Kinematic study of the effect of dispersion in quantum vacuum emission from strong laser pulses

TL;DR

This paper investigates how dispersion affects quantum vacuum emission from strong laser pulses in nonlinear media, revealing that spontaneous emission can occur without horizons and identifying optimal observation angles for Hawking-like radiation.

Contribution

It provides a detailed kinematic analysis of quantum vacuum emission considering realistic dispersion effects, extending previous idealized models.

Findings

Quantum vacuum radiation can occur without horizons due to negative norm modes.

Optimal observation angles for Hawking-like emission are narrowly aligned with pulse propagation.

Dispersion influences the emission characteristics and detection prospects.

Abstract

A strong light pulse propagating in a nonlinear medium causes an effective change in the local refractive index. With a suitable tuning of the pulse velocity, the leading and trailing edge of the pulse were predicted to behave as analogue black and white horizons in the limit of a dispersionless medium. In this paper, we study a more realistic situation where the frequency dispersion of the medium is fully taken into account. As soon as positive frequency modes with negative norm are present in the comoving frame, spontaneous emission of quantum vacuum radiation is expected to arise independently of the presence of horizons. We finally investigate the kinematic constraints put on the emission and we show that the optimal directions to observe Hawking-like emission form a narrow angle with the direction of propagation of the pulse.