2,688 research outputs found

    Peak-Dip-Hump from Holographic Superconductivity

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    We study the fermionic spectral function in a holographic superconductor model. At zero temperature, the black hole has zero horizon and hence the entropy of the system is zero after the back reaction of the condensate is taken into account. We find the system exhibits the famous peak-dip-hump lineshape with a sharp low-energy peak followed by a dip then a hump at higher energies. This feature is widely observed in the spectrum of several high-T_c superconductors. We also find a linear relation between the gap in the fermionic spectrum and the condensate, indicating the condensate is formed by fermion pairing.Comment: 4 pages, revtex

    Prevalence of Dyslipidemia in Patients Receiving Health Checkups: A Hospital-Based Study

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    We used the dataset from one medical center in Taiwan to explore the prevalence of dyslipidemia, which included 2695 subjects receiving private health checkups in 2003-2004. The overall prevalence of hypercholesterolemia was 53.3% in men and 48.2% in women (P = 0.008). The overall prevalence of hypertriglyceridemia was 29.3% in men and 13.7% in women (P < 0.001). The overall prevalence of elevated LDL level was 50.7% in men and 37.9% in women (P < 0.001). The overall prevalence of low HDL level was 47.4% in men and 53% in women (P = 0.004)

    Efficient Third-Order Distributed Feedback Laser with Enhanced Beam Pattern

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    A third-order distributed feedback laser has an active medium disposed on a substrate as a linear array of segments having a series of periodically spaced interstices therebetween and a first conductive layer disposed on a surface of the active medium on each of the segments and along a strip from each of the segments to a conductive electrical contact pad for application of current along a path including the active medium. Upon application of a current through the active medium, the active medium functions as an optical waveguide, and there is established an alternating electric field, at a THz frequency, both in the active medium and emerging from the interstices. Spacing of adjacent segments is approximately half of a wavelength of the THz frequency in free space or an odd integral multiple thereof, so that the linear array has a coherence length greater than the length of the linear array

    Towards A Holographic Model of D-Wave Superconductors

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    The holographic model for S-wave high T_c superconductors developed by Hartnoll, Herzog and Horowitz is generalized to describe D-wave superconductors. The 3+1 dimensional gravitational theory consists a symmetric, traceless second-rank tensor field and a U(1) gauge field in the background of the AdS black hole. Below T_c the tensor field which carries the U(1) charge undergoes the Higgs mechanism and breaks the U(1) symmetry of the boundary theory spontaneously. The phase transition characterized by the D-wave condensate is second order with the mean field critical exponent beta = 1/2. As expected, the AC conductivity is isotropic below T_c and the system becomes superconducting in the DC limit but has no hard gap.Comment: 14 pages, 2 figures, Some typos corrected, Matched with the published versio