16,608 research outputs found
Incommensurate magnetism in cuprate materials
In the low doping region an incommensurate magnetic phase is observed in
LSCO. By means of the composite operator method we show that the single-band 2D
Hubbard model describes the experimental situation. In the higher doping
region, where experiments are not available, the incommensurability is
depressed owing to the van Hove singularity near the Fermi level. A
proportionality between the incommensurability amplitude and the critical
temperature is predicted, suggesting a close relation between superconductivity
and incommensurate magnetism.Comment: 4 pages, 5 figures in one Postscript file, RevTe
Dark energy from modified gravity with Lagrange multipliers
We study scalar-tensor theory, k-essence and modified gravity with Lagrange
multiplier constraint which role is to reduce the number of degrees of freedom.
Dark Energy cosmology of different types (CDM, unified inflation with
DE, smooth non-phantom/phantom transition epoch) is reconstructed in such
models. It is shown that mathematical equivalence between scalar theory and
gravity is broken due to presence of constraint. The cosmological
dynamics of gravity is modified by the second function dictated
by the constraint. Dark Energy cosmology is defined by this function while
standard function is relevant for local tests (modification of newton
regime). A general discussion on the role of Lagrange multipliers to make
higher-derivative gravity canonical is developed.Comment: LaTeX 12 pages, discussion is improve
Patterns on a Roll: A Method for Continuous Feed Nanoprinting
Exploiting elastic instability in thin films has proven a robust method for
creating complex patterns and structures across a wide range of lengthscales.
Even the simplest of systems, an elastic membrane with a lattice of pores,
under mechanical strain, generates complex patterns featuring long-range
orientational order. When we promote this system to a curved surface, in
particular, a cylindrical membrane, a novel set of features, patterns and
broken symmetries appears. The newfound periodicity of the cylinder allows for
a novel continuous method for nanoprinting.Comment: 4 pages, 4 figure
ASCA observations of massive medium-distant clusters of galaxies. II
We have selected seven medium-distant clusters of galaxies (z ~ 0.1 - 0.3)
for multi-wavelength observations with the goal of investigating their
dynamical state. Following Paper I (Pierre et al. 1999) which reported the ASCA
results about two of them, we present here the analysis of the ASCA
observations of the other five clusters; RXJ1023.8-2715 (A3444),
RXJ1031.6-2607, RXJ1050.5-0236 (A1111), RXJ1203.2-2131(A1451), and
RXJ1314.5-2517. Except for RXJ1031.6, whose X-ray emission turned out to be
dominated by an AGN, the ASCA spectra are well fitted by a one-temperature thin
thermal plasma model. We compare the temperature-luminosity relation of our
clusters with that of nearby ones (z<0.1). Two clusters, RXJ1050.5 and
RXJ1023.8, show larger luminosities than the bulk of clusters at similar
temperatures, which suggests the presence of a cooling flow. The temperature
vs. iron-abundance relationship of our sample is consistent with that of nearby
clusters.Comment: 9 pages, 20 figures, A&AS in pres
Explosive Dark Matter Annihilation
If the Dark Matter (DM) in the Universe has interactions with the
standard-model particle, the pair annihilation may give the imprints in the
cosmic ray. In this paper we study the pair annihilation processes of the DM,
which is neutral, however has the electroweak (EW) gauge non-singlet. In this
estimation the non-relativistic (NR) effective theory in the EW sector is a
suitable technique. We find that if the DM mass is larger than about 1 TeV, the
attractive Yukawa potentials induced by the EW gauge bosons have significant
effects on the DM annihilation processes, and the cross sections may be
enhanced by several orders of magnitude, due to the zero energy resonance under
the potentials. Especially, the annihilation to two 's might have a
comparable cross section to other tree-level processes, while the cross section
under the conventional calculation is suppressed by a loop factor. We also
discuss future sensitivities to the ray from the galactic center by
the GLAST satellite detector and the Air Cerenkov Telescope (ACT) arrays.Comment: 5 pages, 6 Postscript figures, revte
Improvement of stabilizer based entanglement distillation protocols by encoding operators
This paper presents a method for enumerating all encoding operators in the
Clifford group for a given stabilizer. Furthermore, we classify encoding
operators into the equivalence classes such that EDPs (Entanglement
Distillation Protocol) constructed from encoding operators in the same
equivalence class have the same performance. By this classification, for a
given parameter, the number of candidates for good EDPs is significantly
reduced. As a result, we find the best EDP among EDPs constructed from [[4,2]]
stabilizer codes. This EDP has a better performance than previously known EDPs
over wide range of fidelity.Comment: 22 pages, 2 figures, In version 2, we enumerate all encoding
operators in the Clifford group, and fix the wrong classification of encoding
operators in version
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