Identifying sources of ultra-high-energy (UHE) particles is one of the key tasks to understand our non-thermal universe in the extreme energy scales. Flares from some astrophysical objects are one of the prominent candidates for producing such UHE particles. The search for sources of UHE neutral particles is easier than for those of UHE charged particles, as the neutrals are not affected by...
Gravitational Waves have proven to be an excellent tool for understanding populations of binaries. For the upcoming LISA detector, Binary White Dwarfs are one of the most promising sources. In this work, we focus on modelling the Gravitational Wave background from White Dwarf Binaries in the LISA sensitivity range and building a model of their population in the Milky Way.
The COMPAS binary...
Slow first-order phase transitions generate large inhomogeneities that can lead to the formation of primordial black holes (PBHs). We show that the gravitational wave (GW) spectrum then consists of a primary component sourced by bubble collisions and a secondary one induced by large perturbations. The latter gives the dominant peak if $\beta/H_0 <12$, impacting, in particular, the...
Terminal velocity reached by bubble walls in cosmological first-order phase transitions is an important parameter determining both primordial gravitational wave spectrum and the production of baryon asymmetry in models of electroweak baryogenesis. We developed a numerical code to study the real-time evolution of expanding bubbles and investigate how their walls reach stationary states. We...
The DarkSide experiment has been designed to search for direct interactions of the cold dark matter particles. Due to the expected very low signal, different techniques have been implemented to minimize the background. Currently the DarkSide-20k (DS-20k) detector is under construction in the underground laboratory at Gran Sasso (LNGS) in Italy.
One of the material which is going to be...
Low-mass galaxies provide a powerful tool with which to investigate departures from the standard cosmological paradigm in models that suppress the abundance of small dark matter structures. One of the simplest metrics that can be used to compare different models is the abundance of satellite galaxies in the Milky Way. Viable dark matter models must produce enough substructure to host the...
The cosmic web is the largest geometric structure in our universe, consisting of an intricate network of voids, walls, filaments, and dense nodes. $\Lambda$CDM predicts that dark matter halos, which trace this multiscale structure, form hierarchically and host smaller substructures known as subhalos. Understanding how the abundance and internal kinematics of subhalos vary across different...
DarkSide-20k, a direct dark matter search experiment, is located at the Gran Sasso National Laboratory (LNGS), Italy. It is designed to achieve groundbreaking 200-tonne-year exposure, nearly free from instrumental backgrounds. The core of the detector is a dual-phase Time Projection Chamber (TPC) containing 50 tonnes (20 tonnes fiducial) of underground liquid argon (UAr) with low levels of...
Blazars, a subclass of active galactic nuclei, exhibit highly variable
non-thermal emission originating from relativistic jets aligned with the line
of sight to Earth. This variability offers key insights into the physical
processes driving these systems. In this study, we analyzed the X-ray spectra
of a sample of X-ray-bright blazars observed with NICER, fitting three
spectral models: a...
What dominates the quasars Spectral Energy Distribution at IR is dusty torus emission. It is described as the thermal reprocessor of the internal X-ray/UV accretion disc continuum.
Thus, internally, its emission strength should correlate with the strength of illuminating radiation and the amount of captured energy (due to covering factor). In the type 1 AGN, where the torus does not cross the...
Residual eccentricity in gravitational waveforms can be a unique tool to identify binary systems formed in dynamical environments. In general relativity, eccentricity is not defined uniquely. Different waveform models rely on gauge-dependent definitions of eccentricity, which leads to incompatibility between them. We remove this ambiguity by employing a gauge-invariant eccentricity definition...
The Hubble constant is a crucial cosmological parameter that is a measure of the rate of change of the cosmic scale factor per unit cosmic scale factor i.e. a_dot / a. There is a considerable discrepancy between the measurements of the Hubble constant from standard candle observations and those from cosmic microwave background (CMB) observations. Data from gravitational wave (GW) events can...
Fast Radio Bursts (FRBs) are bright, millisecond-duration radio transients, a subset of which have been precisely localized to their host galaxies. Due to their high dispersion measures, FRBs offer unique insights into the ionized plasma along their sightlines, enabling their use as cosmological probes. One critical challenge in modern cosmology is the Hubble tension -- a persistent...
The development of radiation detectors has seen significant
advancements over the past decades, particularly in those relying on
electroluminescence. Optical time projection chambers (OTPCs) have
become the preferred choice in the field of direct dark matter
searches (more specifically in WIMP searches), having also been
considered for neutrino experiments. Dark matter experiments...
Relativistic jets are powerful collimated outflows from accreting compact objects, especially spinning black holes. Jets, as well as their associated mechanisms of energy dissipation and particle acceleration, can be investigated by global or local numerical simulations using methods like general-relativistic magneto-hydro-dynamics (GRMHD), particle-in-cell (PIC), etc. This presentation shall...
The nature of dark matter remains unknown and its origin is currently one of the most important questions in physics. In particular direct searches for WIMP dark matter particle interactions with ordinary matter are carried out with large detectors located in underground laboratories to suppress the background of cosmic rays. One of the currently most promising detection technologies is based...
An extensive air shower with a particularly large depth of maximum development, Xmax, (~1200 ) was observed at the Pierre Auger Observatory. With the help of the Top-Down Reconstruction chain, we aim at further studying this air shower. The Top-Down chain is a Monte Carlo simulation scheme which focuses on reconstructing the observed air shower while accounting for the well-known discrepancy...
Neutrino Astronomy is proceeding with the development of new neutrino telescopes. The opaqueness of the Universe to the photons at high energies makes the neutrino an excellent probe to study most of the energetic objects of the cosmos. With this aim, the Pacific Ocean Neutrino Telescope (P-ONE) is planned to be deployed at the Cascadian Basin in the Pacific Ocean, off the coast of Vancouver...
Axions, originally introduced to address the strong CP problem in quantum chromodynamics, if sufficiently abundant, are a compelling candidate for dark matter. Axions or axion-like particles (ALPs), as components of the cold dark matter in our Galaxy, can be treated as a classical field. These ALPs are theorised to couple to the spin of nucleons and nuclei either directly, via the axion wind...
Identification of the primary cosmic rays on an event-by-event basis stands as one of the main goals for any cosmic-ray observatory. Several cosmic-ray air-shower experiments use photon tags for gamma/hadron primary particle discrimination. These photon tag variables, for example Ptail or Sb, are easily built from the total signals measured in an array of detectors and are correlated with the...
