Statistical properties of coherent radiation propagating in a quasi-one-dimensional random medium are studied in the framework of random-matrix theory. Distribution functions for the total transmission coefficient and the angular transmission coefficient are obtained.

We consider RKKY interaction between two magnetic impurities in graphene. The consideration is based on the perturbation theory for the thermodynamic potential in the imaginary time representation. We analyze the symmetry of the RKKY interaction on the bipartite lattice at half filling. Our analytical calculation of the interaction is based on direct evaluation of real space spin susceptibility. We show in the Appendix, added to the published version, that the approach can be easily generalized to the case of finite temperature.Comment: LaTeX, 7 pages. We show in the Appendix, added to the published version, that the approach can be easily generalized to the case of finite temperatur

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We present low-temperature uanspon measurements on the two-dimensional electron gas in 8-doped GaAs which undergoes an insulatorquantum Hall-insulator vansition as the magnetic field is increased. Both low-and high-field vansitions are marked by pe& in ox, and Lhe temperahlre-independent critical value of oxy of 0.5ez/h per spin. We map out the phase diagram versus disorder and magnetic field and study the t e m p e m dependence of ox* throughout. In the quantum Hall region we observe Molt variable range hopping and, around the high-field transitions, s d i g via a single parameter: z = (S -B')T-"'. The functional dependence on L above this transition is fitted by recent network percolation calculations.

We propose an information-theoretic model for the transport of waves through a chaotic cavity in the presence of absorption. The entropy of the S-matrix statistical distribution is maximized, with the constraint =alphan: n is the dimensionality of S, and 0>1 Rayleigh statistics is attained even with no absorption; here, we extend the study to alpha<1. The model is compared with random-matrix-theory numerical simulations: it describes the problem very well for strong absorption, but fails for moderate and weak absorptions. Thus, in the latter regime, some important physical constraint is missing in the construction of the model.