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...
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...
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....
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...
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...
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.
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)
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.
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...
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...
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...
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...
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...
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 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...
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...
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...
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...
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...
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 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...
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...
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...
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...
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...
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...
