A Dicke Type Model for Equilibrium BEC Superradiance

We study the effect of electromagnetic radiation on the condensate of a Bose gas. In an earlier paper we considered the problem for two simple models showing the cooperative effect between Bose–Einstein condensation and superradiance. In this paper we formalize the model suggested by Ketterle et al. in which the Bose condensate particles have a two level structure. We present a soluble microscopic Dicke type model describing a thermodynamically stable system. We find the equilibrium states of the system and compute the thermodynamic functions giving explicit formulæ expressing the cooperative effect between Bose–Einstein condensation and superradiance.     

Potential Approximations to δ': An Inverse Klauder Phenomenon with Norm-Resolvent Convergence

We show that there is a family Schr?dinger operators with scaled potentials which approximates the δ'-interaction Hamiltonian in the norm-resolvent sense. This approximation, based on a formal scheme proposed by Cheon and Shigehara, has nontrivial convergence properties which are in several respects opposite to those of the Klauder phenomenon. Received: 19 March 2001 / Accepted: 18 June 2001     

Structure et proprietes de conduction du compose K0,1Li0,9SbO3

Single-crystals of K_0,1Li_0,9SbO₃ are obtained by ion exchange method from crystals of KSbO₃, $\text{1}\text{6}$ KF and crystallize in the cubic system, space group Pn3, a = 9,681 (3) Å, Z = 4. Using 398 independent reflections, the structure has been refined by full-matrix least squares, to factor R = 0,043.In this space group, the alkaline ions are in an ordered state.The ionic conductivity of cubic KSbO₃ phases is very high and the motion of cations is three-dimensional along <111> tunnels. The authors discusse the influence of ordered (Pn3) and disordered (Im3) states on the conductivity of these compounds.