Compact stars in Eddington-inspired Born-Infeld gravity: Anomalies associated with phase transitions

TL;DR

This paper investigates how phase transitions in compact stars within EiBI gravity cause unique anomalies, such as constant pressure regions and Ricci scalar discontinuities, revealing stricter constraints on stellar matter microphysics.

Contribution

It demonstrates that EiBI gravity introduces novel anomalies during phase transitions in compact stars, including constant pressure regions and Ricci scalar singularities, not present in general relativity.

Findings

Positive ppaEiBI stars show constant pressure regions during phase transitions.

Negative ppaEiBI cannot support equilibrium stellar configurations.

Ricci scalar exhibits elta;function singularities at phase transition discontinuities.

Abstract

We study how generic phase transitions taking place in compact stars constructed in the framework of the Eddington-inspired Born-Infeld (EiBI) gravity can lead to anomalous behavior of these stars. For the case with first-order phase transitions, compact stars in EiBI gravity with a positive coupling parameter $\kappa $ exhibit a finite region with constant pressure, which is absent in general relativity. However, for the case with a negative $\kappa $, an equilibrium stellar configuration cannot be constructed. Hence, EiBI gravity seems to impose stricter constraints on the microphysics of stellar matter. Besides, in the presence of spatial discontinuities in the sound speed $c_s$ due to phase transitions, the Ricci scalar is spatially discontinuous and contains $\delta$-function singularities proportional to the jump in $c_s^2$ acquired in the associated phase transition.