25,071 research outputs found
Predictions for Impurity-Induced Tc Suppression in the High-Temperature Superconductors
We address the question of whether anisotropic superconductivity is
compatible with the evidently weak sensitivity of the critical temperature Tc
to sample quality in the high-Tc copper oxides. We examine this issue
quantitatively by solving the strong-coupling Eliashberg equations numerically
as well as analytically for s-wave impurity scattering within the second Born
approximation. For pairing interactions with a characteristically low energy
scale, we find an approximately universal dependence of the d-wave
superconducting transition temperature on the planar residual resistivity which
is independent of the details of the microscopic pairing. These results, in
conjunction with future systematic experiments, should help elucidate the
symmetry of the order parameter in the cuprates.Comment: 13 pages, 4 figures upon request, revtex version
Blind Normalization of Speech From Different Channels
We show how to construct a channel-independent representation of speech that
has propagated through a noisy reverberant channel. This is done by blindly
rescaling the cepstral time series by a non-linear function, with the form of
this scale function being determined by previously encountered cepstra from
that channel. The rescaled form of the time series is an invariant property of
it in the following sense: it is unaffected if the time series is transformed
by any time-independent invertible distortion. Because a linear channel with
stationary noise and impulse response transforms cepstra in this way, the new
technique can be used to remove the channel dependence of a cepstral time
series. In experiments, the method achieved greater channel-independence than
cepstral mean normalization, and it was comparable to the combination of
cepstral mean normalization and spectral subtraction, despite the fact that no
measurements of channel noise or reverberations were required (unlike spectral
subtraction).Comment: 25 pages, 7 figure
Stereo Computation for a Single Mixture Image
This paper proposes an original problem of \emph{stereo computation from a
single mixture image}-- a challenging problem that had not been researched
before. The goal is to separate (\ie, unmix) a single mixture image into two
constitute image layers, such that the two layers form a left-right stereo
image pair, from which a valid disparity map can be recovered. This is a
severely illposed problem, from one input image one effectively aims to recover
three (\ie, left image, right image and a disparity map). In this work we give
a novel deep-learning based solution, by jointly solving the two subtasks of
image layer separation as well as stereo matching. Training our deep net is a
simple task, as it does not need to have disparity maps. Extensive experiments
demonstrate the efficacy of our method.Comment: Accepted by European Conference on Computer Vision (ECCV) 201
Fluctuation-Driven Molecular Transport in an Asymmetric Membrane Channel
Channel proteins, that selectively conduct molecules across cell membranes,
often exhibit an asymmetric structure. By means of a stochastic model, we argue
that channel asymmetry in the presence of non-equilibrium fluctuations, fueled
by the cell's metabolism as observed recently, can dramatically influence the
transport through such channels by a ratchet-like mechanism. For an
aquaglyceroporin that conducts water and glycerol we show that a previously
determined asymmetric glycerol potential leads to enhanced inward transport of
glycerol, but for unfavorably high glycerol concentrations also to enhanced
outward transport that protects a cell against poisoning.Comment: REVTeX4, 4 pages, 3 figures; Accepted for publication in Phys. Rev.
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Measuring the saturation scale in nuclei
The saturation momentum seeing in the nuclear infinite momentum frame is
directly related to transverse momentum broadening of partons propagating
through the medium in the nuclear rest frame. Calculation of broadening within
the color dipole approach including the effects of saturation in the nucleus,
gives rise to an equation which describes well data on broadening in Drell-Yan
reaction and heavy quarkonium production.Comment: 11 pages, 5 figures, based on the talk presented by B.K. at the INT
workshop "Physics at a High Energy Electron Ion Collider", Seattle, October
200
Minimal Models for a Superconductor-Insulator Conformal Quantum Phase Transition
Conformal field theories do not only classify 2D classical critical behavior
but they also govern a certain class of 2D quantum critical behavior. In this
latter case it is the ground state wave functional of the quantum theory that
is conformally invariant, rather than the classical action. We show that the
superconducting-insulating (SI) quantum phase transition in 2D Josephson
junction arrays (JJAs) is a (doubled) Gaussian conformal quantum critical
point. The quantum action describing this system is a doubled
Maxwell-Chern-Simons model in the strong coupling limit. We also argue that the
SI quantum transitions in frustrated JJAs realize the other possible
universality classes of conformal quantum critical behavior, corresponding to
the unitary minimal models at central charge .Comment: 4 pages, no figure
Charge renormalization and phase separation in colloidal suspensions
We explore the effects of counterion condensation on fluid-fluid phase
separation in charged colloidal suspensions. It is found that formation of
double layers around the colloidal particles stabilizes suspensions against
phase separation. Addition of salt, however, produces an instability which, in
principle, can lead to a fluid-fluid separation. The instability, however, is
so weak that it should be impossible to observe a fully equilibrated
coexistence experimentally.Comment: 7 pages, Europhysics Letters (in press
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