Efectos del campo magn\'etico en un gas de bosones vectoriales neutros: aplicaciones astrof\'isicas

TL;DR

This thesis investigates how magnetic fields influence neutron star matter, especially regarding phase transitions, anisotropic pressures, and star structure, with implications for astrophysical phenomena like jets and magnetic field origins.

Contribution

It introduces a model for the effects of magnetic fields on neutron star matter using neutral vector bosons, including anisotropic equations of state and self-magnetization, applied to star structure and jet formation.

Findings

Magnetic fields promote Bose-Einstein condensation in neutron star matter.

Anisotropic pressures lead to potential magnetic collapse at low densities or high fields.

Self-magnetization of bosons can sustain the magnetic fields of compact stars.

Abstract

In this thesis, the effects of the magnetic field on neutron stars matter are studied, assuming that the neutrons inside these stars are partially or totally paired forming neutral vector bosons. The main effects of the magnetic field on the gas are, first, to favor the phase transition to the Bose-Eintein condensation, and second, to split the pressure in two components, one parallel and the other perpendicular to the magnetic axis, giving rise to anisotropic equations of state. At low densities or high magnetic fields, the lowest pressure can be negative, and the boson system becomes susceptible to suffer a transverse magnetic collapse. On the other hand, when the temperature is low enough, the gas can spontaneously magnetize. The equations of state of the magnetized gas of neutral vector bosons are applied, firstly, to study the magnetic collpase of an ideal gas of neutrons, electrons and protons (npe gas) in which the nucleons are partially bosonized. From the results obtained, a model for the ejection of matter out of the star and the formation of astrophysical jets is proposed. Subsequently, the equations of state of the magnetized vector gas are used to study the magnetic field influence on the structure (mass, radius and deformation) of Bose-Einsten condensate stars, that is, of compact objects composed entirely by a neutron gas fully bosonized. In order to appropriately take into account the magnetic anisotropy in the equations of state of this object, we develope a system of equations to describe the hydrodynamic equilibrium -- the structure -- of spheroidal compact objects starting from an axisymmetric metric. The obtained results validate the bosons self-magnetization as a feasible source for the magnetic field of compact objects.