Loschmidt Daemons, Waves, and Holography

Mathias FINK (ESPCI ParisTech, CNRS)

Auditorium, Central Building - ESRF

Starting from the famous argument opposing Boltzmann and Loschmidt about time's arrow and certain paradoxes related to the reversibility of the laws of mechanics, we shall introduce various ways of building a "time machine" in classical physics. More specifically, we shall be interested in the case of waves (of broad spectral composition). We shall compare the ways of building a "time machine" for various types of waves": sound, electro-magnetic radiation, and water surface waves.

We shall show that there actually exist two dual, very different, approaches to steer a wave to travel back in time. One possibility is to manipulate a wave on a two-dimensional surface meshed with a network of reversible antennas. This is the approach used with "time-reversal mirrors", which have numerous applications. Another very different possibility consists in creating "temporal discontinuities" in the whole space. This is the approach of "temporal mirrors", in which the space discontinuity of usual mirrors are replaced by temporal discontinuities.

We shall see that these different approaches enable us to revisit the holographic method and the diffraction limit in imaging and wave control techniques.

-  Coffee will be served at 14:30 -

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