Dynamical gravastars may evade no-go results for exotic compact objects, together with further analytical and numerical results for the dynamical gravastar model

TL;DR

This paper demonstrates that dynamical gravastars lack a hard surface and contain an interior light sphere, which may allow them to avoid certain no-go results for exotic compact objects, supported by analytical and numerical analysis.

Contribution

The paper provides new analytical and numerical insights into the structure of dynamical gravastars, showing how they evade singularities and no-go theorems, and explores model extensions.

Findings

Dynamical gravastars have no hard surface.

A second light sphere exists in the interior with maximum time dilation.

They can evade no-go results for exotic compact objects.

Abstract

Using graphs plotted from the Mathematica notebooks posted with our paper ``Dynamical Gravastars'', we show that a dynamical gravastar has no hard surface, and that a second light sphere resides in the deep interior where there is maximum time dilation. These facts may permit dynamical gravastars to evade no-go results for exotic compact objects relating to light leakage inside the shadow, and nonlinear instabilities arising from an interior light sphere. Testing these surmises will require further detailed modeling calculations, beyond what we commence in this paper, using the numerical dynamical gravastar solution. We also discuss the effect of replacing the sigmoidal function in the gravastar calculation by a unit step function, and we analyze why the dynamical gravastar evades the singularities predicted by the Penrose and Hawking singularity theorems, despite satisfying both the null and strong energy conditions. We then give a simplified two-step process for tuning the initial value $\nu(0)={\rm nuinit}$ to achieve $\nu(\infty)=0$, and give exact integrals for the pressure differential equation in terms of $\nu(r)$ in the interior and exterior regions. Finally, we briefly discuss an extension of the model that includes an external shell of massive particles.