1,061 research outputs found
Origin of strange metallic phase in cuprate superconductors
The origin of strange metallic phase is shown to exist due to these two
conditions---(i) the electrons are strongly interacting such that there are no
band and Mott-Hubbard gaps, and (ii) the electronic energy levels are crossed
in such a way that there is an electronic energy gap between two energy levels
associated to two different wave functions. The theory is also exploited to
explain (i) the upward- and downward-shifts in the -linear resistivity
curves, and (ii) the spectral weight transfer observed in the soft X-ray
absorption spectroscopic measurements of the La-Sr-Cu-O Mott insulator.Comment: To be published in J. Supercond. Nov. Mag
Unitarity and the Bethe-Salpeter Equation
We investigate the relation between different three-dimensional reductions of
the Bethe-Salpeter equation and the analytic structure of the resultant
amplitudes in the energy plane. This correlation is studied for both the
interaction Lagrangian and the system with -, -,
and -channel pole diagrams as driving terms. We observe that the equal-time
equation, which includes some of the three-body unitarity cuts, gives the best
agreement with the Bethe-Salpeter result. This is followed by other 3-D
approximations that have less of the analytic structure.Comment: 17 pages, 8 figures; RevTeX. Version accepted for publication in
Phys. Rev.
QPSK 3R regenerator using a phase sensitive amplifier
A black box phase sensitive amplifier based 3R regeneration scheme is proposed for non-return to zero quadrature phase shift keyed formatted signals. Performance improvements of more than 2 dB are achieved at the presence of input phase distortion
First experimental demonstration of nonlinear inverse synthesis transmission over transoceanic distances
We demonstrate for the first time, the transmission performance of 10Gbaud nonlinear inverse synthesis based signal over transoceanic distances, showing a significant improvement in data capacity x distance product (x12) compared with other NFT-based systems
Self-organised criticality in base-pair breathing in DNA with a defect
We analyse base-pair breathing in a DNA sequence of 12 base-pairs with a
defective base at its centre. We use both all-atom molecular dynamics (MD)
simulations and a system of stochastic differential equations (SDE). In both
cases, Fourier analysis of the trajectories reveals self-organised critical
behaviour in the breathing of base-pairs. The Fourier Transforms (FT) of the
interbase distances show power-law behaviour with gradients close to -1. The
scale-invariant behaviour we have found provides evidence for the view that
base-pair breathing corresponds to the nucleation stage of large-scale DNA
opening (or 'melting') and that this process is a (second-order) phase
transition. Although the random forces in our SDE system were introduced as
white noise, FTs of the displacements exhibit pink noise, as do the
displacements in the AMBER/MD simulations.Comment: 18 pages, 8 figure
Twisted equivariant K-theory, groupoids and proper actions
In this paper we define twisted equivariant K-theory for actions of Lie
groupoids. For a Bredon-compatible Lie groupoid, this defines a periodic
cohomology theory on the category of finite CW-complexes with equivariant
stable projective bundles. A classification of these bundles is shown. We also
obtain a completion theorem and apply these results to proper actions of
groups.Comment: 26 page
Dynamics of ions in the selectivity filter of the KcsA channel
The statistical and dynamical properties of ions in the selectivity filter of the KcsA ion channel are considered on the basis of molecular dynamics (MD) simulations of the KcsA protein embedded in a lipid membrane surrounded by an ionic solution. A new approach to the derivation of a Brownian dynamics (BD) model of ion permeation through the filter is discussed, based on unbiased MD simulations. It is shown that depending on additional assumptions, ion’s dynamics can be described either by under-damped Langevin equation with constant damping and white noise or by Langevin equation with a fractional memory kernel. A comparison of the potential of the mean force derived from unbiased MD simulations with the potential produced by the umbrella sampling method demonstrates significant differences in these potentials. The origin of these differences is an open question that requires further clarifications
Relativistic effects and quasipotential equations
We compare the scattering amplitude resulting from the several quasipotential
equations for scalar particles. We consider the Blankenbecler-Sugar, Spectator,
Thompson, Erkelenz-Holinde and Equal-Time equations, which were solved
numerically without decomposition into partial waves. We analyze both
negative-energy state components of the propagators and retardation effects. We
found that the scattering solutions of the Spectator and the Equal-Time
equations are very close to the nonrelativistic solution even at high energies.
The overall relativistic effect increases with the energy. The width of the
band for the relative uncertainty in the real part of the scattering
matrix, due to different dynamical equations, is largest for
backward-scattering angles where it can be as large as 40%.Comment: Accepted for publication in Phys. Rev.
The Topology and Size of the Universe from the Cosmic Microwave Background
We study the possibility that the universe has compact topologies T^3, T^2 x
R^1, or S^1 x R^2 using the seven-year WMAP data. The maximum likelihood 95%
confidence intervals for the size L of the compact direction are 1.7 < L/L_0 <
2.1, 1.8 < L/L_0 < 2.0, 1.2 < L/L_0 < 2.1 for the three cases, respectively,
where L_0=14.4 Gpc is the distance to the last scattering surface. An infinite
universe is compatible with the data at 4.3 sigma. We find using a Bayesian
analysis that the most probable universe has topology T^2 x R^1, with
L/L_0=1.9.Comment: Additional checks, Monte-Carlo skies, and study of dipole
contamination added. References added. 13 pages, 11 figure
Threshold criterion for wetting at the triple point
Grand canonical simulations are used to calculate adsorption isotherms of
various classical gases on alkali metal and Mg surfaces. Ab initio adsorption
potentials and Lennard-Jones gas-gas interactions are used. Depending on the
system, the resulting behavior can be nonwetting for all temperatures studied,
complete wetting, or (in the intermediate case) exhibit a wetting transition.
An unusual variety of wetting transitions at the triple point is found in the
case of a specific adsorption potential of intermediate strength. The general
threshold for wetting near the triple point is found to be close to that
predicted with a heuristic model of Cheng et al. This same conclusion was drawn
in a recent experimental and simulation study of Ar on CO_2 by Mistura et al.
These results imply that a dimensionless wetting parameter w is useful for
predicting whether wetting behavior is present at and above the triple
temperature. The nonwetting/wetting crossover value found here is w circa 3.3.Comment: 15 pages, 8 figure
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