Peak-Dip-Hump from Holographic Superconductivity

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

The loop corrections to the parity-violating electron-proton elastic scattering

We calculate the two-boson-exchange (TBE) corrections to the parity asymmetry of the elastic electron-proton scattering in a model using the formalism of generalized parton distributions (GPDs).Comment: 7 pages, talk given at "Particle Physics, Astrophysics and Quantum Field Theory, 75 years since Solvay" 27th-29th Nov, 2008, Singapor

The Intention to Download Music Files in a P2P Environment: Rational Choice, Fashion, and Ethical Decision Perspectives

Downloading unauthorized music file is deemed illegal and immoral, but the peer-to-peer systems have boosted its popularity. Many authors attributed this phenomenon to the low morality of Internet users, but inconclusive evidence to this argument was found. Extant literature seldom noticed that downloading music files is a new mean of music consumption. People, especially young generation, might rationally choose between downloading music files and buying CDs for greater utility for enjoying and pursuing after the fashion of music. This paper presents a conceptual model of file downloading by looking at and integrating these perspectives. An analysis of 834 samples drew from a questionnaire survey of P2P users in Taiwan generally supports the above assertion

Supersolidity from defect-condensation in the extended boson Hubbard model

We study the ground state phase diagram of the hard-core extended boson Hubbard model on the square lattice with both nearest- (nn) and next-nearest-neighbor (nnn) hopping and repulsion, using Gutzwiller mean field theory and quantum Monte Carlo simulations. We observe the formation of supersolid states with checkerboard, striped, and quarter-filled crystal structures, when the system is doped away from commensurate fillings. In the striped supersolid phase, a strong anisotropy in the superfluid density is obtained from the simulations; however, the transverse component remains finite, indicating a true two-dimensional superflow. We find that upon doping, the striped supersolid transitions directly into the supersolid with quarter-filled crystal structure, via a first-order stripe melting transition.Comment: Revtex 4, 6 pages, 9 figure