavy DM
- Melissa Diamond
Parallel 2: Astrophysical / cosmological DM probes II
- Melissa Diamond
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Tammi Chowdhury (University of Manitoba)07/07/2025, 13:30
Cosmic Inflation provides clues to the conditions of the early universe and the highest energy scales our universe has reached. Non-thermal relics can be produced through gravitational particle production, providing dark matter candidates or unstable particles that decay into the baryon asymmetry. A minimal framework that incorporates inflation into the Standard Model is Higgs Inflation, where...
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RAJESH MONDAL (IIT Guwahati)07/07/2025, 13:50
Despite having important cosmological implications, the reheating phase is believed to play a crucial role in both cosmology and particle physics model building. Conventional reheating models primarily rely on arbitrary coupling between the inflaton and massless fields, which lacks robust predictions. In this talk, I will discuss our recently proposed novel reheating mechanism where the...
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Prof. Vahid Kamali (BASU & McGill)07/07/2025, 14:10
This study investigates the alignment of theoretical and observational Cosmic Microwave Back-
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ground (CMB) power spectra, focusing on the high-dissipative regime of the most reliable effective
theory of inflation. Using marginalized posterior distributions, we analyze parameter spaces con-
strained by our model and compare them to observational data from the Planck 2018 results.... -
Dr Junsei Tokuda (McGill university)07/07/2025, 14:30
Quantum fluctuations of the metric are amplified during inflation, producing the macroscopic perturbations observed in the late universe. To clarify whether these fluctuations retain their quantum coherence, we investigate the decoherence of superhorizon modes induced by gravitational nonlinearities. We show that cubic gravitational couplings, constrained by the soft theorem, lead to IR and UV...
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Prof. Dong-han Yeom (Pusan National University)07/07/2025, 14:50
What happens if our universe was created from an Euclidean instanton? The no-boundary proposal is not the unique choice; instead, a more natural option is to introduce Euclidean wormholes, but as a result, we need to accept that our universe was indeed an outcome of a pair creation. Invoking the Klebanov-Susskind-Banks Euclidean wormhole as a bridge, we investigate the power spectrum and the...
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Prof. Keith A. Olive (University of Minnesota (US))07/07/2025, 15:40
Without assuming instantaneous reheating, there is an extended period
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and several particle process which lead to the production of Dark Matter.
These are reviewed and compared. -
Duarte Miguel da Silva Feiteira (University of Helsinki)07/07/2025, 16:00
Gravitational particle production provides an ever-present background in non-thermal dark matter studies. I discuss the correspondence between the Starobinsky and Bogolyubov approaches to the problem of inflationary particle production, and derive strong constraints on frameworks with scalar dark relics.
(Based on D. Feiteira, O. Lebedev, arXiv:2503.14652)
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Yann MAMBRINI07/07/2025, 16:20
We will review different mechanisms for dark matter production in the early Universe, with gravitational sources. From the graviton exchange, to the perturbation during inflation and the PBH decay.
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Francisco Barreto Basave (Instituto de Física, UNAM)07/07/2025, 16:40
We investigate the production of Weakly Interacting Massive Particles (WIMPs) in the early Universe, focusing on the reheating epoch. Using an inflationary potential approximated by a quartic power law near its minimum, we analyze how inflaton self-interactions trigger exponential growth of inhomogeneities in the field resulting in the fragmentation of the condensate. We study the impact of...
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Marcos Alejandro García García (Instituto de Física, UNAM)07/07/2025, 17:00
The excitation of scalar dark matter during inflation may result in large isocurvature perturbations, which can be avoided by inducing a sizable effective dark matter mass during the inflationary phase. This can be achieved by a direct coupling to the inflaton, through a nonminimal coupling to the curvature, or by a large bare mass. Notably, when the isocurvature is suppressed at CMB scales, a...
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William DeRocco (University of Maryland, College Park)08/07/2025, 13:30
Primordial black holes (PBHs) are a well-motivated candidate for dark matter that may constitute a sub-fraction of the dark sector in the Earth-mass range. The strongest observational probe of this population is through gravitational microlensing, an effect in which the bending of light by a massive object results in the apparent transient magnification of a distant source. While ground-based...
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Dr Juan Carlos Hidalgo (UNAM Mexico)08/07/2025, 13:50
We present the formation of Primordial Black Holes (PBHs) from the gravitational collapse of inhomogeneities in a scalar field dominated universe, featuring a code that solves Einstein Equations plus the matter evolution in spherical symmetry. We focus on prospects of reheating for the scalar field potentials. We report on threshold amplitudes for the formation of PBHs, as well as...
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Melissa Diamond08/07/2025, 14:10
I present a novel mechanism for creating primordial black holes and MACHOs. A heavy dissipative dark sector can come to dominate the universe, creating an early matter dominated era prior to Big Bang Nucleosynthesis (BBN). At this time the dark matter can form halos which persist after the phase transition back to radiation domination, and slowly collapse at late times. This leads to the...
