Double shadows of reflection-asymmetric wormholes supported by positive energy thin-shells

TL;DR

This paper explores stable, reflection-asymmetric wormholes in Palatini f(R) gravity supported by positive-energy matter, revealing unique double-shadow phenomena that could indicate new gravitational physics beyond General Relativity.

Contribution

It introduces a method to construct and analyze stable, reflection-asymmetric wormholes in Palatini f(R) gravity with positive-energy matter sources, highlighting observable double-shadow effects.

Findings

Stable wormholes supported by positive-energy matter are achievable.

Existence of double photon spheres allows for multiple shadows observable by an external observer.

Double shadows could serve as signatures of physics beyond General Relativity.

Abstract

We consider reflection-asymmetric thin-shell wormholes within Palatini $f(\mathcal{R})$ gravity using a matching procedure of two patches of electrovacuum space-times at a hypersurface (the shell) via suitable junction conditions. The conditions for having (linearly) stable wormholes supported by positive-energy matter sources are determined. We also identify some subsets of parameters able to locate the shell radius above the event horizon (when present) but below the photon sphere (on both sides). We illustrate with an specific example that such two photon spheres allow an observer on one of the sides of the wormhole to see another (circular) shadow in addition to the one generated by its own photon sphere, which is due to the photons passing above the maximum of the effective potential on its side and bouncing back across the throat due to a higher effective potential on the other side. We finally comment on the capability of these double shadows to seek for traces of new gravitational physics beyond that described by General Relativity.