The hypothesis of Cold Dark Matter (CDM) has been confirmed on the largest scales of the Universe and must now be stress-tested on sub-galactic scales. Many well-motivated and generic alternatives to CDM can leave spectacular signatures on precisely these scales, affecting the evolution of galaxies as well as their population statistics. Excitingly, over the course of the next decade, a...
Stars are large, plentiful and the Universe provides them to us for free. They provide us with unique laboratories to test fundamental physics at high densities and temperatures, and their large volumes potentially give us access to very rare processes. While stars have been used for decades to probe fundamental physics, they still offer new exciting avenues to search for...
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...
In my presentation, I will investigate the interplay between dynamical symmetry breaking mechanisms and dark matter. More precisely, I will focus on several important details of the recently proposed Higgs-dilaton model augmented with a dark matter candidate inducing quantum corrections. In contrast to the previous studies, I will consider the effects of the renormalisation group improvement...
Strongly interacting dark sectors, colloquially referred to as dark-QCD, is becoming increasingly popular in the collider community, primarily because of the rich phenomenology and the novel signatures it offers. The author pioneered the first search for semi-visible jets in ATLAS, and is following that up with multiple studies focussing on other final states (arXiv:2207.01885), new generator...
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...
The LUX-ZEPLIN collaboration operates a 7-tonne active mass, two-phase xenon Time Projection Chamber surrounded by multiple anti-coincidence vetoes. In its search for the elusive dark matter, the LZ experiment involves researchers from 6 countries and 4 continents. It is located at the Sanford Underground Research Facility in Lead, South Dakota. LZ seeks standard Weakly Interacting Massive...
The Belle and Belle II experiment have collected samples of $e^+e^-$
collision data at centre-of-mass energies near the $\Upsilon(nS)$
resonances. These data have constrained kinematics and low
multiplicity, which allow searches for dark sector particles in the mass
range from a few MeV to 10 GeV. Using a 426 fb$^{-1}$ sample collected
by Belle II, we search for inelastic dark matter...
In this talk, I aim to present the phenomenology of Electroweak (EW) multiplets as potential Dark Matter (DM) candidates in the coming years. I will begin by discussing the thermal production mechanism in the early Universe and providing an overview of the current phenomenological landscape in the search for Weakly Interacting Massive Particles (WIMPs). It is worth emphasizing that WIMPs...
This study investigates the alignment of theoretical and observational Cosmic Microwave Back-
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....
CRESST-III (Cryogenic Rare Event Search with Superconducting Thermometers) installed at Laboratori Nazionali del Gran Sasso, is looking to directly detect dark matter particles scattering off CaWO4 target nuclei in cryogenic detectors. Thanks to its energy threshold O(30 eV), CRESST-III is particularly suitable in probing sub-GeV DM masses. This contribution presents an overview of CRESST-III,...
Over the past twenty-eight years, the DAMA/LIBRA experiment has observed an annual modulation signal that is consistent with a dark matter explanation. Unfortunately, the signal is contradicted by the null results of numerous experiments utilizing different target materials. In order to perform a truly model-independent investigation of the DAMA/LIBRA result, a study with the same target...
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...
We study vector dark matter (DM) production with Higgs-portal type interactions in the scenarios with a low reheating temperature which can be realized by a prolonged decay of the inflaton after inflation. We take the reheating temperature to be large enough to match the observations in Standard Cosmology such as Big Bang Nucleosynthesis but small enough below the DM mass for the DM...
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...
If dark matter is blind to standard model gauge interactions, the dark sector might not be totally secluded but connect to the visible sector via the introduction of portal interactions. In this talk, I will discuss a novel scenario where an axion-like particle acts as mediator between the SM and a complex scalar singlet dark matter candidate. The identification of physical couplings crucially...
Launched at the end of 2021, the James Webb Space Telescope (JWST) has already begun to revolutionize our view of the cosmic dawn era. Specifically, it discovered an unexpectedly large number of extremely bright objects in the sky from the early Universe, whose light was emitted more than thirteen billion years ago. If these objects are interpreted as some of the first galaxies ever...
The standard model of cosmology, $\Lambda$CDM, has been a fundamental framework for understanding the universe from a theoretical perspective and for explaining a wide range of astrophysical and cosmological observations. Nonetheless, the increasing amount of observational data have given rise to the era of precision cosmology, revealing discrepancies in parameter values across different...
