Twin Stars in General Relativity and Extended Theories of Gravity

TL;DR

This paper investigates the properties of twin stars within General Relativity and extended gravity theories, highlighting differences in their behavior and addressing challenges related to energy-momentum tensor properties.

Contribution

It introduces a classification of gravity-independent neutron star equations of state and examines their twin star phenomena across different gravity theories.

Findings

Twin star phenomena vary between General Relativity and modified gravity.

Type I subcategory shows twin stars only in extended gravity.

Negative energy-momentum tensor trace poses challenges in both theories.

Abstract

We explore gravity-independent equations of state for neutron stars, particularly focusing on twin stars. Examining four categories, we emphasize their behavior in both General Relativity and Palatini gravity. Additionally, we discuss a subcategory of type I, which, in the context of General Relativity, does not exhibit twin star phenomena, yet demonstrates this phenomenon in modified gravity. Furthermore, we briefly address challenges associated with the negative trace of the energy-momentum tensor, prevalent in both theories.