Wormholes without exotic matter: quasinormal modes, echoes and shadows

TL;DR

This paper presents analytical and numerical solutions for traversable wormholes without exotic matter, analyzes their quasinormal modes and echoes, and calculates their shadow radii, challenging the necessity of exotic matter in wormhole physics.

Contribution

It introduces new wormhole solutions in different theories without exotic matter and studies their observational signatures like echoes and shadows.

Findings

Wormholes without exotic matter can mimic black hole signatures.

Echoes are observed in near extremal regimes.

Shadow sizes are computed for these wormholes.

Abstract

An analytical solution representing traversable asymptotically flat and symmetric wormholes was obtained without adding exotic matter in two different theories independently: in the Einstein-Maxwell-Dirac theory and in the second Randall-Sundrum brane-world model. Further, a smooth normalizable asymmetric wormhole solution has been recently obtained numerically in the Einstein-Maxwell-Dirac theory. Using the time-domain integration method we study quasinormal ringing of all these wormholes with emphasis to the regime of mimicking the near extremal Reissner-Nordstr\"om black holes, which is characterised by echoes. In addition, we calculate radius of shadows cast by these wormholes.