On the Cuspy Structure of Rotating Wormhole Shadows

TL;DR

This paper studies the shadow shapes of rotating wormholes, revealing how varying redshift parameters lead to cuspy structures and identifying a universal critical value for cusp formation.

Contribution

It introduces a detailed analysis of wormhole shadow morphologies, highlighting the role of redshift and spin parameters in cusp development and classifying four distinct shadow types.

Findings

Cuspy structures emerge when the redshift parameter varies.

A universal critical redshift value signals cusp onset.

Four shadow morphologies are identified based on parameters.

Abstract

We investigate the shadow cast by a rotating traversable wormhole in the Teo class endowed with a general redshift function, with particular emphasis on the emergence of cuspy structures. The shadow boundary is the common envelope of two critical orbit families: unstable circular orbits outside the throat and orbits at the throat itself. The formation of cusps, marking the transition between smooth and cuspy shadow boundaries, only becomes possible when the redshift parameter $\lambda$ is allowed to vary. Moreover, we uncover a universal critical value $\lambda_c$ that signals the onset of the cusp. A phase diagram characterized by the spin and redshift parameters reveals four distinct morphologies: smooth, cuspy, ears touching, and throat drowning. The morphology of the wormhole shadow may provide observational diagnostics for the different compact objects in future high-resolution imaging observations.