Effective medium approach of the resonance distribution in a random point field

In a previous paper, the distribution of resonance poles in the complex plane of the wavenumber $k$ associated to the multiple scattering of a quantum particle in a random point field was numerically discovered. This distribution presented two distinctive structures: a set of peaks at small $k$ when the wavelength is larger than the interscatterer distance, and a band almost parallel to the real axis at larger $k$. In this paper, a detailed theoretical study based on wave transport theory is proposed to explain the origin of these structures and to predict their location in the complex $k$ plane. First, it is shown that the peaks at small $k$ can be understood using an effective wave equation for the average wave function over the disorder. Then, that the band at large $k$ can be described by the Bethe-Salpeter equation for the square modulus of the wavefunction, which is derived from the diagrammatic method. This study is supported by careful comparisons with numerical simulations. The largest simulations revealed the presence of quantum scars in the bulk of the disordered medium.Comment: 31 pages, 15 figure