Electron-Phonon Interactions for Optical Phonon Modes in Few-Layer Graphene

We present a first-principles study of the electron-phonon (e-ph) interactions and their contributions to the linewidths for the optical phonon modes at $\Gamma$ and K in one to three-layer graphene. It is found that due to the interlayer coupling and the stacking geometry, the high-frequency optical phonon modes in few-layer graphene couple with different valence and conduction bands, giving rise to different e-ph interaction strengths for these modes. Some of the multilayer optical modes derived from the $\Gamma$-$E_{2g}$ mode of monolayer graphene exhibit slightly higher frequencies and much reduced linewidths. In addition, the linewidths of K-$A'_1$ related modes in multilayers depend on the stacking pattern and decrease with increasing layer numbers.Comment: 6 pages,5 figures, submitted to PR

Symmetric multiparty-controlled teleportation of an arbitrary two-particle entanglement

We present a way for symmetric multiparty-controlled teleportation of an arbitrary two-particle entangled state based on Bell-basis measurements by using two Greenberger-Horne-Zeilinger states, i.e., a sender transmits an arbitrary two-particle entangled state to a distant receiver, an arbitrary one of the $n+1$ agents via the control of the others in a network. It will be shown that the outcomes in the cases that $n$ is odd or it is even are different in principle as the receiver has to perform a controlled-not operation on his particles for reconstructing the original arbitrary entangled state in addition to some local unitary operations in the former. Also we discuss the applications of this controlled teleporation for quantum secret sharing of classical and quantum information. As all the instances can be used to carry useful information, its efficiency for qubits approaches the maximal value.Comment: 9 pages, 3 figures; the revised version published in Physical Review A 72, 022338 (2005). The detail for setting up a GHZ-state quantum channel is adde

An external potential dynamic study on the formation of interface in polydisperse polymer blends

The formation of interface from an initial sharp interface in polydisperse A/B blends is studied using the external potential dynamic method. The present model is a nonlocal coupling model as we take into account the correlation between segments in a single chain. The correlation is approximately expressed by Debye function and the diffusion dynamics are based on the Rouse chain model. The chain length distribution is described by the continuous Schulz distribution. Our numerical calculation indicates that the broadening of interface with respect to time obeys a power law at early times, and the power law indexes are the same for both monodisperse and polydisperse blend. The power law index is larger than that in the local coupling model. However there is not a unified scaling form of the broadening of the interface width if only the interfacial width at equilibrium is taken into account as the characteristic length of the system, because the correlation makes an extra characteristic length in the system, and the polydispersity is related to this length.Comment: 15 pages, 5 figure

Two Component Model of Dark Energy

We consider the possibility that the dark energy is made up of two or more independent components, each having a different equation of state. We fit the model with supernova and gamma-ray burst (GRB) data from resent observations, and use the Markov Chain Monte Carlo (MCMC) technique to estimate the allowed parameter regions. We also use various model selection criteria to compare the two component model with the LCDM, one component dark energy model with static or variable w(XCDM), and with other multi-component models. We find that the two component models can give reasonably good fit to the current data. For some data sets, and depending somewhat on the model selection criteria, the two component model can give better fit to the data than XCDM with static w and XCDM with variable w parameterized by w = w_0 + w_az/(1+z).Comment: 10 pages, 8 figures, 3 tables; Version accepted by PR

Collective Modes in the Loop Ordered Phase of Cuprates

We show that the two branches of collective modes discovered recently in under-doped Cuprates with huge spectral weight are a necessary consequence of the loop-current state. Such a state has been shown in earlier experiments to be consistent with the symmetry of the order parameter competing with superconductivity in four families of Cuprates. We also predict a third branch of excitations and suggest techniques to discover it. Using parameters to fit the observed modes, we show that the direction of the effective moments in the ground state lies in a cone at an angle to the c-axis as observed in experiments

Mechanisms of modulation of brain microvascular endothelial cells function by thrombin.

Brain microvascular endothelial cells are a critical component of the blood-brain barrier. They form a tight monolayer which is essential for maintaining the brain homeostasis. Blood-derived proteases such as thrombin may enter the brain during pathological conditions like trauma, stroke, and inflammation and further disrupts the permeability of the blood-brain barrier, via incompletely characterized mechanisms. We examined the underlying mechanisms evoked by thrombin in rat brain microvascular endothelial cells (RBMVEC). Our results indicate that thrombin, acting on protease-activated receptor 1 (PAR1) increases cytosolic C

Variation of the Fine-Structure Constant from the de Sitter Invariant Special Relativity

There are obvious discrepancies among various experimental constraints on the variation of the fine-structure constant, $\alpha$. We attempt to discuss the issue in the framework of de Sitter invariant Special Relativity (${\cal SR}_{c,R}$) and to present a possible solution to the disagreement. In addition, on the basis of the observational data and the discussions presented in this Letter, we derive a rough theoretical estimate of the radius of the Universe.Comment: 8 pages, no figure

Long-range interactions of metastable helium atoms

Polarizabilities, dispersion coefficients, and long-range atom-surface interaction potentials are calculated for the n=2 triplet and singlet states of helium using highly accurate, variationally determined, wave functions.Comment: RevTeX, epsf, 4 fig