Annual Report 2008.pdf - SAMSI

garnier@math.jussieu.fr
“Wave Propagation and Time Reversal in Random Media”
Time reversal for waves propagating in inhomogeneous media have been intensively studied
experimentally. A time-reversal mirror is a device which is capable of receiving a signal in time,
keeping it in memory and sending it back into the medium in the reversed direction of time. The
main effect is the refocusing of the scattered signal after time reversal in a random medium. In
this talk we will show how an asymptotic analysis based on separation of scales can give a
quantitative description of the statistically stable refocusing properties of time reversal. We will
also discuss applications to imaging in random media, in particular background velocity
estimation.
Lenya Ryzhik
University of Chicago
ryzhik@math.uchicago.edu
"Waves and Particles in Slowly Decorrelating Media"
Waves and particles in random media behave diffusively on large temporal and spatial scales.
This behavior may break down when media fluctuations have long range correlations. I will
discuss one such example, of a particle in a random velocity field, when one observes the
fractional Brownian motion type of behavior with different spreading rates.
Knut Solna
University of California, Irvine
ksolna@math.uci.edu
“Coherent Interferometric Imaging for Synthetic Aperture Radar in the Presence of Noise”
We discuss the coherent interferometric imaging strategy in the context of synthetic aperture
radar, in which a single antenna is used as an emitter and as a receiver at successive positions
along a trajectory. The theoretical analysis shows that the signal-to-noise ratio can be enhanced
dramatically compared to the standard matched filter processing when the fluctuations of the
recorded signals have a spatial correlation (along the antenna trajectory) that is larger than the
distance between two successive positions of the antenna and smaller than the length of the
antenna trajectory.
John C. Schotland
University of Pennsylvania
johns@seas.upenn.edu
“Image Reconstruction in Optical Tomography”
The inverse problem of optical tomography is to reconstruct the optical properties of a highlyscattering
medium from boundary measurements. I will review recent work on associated inverse