In this presentation I will show how we can constrain Dark Matter (DM) scenarios with the supernova remnant HESS J1731-347. We assume the compact object to be an admixture of DM and Neutron Star, and presume the former to behave as a free Fermi gas. For the Neutron Star we use recently calculated regulator-independent equations of state for neutron stars obtained from first principles. Using...
The impact of dark matter (DM) on highly magnetized neutron stars (NSs) is explored using a two-fluid approach. Our model considers self-interacting, non-annihilating, asymmetric fermionic DM coupled to baryonic matter via gravity. Using the relativistic mean-field model with density-dependent magnetic fields, we examine how DM particle mass, mass fraction, and magnetic field strength affect...
The direct Urca (dUrca) process is a key mechanism driving rapid neutrino cooling in neutron stars, with its baryon density activation threshold determined by the microscopic model for nuclear matter. Understanding how nuclear interactions shape the dUrca threshold is essential for interpreting neutron star thermal evolution, particularly in light of recent studies on exceptionally cold...
We explore "ridges" in the macroscopic properties of rotating neutron stars as potential indicators of first-order phase transitions in their matter. These phase transitions induce non-analytic behavior in observables like angular momentum, moment of inertia, mass, and radii, with the intensity of this behavior directly tied to the latent heat of the transition. Notably, the Seidov limit sets...
We study the thermal index of low-density, high-temperature dense matter. We use the virial expansion to account for nuclear interaction effects. We focus on the region of validity of the expansion, which reaches $10^{-3}$ fm$^{-3}$ at $T=5$ MeV up to almost saturation density at $T=50$ MeV.
In pure neutron matter, we find an analytical expression for the thermal index, and show that it is...
The core of a neutron star is an entity of enigma due to the mystery surrounding its composition. Insights from nuclear theory and perturbative QCD suggest the possible existence of hybrid stars having a phase transition from hadronic matter to quark matter. This study presents how different types of phase transition (namely, Maxwell and Gibbs) can leave imprints on gravitational waves from...
Unlike the widely used Walecka-type models for studying nuclear matter properties and neutron star structures, we extended the linear sigma model, originally developed by Schechter and his colleagues, to the baryonic sector to explore dense nucleon systems. This extended framework is termed the baryonic extended linear sigma model (bELSM).
The bELSM incorporates 2-quark and 4-quark...
An intriguing hypothesis states that ordinary hadronic matter in bulk is a metastable state (i.e., a local minimum) of strongly interacting matter, while strange quark matter (SQM) is absolutely stable (i.e., the global minimum). These two phases would be separated by a potential barrier that prevents a spontaneous deconfinement transition of ordinary hadronic matter into SQM.
Our work aims...
Matter with extreme baryon density is believed to occur in the core of a neutron star, allowing for various novel phases, from conventional nucleon superfluid phase to exotic high baryon density QCD phases. Here, we point out a unique phenomenon associated with phase transitions to a superfluid phase, which may be the nucleon superfluid phase, or a phase like CFL phase, allowing for superfluid...
While symmetric nuclear matter has been studied in laboratories, neutron star matter is characterized by high asymmetry. Therefore, by examining the strongly interacting matter properties in a wide range of densities and isospin asymmetry we confront two regimes to understand how the enforced electric neutrality and beta equilibrium alter the onset density of quark matter. Particularly, we...
The influence of modified gravity on the bulk properties of neutron stars can be constrained through integration of the Tolman–Oppenheimer–Volkoff (TOV) equations, provided the input equation of state (EoS) is derived solely from microscopic physics. This becomes particularly challenging in the intermediate to high baryon-density regime, where neither nuclear nor chiral effective field...
We investigate the properties of non-accreted crusts of neo-neutron stars, i.e., of inhomogeneous subsaturation warm dense matter in beta equilibrium. We present two novel results and one known, but frequently ignored property of such matter. The new features include: the presence of an exotic light nucleus, $^{14}$He, starting from the baryon density of $\approx~0.01~$fm$^{-3}$ and up to the...
Matching the equation of state (EoS) of pure neutron matter (PNM) with the EoS of the crust (outer and inner) of a neutron star (NS) is fundamental to understanding the properties of neutron stars, but remains a major challenge.
Our starting point here is the EoS band obtained for PNM at zero temperature and very low densities, expressed in terms of the nucleon scattering data [1], and...
The Equation of State (EoS) of nuclear matter is related to many topics in nuclear physics. In particular, it is crucial for understanding the structure of compact objects such as neutron stars. In the conservative hypothesis of a purely nucleonic composition of neutron star matter, the EoS is fully determined in terms of the so-called nuclear matter parameters (NMPs), which, in principle, can...
This talk investigates the impact of assuming a barotropic equation of state (EoS) for neutron stars, which neglects potential out-of-β-equilibrium effects, on the calculation of oscillation modes. We focus on how the assumption of β-equilibrated EoS influences the frequencies of the non-radial fundamental (f) and first pressure (p1) modes. These calculations are performed using a wide set of...
We investigate the hyperonic equation of state (EoS) within the non-linear derivative model that incorporates a momentum dependence on the interactions, with a special emphasis on properly establishing the conditions for hyperon appearance in neutron star matter. We demonstrate that hyperons can appear at finite momentum, forming a so-called “moat” region, even when they are
absent at zero...
