The detection of the stochastic gravitational wave background by NANOGrav imposes constraints on the mass of compact cores of ultra-light dark matter, also known as "solitons", surrounding supermassive black holes found at the centers of large galaxies. The strong dynamical friction between the rotating black holes and the solitons competes with gravitational emission, resulting in a...
Fermion soliton stars are a motivated model of exotic compact objects in which a nonlinear self-interacting real scalar field couples to a fermion via a Yukawa term, giving rise to an effective fermion mass that depends on the fluid properties. For the first time, we study this model within General Relativity without approximations, finding static and spherically symmetric solutions. If the...
The relation between gravity and quantum mechanics is investigated in this work. The link is given by the wave packet expansion process, rooted from the Uncertainty Principle.
The wave packet spreading is studying in spherical coordinates, whose width $\sigma(t)$ is expressed in terms of $G$ and $c$, instead of $\hbar$. Therefore, for masses larger than the Planck mass, a faster dispersion...
Ultracold neutrons are a great tool to explore the quantum nature of the gravitational interaction. From a theoretical perspective, starting from a Dirac equation in curved spacetime, one can derive the non-relativistic Schrodinger equation that governs the evolution of the neutron's wave function in the Earth's gravitational field. At the lowest order, this procedure simply reproduce a...
Since the first LIGO/Virgo detection, Gravitational Waves (GWs) have been very promising as a new complementary probe to understand our Universe. One of the next challenges of GW search is the detection and characterization of the stochastic gravitational wave background (SGWB), that is expected to open a window on the very early Universe (cosmological background) and to provide us new...
Primordial black holes are proposed to have formed in the very early universe and a first detection of them would provide valuable insights into cosmology, dark matter, and physics of the very early universe. Primordial black holes could form binaries systems with chirp masses of the order of $\mathcal{O}(10^{-5})M_\odot - \mathcal{O}(10^{-3})M_\odot$, which would emit long transient...
In this presentation, I will provide a comprehensive analysis of the uncertainty regarding the merger rate density and mass spectrum of binary black holes (BBHs) originating from Population III (Pop. III) stars. I will explore four distinct formation histories of Pop. III stars and investigate 11 models concerning the initial orbital properties of their binary systems.
The results I have...
In massive scalar-tenor theories, a Compton length-scale will be introduced by the scalar mass. In the context of binary systems, the influences of such length-scale include the suppressions in the scalar interaction between the two members when the orbital separation well exceeds the scale, and in the emissivity of scalar radiation with wavelength longer than that. We focus here on coalescing...
Accretion discs formed in binary neutron star (BNS) mergers are the engine responsible for many relevant physical processes. Numerical simulations of accretion discs have been used to investigate the outcome of such processes, but the initial configuration of the disc lack of an unique analytical description and some assumptions are still needed. In this work we analyze in detail the...
An accurate modeling of the gravitational waves emitted by coalescing binary systems, comprising black holes and neutron stars, is fundamental to fully leverage the capabilities of current and next-generation gravitational wave detectors.
In particular the inspiral phase of the binary system can be described using several approximation schemes, among which the post-Newtonian (PN)...
Star clusters are the dynamical formation channel for binary black holes (BBHs). In these dense systems, BBH mergers are not only driven by gravitational wave (GW) emission but also by binary-single encounters with other objects in the environment. The focus of the talk will be on the GW signals generated by close encounters between a BBH and a third black hole. We characterized diverse GW...
Primordial Black Holes (PBHs) may form in the early Universe by formation mechanisms such as large density fluctuations, bubble collisions, collapse of domain walls or collapse of cosmic strings. PBHs are considered as one of the possible candidates for dark matter. A huge amount of work has been done on PBHs because it is considered that the merger of PBHs binaries can also lead to the origin...
Measuring eccentricity from gravitational wave signals is of fundamental importance in order to address questions about the origin and formation of stellar-mass binary black holes. In this work we present a new, systematic set of spinning but non-precessing numerical relativity (NR) simulations of eccentric binary black hole coalescences, with initial eccentricities up to 0.3 and mass ratios...
Elementary particles such as quarks and gluons are expected to be fundamental degrees of freedom at ultra high temperatures or densities, while natural phenomena in our daily lives are described in terms of hadronic degrees of freedom. Massive neutron stars and remnants of binary neutron star mergers may contain quark matter, but it is not known how the transition from hadron matter to quark...
The detection of continuous gravitational wave emission from a neutron star in a binary system is challenging for present and future LIGO-VIRGO-KAGRA searches. The motivation is the accurate modelling of the phase that depends on the binary orbital parameters. Indeed, even when the parameters are known within some uncertainties, search strategies are usually computationally prohibitive due to...
Black hole superradiance induces the formation of a cloud of ultralight bosons, such as axions. To detect the signature of the cloud, it is important to consider black holes in binary systems. As a binary inspirals and the separation becomes sufficiently small, the cloud is disrupted by the tidal interaction from the companion. Although axions generally have self-interactions, this effect has...
In this study we investigate the nexus between the Spin( 12 ) and the SU(1, 1)−quasi boson Lie structure and reveal related properties as well as some decomposition of spin particles. We show that the SU(1, 1)−quasi boson has a left invariant Haar measure and we ascertain its spherical Fourier transformation. We finally show that this spherical Fourier transformation of type delta is a...
The Kruskal-Szekeres coordinates construction for the Schwarzschild spacetime could be viewed geometrically as a squeezing of the $t$-line associated with the asymptotic observer into a single point, at the event horizon $r=2M$. Starting from this point, we extend the Kruskal charting to spacetimes with two horizons, in particular the Reissner-Nordström manifold, $\mathcal{M}_{RN}$. We develop...
Einstein Telescope (ET) is a proposed third generation, wide-band gravitational wave (GW) detector. Given its improved detection sensitivity in comparison to the second generation detectors, it will be capable of exploring the universe with GWs up to very high redshifts. In this work we present the algorithm to answer three main questions regarding the star formation rate density (SFR) (i)...
We present LANCELOT: LibrAry for N-body large sCale structurE simuLations in mOdified Theories of gravitation. This library not only incorporates various modified cosmologies but additionally includes massive neutrinos. For modified theories of gravitation, in the current work, we consider three cases: modified teleparallel gravitation $f(T) = T + \alpha(1-e^{-p\frac{T}{T_0}})$, it's...
The main objective of this article is to study the fractal FRW cosmological model consisting two forms of dark energy. We studied behavior of the universe in a fractal framework using dark energy accommodated in our universe. The solution of field equations are obtained by using Hubble parameter for transit scale factor $ H(z)=\epsilon \left( a^{-\delta}+\lambda\right)$
. We have obtained...
