61,689 research outputs found
A Tight Lower Bound on the Sub-Packetization Level of Optimal-Access MSR and MDS Codes
The first focus of the present paper, is on lower bounds on the
sub-packetization level of an MSR code that is capable of carrying out
repair in help-by-transfer fashion (also called optimal-access property). We
prove here a lower bound on which is shown to be tight for the case
by comparing with recent code constructions in the literature.
We also extend our results to an MDS code over the vector alphabet.
Our objective even here, is on lower bounds on the sub-packetization level
of an MDS code that can carry out repair of any node in a subset of
nodes, where each node is repaired (linear repair) by
help-by-transfer with minimum repair bandwidth. We prove a lower bound on
for the case of . This bound holds for any and
is shown to be tight, again by comparing with recent code constructions in the
literature. Also provided, are bounds for the case .
We study the form of a vector MDS code having the property that we can repair
failed nodes belonging to a fixed set of nodes with minimum repair
bandwidth and in optimal-access fashion, and which achieve our lower bound on
sub-packetization level . It turns out interestingly, that such a code
must necessarily have a coupled-layer structure, similar to that of the Ye-Barg
code.Comment: Revised for ISIT 2018 submissio
Magnetization and Magneto-resistance in Y(Ba1-xSrx)2Cu3O7-{\delta} (x = 0.00 - 0.50) superconductor
Here we present the magnetic properties and upper critical field (BC2) of
polycrystalline Y(Ba1-xSrx)2Cu3O7-{\delta} superconductors, which are being
determined through detailed ac/dc susceptibility and resistivity under magnetic
field (RTH) study. All the samples are synthesized through solid state reaction
route. Reduction in Meissner fraction (the ratio of field cooled to zero field
cooled magnetization) is observed with increasing Sr content, suggesting
occurrence of flux pining in the doped samples. The ac susceptibility and
resistivity measurements reveal improved grain couplings in Sr substituted
samples. Consequently the inter-grain critical current density (Jc), upturn
curvature near the Tc in temperature dependence of upper critical field
[BC2(T)], and BC2 are enhanced. Both Jc and BC2 increase in lower Sr
substitution (up to x = 0.10) samples followed by decrease in higher doping due
to degradation in effective pining and grain coupling.Comment: 17 pages text + Figs, [email protected]
Superfield Approach to Nilpotency and Absolute Anticommutativity of Conserved Charges: 2D non-Abelian 1-Form Gauge Theory
We exploit the theoretical strength of augmented version of superfield
approach (AVSA) to Becchi-Rouet-Stora-Tyutin (BRST) formalism to express the
nilpotency and absolute anticommutativity properties of the (anti-)BRST and
(anti-)co-BRST conserved charges for the two -dimensional (2D)
non-Abelian 1-form gauge theory (without any interaction with matter fields) in
the language of superspace variables, their derivatives and suitable
superfields. In the proof of absolute anticommutativity property, we invoke the
strength of Curci-Ferrari (CF) condition for the (anti-)BRST charges. No such
outside condition/restriction is required in the proof of absolute
anticommutativity of the (anti-)co-BRST conserved charges. The latter
observation (as well as other observations) connected with (anti-)co-BRST
symmetries and corresponding conserved charges are novel results of our present
investigation. We also discuss the (anti-)BRST and (anti-)co-BRST symmetry
invariance of the appropriate Lagrangian densities within the framework of
AVSA. In addition, we dwell a bit on the derivation of the above fermionic
(nilpotent) symmetries by applying the AVSA to BRST formaism where only the
(anti-)chiral superfields are used.Comment: LaTeX file, 33 pages, journal referenc
Anomalously Slow Domain Growth in Fluid Membranes with Asymmetric Transbilayer Lipid Distribution
The effect of asymmetry in the transbilayer lipid distribution on the
dynamics of phase separation in fluid vesicles is investigated numerically for
the first time. This asymmetry is shown to set a spontaneous curvature for the
domains that alter the morphology and dynamics considerably. For moderate
tension, the domains are capped and the spontaneous curvature leads to
anomalously slow dynamics, as compared to the case of symmetric bilayers. In
contrast, in the limiting cases of high and low tensions, the dynamics proceeds
towards full phase separation.Comment: 4 pages, 5 figure
Noncommutative BTZ Black Hole and Discrete Time
We search for all Poisson brackets for the BTZ black hole which are
consistent with the geometry of the commutative solution and are of lowest
order in the embedding coordinates. For arbitrary values for the angular
momentum we obtain two two-parameter families of contact structures. We obtain
the symplectic leaves, which characterize the irreducible representations of
the noncommutative theory. The requirement that they be invariant under the
action of the isometry group restricts to symplectic leaves,
where is associated with the Schwarzschild time. Quantization may then lead
to a discrete spectrum for the time operator.Comment: 10 page
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