Wave Propagation and Effective Refraction in Lorentz-Violating Wormhole Geometries

TL;DR

This paper investigates how Lorentz-violating modifications to wormhole spacetimes affect scalar wave propagation, revealing frequency-dependent refraction, horizon-related divergences, and new wave confinement phenomena.

Contribution

It introduces a geometric-optical framework for analyzing wave behavior in Lorentz-violating wormholes, highlighting novel effects like graded-index analogues and mode confinement without singularities.

Findings

Refractive index diverges at Killing horizons.

Lorentz violation induces asymmetric wave propagation.

Multi-horizon trapping structures enable wave confinement.

Abstract

We study the propagation of massless scalar waves in static, spherically symmetric Lorentz-violating wormhole spacetimes within a geometric-optical framework. Starting from a general metric characterized by an arbitrary lapse function and areal radius, we derive curvature invariants, establish regularity conditions at the wormhole throat, and reduce the Klein-Gordon equation to a Helmholtz-type radial wave equation. This formulation naturally leads to a position- and frequency-dependent effective refractive index determined by the underlying spacetime geometry and Lorentz-violating structure, resulting in effective frequency-dependent wave-optical behavior. We show that divergences of the refractive index coincide with Killing horizons, while curvature-induced turning points control reflection, transmission, and confinement of scalar waves. By analyzing constant, linear, and quadratic lapse profiles, we identify horizonless transmission regimes, asymmetric wave propagation, and multi-horizon trapping structures. Our results reveal that Lorentz violation can significantly modify wave-optical properties of curved spacetime, generating graded-index analogues and geometric confinement of modes without curvature singularities. This unified optical perspective provides a robust framework for investigating wave scattering, resonances, and potential observational signatures in Lorentz-violating gravitational backgrounds.