# Cherenkov Radiation of Light Bullets

## TL;DR

This paper theoretically predicts Cherenkov radiation emitted by light bullets, revealing spectral discontinuities at threshold and suggesting experimental observations support longstanding puzzles in Cherenkov radiation phenomena.

## Contribution

It introduces a theoretical framework for Cherenkov radiation from light bullets, extending classical theory to new sources and explaining observed spectral features.

## Key findings

- Spectral discontinuity at threshold for point-like sources
- Spectral peak at threshold for extended sources
- Experimental evidence linked to Hawking radiation measurements

## Abstract

Electrically charged particles, moving faster than the speed of light in a medium, emit Cherenkov radiation. Theory predicts electric and magnetic dipoles to radiate as well, with a puzzling behavior for magnetic dipoles pointing in transversal direction [I. M. Frank, Izv. Akad. Nauk SSSR, Ser. Fiz. 6, 3 (1942)]. A discontinuous Cherenkov spectrum should appear at threshold, where the particle velocity matches the phase velocity of light. Here we deduce theoretically that light bullets [Y. Silberberg, Opt. Lett. 15, 1282 (1990)] emit an analogous radiation with exactly the same spectral discontinuity for point-like sources. For extended sources the discontinuity turns into a spectral peak at threshold. We argue that this Cherenkov radiation has been experimentally observed in the first attempt to measure Hawking radiation in optics [F. Belgiorno et al., Phys. Rev. Lett. 105, 203901 (2010)] thus giving experimental evidence for a puzzle in Cherenkov radiation instead.