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Edward Wilson-Ewing (University of New Brunswick)08/07/2025, 14:30
I will explain how corrections motivated by loop quantum gravity can be included in the Tolman-Oppenheimer-Volkoff equation for spherically symmetric static stars. The quantum-corrected equation has new star solutions with a Planck mass, Planck radius, and no horizon. These bound objects could form in the early universe, be an end state for an evaporating black hole, and could potentially...
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Christopher Hirata (Ohio State University)08/07/2025, 14:50
Low-mass primordial black holes (PBHs) have re-emerged as a promising dark matter candidate. At the lowest allowed masses (of order $10^{17}$ g), the leading tool for constraining PBHs is Hawking radiation, either in gamma rays or in electrons and positrons (since the peak of the Hawking graybody spectrum is at an energy of order the electron mass). Our group is carrying out a systematic...
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Sushant Yadav 202050408/07/2025, 15:40
The Dirac Scotogenic model provides an elegant mechanism for generating small Dirac neutrino masses at the one-loop level. A single abelian discrete $\mathcal{Z}_6$ symmetry simultaneously protects the ``Diracness'' of the neutrinos and the stability of the dark matter candidate. This symmetry originates as an unbroken subgroup of the so-called $\textit{445}$ $U(1)_{B-L}$ symmetry.
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Here, we... -
Urjit Yajnik (IIT Bombay Mumbai India)08/07/2025, 16:00
The Alternative Left-Right Model is an attractive variation of the usual Left-Right Symmetric Model because it avoids flavour-changing neutral currents, thus allowing the additional Higgs bosons in the model to be light. We show here that the model predicts several dark matter candidates naturally, through introduction of an R-parity similar to the one in supersymmetry. Dark matter candidates...
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Micah Mellors08/07/2025, 16:20
The fermion mass hierarchy of the Standard Model (SM) spans many orders of magnitude and begs for a further explanation. The Froggatt-Nielsen (FN) mechanism is a popular solution which introduces an additional $U(1)$ symmetry to the SM under which SM fermions are charged. We examine the phenomenological implications of the FN mechanism for the lepton sector in the most general way, by...
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Linda Yuan08/07/2025, 16:40
Atomic dark matter (ADM) models, with a minimal content of a dark proton, dark electron, and a massless dark photon, are motivated by theories such as Mirror Twin Higgs. ADM models might address the seeming tension between cold dark matter (CDM) and observations at small scales: excessive number of dwarf galaxies in the Milky Way, and the cuspiness of galactic cores. ADM has been shown to...
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Dr Takashi Toma (Kanazawa University)09/07/2025, 11:00
In some scenarios, the dark matter relic abundance is set by the semi-annihilation of two dark matter particles into one dark matter particle and one Standard Model particle. These semi-annihilations might still be occurring today in the Galactic Center at a significant rate, generating a flux of boosted dark matter particles. We investigate the possible signals of this flux component in...
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Alejandro Ibarra (Technical University of Munich)09/07/2025, 11:20
The existence of dark matter in our Universe and the existence of an asymmetry between nucleons and antinucleons are two of the most solid evidences for physics beyond the Standard Model. Many mechanisms have been proposed to explain these two phenomena. On the other hand, these mechanisms typically involve different particles and different energy scales, therefore the observed similarity...
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Hugo Schérer (McGill University)09/07/2025, 11:40
Particles properties in an ambient medium are very different from those in vacuum. Their masses and lifetimes change, and new processes even become possible. For example, in the Standard Model, photons in a plasma (plasmons) acquire an effective mass and can decay into neutrinos, a process forbidden in vacuum. These kinds of thermal effects are especially relevant for dark matter...
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Tushar Gupta09/07/2025, 12:00
Direct detection of light dark matter can be significantly enhanced by upscattering of dark matter with energetic particles in the cosmic ambient. This boosted dark matter flux can reach kinetic energies up to tens of MeV, while the typical kinetic energies of GeV mass dark matter particles in the Milky Way halo are of the order of keV. Dark matter boosted by energetic diffuse supernova...
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Stephen Henrich (University of Minnesota)09/07/2025, 12:20
We re-examine the case for cold dark matter (DM) produced by ultra-relativistic freeze-out (UFO). UFO is the mechanism by which Standard Model (SM) neutrinos decouple from the radiation bath in the early universe at a temperature $T_{d} \approx 1$ MeV. This corresponds to chemical freeze-out without Boltzmann suppression, such that the freeze-out (decoupling) temperature $T_{d}$ is much...
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Saeid Foroughi-Abari (Carleton University)10/07/2025, 13:30
High luminosity colliders and fixed target facilities using proton beams are sensitive to new weakly coupled degrees of freedom across a broad mass range. Among the various production modes in proton-proton collisions, bremsstrahlung is particularly important for dark sector degrees of freedom with masses between 0.5 and 2.0 GeV, due to mixing with hadronic resonances. In this talk, I will...
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Patrick Foldenauer10/07/2025, 13:50
We study a consistent minimal Dark Abelian Higgs model as the portal to a GeV-scale DM candidate. This scenario has been previously studied in the literature and has been deemed to be ruled out by indirect detection constraints. However, we find that when taking correctly into account the production and resulting abundance of the GeV DM candidate, there is still a viable window in the...
