A numerical simulation of three-dimensional flow in an adaptive wall wind tunnel

Numerical simulations of three dimensional flows in a prototype adaptive wall wind tunnel are conducted at the Mach number of 0.6 to investigate: (1) wind tunnel wall interference, (2) active streamline control by varying air removal or injection along the walls, and (3) to develop a method for establishing wall boundary conditions for interference free flows. Wind tunnel wall interference could be controlled by using only the vertical velocity components. For the configuration tested, interference free flow with solid sidewalls can be approximated by using only floor and ceiling blowing/suction

Possible cosmological implications in electrodynamics due to variations of the fine structure constant

Astronomical observations are suggesting that the fine structure constant varies cosmologically. We present an analysis on the consequences that these variations might induce on the electromagnetic field as a whole. We show that under these circumstances the electrodynamics in vacuum could be described by two fields, the ``standard'' Maxwell's field and a new scalar field. We provide a generalised Lorentz force which can be used to test our results experimentally.Comment: 7 pages, no figures. Accepted for publication in Rev. Mex. Fis. (Some extra information included, references added and small corrections made to the original version

Exclusive W^+ + photon production in proton-antiproton collisions II: results

We present results for total cross sections, single and double differential distributions and correlations between pairs of outgoing particles in the reactions p + antip --> W^+ + photon and p + antip --> W^+ + photon + jet at sqrt(S)=1.8 TeV. Order alpha-strong QCD corrections and leading logarithm photon bremsstrahlung contributions are included in the MS-bar mass factorization scheme for three experimental scenarios: 1) 2-body inclusive production of W^+ and photon, 2) exclusive production of W^+, photon and 1 jet and 3) exclusive production of W^+ and photon with 0 jet. The latest CTEQ parton distribution functions, which fit the newly released HERA data, are used in our analysis. The dependence of our results on the mass factorization scale is used to place error bars on our predictions for the single differential distributions and correlations.Comment: 15 pages (LateX). 50 pages of postscript figures available via ftp anonymous from max.physics.sunysb.edu in the directory preprints/mendoza/EXCLUSIVE_W_GAMMA_II.dir (files named fig_*.ps) ITP-SB-93-80. ([email protected])([email protected]

Landau levels in wrinkled and rippled graphene sheets

We study the discrete energy spectrum of curved graphene sheets in the presence of a magnetic field. The shifting of the Landau levels is determined for complex and realistic geometries of curved graphene sheets. The energy levels follow a similar square root dependence on the energy quantum number as for rippled and flat graphene sheets. The Landau levels are shifted towards lower energies proportionally to the average deformation and the effect is larger compared to a simple uni-axially rippled geometry. Furthermore, the resistivity of wrinkled graphene sheets is calculated for different average space curvatures and shown to obey a linear relation. The study is carried out with a quantum lattice Boltzmann method, solving the Dirac equation on curved manifolds.Comment: 6 pages, 4 figures, 27th International Conference on Discrete Simulation of Fluid Dynamic

Hydrodynamic Model for Conductivity in Graphene

Based on the recently developed picture of an electronic ideal relativistic fluid at the Dirac point, we present an analytical model for the conductivity in graphene that is able to describe the linear dependence on the carrier density and the existence of a minimum conductivity. The model treats impurities as submerged rigid obstacles, forming a disordered medium through which graphene electrons flow, in close analogy with classical fluid dynamics. To describe the minimum conductivity, we take into account the additional carrier density induced by the impurities in the sample. The model, which predicts the conductivity as a function of the impurity fraction of the sample, is supported by extensive simulations for different values of ${\cal E}$, the dimensionless strength of the electric field, and provides excellent agreement with experimental data.Comment: 19 pages, 4 figure