Virtual absorption modes of Schwarzschild-de Sitter spacetimes in semi-open systems

TL;DR

This paper investigates virtual absorption modes in Schwarzschild-de Sitter spacetimes, showing their role as spectral signatures of coherent perfect absorption in exotic compact objects through numerical analysis.

Contribution

It introduces the concept of virtual absorption modes in SdS spacetime and links them to coherent perfect absorption phenomena using spectral collocation methods.

Findings

VAM spectra shift with reflectivity changes

Critical reflectivity where Im(ω_VAM)=0 identified

Excitation at VAM spectrum induces CPA

Abstract

We present a study of virtual absorption modes (VAMs) in Schwarzschild-de Sitter (SdS) spacetime under semi-open boundary conditions, where the VAMs correspond to total transmission modes (TTMs) with the reflection amplitude being vanished. Our numerical analysis reveals that as the reflectivity $|\mathcal{K}|$ decreases, the VAM spectra migrate systematically toward regions of less negative imaginary parts, with each overtone exhibiting a critical reflectivity at which $\text{Im}(\omega_{\text{VAM}})=0$. Using simulations based on spectral collocation methods, it is demonstrated that excitation precisely at a VAM spectrum leads to coherent perfect absorption (CPA). These results establish VAMs as the spectrum signatures of CPA for exotic compact objects (ECOs).