On the Stability of (M theory) Stars against Collapse : Role of Anisotropic Pressures

TL;DR

This paper investigates how anisotropic pressures can influence the stability of horizonless stars in higher dimensions and M theory, suggesting anisotropy may enable stable, non-collapsing compact objects.

Contribution

It demonstrates that anisotropic pressures can stabilize static, spherically symmetric stars in higher dimensions and M theory, potentially allowing stable horizonless objects.

Findings

Non oscillatory perturbations suggest possible stability with anisotropy.

Anisotropic pressures can prevent collapse in higher-dimensional stars.

Stable horizonless objects may exist in M theory with appropriate anisotropy.

Abstract

Unitarity of evolution in gravitational collapses implies existence of macroscopic stable horizonless objects. With such objects in mind, we study the effects of anisotropy of pressures on the stability of stars. We consider stars in four or higher dimensions and also stars in M theory made up of (intersecting) branes. Taking the stars to be static, spherically symmetric and the equations of state to be linear, we study `singular solutions' and the asymptotic perturbations around them. Oscillatory perturbations are likely to imply instability. We find that non oscillatory perturbations, which may imply stability, are possible if an appropriate amount of anisotropy is present. This result suggests that it may be possible to have stable horizonless objects in four or any higher dimensions, and that anisotropic pressures may play a crucial role in ensuring their stability.