Without assuming instantaneous reheating, there is an extended period
and several particle process which lead to the production of Dark Matter.
These are reviewed and compared.
Observations of intermediate mass and dwarf galaxies are hard to reconcile with the results of numerical simulations of cold collisionless dark matter (CDM). The most notable problems are (i) the core-cusp problem, or the inability of DM-only simulations to reproduce flat density profiles, i.e., cores, in the centers of dwarf galaxies, (ii) the diversity of the central density profile slopes,...
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)
In light of recent observations by the Dark Energy Spectroscopic Instrument (DESI), we study evidence for thawing quintessence over a cosmological constant as dark energy, with emphasis on the effect of the choice of priors. Working with a parametrization for the equation of state parameter motivated by the theory, we analyse the DESI BAO data jointly with Planck 2018 and Pantheon+ supernovae...
Recent observations suggest dark energy might have been of phantom type in the past, implying violation of the null energy condition (NEC). It is a well-known fact that quantum states can violate the NEC, but at the same time, it is a challenge to come up with theoretically robust and stable quantum field theories that could behave as phantom dark energy. In fact, there should be a theoretical...
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.
Based on arXiv: 2409.13022 (published in ApJ Letters). We update constraints on cosmological parameters in a 12-parameter model, which extends the standard 6-parameter ΛCDM to include dynamical dark energy and massive neutrinos, along with other new parameters. We use the latest Planck PR4 (2020) likelihoods, DESI DR1 BAO, and the latest uncalibrated type Ia Supernovae (SNe) datasets. In this...
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...
Disk-halo decompositions of star-forming galaxies (SFGs) at redshifts z > 1 typically focus on massive galaxies with stellar masses exceeding log(M⋆/M⊙) > 10.
In this study, we analyse the dark matter (DM) halo properties of 127 intermediate-redshift (0.3 < z < 1.5) SFGs down to low stellar masses (7 < log(M⋆/M⊙) < 11). To do so, we use integral field unit observations from the MUSE Hubble...
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...
Over the last decade, one of the most popular solutions to the dark matter problem has been a hypothetical class of particles known as axions or axion-like particles. In this talk, I will discuss why the axion is such an attractive candidate and also explain the challenges we face in determining whether axions are the dark matter and which axion(s) are the dark matter. I will highlight results...
The nature of dark matter remains one of the biggest mysteries in cosmology. Among the many possible candidates, one of the most well-motivated class of models and leading candidate is the ultra-light dark matter (ULDM). ULDM represents the lightest possible dark matter candidates and exhibits wave-like behavior on galactic scales, offering a unique opportunity to probe its properties through...
The fundamental nature of dark matter remains one of the central open questions in physics. A leading hypothesis is that dark matter consists of new elementary particles, whose masses and interaction cross sections span a vast parameter space. Among the various detection technologies, liquid xenon detectors have emerged as the most sensitive for dark matter particles with masses above a few...
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...
SABRE is an international collaboration that will operate similar particle de-
tectors in the Northern (SABRE North) and Southern Hemispheres (SABRE
South). This innovative approach distinguishes possible dark matter signals
from seasonal backgrounds, a pioneering strategy only possible with a southern
hemisphere experiment. SABRE South is located at the Stawell Underground
Physics...
It is well-established that Dark Matter can be captured and accumulate in celestial objects. While this phenomenon has been extensively studied for the Sun and Earth, recent interest has shifted towards compact objects such as White Dwarfs and Neutron Stars. In this presentation, I will discuss two recent results related to these objects.
For Neutron Stars, we consider Dark Matter...
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...
The presence of a non-baryonic Dark Matter (DM) component in the Universe is inferred from the observation of its gravitational interaction. If Dark Matter interacts weakly with the Standard Model (SM) it could be produced at the LHC. The ATLAS Collaboration has developed a broad search program for DM candidates in final states with large missing transverse momentum produced in association...
The initiative to detect dark matter directly has been prominent for decades after the WIMP miracle was proposed. Following this, many institutions have come forward with a variety of dark matter direct detection experiments, each trying to find the possible missing particle of the universe. Most prominently, the DAMA collaboration published their results during the end of the last century,...
The detection of dark matter presents one of the greatest challenges of modern astronomy.
Possibly one of the most promising avenues is via high energy particles created by dark matter self-annihilation events.
