277 research outputs found
Characteristic length of a Holographic Superconductor with -wave gap
After the discovery of the -wave and -wave holographic superconductors,
holographic models of -wave superconductor have also been constructed
recently. We study analytically the perturbation of the dual gravity theory to
calculate the superconducting coherence length of the -wave
holographic superconductor near the superconducting phase transition point. The
superconducting coherence length divergents as near
the critical temperature . We also obtain the magnetic penetration depth
by adding a small external homogeneous magnetic
field. The results agree with the -wave and -wave models, which are also
the same as the Ginzburg-Landau theory.Comment: last version, 10 pages, accepted by PR
Time-dependent energetic proton acceleration and scaling laws in ultra-intense laser pulses interactions with thin foils
A two-phase model, where the plasma expansion is an isothermal one when laser
irradiates and a following adiabatic one after laser ends, has been proposed to
predict the maximum energy of the proton beams induced in the ultra-intense
laser-foil interactions. The hot-electron recirculation in the ultra-intense
laser-solid interactions has been accounted in and described by the
time-dependent hot-electron density continuously in this model. The dilution
effect of electron density as electrons recirculate and spread laterally has
been considered. With our model, the scaling laws of maximum ion energy have
been achieved and the dependence of the scaling coefficients on laser
intensity, pulse duration and target thickness have been obtained. Some
interesting results have been predicted: the adiabatic expansion is an
important process of the ion acceleration and cannot be neglected; the whole
acceleration time is about 10-20 times of laser pulse duration; the larger the
laser intensity, the more sensitive the maximum ion energy to the change of
focus radius, and so on.Comment: 15 pages, 4 figures, submitted to PR
d-wave Holographic Superconductor Vortex Lattice and Non-Abelian Holographic Superconductor Droplet
A d-wave holographic superconductor is studied under a constant magnetic
field by perturbation method, we obtain both droplet and triangular vortex
lattice solution. The results are the same as the s-wave holographic
superconductor. The non-Abelian holographic superconductor with -wave
background is also studied under magnetic field, unlike the d-wave and s-wave
models, we find that the non-Abelian model has only droplet solution.Comment: Version2, 12 pages,2 figures. Accepted by PR
Underdetermined Separation of Speech Mixture Based on Sparse Bayesian Learning
This paper describes a novel algorithm for underdetermined speech separation problem based on compressed sensing which is an emerging technique for efficient data reconstruction. The proposed algorithm consists of two steps. The unknown mixing matrix is firstly estimated from the speech mixtures in the transform domain by using K-means clustering algorithm. In the second step, the speech sources are recovered based on an autocalibration sparse Bayesian learning algorithm for speech signal. Numerical experiments including the comparison with other sparse representation approaches are provided to show the achieved performance improvement
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