Thermodynamics of MgB2 described by the weak-coupling two-band BCS model

Journals published by the American Physical Society can be found at http://journals.aps.org/Based on weak-coupling anisotropic BCS theory, the temperature dependence of energy gap and the specific heat are evaluated for the MgB2 superconductor, and the results are compared with experimental data. We show that the weak-coupling anisotropic BCS theory describes thermodynamic experimental data with high precision, 3-6%

Synchronization of delayed fluctuating complex networks

In this communication we present some of our recent results on the synchronization properties of directed delay-coupled networks of a small-world type, whose topology changes with time. Our simulations of a network of non-linear elements show that a random change of topology enhances the stability of a synchronized state, depending on the interplay between different time-scales in the dynamics. The results are analytically explained in the linear limit, where the dynamics is expressed in terms of an effective connectivity matrix. In the limit of fast network fluctuations, this effective connectivity is given by the arithmetic mean of the temporal adjacency matrices. When the coupling topology changes slowly, the effective adjacency matrix is given by the geometric mean. The transition between both regimes is numerically studied for linear network elements

Evidence for nonmonotonic magnetic field penetration in a type-I superconductor

The ability of the polarized neutron reflectivity (PNR) technique to reveal the non-local electrodynamics effect in the profile of magnetic field penetrated into a superconductor in the Meissner state is explored with an extreme low-¿ type-I superconductor. The sample is a thick film of pure indium deposited on a silicon oxide substrate having a neutron refraction index smaller than that for indium. It is shown that the PNR technique allows one to distinguish between exponential and non-exponential shape of the field profile. The data obtained are consistent with the magnetic field distribution following from the non-local theory