191 research outputs found
Disordered free fermions and the Cardy Ostlund fixed line at low temperature
Using functional RG, we reexamine the glass phase of the 2D random-field Sine
Gordon model. It is described by a line of fixed points (FP) with a
super-roughening amplitude as
temperature is varied. A speculation is that this line is identical to the
one found in disordered free-fermion models via exact results from ``nearly
conformal'' field theory. This however predicts , contradicting
numerics. We point out that this result may be related to failure of
dimensional reduction, and that a functional RG method incorporating higher
harmonics and non-analytic operators predicts a non-zero which
compares reasonably with numerics.Comment: 8 pages, 3 figures, only material adde
Wing-Body Aeroelasticity Using Finite-Difference Fluid/Finite-Element Structural Equations on Parallel Computers
This paper presents a procedure for computing the aeroelasticity of wing-body configurations on multiple-instruction, multiple-data (MIMD) parallel computers. In this procedure, fluids are modeled using Euler equations discretized by a finite difference method, and structures are modeled using finite element equations. The procedure is designed in such a way that each discipline can be developed and maintained independently by using a domain decomposition approach. A parallel integration scheme is used to compute aeroelastic responses by solving the coupled fluid and structural equations concurrently while keeping modularity of each discipline. The present procedure is validated by computing the aeroelastic response of a wing and comparing with experiment. Aeroelastic computations are illustrated for a High Speed Civil Transport type wing-body configuration
High-temperature hardness of Ga_(1−x)In_xAs
Substantial solid‐solution strengthening of GaAs by In acting as InAs_4 units has recently been predicted for an intermediate‐temperature plateau region. This strengthening could account, in part, for the reduction of dislocation density in GaAs single crystals grown from the melt. Hardness measurements at high temperatures up to 900 °C have been carried out on (100) GaAs, Ga_(0.9975)In_(0.0025)As, and Ga_(0.99)In_(0.01)As wafers, all of which contain small amounts of boron. Results show a significant strengthening effect in In‐doped GaAs. A nominally temperature‐independent flow‐stress region is observed for all three alloys. The In‐doped GaAs shows a higher plateau stress level with increasing In content. The results are consistent with the solid‐solution strengthening model. The magnitude of the solid‐solution hardening is sufficient to explain the reduction in dislocation density with In addition
Aging in the glass phase of a 2D random periodic elastic system
Using RG we investigate the non-equilibrium relaxation of the (Cardy-Ostlund)
2D random Sine-Gordon model, which describes pinned arrays of lines. Its
statics exhibits a marginal () glass phase for described by a
line of fixed points. We obtain the universal scaling functions for two-time
dynamical response and correlations near for various initial conditions,
as well as the autocorrelation exponent. The fluctuation dissipation ratio is
found to be non-trivial and continuously dependent on .Comment: 5 pages, RevTex, Modified Versio
Deformation behavior of undoped and In-doped GaAs in the temperature range 700–1100 °C
Compressive deformation of undoped and In‐doped GaAs single crystals has been carried out in [001] and [123] orientations in the temperature range 700–1100 °C. Indium additions, at levels of 1–2×10^(20) atoms cm^(−3), result in critical resolved shear stress (CRSS) values that are about twice as large as the undoped crystals in the temperature range of 700–1100 °C. The CRSS was weakly dependent on temperature in the temperature range investigated as expected for a model of athermal solid solution hardening. The CRSS value of 3.3 MPa for the In‐doped crystal is sufficient to eliminate profuse dislocation formation in a 75‐mm‐diam crystal on the basis of current theories for the magnitude of the thermal stress experienced during growth. The results also suggest that the process of dislocation climb is slowed appreciably by In doping
K-matrices for non-abelian quantum Hall states
Two fundamental aspects of so-called non-abelian quantum Hall states (the
q-pfaffian states and more general) are a (generalized) pairing of the
participating electrons and the non-abelian statistics of the quasi-hole
excitations. In this paper, we show that these two aspects are linked by a
duality relation, which can be made manifest by considering the K-matrices that
describe the exclusion statistics of the fundamental excitations in these
systems.Comment: LaTeX, 12 page
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