These annihilation events, naturally, depend strongly on the particle physics of the dark matter, but also on the astrophysics of the Universe.
More specifically, the small...
I show that the decay, self-annihilation or nucleonic scatters of dark matter can trigger phase transitions from a hadronic to a quark/hybrid phase in neutron stars. For certain high-density equations of state of nuclear matter and stellar mass-radius configurations, the phase transition would convert the neutron star to a black hole. Consequently, the observed existence of neutron stars and...
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...
We propose a novel method to determine the mass scale of ambient dark matter that can be generally applied to the (at least effectively) two-dimensional direct detection experiments allowing for directional observables. Due to the motions of the solar system and the Earth relative to the galactic center and the Sun, the dark-matter flux carries a directional preference. We first formulate that...
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...
The primary science goal of the General Anti Particle Spectrometer (GAPS) is to search for light antinuclei in cosmic rays at kinetic energies below 0.25 GeV/n, as a possible indirect dark matter signature. GAPS is a balloon-borne cosmic-ray experiment expected to be launched during the Antarctic summer season 25/26. It consists of a ten-layer silicon tracker, cooled by a novel oscillating...
Phase transitions in the early universe provide a rich testing ground for fundamental symmetries and the generation of gravitational waves. In this talk, I will explore the connection between symmetry breaking, phase transitions, and the resulting gravitational wave signatures. I will present recent theoretical and numerical developments that shed light on the dynamics of these transitions,...
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...
The stochastic gravitational wave background (SGWB) has recently emerged as a promising new probe of new particle physics and the dark side of the Universe. In this talk, we present well-motivated examples of SGWB sourced by the early Universe dynamics of light scalar fields with masses well below the electroweak scale. These include mechanisms such as post-inflation parametric resonance of...
Within present observational uncertainties, the time evolution of dark
energy discovered by DESI (2025) is consistent with a simple model in
which the dark energy density maintains a direct dependence on the
${\mid \Omega - 1 \mid}$ measure of spatial curvature. This, together
with Bousso’s (2002) conjecture that the holographic bound of the
universe saturates at the observer’s apparent...
We consider different observational effects to test modified gravity approach involving the cosmological constant in the common description of the dark matter and the dark energy. We obtain upper limits for the cosmological constant by studying the scaling relations for 12 nearby galaxy clusters, the radiated power from gravitational waves and the Tully-Fisher relation for super spiral...
Primordial gravitational waves (GWs) provide a unique way to look into the early Universe, revealing the connection among inflationary reheating, dark matter (DM) and baryogenesis. I will explore how distinct GW signatures can test new physics scenarios beyond the standard model, offering insights into the fundamental nature of the DM and leptogenesis. I will first discuss how inflationary GWs...
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...
A number of theories predict that dark matter is a very massive particle or composite state. Discovering dark matter in this high mass regime requires different approaches. This talk covers recent developments, including composite dark matter that produces unique signatures in underground experiments and dark matter detectable through Bremsstrahlung radiation in Antarctic ice. We also survey...
The global network of pulsar timing arrays have recently announced the detection of a stochastic gravitational wave background (SGWB) in the nano-Hertz frequency regime. In this talk, I will discuss the implications of early seeding of supermassive black holes (SMBHs) for the observed SGWB. Assuming that these SMBHs were seeded by the collapse of supermassive, dark matter–powered stars (dark...
Dark matter (DM) might have non-gravitational interactions with the standard sector, which would leave signatures in the cosmic microwave background (CMB). Traditional searches for such interactions focus on their imprints in CMB power spectra, or 2-point functions. In this talk I will argue that there is valuable information in both the CMB monopole's frequency spectrum, i.e. deviations...
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...
The mystery of dark matter (DM) is a long-standing issue in physics, with numerous dedicated experiments returning no confirmed detections. As many direct detection experiments rely on catching a signal of nuclear recoil, these types of experiments are not applicable to many DM models.
Instead, we can utilise the precision that atomic physics allows to search for potential interactions...
Compact objects as dark matter have historically been constrained by their dynamical effects. Since these objects can participate in hard few-body scattering processes, they can readily transfer energy to visible objects, with effects such as the disruption of wide binaries. However, binary disruption is not the only possible outcome of such few-body encounters. I will discuss recent work on...
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...
