We propose a new class of inflationary attractors in metric-affine gravity. Such class features a non-minimal coupling $\tilde\xi \, \Omega(\phi)$ with the Holst invariant $\tilde {\cal R}$ and an inflaton potential proportional to $\Omega(\phi)^2$. The attractor behaviour of the class takes place with two combined strong coupling limits. The first limit is realized at large $\tilde\xi$, which...
Abstract:
Numerical relativity (NR) has revolutionized our understanding of strong-field gravity, enabling high-fidelity simulations of compact binary systems. This paper reviews recent breakthroughs in NR methodologies, with emphasis on binary neutron star (BNS) and black hole–neutron star (BHNS) mergers. We discuss advancements in adaptive mesh refinement, constraint-damping formulations,...
Observations of massive pulsars indicate that the core densities of compact stars can greatly exceed nuclear saturation density, possibly giving rise to exotic forms of matter such as hyperons, meson condensates, and quark matter. Among meson condensates, anti-kaon ($K^-$) condensation stands out as a promising candidate, though the nature of kaon-meson interactions remains incompletely...
The neutron star equation of state (EOS) remains one of the fundamental challenges in nuclear astrophysics, with current modeling approaches facing distinct limitations. Phenomenological models, while successful in reproducing nuclear and astrophysical constraints, suffer from inherent model dependencies in their parametrizations. These dependencies can introduce biases in posterior...
We study rotating hybrid stars, with a particular emphasis on the effect of a deconfinement phase
transition on their properties at high spin. Our analysis is based on a hybrid equation of state with
a phase transition from hypernuclear matter to color-superconducting quark matter, where both
phases are described within a relativistic density functional approach. By varying the vector...
Born from gravitational-core collapse supernovae, with initial temperatures as high as $\sim 10^{12}$K, neutron stars cool down to temperatures $10^9$ K within a few days, providing a unique opportunity to explore matter under extreme conditions. In particular, neutron stars contain nuclear superfluids whose presence is supported by observations of pulsar frequency glitches, rapid decline in...
Understanding the dynamics of magnetically arrested accretion disks (MAD) is crucial for deciphering relativistic jet launching mechanisms in black hole systems. General relativistic magnetohydrodynamics (GRMHD) simulations provide the most comprehensive framework for probing these extreme environments, where angular momentum transport efficiency fundamentally governs accretion-ejection...
We perform a Bayesian analysis of the equation of state (EOS) constraints using recent observational data, including pulsar masses, radii, and tidal deformabilities. Our focus is on a class of hybrid neutron star EOS that incorporates color superconducting quark matter, based on a recently developed nonlocal chiral quark model. The nuclear matter phase is described using a relativistic density...
We have conducted an extensive study using a diverse set of equations of state (EoSs) to uncover strong relationships between neutron star (NS) observables and the underlying EoS parameters using symbolic regression method. These EoS models, derived from a mix of agnostic and physics-based approaches, considered neutron stars composed of nucleons, hyperons, and other exotic degrees of freedom...
The relationship between cosmic strings and black holes is examined in this work, with particular attention paid to how cosmic strings affect the spin and accretion processes of black holes. The study investigates the effects of a cosmic string on the mass, spin, and rotational energy of black holes and how changes in the innermost stable circular orbit (ISCO) of accretion disks can be used to...
The pseudo-Riemann metric organization of spacetime can describe the quasi-elastic field hierarchy with the constant rest energy integral in the case of negligible inelastic losses or non-metric intrusions. Visible matter consists of very dense regions of massive fields associated with the material analogue of the Einstein tensor. The non-Schwarzschild metric solution of the non-dual analogue...
We investigate the dynamics of test particles near a magnetized black hole surrounded by quintessence which is modeled as an anisotropic fluid with a specific equation of state [1,2]. The motion of both massive and massless test particles is analyzed using the Lagrangian formalism, with particular focus on the effective potential governing their trajectories. Quintessence modifies the...
Abstract
We analyzed the recent controversies in the definitions of the
Feynman-Dyson propagator for the field operator. In this work we
present some insights with respect to this for spin 1/2. Both
algebraic equation $Det(\hat p − m) = 0$ and $Det(\hat p + m) = 0$ for
u− and v− 4-spinors have solutions with
$p_0 = \pm E_p = \pm \sqrt{p^2 + m^2}$. The same is true for
higher-spin...
Gaia detected a new population of neutron stars. They are the oldest neutron stars known, which are members of wide binaries with small orbital velocities. I argue that their current orbits are fossils of their turbulent youth and present considerable clues to the physics of their younger selves.
Transiently accreting low-mass x-ray binaries have the potential to probe the core composition of their neutron stars via deep crustal heating caused by nuclear reactions. We statistically assess this deep crustal heating scenario, taking into account the various microphysical and astrophysical uncertainties. We find that despite the sizable uncertainties, there is a chance to discriminate...
One of the important properties of nuclear forces is
the nuclear repulsive core which provides a stability for atomic nuclei, making
possible the emergence of a structure for the visible matter.
However the origin of the nuclear core is poorly understood. We discuss how
the strong repulsive nuclear core at short distances can emerge from QCD,
even though one should expect a...
The combined effects of spatial curvature and topology are investigated on the properties of the vacuum state for a charged scalar field localized on the (2+1)-dimensional Beltrami pseudosphere. It is assumed that the field obeys the quasiperiodicity condition along azimuthal angle with a constant phase. As important local characteristics of the vacuum state the vacuum expectation values...
Spherical orbits around rotating black holes have a major astrophysical importance. In the presence of quintessential matter [1, 2], the geodesic equations can be investigated using a combined numerical-analytical approach [3]. One may notice significant differences compared to the results previously derived for Kerr black holes [4]. Also, as it is known, the rotating black holes produce...
The ground based gravitational wave detectors such as LIGO, measures metric perturbation in to a preferred polarization basis. The initial Ligo configuration runs were based on second post Newtonian approximation of quadrupolar moments. A post Minkowskian and a post Newtonian approach is adopted for the wave form generation of slow moving and non-spinning binaries. The non linearity of...
We investigate Tsallis holographic dark energy (THDE) model in light of modern observations of supernovae, Hubble parameter measurements, data for baryon acoustic oscillations and fluctuations of matter density. The dark energy density for THDE model is written as ρd=3C2/L4−2γ where C and γ are some constants. Scale L is infrared cut-off length for which we use the event horizon. For analysis...
Models of neutron and quark stars are considered in the case of a uniform density distribution. A universal
algebraic equation, valid for any equation of state, is obtained in General Relativity. This equation allows one to find
the approximate mass of a star for a given density without resorting to the integration of differential equations. The solutions neutron star models for various...
