Resumen:

Neutron stars reach densities several times higher than nuclear atomic density in their interiors. This causes their cores to be in a state of matter that is impossible to reproduce in terrestrial laboratories. A phase transition between hadronic matter and pure quark matter is expected to occur within these objects, giving rise to hybrid stars. We build the hybrid equation of state by considering a crust equation of state which is added to the outer core of these compact objects using a new thermodynamically consistent formalism. This new way of "gluing" two equations of state will be compared with the classical one, which does not consider the causal and thermodynamic consistency. Then, using the relativistic hydrostatic equilibrium TOV equations, we will obtain the mass-radius relationship for our stellar objects, in order to compare them with the existing observational constraints of neutron stars. In addition, we investigate possible changes that the new matching formalism can cause in the frequencies of the oscillation modes of these hybrid stars.

Resumen:

The mean free path (MFP) approximation is a simple but popular analytic model that describes the rate at which objects collide in dense environments. In this contribution, we aim to quantify the validity of the MFP approximation by confronting analytic theory with numerical simulations. We focus on stellar collisions in dense astrophysical environments as our case study, varying the number of interacting particles from the low- (i.e., N = 3, 4, 5, ...) to high-particle (i.e., N > 100) number limits and exploring a range of particle masses and radii. Our results illustrate that the MFP approximation performs very well for the considerable parameter space explored in this work, with the simulated and theoretical predictions typically agreeing to with a factor of two or better.

Resumen:

In the context of multi-messenger neutron star astronomy, we explore the frequency and damping time of the fundamental f-mode, responsible for most of the gravitational wave energy, of compact objects, considering a range of model-independent hybrid equations of state. We analyze the impact of the slow conversion of hadrons to quarks, leading to slow and stable hybrid stars. We also study the validity of universal relationships when slow and stable hybrid stars are considered. The latter, potentially limits the applicability of asteroseismology methods in estimating the properties of pulsating compact objects.