Change of Location:
This talk will be in Room FINE 214 (second floor of Fine Hall) !

Guillaume Bal

Time Reversal for Waves in Random Media

 Abstract:  In time reversal acoustics experiments, a signal is emitted
            from a localized source, recorded at an array of
            receivers-transducers, time reversed, and finally re-emitted
            into the medium.  A striking feature of time reversal
            experiments is that the refocusing of the re-emitted signals
            at the location of the initial source is improved when the
            medium is heterogeneous.  Contrary to intuition, multiple
            scattering enhances the spatial resolution of the refocused
            signal and allows one to beat the diffraction limit obtained
            in homogeneous media. This talk will present new results on a
            quantitative description of time reversal and other more
            general refocusing phenomena for general classical waves in
            heterogeneous media.  The theory is based on the
            asymptotic analysis of the Wigner transform of wave fields in
            the high frequency limit. This is joint work with Leonid
            Ryzhik.