Origin of the Thermal Radiation in a Solid-State Analog of a Black-Hole

TL;DR

This paper investigates how Hawking radiation can occur in a dispersive medium with a black-hole-like horizon, even when the horizon disappears for high wave numbers, by analyzing the ground state of free field modes.

Contribution

It demonstrates that Hawking radiation persists in dispersive media beyond the horizon's disappearance for high wave numbers, revealing new insights into black-hole analogs in matter.

Findings

Hawking radiation is emitted even when the horizon is absent for certain wave numbers.

Ground state modes with high wave numbers can produce Hawking radiation.

Dispersive effects modify the conditions for horizon existence without suppressing radiation.

Abstract

An effective black-hole-like horizon occurs, for electromagnetic waves in matter, at a surface of singular electric and magnetic permeabilities. In a physical dispersive medium this horizon disappears for wave numbers with $k>k_c$. Nevertheless, it is shown that Hawking radiation is still emitted if free field modes with $k>k_c$ are in their ground state.