Warped space-time for phonons moving in a perfect nonrelativistic fluid

¹ Helsinki University of Technology, Low Temperature Laboratory P.O. Box 2200, FIN-02015 HUT, Finland
² Leopold-Franzens-Universität Innsbruck, Institut für Theoretische Physik Technikerstrasse 25, A-6020 Innsbruck, Austria
³ School of Mathematical and Computing Sciences, Victoria University of Wellington P.O. Box 600, Wellington, New Zealand

Received: 25 November 2002
Accepted: 31 January 2003

Abstract

We construct a kinematical analogue of superluminal travel in the “warped” space-times curved by gravitation, in the form of “super-phononic” travel in the curved effective space-times of perfect nonrelativistic fluids. These warp-field space-times are most easily generated by considering a solid object that is placed as an obstruction in an otherwise uniform flow. No violation of any condition on the positivity of energy is necessary, because the effective curved space-times for the phonons are ruled by the Euler and continuity equations, and not by the Einstein field equations.