Brown dwarfs (BDs) are celestial objects representing the link between the least massive main-sequence stars and giant gas planets. I will present a recent analysis (Bhattacharjee et al.,2023) where consider a sample of nine nearby ($<$ 11 pc distance), cold and old BDs and look for gamma-ray signal from the direction of these objects using 13 years of \textit{Fermi}-LAT data. In the absence...
Precision analysis of galaxy-galaxy strong gravitational lensing images provides a unique way of characterizing dark matter (DM) substructures and could allow us to uncover the fundamental properties of DM's constituents. In reality, this analysis is extremely challenging due to the high dimensionality of lensing observations and the richly-structured parameter space of lensing systems....
Upcoming neutrino experiments are expected to detect the Diffuse Supernova Neutrino Background (DSNB). This requires pondering all possible sources of background. Sub-GeV dark matter (DM) which annihilates into neutrinos is a potential background that has not been considered so far. We simulate DSNB and DM signals, as well as backgrounds in the Hyper-Kamiokande detector. We find that...
Fuzzy dark matter (FDM) modifies the internal properties of dark matter halos and large-scale cosmic environments. In this talk I will share selected insights from recent work based on cosmological $N$-body simulations. We find that the concentration of FDM-like halos peaks around two decades above the half-mode mass, breaking the approximate universality of halo density profiles observed in...
The hidden hand of dark matter (DM) shaping the Milky Way remains elusive as the dark substructure of the Galaxy is probed by tracing the dance of celestial bodies in the cosmic shadows. In our work, we exploit the increase of volume and precision in data brought about by ongoing large-scale stellar surveys and use approximately 1.6 million Red Giant Branch stars from Gaia DR3. We present a...
Electroweak multiplets, i.e. $n$-plets which are colour singlets and are charged under the $SU(2)$ gauge group of the Standard Model, are the prototype of WIMP Dark Matter (DM). The phenomenology of these candidates is significantly affected by two non-perturbative effects: Sommerfeld enhancement and bound states formation (BSF). While the former has been the focus of many studies, the latter...
Stellar observables have often been shown to be powerful probes in searches for Feebly interacting particles (FIPs), such as axions, scalars, dark photons, and majorons. In this talk, I will summarize some of the most recent developments, with a focus on supernovae and astrophysical transients.
In this work, we explore the consequences of neutrino decay facilitated by a neutral scalar on possible cosmic neutrino background (CνB) detection in the future, especially in the PTOLEMY experiment. We analyze the distortion of the expected event spectrum as a function of the singlet mass and Yukawa couplings, and we consider both a three-neutrino scenario and a scenario with an extra sterile...
Lorentz invariance is a pillar symmetry of the Standard Model. Yet, it may be violated in proposed extensions, inducing preference for particular directions in the propagation of particles. This type of Lorentz-invariance violation (LIV) is difficult to test. Fortunately, high-energy astrophysical neutrinos, with TeV–PeV energies and cosmological-scale baselines, provide us with a unique...
The aim of this presentation is to introduce a dark extension of the SM that communicates to it through three portals: neutrino, vector and scalar mixing, by which it could be possible to explain the Low Energy Excess (LEE) at MiniBooNE. In the model, Heavy Neutral leptons are produced by upscattering via a dark photon, with masses around 10 MeV – 2 GeV, and subsequently decay into an...
TeV blazars dominate the extragalactic gamma-ray sky and highly energetic pair beams arising from such blazar jets underproduce gamma rays in the GeV band while inverse-Compton scattering off the cosmic microwave background. Recent Fermi-LAT isotropic gamma-ray background measurements suggest that space plasma instabilities can play a crucial role in alleviating this GeV-TeV tension by...
Recently, the ANITA collaboration announced the detection of new, unsettling Ultra-High-Energy (UHE) events. Understanding their origin is pressing to ensure success of the incoming UHE neutrino program.
In this talk, I will discuss the ANITA-IV events in contrast with the lack of observations in the IceCube Neutrino Observatory. I will introduce a general framework to study the...
The creation of anti-nuclei in the Galaxy has been has been discussed as a possible signal of exotic production mechanisms such as primordial black hole evaporation or dark matter decay/annihilation in addition to the more conventional production from cosmic-ray (CR) interactions. Tentative observations of cosmic-ray antihelium by the AMS-02 collaboration have re-energized the quest to use...
Although the CMB and galaxy surveys provide precise measurements of the primordial power spectrum at large scales, the small-scale power spectrum remains largely unconstrained. An enhancement in the small-scale primordial spectrum can lead to the formation of Ultra-Compact-Mini-Halos (UCMH) much earlier than standard halo can form. As a result, the DM annihilation signal receives a boost than...
We show that a minimal scenario, utilizing only the graviton as an intermediate messenger between the inflaton, the dark sector and the Standard Model (SM), is able to generate simultaneously the observed relic density of dark matter (DM), the baryon asymmetry through leptogenesis, as well as a sufficiently hot thermal bath after inflation. The possibility of reheating via minimal...
