Modeling the Multi-band Afterglows of GRB 060614 and GRB 060908: Further Evidence for a Double Power-Law Hard Electron Energy Spectrum

Electrons accelerated in relativistic collisionless shocks are usually assumed to follow a power-law energy distribution with an index of $p$. Observationally, although most gamma-ray bursts (GRBs) have afterglows that are consistent with $p>2$, there are still a few GRBs suggestive of a hard ($p<2$) electron energy spectrum. Our previous work showed that GRB 091127 gave strong evidence for a double power-law hard electron energy (DPLH) spectrum with $12$ and an "injection break" assumed as $\gamma_{\rm b}\propto \gamma^q$ in the highly relativistic regime, where $\gamma$ is the bulk Lorentz factor of the jet. In this paper, we show that GRB 060614 and GRB 060908 provide further evidence for such a DPLH spectrum. We interpret the multi-band afterglow of GRB 060614 with the DPLH model in an homogeneous interstellar medium by taking into account a continuous energy injection process, while for GRB 060908, a wind-like circumburst density profile is used. The two bursts, along with GRB 091127, suggest a similar behavior in the evolution of the injection break, with $q\sim0.5$. Whether this represents a universal law of the injection break remains uncertain and more such afterglow observations are needed to test this conjecture.Comment: 14 pages, 2 figure, submitted to ApJ, revised versio

Generation of GHZ and W states for stationary qubits in spin network via resonance scattering

We propose a simple scheme to establish entanglement among stationary qubits based on the mechanism of resonance scattering between them and a single-spin-flip wave packet in designed spin network. It is found that through the natural dynamical evolution of an incident single-spin-flip wave packet in a spin network and the subsequent measurement of the output single-spin-flip wave packet,multipartite entangled states among n stationary qubits, Greenberger-Horne-Zeilinger (GHZ) and W states can be generated.Comment: 8 pages, 6 figure

Quantum state swapping via qubit network with Hubbard interaction

We study the quantum state transfer (QST) in a class of qubit network with on-site interaction, which is described by the generalized Hubbard model with engineered couplings. It is proved that the system of two electrons with opposite spins in this quantum network of $N$ sites can be rigorously reduced into $N$ one dimensional engineered single Bloch electron models with central potential barrier. With this observation we find that such system can perform a perfect QST, the quantum swapping between two distant electrons with opposite spins. Numerical results show such QST and the resonant-tunnelling for the optimal on-site interaction strengths.Comment: 4 pages, 3 figure

Intrinsic Charm Flavor and Helicity Content in the Proton

Contributions to the quark flavor and spin observables from the intrinsic charm in the proton are discussed in the SU(4) quark meson fluctuation model. Our results suggest that the probability of finding the intrinsic charm in the proton is less than 1%. The intrinsic charm helicity is small and negative, $\Delta c \simeq -(0.003\sim 0.015)$. The fraction of the total quark helicity carried by the intrinsic charm is less than 2%, and c_\up/c_\dw=35/67.Comment: 4 pages, 2 tables (revised version

The effects of disorder and interactions on the Anderson transition in doped Graphene

We undertake an exact numerical study of the effects of disorder on the Anderson localization of electronic states in graphene. Analyzing the scaling behaviors of inverse participation ratio and geometrically averaged density of states, we find that Anderson metal-insulator transition can be introduced by the presence of quenched random disorder. In contrast with the conventional picture of localization, four mobility edges can be observed for the honeycomb lattice with specific disorder strength and impurity concentration. Considering the screening effects of interactions on disorder potentials, the experimental findings of the scale enlarges of puddles can be explained by reviewing the effects of both interactions and disorder.Comment: 7 pages, 7 figure