Composite dark matter models, where dark matter exists in bound states formed in the early universe, have long been a source of scientific interest. In this talk, I will focus on loosely bound dark matter composite states, where the binding energy per constituent is small compared to the constituent’s bare mass. If this binding energy is sufficiently small, scattering with Standard Model...
Sub-GeV neutrinos produced in a stellar core may emerge from main sequence stars, white dwarfs and brown dwarfs producing possible observable signals of dark matter capture. A distribution of these stars near the Milky Way galactic center will produce a neutrino flux that can be probed at Earth based neutrino observatories like Super-Kamiokande and Hyper-Kamiokande. In this talk we demonstrate...
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...
The Atacama Cosmology Telescope recently published results from the sixth data release (DR6). I will present these DR6 data and the implications for several cosmological models beyond the standard picture.
The ΛCDM model has long served as the standard paradigm in cosmology, offering a remarkably successful description of the Universe’s evolution. Yet, as observational precision continues to improve, persistent tensions have emerged across a range of probes, including the well-known Hubble constant discrepancy. While individual datasets may each align with ΛCDM, their collective interpretation...
This talk describes recent progress in the Highland Program: an effort to identify useful non-swampy UV clues guiding a low-energy understanding of the Dark Sector.
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...
We investigate the possibility that parametric resonant excitation of photons in an ultralight dark matter halo could generate the required flux of Lyman-Werner photons to allow the direct collapse formation of supermassive black hole seeds. This scenario provides a plausible explanation for the origin of quasars observed at high redshifts.
The cosmological principle assumes the isotropy of the Universe. The high coverage of the Zwicky Transient Facility survey (ZTF) makes it possible to carry out an unprecedented study of the veracity of this principle by using observation of type Ia supernovae (SNe Ia).
This unique low redshift (z<0.15) survey with more than 3000 SNe Ia in the second data release (ZTF-DR2-SNe Ia) increases...
Supernova explosions are extreme cosmic events that may impact not only ordinary matter but also dark matter (DM) halos. In this talk, I explore the possibility that a fraction of supernova energy is released as dark radiation, which could transform a cuspy DM halo into a cored one, potentially explaining observed cores in some dwarf galaxies. Alternatively, limits on DM core sizes provide...
As the search for dark matter progresses, it is useful to refine past and future searches for heavy dark matter, including for dark matter masses well above a TeV. I demonstrate the importance of properly modelling the local dark matter velocity distribution, beyond the standard Maxwellian halo model, and in particular how accurate modeling of the Large Magellanic Cloud and Milky Way impact...
The Zwicky Transient Facility (ZTF) is scanning the Northern sky since 2018 with a 1.2 m class telescope installed at the Mont Palomar Observatory. This survey detects any transient in the nearby Universe within its magnitude limit, typically up to a redshift of 0.15. In February 2025, the Cosmology working group has released a set of more than 3600 Type Ia supernovae (SN Ia) corresponding to...
The Vera C. Rubin Observatory will conduct the Legacy Survey of Space and Time (LSST), a synoptic astronomical survey of large étendue (more than 20000 deg2) starting in october 2025. A systematic scan of the celestial sphere will be perform for ten years, leading to the largest astronomical catalog ever compiled (83 pB) with 17 billions of stars and 20 billions of galaxies.
With a high...
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...
For nearly five decades, the interplay between dark matter (DM) halos and baryonic (or luminous) matter has shaped our understanding of galaxy formation and evolution. Recent observational data (e.g., the latest DESI results) suggests that the standard $\Lambda$-CDM model, although remarkably successful, may need to be revisited to fully explain the Universe. This tension motivates a more...
Cold dark matter halos are known to harbor universal density profiles such as the NFW, Einasto and prompt cusp profiles in cosmological N-body simulations. Despite decades of research, the origin of these profiles has remained elusive. I will present a first principles kinetic theory calculation based on the Vlasov-Poisson equations that, for the first time, provides a microscopic description...
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...
Dark kinetic heating of neutron stars has been extensively studied as a promising dark matter detection avenue. This occurs when dark matter is accelerated to relativistic speeds in the gravitational well of high-escape velocity objects, and deposits its kinetic energy after becoming captured by the object, thereby increasing its temperature. I will show how this effect can also arise in...
