Neutron stars - Investigating candidates for the equation of state in the relativistic mean-field approximation
Master thesis
Permanent lenke
http://hdl.handle.net/11250/2501935Utgivelsesdato
2018Metadata
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- Institutt for fysikk [2653]
Sammendrag
Various models for the equation of state (EoS) for a neutron star have been considered using the relativistic mean-field approximation. Firstly, we derive Einstein's field equations and apply them to a spherically symmetric mass-distribution, giving us a mass-radius relation for the stars in each model. Using the path-integral approach, the EoS for an ideal cold neutron gas is derived. Then we introduce the $\sigma$--$\omega$ model where the strong force is mimicked by the exchange of scalar and vector mesons. Furthermore, scalar self-interactions are included for the $\sigma$-field, as well as an isospin force carried by the $\rho$-meson. Leptons are also added to enforce global charge neutrality. Lastly, the existence of hyperons in neutron stars is discussed. It is found that, though energetically unavoidable, including hyperons decreases the theoretical limit for neutron star masses below the most massive neutron star measured. Possible resolutions to this issue involves repulsive hyperon-hyperon interactions or a phase transition to quark matter.