Vortex glass transition in a frustrated 3D XY model with disorder

The anisotropic frustrated three dimensional (3D) XY model with disorder in the coupling constants is simulated as a model of a point disordered superconductor in an applied magnetic field. From a finite size scaling analysis of the helicity modulus it is concluded that the data is consistent with a finite temperature transition with isotropic scaling and the correlation length exponent is found to be \nu=1.50+/-0.12, consistent with 3D gauge glass universality.Comment: For additional information, see http://www.tp.umu.se/~olsson/VortexGlass.htm

Two phase transitions in the fully frustrated XYXY model

The fully frustrated $XY$ model on a square lattice is studied by means of Monte Carlo simulations. A Kosterlitz-Thouless transition is found at $T_{\rm KT} \approx 0.446$, followed by an ordinary Ising transition at a slightly higher temperature, $T_c \approx 0.452$. The non-Ising exponents reported by others, are explained as a failure of finite size scaling due to the screening length associated with the nearby Kosterlitz-Thouless transition.Comment: REVTEX file, 8 pages, 5 figures in uuencoded postscrip

Polarization effects in tau production by neutrino

We studied polarization effects in tau production by neutrino-nucleon scattering. Quasi-elastic scattering, $Delta$ resonance production and deep inelastic scattering processes are taken into account for the CERN-to-Gran Sasso projects. We show that the tau produced by neutrino has high degree of polarization, and its spin direction depends non-trivially on the energy and the scattering angle of tau in the laboratory frame.Comment: 6 pages, 5 eps figures, espcrc2.sty; Proceedings of the 3rd International Workshop on Neutrino-Nucleus Interactions in the Few GeV Region (NuInt04), March 17-21, 2004, Gran Sasso, Italy; minor changes, typos in Eq. (6) correcte

In Search of the Vortex Loop Blowout Transition for a type-II Superconductor in a Finite Magnetic Field

The 3D uniformly frustrated XY model is simulated to search for a predicted "vortex loop blowout" transition within the vortex line liquid phase of a strongly type-II superconductor in an applied magnetic field. Results are shown to strongly depend on the precise scheme used to trace out vortex line paths. While we find evidence for a transverse vortex path percolation transition, no signal of this transition is found in the specific heat.Comment: 11 pages, 17 figure

Dynamic Approach to the Fully Frustrated XY Model

Using Monte Carlo simulations, we systematically investigate the non-equilibrium dynamics of the chiral degree of freedom in the two-dimensional fully frustrated XY model. The critical initial increase of the staggered chiral magnetization is observed. By means of the short-time dynamics approach, we estimate the second order phase transition temperature $T_{c}$ and all the dynamic and static critical exponents $\theta$, z, $\beta$ and $\nu$.Comment: 5 pages with 6 figures include

The Impact of NLO-Corrections on the Determination of the $\bar{u},\bar{d} Content of Nucleons from Drell-Yan Production

The interpretation of Drell-Yan production in terms of the antiquark densities depends on NLO corrections. Besides the NLO corrections to the familiar annihilation $q\bar{q}\to \gamma^* \to l^+ l^-$, there is a substantial contribution from the QCD Compton subprocesses $gq \to q\gamma^* \to q l^+ l^-$ and $g\bar{q} \to q\gamma^* \to q l^+ l^-$. The beam and target dependence of the two classes of corrections is different. We discuss the impact of this difference on the determination of the $\bar{d}-\bar{u}$ asymmetry in the proton from the comparison of the $pp$ and $pn$ Drell-Yan production.Comment: 4 pages, 1 eps-figure. To be published in Proceedings of DIS'9

Ground State Phase Diagram of Frustrated S=1 XXZ chains : Chiral Ordered Phases

The ground-state phase diagram of frustrated S=1 XXZ spin chains with the competing nearest- and next-nearest-neighbor antiferromagnetic couplings is studied using the infinite-system density-matrix renormalization-group method. We find six different phases, namely, the Haldane, gapped chiral, gapless chiral, double Haldane, N\'{e}el, and double N\'{e}el (uudd) phases. The gapped and gapless chiral phases are characterized by the spontaneous breaking of parity, in which the long-range order parameter is a chirality, \kappa_l = S_l^xS_{l+1}^y-S_l^yS_{l+1}^x, whereas the spin correlation decays either exponentially or algebraically. These chiral ordered phases appear in a broad region in the phase diagram for \Delta < 0.95, where \Delta is an exchange-anisotropy parameter. The critical properties of phase transitions are also studied.Comment: 13 pages, 9 figures, to appear in J. Phys. Soc. Jp

Nature of the vortex-glass order in strongly type-II superconductors

The stability and the critical properties of the three-dimensional vortex-glass order in random type-II superconductors with point disorder is investigated in the unscreened limit based on a lattice {\it XY} model with a uniform field. By performing equilibrium Monte Carlo simulations for the system with periodic boundary conditions, the existence of a stable vortex-glass order is established in the unscreened limit. Estimated critical exponents are compared with those of the gauge-glass model.Comment: Error in the reported value of the exponent eta is correcte

Repeated lumbar punctures within 3 days may affect CSF biomarker levels

Lumbar puncture (LP) is a common way of collecting cerebrospinal fluid (CSF) both in the clinic and in research. In this extension of a study on the relationship between sleep deprivation and CSF biomarkers for Alzheimer’s disease, we investigated CSF biomarker dynamics in relation to rebound sleep after sleep deprivation. Two LPs were performed within 3 days in 13 healthy volunteers. We noticed an unexpected sharp rise in biomarker concentrations in the second sample and therefore repeated the experiment, but without sleep intervention, in four additional individuals. The findings were similar in these subjects, suggesting an inherent methodological problem with repeated LPs. The result corroborates findings in studies with repeated CSF collection via indwelling lumbar catheters, and needs to be addressed in, for instance, pharmacodynamic studies employing these techniques

The anomalous threshold, confinement, and an essential singularity in the heavy-light form factor

The analytic behavior of the heavy-light meson form factor is investigated using several relativistic examples including unconfined, weakly confined, and strongly confined mesons. It is observed that confinement erases the anomalous threshold singularity and also induces an essential singularity at the normal annihilation threshold. In the weak confinement limit, the "would be" anomalous threshold contribution is identical to that of the real singularity on its space-like side.Comment: Latex 2.09 with epsf.sty. 24 pages of text and 8 postscript figures. Postscript version of complete paper will also be available soon at http://phenom.physics.wisc.edu/pub/preprints/1997/madph-97-983 or at ftp://phenom.physics.wisc.edu/pub/preprints/1997/madph-97-98