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

S. Finazzi; I. Carusotto

doi:10.1140/epjp/i2012-12078-x

EPJ

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

S. Finazzi^* and I. Carusotto

INO-CNR BEC Center and Dipartimento di Fisica, Università di Trento, via Sommarive 14, 38123, Povo-Trento, Italy

Received: 18 April 2012
Revised: 27 June 2012
Accepted: 3 July 2012
Published online: 24 July 2012

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.