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Benjamin Roberts10/07/2025, 14:10
We devise and demonstrate a method to search for nongravitational couplings of ultralight dark matter to standard model particles using space-time separated atomic clocks and cavity-stabilized lasers. By making use of space-time separated sensors, which probe different values of an oscillating dark matter field, we can search for couplings that cancel in typical local experiments. This...
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Siyang Ling (City University of Hong Kong)10/07/2025, 14:30
We provide a framework for numerically computing the effects of free-streaming in scalar fields produced after inflation. First, we provide a detailed prescription for setting up initial conditions in the field. This prescription allows us to specify the power spectra of the fields (peaked on subhorizon length scales and without a homogeneous field mode), and importantly, also correctly...
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Prof. Pyungwon Ko (KIAS (Korea Institute for Advanced Study))10/07/2025, 15:40
Some cosmic ray observations such as PAMELA/AMS02 positron excesses, and high energy neutrino events reported by IceCUBE and KM3 Collaborations may be interpreted as signals of heavy decaying dark matter (DM). In this talk, I will interpret them using heavy decaying DM with right-handed neutrino (RHN) portals with dark gauge symmetry,dark photon and dark Higgs boson. Including dark gauge...
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Han Wu (Queen's University, McDonald Institute)10/07/2025, 16:00
If millicharged particles (MCPs) exist they can be created in the atmosphere when high energy cosmic rays collide with nuclei and could subsequently be detected at neutrino experiments. We extend previous work, which considered MCPs from decays of light mesons and proton bremsstrahlung, by including production from ϒ meson decays and the Drell-Yan process. MCPs with masses below a GeV...
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Fa Peng Huang10/07/2025, 16:20
Motivated by the current status of dark matter search, we discus new production mechanism for heavy dark matter based on non-thermal processes, such as cosmic phase transition, Hawking radiation, and superradiance process. Furthermore, we explore potential signatures of this mechanism in various experiments including the gravitational wave signals. This study provides a viable pathway to...
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Walter Tangarife (Loyola University Chicago)10/07/2025, 16:40
The capture of dark matter by astrophysical compact objects has been of great interest in recent years. In this talk, we present the capture of heavy dark matter by Population III stars at both the early and late stages of their evolution. In the early phase, we calculate dark matter capture via multiple scatterings of the dark matter with two different target species. For the late stage, we...
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Yawen Xiao10/07/2025, 17:00
Detection of millicharged dark matter with trapped ions has emerged as a powerful technique. Millicharged particles scatter off the ions, producing detectable signals either through individual quantum jumps or via an increase in the ions’ overall heating rate. Prior studies have shown that this approach can probe a vast parameter space for superheavy mCPs in the $10^2 \sim 10^9$ GeV mass...
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Prof. Brooks Thomas (Lafayette College)11/07/2025, 11:30
Cosmological stasis is a phenomenon wherein the abundances of multiple cosmological energy components with different equations of state remain constant for an extended period despite the expansion of the universe. This stasis phenomenon can give rise to cosmological epochs in which the effective equation-of-state parameter $\langle w\rangle$ for the universe is constant, but differs from the...
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Dr Saniya Heeba (McGill University)11/07/2025, 11:50
Millicharged particles (MCPs) i.e., particles with a small effective charge are a key component of various dark sectors. If these particles exist, they will be produced both in the early universe and in various astrophysical plasmas. The former results in an irreducible density of these particles, the so-called millicharged background, which can be detected using direct detection...
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Gonzalo Alonso Alvarez (University of Toronto)11/07/2025, 12:10
The dark sector may feature dissipative interactions that can lead to the formation of dark matter substructure including dark stellar objects. A general prediction of these scenarios is that dark matter may be shinning in the particles that mediate the self interactions. I will describe the conditions under which conventional dark matter experiments are sensitive to this dark starlight, and...
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Tianyi Xie (McGill University)11/07/2025, 12:30
We propose a fifth force model in which dark matter (DM) couples to a scalar field, leading to deviations from standard cosmology.
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The scalar field acquires an effective mass through its quadratic coupling to DM, which screens the fifth force on large scales and in the early universe. At late times, the scalar field evolves into two components: an attractor tightly coupled to DM and an... -
Jaime Forero-Romero (Universidad de los Andes)
I present ASTRA (Algorithm for Stochastic Topological RAnking), a new method for classifying cosmic web structures, designed to explore the dark universe. While traditional approaches struggle to map both dense regions and cosmic voids—critical tracers of dark matter and cosmic acceleration—ASTRA leverages probabilistic reconstruction of underdense regions using random catalogs. This allows us...
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Yuxuan He
Alkali-noble-gas spin systems have been widely used in searches for ultra-light dark matter coupling to nucleon spins. These searches usually confronted limitations of bandwidth and sensitivity. In this talk, we demonstrated two strategies to broaden the sensitive bandwidths in dark matter searches with alkali-noble-gas spin systems. The system has been implemented in the hybrid spin-coupled...
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