Berry's Phase for Standing Wave Near Graphene Edge

Standing waves near the zigzag and armchair edges, and their Berry's phases are investigated. It is suggested that the Berry's phase for the standing wave near the zigzag edge is trivial, while that near the armchair edge is non-trivial. A non-trivial Berry's phase implies the presence of a singularity in parameter space. We have confirmed that the Dirac singularity is absent (present) in the parameter space for the standing wave near the zigzag (armchair) edge. The absence of the Dirac singularity has a direct consequence in the local density of states near the zigzag edge. The transport properties of graphene nanoribbons observed by recent numerical simulations and experiments are discussed from the point of view of the Berry's phases for the standing waves.Comment: 6 pages, 4 figure

Black Strings in Our World

The brane world scenario is a new approach to resolve the problem on how to compactify the higher dimensional spacetime to our 4-dimensional world. One of the remarkable features of this scenario is the higher dimensional effects in classical gravitational interactions at short distances. Due to this feature, there are black string solutions in our 4-dimensional world. In this paper, assuming the simplest model of complex minimally coupled scalar field with the local U(1) symmetry, we show a possibility of black-string formation by merging processes of type I long cosmic strings in our 4-dimensional world. No fine tuning for the parameters in the model might be necessary.Comment: 11pages, no figur

Weakened Constraints from b→sγb \to s \gamma on Supersymmetry Flavor Mixing Due to Next-To-Leading-Order Corrections

We examine the process $B \to X_s \gamma$ in minimal supersymmetry (SUSY) with general squark flavor mixings. We include all relevant next--to--leading order (NLO) QCD corrections and dominant NLO SUSY effects from the gluino. We find that gluino--squark corrections to down--type quark masses induce large NLO corrections to the dominant Wilson coefficients whose size is often similar to those at LO, especially at large $\tan\beta$. For $\mu>0$, destructive interference, and suppression by the renormalization group running lead to a ``focusing effect'' of reducing the size of gluino corrections to the branching ratio, and also of reducing the LO sensitivity to flavor mixings among squarks. Constraints from $B(B \to X_s \gamma)$ on the SUSY--breaking scale can become significantly weakened relative to the minimal flavor violation case, even, at large $\tan\beta$, for small flavor mixings. The case of $\mu<0$ can also becomes allowed.Comment: Revtex4, 4 pages, 6 figures, title changed, version accepted by PR

Parity-Odd Asymmetries in W-Jet Events at the Tevatron

Parity-odd asymmetries in the decay angular distribution of a W boson produced with a hard jet in p\bar{p} collisions arise only from QCD rescattering effects. If observed, these asymmetries will provide a first demonstration that perturbative QCD calculation is valid for the absorptive part of scattering amplitudes. We propose a simple observable to measure these asymmetries and perform realistic Monte Carlo simulations at Tevatron energies. It is shown that the Tevatron Run-II should provide sufficient statistics to test the prediction.Comment: 4pages, 2figures, revtex, references and discussions added, version to appear in PRL, typo correcte

Tyrosine Kinase-Dependent Activation of Phospholipase Cγ Is Required for Calcium Transient in Xenopus Egg Fertilization

AbstractIn a previous study (K.-I. Sato et al., 1999, Dev. Biol. 209, 308–320), we presented evidence that a Src-related protein-tyrosine kinase (PTK), named Xyk, may act upstream of the calcium release in fertilization of the Xenopus egg. In the present study, we examined whether PTK activation of phospholipase Cγ (PLCγ) plays a role in the fertilization-induced calcium signaling. Immunoprecipitation studies show that Xenopus egg PLCγ is tyrosine phosphorylated and activated within a few minutes after fertilization but not after A23187-induced egg activation. Consistently, we observed a fertilization-induced association of PLCγ with Xyk activity that was not seen in A23187-activated eggs. A Src-specific PTK inhibitor, PP1, blocked effectively the fertilization-induced association of PLCγ with Xyk activity and up-regulation of PLCγ, when microinjected into the egg. In addition, a PLC inhibitor, U-73122, inhibited sperm-induced inositol 1,4,5-trisphosphate production and the calcium transient and subsequent calcium-dependent events such as cortical contraction, elevation of fertilization envelope, and tyrosine dephosphorylation of p42 MAP kinase, all of which were also inhibited by PP1. On the other hand, A23187 could cause the calcium response and calcium-dependent events in eggs injected with PP1 or U-73122. These results support the idea that Xenopus egg fertilization requires Src-family PTK-dependent PLCγ activity that acts upstream of the calcium-dependent signaling pathway

Continuous-wave and Q-switched microchip laser performance of Yb : Y3Sc2Al3O12 crystals

Optical properties of Yb:Y3Sc2Al3O12 crystal were investigated and compared with those from Yb:YAG crystals. The broad absorption and emission spectra of Yb:Y3Sc2Al3O12 show that this crystal is very suitable for laser-diode pumping and ultrafast laser pulse generation. Laser-diode pumped continuous-wave and passively Q-switched Yb:Y3Sc2Al3O12 lasers with Cr4+: YAG crystals as saturable absorber have been demonstrated for the first time. Continuous-wave output power of 1.12 W around 1032 nm ( multi-longitudinal modes) was measured with an optical-to-optical efficiency of 30%. Laser pulses with pulse energy of over 31 mu J and pulse width of 2.5 ns were measured at repetition rate of over 12.7 kHz; a corresponding peak power of over 12 kW was obtained. The longitudinal mode selection by a thin plate of Cr4+: YAG as an intracavity etalon was also observed in passively Q-switched Yb:Y3Sc2Al2O12 microchip lasers. (C) 2008 Optical Society of America

Dynamic Transition in the Structure of an Energetic Crystal during Chemical Reactions at Shock Front Prior to Detonation

Mechanical stimuli in energetic materials initiate chemical reactions at shock fronts prior to detonation. Shock sensitivity measurements provide widely varying results, and quantum-mechanical calculations are unable to handle systems large enough to describe shock structure. Recent developments in reactive force-field molecular dynamics (ReaxFF-MD) combined with advances in parallel computing have paved the way to accurately simulate reaction pathways along with the structure of shock fronts. Our multimillion-atom ReaxFF-MD simulations of l,3,5-trinitro-l,3,5-triazine (RDX) reveal that detonation is preceded by a transition from a diffuse shock front with well-ordered molecular dipoles behind it to a disordered dipole distribution behind a sharp front

Derivation of Amplitude Equations by Renormalization Group Method

A proper formulation in the perturbative renormalization group method is presented to deduce amplitude equations. The formulation makes it possible not only avoiding a serious difficulty in the previous reduction to amplitude equations by eliminating all of the secular terms but also consistent derivation of higher-order correction to amplitude equations.Comment: 6 page, revte