2,854 research outputs found
Odd-frequency superconducting pairing in Kitaev-based junctions
We investigate odd-frequency superconducting correlations in
normal-superconductor (NS) and short superconductor-normal-superconductor (SNS)
junctions with the S region described by the Kitaev model of spinless fermions
in one dimension. We demonstrate that, in both the trivial and topological
phases, Andreev reflection is responsible for the coexistence of even- and
odd-frequency pair amplitudes at interfaces, while normal reflections solely
contribute to odd-frequency pairing. At NS interfaces we find that the
odd-frequency pair amplitude exhibits large, but finite, values in the
topological phase at low frequencies. This enhancement is due to the emergence
of a Majorana zero mode at the interface, but notably there is no divergence
and a finite odd-frequency pair amplitude also exists outside the topological
phase. We also show that the local density of states and local odd-frequency
pairing can be characterized solely by Andreev reflections deep in the
topological phase. Moreover, in the topological phase of short SNS junctions,
we find that both even- and odd-frequency amplitudes capture the emergence of
topological Andreev bound states. For a superconducting phase difference
the odd-frequency magnitude exhibits a linear frequency () dependence at low-frequencies, while at it develops a
resonance peak () due to the protected Majorana zero modes.Comment: 12 pages, 7 figures + 7 pages of supplemental material. Published
versio
Relative entropy in diffusive relaxation
We establish convergence in the diffusive limit from entropy weak solutions of
the equations of compressible gas dynamics with friction to the porous media equation away from vacuum.
The result is based on a Lyapunov type of functional provided by a calculation of the relative entropy.
The relative entropy method is also employed to establish convergence from entropic weak solutions
of viscoelasticity with memory to the system of viscoelasticity of the rate-type
On Optimal and Fair Service Allocation in Mobile Cloud Computing
This paper studies the optimal and fair service allocation for a variety of
mobile applications (single or group and collaborative mobile applications) in
mobile cloud computing. We exploit the observation that using tiered clouds,
i.e. clouds at multiple levels (local and public) can increase the performance
and scalability of mobile applications. We proposed a novel framework to model
mobile applications as a location-time workflows (LTW) of tasks; here users
mobility patterns are translated to mobile service usage patterns. We show that
an optimal mapping of LTWs to tiered cloud resources considering multiple QoS
goals such application delay, device power consumption and user cost/price is
an NP-hard problem for both single and group-based applications. We propose an
efficient heuristic algorithm called MuSIC that is able to perform well (73% of
optimal, 30% better than simple strategies), and scale well to a large number
of users while ensuring high mobile application QoS. We evaluate MuSIC and the
2-tier mobile cloud approach via implementation (on real world clouds) and
extensive simulations using rich mobile applications like intensive signal
processing, video streaming and multimedia file sharing applications. Our
experimental and simulation results indicate that MuSIC supports scalable
operation (100+ concurrent users executing complex workflows) while improving
QoS. We observe about 25% lower delays and power (under fixed price
constraints) and about 35% decrease in price (considering fixed delay) in
comparison to only using the public cloud. Our studies also show that MuSIC
performs quite well under different mobility patterns, e.g. random waypoint and
Manhattan models
Complete One-Loop MSSM Predictions for B --> lepton lepton' at the Tevatron and LHC
During the last few years the Tevatron has dramatically improved the bounds
on rare B-meson decays into two leptons. In the case of B_s --> mu+ mu-, the
current bound is only ten times greater than the Standard Model expectation.
Sensitivity to this decay is one of the benchmark goals for LHCb performance
and physics. The Higgs penguin dominates this rate in the region of large
tan(beta) of the MSSM. This is not necessarily the case in the region of low
tan(beta), since box and Z-penguin diagrams may contribute at a comparable
rate. In this article, we compute the complete one-loop MSSM contribution to B
--> l+l'- for l,l' = e, mu. We study the predictions for general values of
tan(beta) with arbitrary flavour mixing parameters. We discuss the possibility
of both enhancing and suppressing the branching ratios relative to their
Standard Model expectations. In particular, we find that there are
"cancellation regions" in parameter space where the branching ratio is
suppressed well below the Standard Model expectation, making it effectively
invisible to the LHC.Comment: 30 pages, 4 figures; v.3: corrected factors of (2 pi) in (2.11),
(3.1), (A.11), (A.13-14
Superposition of DC voltage and submicrosecond impulses for energization of electrostatic precipitators
This paper discusses the development of an impulsive microelectrostatic precipitation technology, which uses superposition of submicrosecond high-field pulses and dc electric field. Short impulses allow the application of higher voltages to the ionization electrodes of a precipitation system without the initiation of breakdown. These higher levels of electric field generate higher ionic concentrations, resulting in more efficient charging of the airborne particles, and can potentially improve precipitation efficiency. This work is focused on the analysis of the behavior of impulsive positive corona discharges in a coaxial reactor designed for precipitation studies. The efficiency of precipitation of coarse and fine particles has been investigated using different dc and impulse voltage levels in order to establish optimal energization modes
Naturally small Dirac neutrino masses in supergravity
We show that Dirac neutrino masses of the right size can arise from the
Kahler potential of supergravity. They are proportional to the supersymmetry
and the electroweak breaking scales. We find that they have the experimentally
observed value provided that the ultraviolet cut-off of the Minimal
Supersymmetric Standard Model (MSSM) is between the Grand Unification (GUT)
scale and the heterotic string scale. If lepton number is not conserved, then
relatively suppressed Majorana masses can also be present, resulting in
pseudo-Dirac neutrino masses.Comment: 6 pages, Revtex 4, published versio
Strain-stiffening in random packings of entangled granular chains
Random packings of granular chains are presented as a model polymer system to
investigate the contribution of entanglements to strain-stiffening in the
absence of Brownian motion. The chain packings are sheared in triaxial
compression experiments. For short chain lengths, these packings yield when the
shear stress exceeds a the scale of the confining pressure, similar to packings
of spherical particles. In contrast, packings of chains which are long enough
to form loops exhibit strain-stiffening, in which the effective stiffness of
the material increases with strain, similar to many polymer materials. The
latter packings can sustain stresses orders-of-magnitude greater than the
confining pressure, and do not yield until the chain links break. X-ray
tomography measurements reveal that the strain-stiffening packings contain
system-spanning clusters of entangled chains.Comment: 4 pages, 4 figures. submitted to Physical Review Letter
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