title: Universal structure of field correlations within a fluctuating medium.
abstract: We study the structure of the second-order correlation function of scalar wave fields, which are generated by statistically stationary sources, fluctuating within a homogeneous dissipative medium. We derive a closed-form analytical expression for the spectral degree of coherence of the wave field. If the dissipation in the medium is sufficiently small, and the source fluctuations are statistically isotropic, the degree of spatial coherence of the field produced by any such source is shown to be proportional to the imaginary part of the Green's function of the system, with a proportionality factor depending on the dimensionality of the field. The result holds for wave fields in both three and two spatial dimensions, but not in one dimension. We discuss the physical nature of such universal forms of the spectral degree of coherence.
authors.affiliation: Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA.
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Ponomarenko
authors.forename: Emil
authors.initials: E
authors.lastname: Wolf