Abstract
A
time-reversal experiments for waves consist of emitting a localized
signal, recording it at a distant location and re-transmitting it
back, reversed in time. Such an experiment in a uniform medium would
lead to a poorly refocused signal at the orginal source as most of
information is lost. Surprisingly, random inhomogeneities in the
medium lead to a much better refocusing (a kind of a hologram
effect). I will describe the relation between this beautiful phenomenon
and the diffusive behavior of a particle in a weakly random
Hamiltonian field. I will also try to discuss more general issues
of long time behavior of wave propagation in random media.