We demonstrate that the co-genesis of baryon asymmetry and dark matter can be achieved through the rotation of an axion-like particle, driven by a flip in the vacuum manifold's direction at the end of inflation. This can occur if the axion has a periodic non-minimal coupling to gravity, while preserving the discrete shift symmetry. In non-oscillating inflation models, after inflation there is...
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...
Some of the most stringent constraints on axions arise from considerations of it's emission from astrophysical plasmas. However, many studies assume that particle production occurs in an isotropic plasma environment. This condition is rarely (if ever) met in astrophysical settings, for instance due to the ubiquitous presence of magnetic fields. The effects of the magnetic fields are only taken...
The gravitational lensing parallax of gamma-ray bursts (GRB), also known as picolensing, is a promising probe of compact dark matter, such as primordial black holes (PBH). A future space mission consisting of two X-ray/gamma-ray detectors in the Swift/BAT class can probe PBHs in the asteroid-mass window — a range of masses that has been notoriously hard to constrain by any other means. I will...
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...
Axions with a mass around 1 eV can decay into near-infrared photons. Using blank-sky observations from the James Webb Space Telescope, I search for a narrow emission line due to decaying dark matter and derive leading constraints on the axion-photon coupling in the eV-scale mass range.
The fundamental natures of dark energy and dark matter remain two of the biggest mysteries in modern cosmology. We show that a simple coupling between dark energy and dark matter can simultaneously address two distinct hints at new physics coming from cosmological observations. The first is the recent evidence from the DESI project and supernovae observations that the dark energy equation of...
Pulsar timing array (PTA) experiments aim to detect nHz-frequency gravitational waves using high-precision timing of millisecond pulsars. Multiple PTA collaborations have recently reported evidence for a stochastic gravitational wave background (SGWB), expected to arise predominantly from a population of inspiraling supermassive black hole binaries. In this talk, I will discuss how PTA...
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...
In recent years, attention has shifted to probes of sub-GeV dark matter. In this work, we explore the direct detection prospects of crystal targets through their single (or multi) phonon response to dark matter scattering in the keV-GeV mass range, which couples effectively to protons/neutrons via spin-dependent interactions. In particular, we consider coupling the SM to the dark matter...
The nature of a certain type of supercooled phase transition, where the supercooling is guaranteed to end due to the curvature of the potential at the origin experiencing a sign flip at some temperature. As the potential barrier is quickly vanishing at the temperature scale of the phase transition, is not immediately clear if critical bubbles are able to form. This clearly can have large...
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...
We study a mechanism to make dark matter stable based on the Pauli blocking in the fermion background. We examine this scenario in both Boltzmann equation and quantum field formulation and evaluate the evolution equations. We apply this mechanism to a realistic model of neutrino and dark matter.
Primordial black holes (PBHs) have been invoked as a component of dark matter, and PBH mergers will produce copious gravitational radiation. The future launch of the Laser Interferometer Space Antenna (LISA), an ESA/NASA gravitational wave observatory set to launch in 2035, will open a new low-frequency band of the gravitational wave sky, one that may include PBH mergers. Our work focuses on...
We propose a mechanism for the generation of magnetic fields on cosmological scales that is operative after recombination. An essential
ingredient is an instability of the electromagnetic field driven by an oscillating pseudo-scalar dark matter field, $\phi$, that is coupled to the electromagnetic field tensor via a $\phi F \wedge F$ term in the Lagrangian of axion-electrodynamics. We find...
Gravitational waves from compact binary coalescences offer a promising avenue for inferring the Hubble parameter independently of electromagnetic distance ladders or cosmic microwave background observations. As an independent probe of cosmic expansion, it has the potential to contribute to ongoing efforts to resolve the Hubble tension and to shed light on the properties of the dark sector. In...
In the Fuzzy Dark Matter (FDM) scenario, the dark matter is composed of an ultra-light scalar field with coherence length and wave interference on astrophysical scales. Scalar fields generically have quartic self-interactions that modify their dispersion relation and the associated evolution of density perturbations. In this talk, I will present the first dedicated analysis of the relationship...
In the era of upcoming cosmic surveys, the bright sky will be more revealing than ever, allowing us to disentangle the most intriguing mysteries of the origins, content, and evolution of the universe. In this talk, I will highlight the fundamentals of extended gravity theories, and I will focus on the quintessence, probabilistic gravity, and functors of action theories (FAT). I will emphasize...
