title: From Loschmidt daemons to time-reversed waves.
abstract: Time-reversal invariance can be exploited in wave physics to control wave propagation in complex media. Because time and space play a similar role in wave propagation, time-reversed waves can be obtained by manipulating spatial boundaries or by manipulating time boundaries. The two dual approaches will be discussed in this paper. The first approach uses 'time-reversal mirrors' with a wave manipulation along a spatial boundary sampled by a finite number of antennas. Related to this method, the role of the spatio-temporal degrees of freedom of the wavefield will be emphasized. In a second approach, waves are manipulated from a time boundary and we show that 'instantaneous time mirrors', mimicking the Loschmidt point of view, simultaneously acting in the entire space at once can also radiate time-reversed waves.
authors.affiliation: Institut Langevin, ESPCI Paris Tech, CNRS UMR 7587, PSL Research University, 1 rue Jussieu, Paris 75005, France mathias.fink@espci.fr.
authors.forename: Mathias
authors.identifier: http://orcid.org/0000-0002-8494-7562
authors.initials: M
authors.lastname: Fink
keywords: Green’s functions; Loschmidt daemons; subwavelength focusing; time-reversed waves; wave propagation in complex media