Correlation functions of primordial density fluctuations provide an exciting probe of the physics governing the earliest moments of our Universe. However, the standard approach to compute them is technically challenging. Theoretical predictions are therefore available only in restricted classes of theories, which can completely bias the interpretation of data.
In this talk, I will present...
In the Standard Model the electroweak phase transition is a crossover, but in many beyond the Standard Model theories the transition is of first order. Strong first order phase transitions could produce gravitational waves that might be detectable by the Laser Interferometer Space Antenna (LISA). Perturbation theory is commonly used to estimate the parameters that enter the calculation of...
Introducing an energy transfer between the inflaton field and a thermal bath modifies the primordial power spectrum $\mathcal{P}_\mathcal{R}$ due to the thermal fluctuations acting as a stochastic source for the curvature perturbations. We propose a fast and accurate method to compute $\mathcal{P}_\mathcal{R}$ in this context based on the Fokker-Planck equation, and verify its consistency...
As the nature of dark matter remains unresolved, existence of a whole dark sector is an intriguing possibility. It is also natural to assume that such dark sector couples to inflationary dynamics. As an example, we consider the case of warm axion inflation coupled to a non-Abelian dark sector, both in weakly and strongly coupled regime. We show that this simple setup provides rich...
Cosmic birefringence is the in-vacuo rotation of the linear polarization plane experienced by photons of the Cosmic Microwave Background (CMB) radiation when theoretically well-motivated parity-violating extensions of Maxwell electromagnetism are considered. If the angle parametrizing such a rotation is dependent on the photon's direction, then this phenomenon is called Anisotropic Cosmic...
The weak gravitation lensing of the Cosmic Microwave Background
(CMB) [1] rows a wealth of information about the late-time universe in the
CMB data we observe through ground-based and space-based telescopes.
In this talk, I propose a method to probe Galaxy-cluster mass profiles
from the lensing signature of CMB in arcmin scales. In the first part, I
describe how a theoretical halo model...
LSST will provide an unprecedented wealth of astronomical data, with which we will be able to tightly constrain the values of the cosmological parameters, notably those which describe the poorly understood dark energy component. As weak lensing and galaxy clustering measurements provide a way to infer key cosmological quantities such as the dark matter distribution, the evolution of cosmic...
As a result of the observed discrepancies within the $\Lambda \mathrm{CDM}$ model, a lot of work is being done to reconcile the observations from the early and late universe with new cosmological models. The resulting model testing is often based on inference algorithms that depend on a large number of computationally intensive simulations that conclude in large computational efforts.
In...
Galaxies are biased tracers of the underlying dark matter density field. If we work with a single tracer, its two-point function will be symmetric under exchange of the pair of galaxies under consideration. But if we look at two different tracers, then in principle their cross-correlation could be not symmetric (Dai et al. 2016). This locally antisymmetric signal arises naturally when the two...
We determine the dipole in the Pantheon+ data. We find that, while its amplitude roughly agrees with the dipole found in the cosmic microwave background which is attributed to the motion of the solar system with respect to the cosmic rest frame, the direction is different at very high significance. While the amplitude depends on the lower redshift cutoff, the direction is quite stable. For...
We consider a minimal non-supersymmetric SO(10) Grand Unified Theory (GUT) model that can reproduce the observed fermionic masses and mixing parameters of the Standard Model. We calculate the scales of spontaneous symmetry breaking from the GUT to the Standard Model gauge group using two-loop renormalisation group equations. This procedure determines the proton decay rate and the scale of...
The anisotropies of the stochastic gravitational wave background, as produced in the early phases of cosmological evolution, can act as a key probe of the primordial universe particle content. We point out a universal property of gravitational wave anisotropies of cosmological origin: for adiabatic initial conditions, their angular power spectrum is insensitive to the equation of state of the...
Primordial Black Holes (PBH) have attracted much attention in the last years as they may explain some of the LIGO/Virgo/KAGRA observations and significantly contribute to the dark matter in our universe.
The third generation of ground-based gravitational wave detectors will have the unique opportunity to set stringent bounds on this putative population of objects.
Focusing on the...
Besides the transient effect, the passage of a gravitational wave also causes a persistent displacement in the relative position of an interferometer's test masses through the "nonlinear memory effect".
This effect is generated by the gravitational backreaction of the waves themselves and encodes additional information about the source.
In this talk, we present the implications of...
Long baseline atom interferometers (LBAI) offer an exciting opportunity to explore mid-frequency gravitational waves. In this talk I will advocate for targeting the total 'gravitational wave background', surveying the landscape of possible contributions within this frequency band. I will demonstrate that the cumulative signal from the inspirals of the LIGO-Virgo stellar-mass binaries is well...
Effective Field Theories (EFTs) are crucial for new physics searches in the electroweak sector. They are a model-independent framework which can be used to classify the low-energy effects of heavy, new physics on experimental results which deviate from the standard model prediction. For this reason, the Standard Model Effective Field Theory (SMEFT), where the Higgs doublet transforms linearly...
