Domain walls and other defects in Eddington-inspired Born-Infeld gravity

TL;DR

This paper explores how domain walls and other defects behave in Eddington-inspired Born-Infeld gravity, revealing significant differences from General Relativity, especially regarding internal structure and pressure conditions.

Contribution

It provides the first detailed analysis of defect solutions in EiBI gravity, highlighting the dependency on the parameter ppa and the violation of the von Laue condition.

Findings

Pressure perpendicular to domain walls can be significantly altered by ppa.

The von Laue condition does not hold in EiBI gravity for defects.

Defect structures are sensitive to the sign and magnitude of ppa.

Abstract

We investigate domain wall and other defect solutions in the weak-field limit of Eddington-inspired Born-Infeld gravity as a function of $\kappa$, the only additional parameter of the theory with respect to General Relativity. We determine, both analytically and numerically, the internal structure of domain walls, quantifying its dependency on $\kappa$ as well as the impact of such dependency on the value of the tension measured by an outside observer. We find that the pressure in the direction perpendicular to the domain wall can be, in contrast to the weak-field limit of General Relativity, significantly greater or smaller than zero, depending, respectively, on whether $\kappa$ is positive or negative. We further show that the generalized von Laue condition, which states that the average value of the perpendicular pressure is approximately equal to zero in the weak-field limit of General Relativity, does not generally hold in EiBI gravity not only for domain walls, but also in the case cosmic strings and spherically symmetric particles. We argue that a violation of the generalized von Laue condition should in general be expected in any theory of gravity whenever geometry plays a significant role in determining the defect structure.