Electron tunneling time measured by photoluminescence excitation correlation spectroscopy

The tunneling time for electrons to escape from the lowest quasibound state in the quantum wells of GaAs/AlAs/GaAs/AlAs/GaAs double-barrier heterostructures with barriers between 16 and 62 Å has been measured at 80 K using photoluminescence excitation correlation spectroscopy. The decay time for samples with barrier thicknesses from 16 Å (≈12 ps) to 34 Å(≈800 ps) depends exponentially on barrier thickness, in good agreement with calculations of electron tunneling time derived from the energy width of the resonance. Electron and heavy hole carrier densities are observed to decay at the same rate, indicating a coupling between the two decay processes

Single-charge rotating black holes in four-dimensional gauged supergravity

We consider four-dimensional U(1)^4 gauged supergravity, and obtain asymptotically AdS_4, non-extremal, charged, rotating black holes with one non-zero U(1) charge. The thermodynamic quantities are computed. We obtain a generalization that includes a NUT parameter. The general solution has a discrete symmetry involving inversion of the rotation parameter, and has a string frame metric that admits a rank-2 Killing-Stackel tensor.Comment: 9 page

eHealth interventions for people with chronic kidney disease

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows: This review aims to look at the benefits and harms of using eHealth interventions in the CKD population

Multiplpe Choice Minority Game With Different Publicly Known Histories

In the standard Minority Game, players use historical minority choices as the sole public information to pick one out of the two alternatives. However, publishing historical minority choices is not the only way to present global system information to players when more than two alternatives are available. Thus, it is instructive to study the dynamics and cooperative behaviors of this extended game as a function of the global information provided. We numerically find that although the system dynamics depends on the kind of public information given to the players, the degree of cooperation follows the same trend as that of the standard Minority Game. We also explain most of our findings by the crowd-anticrowd theory.Comment: Extensively revised, to appear in New J Phys, 7 pages with 4 figure

Propagating Wave Patterns in a Derivative Nonlinear Schr\"odinger System with Quintic Nonlinearity

Exact expressions are obtained for a diversity of propagating patterns for a derivative nonlinear Schr\"odinger equation with a quintic nonlinearity. These patterns include bright pulses, fronts and dark solitons. The evolution of the wave envelope is determined via a pair of integrals of motion, and reduction is achieved to Jacobi elliptic cn and dn function representations. Numerical simulations are performed to establish the existence of parameter ranges for stability. The derivative quintic nonlinear Schr\"odinger model equations investigated here are important in the analysis of strong optical signals propagating in spatial or temporal waveguides.Comment: J. Phys. Soc. Jpn. in pres

Charged rotating black holes in six-dimensional gauged supergravity

We obtain non-extremal charged rotating black holes in six-dimensional SU(2) gauged supergravity with two independent angular momenta and one U(1) charge. These include supersymmetric black holes without naked closed timelike curves.Comment: 9 pages; v2: minor change

Low-Energy Charge-Density Excitations in MgB2_{2}: Striking Interplay between Single-Particle and Collective Behavior for Large Momenta

A sharp feature in the charge-density excitation spectra of single-crystal MgB$_{2}$, displaying a remarkable cosine-like, periodic energy dispersion with momentum transfer ($q$) along the $c^{*}$-axis, has been observed for the first time by high-resolution non-resonant inelastic x-ray scattering (NIXS). Time-dependent density-functional theory calculations show that the physics underlying the NIXS data is strong coupling between single-particle and collective degrees of freedom, mediated by large crystal local-field effects. As a result, the small-$q$ collective mode residing in the single-particle excitation gap of the B $\pi$ bands reappears periodically in higher Brillouin zones. The NIXS data thus embody a novel signature of the layered electronic structure of MgB$_{2}$.Comment: 5 pages, 4 figures, submitted to PR

Threshold effects in excited charmed baryon decays

Motivated by recent results on charmed baryons from CLEO and FOCUS, we reexamine the couplings of the orbitally excited charmed baryons. Due to its proximity to the [Sigma_c pi] threshold, the strong decays of the Lambda_c(2593) are sensitive to finite width effects. This distorts the shape of the invariant mass spectrum in Lambda_{c1}-> Lambda_c pi^+pi^- from a simple Breit-Wigner resonance, which has implications for the experimental extraction of the Lambda_c(2593) mass and couplings. We perform a fit to unpublished CLEO data which gives M(Lambda_c(2593)) - M(Lambda_c) = 305.6 +- 0.3 MeV and h2^2 = 0.24^{+0.23}_{-0.11}, with h2 the Lambda_{c1}-> Sigma_c pi strong coupling in the chiral Lagrangian. We also comment on the new orbitally excited states recently observed by CLEO.Comment: 9 pages, 3 figure

Kundt spacetimes as solutions of topologically massive gravity

We obtain new solutions of topologically massive gravity. We find the general Kundt solutions, which in three dimensions are spacetimes admitting an expansion-free null geodesic congruence. The solutions are generically of algebraic type II, but special cases are types III, N or D. Those of type D are the known spacelike-squashed AdS_3 solutions, and of type N are the known AdS pp-waves or new solutions. Those of types II and III are the first known solutions of these algebraic types. We present explicitly the Kundt solutions that are CSI spacetimes, for which all scalar polynomial curvature invariants are constant, whereas for the general case we reduce the field equations to a series of ordinary differential equations. The CSI solutions of types II and III are deformations of spacelike-squashed AdS_3 and the round AdS_3, respectively.Comment: 30 pages. This material has come from splitting v1 of arXiv:0906.3559 into 2 separate papers. v2: minor changes

Plasma heating in highly excited GaN/AlGaN multiple quantum wells

Time-resolvedphotoluminescence(PL)spectroscopy was used to investigate carrier distributions in a GaN/AlGaN multiple quantum well(MQW) sample under high excitation intensities necessary to achieve lasing threshold. Room temperaturePL spectra showed optical transitions involving both confined and unconfined states in the quantum well structure. Analysis of the experimental results using a microscopic theory, indicates that at high excitation the carrier distributions are characterized by plasma temperatures which are significantly higher than the lattice temperature. The implications of our findings on GaN MQW laser design are also discussed