Analog wormholes and black hole laser effects in hydrodynamics

We numerically study water wave packets on a spatially varying countercurrent in the presence of surface tension. Depending on the details of the velocity profile, we show that traversable and bidirectional analogue wormholes exist in fluid mechanics. The limitations on traversability of wormholes in general relativity are absent here because of the dispersion of water waves and the ability to form flow profiles that are not solutions of Einstein's equations. We observe that negative energy can be trapped between analogue horizons forming a laserlike cavity. Six horizons are involved in the trapping cavity because of the existence of two dispersive scales, in contrast to previous treatments which considered two horizons and one dispersive scale.