Tunneling method for Hawking quanta in analogue gravity

TL;DR

This paper revisits analogue Hawking radiation using the tunneling method to clarify the physical mechanism behind its robustness against ultraviolet modifications in various flow regimes.

Contribution

It introduces a unified tunneling approach to analyze analogue Hawking radiation across different flow and dispersion conditions, enhancing physical intuition.

Findings

Hawking radiation persists despite modified dispersion relations.

The tunneling method explains the origin of radiation robustness.

Excitations occur even in flows without true horizons.

Abstract

Analogue Hawking radiation from acoustic horizons is now a well-established phenomenon, both theoretically and experimentally. Its persistence, despite the modified dispersion relations characterising analogue models, has been crucial in advancing our understanding of the robustness of this phenomenon against ultraviolet modifications of our spacetime description. However, previous theoretical approaches, such as the Bogoliubov transformation relating asymptotic states, have somewhat lacked a straightforward physical intuition regarding the origin of this robustness and its limits of applicability. To address this, we revisit analogue Hawking radiation using the tunneling method. We present a unified treatment that allows us to consider flows with and without acoustic horizons and with superluminal or subluminal dispersion relations. This approach clarifies the fundamental mechanism behind the resilience of Hawking radiation in these settings and explains the puzzling occurrence of excitations even in subcritical (supercritical) flows with subluminal (superluminal) dispersion relations.