4,275 research outputs found
Apparent Clustering of Intermediate-redshift Galaxies as a Probe of Dark Energy
We show the apparent redshift-space clustering of galaxies in redshift range
of 0.2--0.4 provides surprisingly useful constraints on dark energy component
in the universe, because of the right balance between the density of objects
and the survey depth. We apply Fisher matrix analysis to the the Luminous Red
Galaxies (LRGs) in the Sloan Digital Sky Survey (SDSS), as a concrete example.
Possible degeneracies in the evolution of the equation of state (EOS) and the
other cosmological parameters are clarified.Comment: 5 pages, 3 figures, Phys.Rev.Lett., replaced with the accepted
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Ground-State Properties of a Heisenberg Spin Glass Model with a Hybrid Genetic Algorithm
We developed a genetic algorithm (GA) in the Heisenberg model that combines a
triadic crossover and a parameter-free genetic algorithm. Using the algorithm,
we examined the ground-state stiffness of the Heisenberg model in three
dimensions up to a moderate size range. Results showed the stiffness constant
of in the periodic-antiperiodic boundary condition method and that
of in the open-boundary-twist method. We considered the
origin of the difference in between the two methods and suggested that
both results show the same thing: the ground state of the open system is stable
against a weak perturbation.Comment: 11 pages, 5 figure
Attracting shallow donors: Hydrogen passivation in (Al,Ga,In)-doped ZnO
The hydrogen interstitial and the substitutional Al_Zn, Ga_Zn and In_Zn are
all shallow donors in ZnO and lead to n-type conductivity. Although shallow
donors are expected to repel each other, we show by first principles
calculations that in ZnO these shallow donor impurities attract and form a
complex, leading to a donor level deep in the band gap. This puts a limit on
the n-type conductivity of (Al,Ga,In)-doped ZnO in the presence of hydrogen.Comment: 4 pages, 5 figure
London Penetration Length and String Tension in SU(2) Lattice Gauge Theory
We study the distribution of the color fields due to a static quark-antiquark
pair in SU(2) lattice gauge theory. We find evidence of dual Meissner effect.
We put out a simple relation between the penetration length and the string
tension.Comment: uuencoded compressed Postscript file (text+figures
Dephasing of Local Vibrations in a Planar Lattice of Adsorbed Molecules
We investigate anharmonically coupled high- and low-frequency excitations in
a planar lattice of adsorbed molecules interacting with phonons of a crystal.
Dephasing of high-frequency local vibrations by low-frequency resonance modes
is described in terms of temperature Green's function. The equations obtained
are solved, first, with a small ratio of the anharmonic coupling coefficient
for high- and low-frequency modes to the resonance width, and second, in the
low-temperature limit. High-frequency spectral line positions and widths depend
on dispersion laws and resonance mode lifetimes. It is shown that lateral
interactions of low-frequency modes of adsorbed molecules can lead to a
significant narrowing of high-frequency spectral lines, which is consistent
with experimental data.Comment: REVTeX, 11 pages, no figure
A Macrophage Phenotype for a Constitutive, Class II Antigen-Expressing, Human Dermal Perivascular Dendritic Cell
A previously uncharacterized population of class II antigen-bearing dendritic cells that are intimately associated with the dermal microvasculature was identified in normal human skin using a double-label, indirect immunofluorescence technique. The only other major HLA-DR positive dermal cell type noted in these studies, the dermal microvascular endothelial cell (DMVEC), appeared to express lesser amounts of HLA-DR region gene product than did this dermal perivascular dendritic cell (DPDC). These DPDC were particularly common around small vessels in the superficial vascular plexus of the papillary dermis and were distinct from the mast cell, another cell type normally seen in a similar location. Phenotypic and ultrastructural studies have determined that the DPDC is more closely related to the monocyte/macro-phage lineage than the dendritic cell lineage. The perivascular location and phenotype of this cell distinguishes it from other previously described constitutive dermal cell types such as the classic âhistiocyte,â veiled cell, and dendrocyte. The relatively rich expression of all three major HLA-D region gene products by this dermal perivascular dendritic macro-phage would suggest that it could play a significant role in the immunobiology of the dermal microvascular unit
The thermal operator representation for Matsubara sums
We prove in full generality the thermal operator representation for Matsubara
sums in a relativistic field theory of scalar and fermionic particles. It
states that the full result of performing the Matsubara sum associated to any
given Feynman graph, in the imaginary-time formalism of finite-temperature
field theory, can be directly obtained from its corresponding zero-temperature
energy integral, by means of a simple linear operator, which is independent of
the external Euclidean energies and whose form depends solely on the topology
of the graph.Comment: 9 pages, 1 figure, RevTe
Spin-Glass and Chiral-Glass Transitions in a Heisenberg Spin-Glass Model in Three Dimensions
The three-dimensional Heisenberg spin-glass model is investigated by
the non-equilibrium relaxation method from the paramagnetic state. Finite-size
effects in the non-equilibrium relaxation are analyzed, and the relaxation
functions of the spin-glass susceptibility and the chiral-glass susceptibility
in the infinite-size system are obtained. The finite-time scaling analysis
gives the spin-glass transition at and the
chiral-glass transition at . The results
suggest that both transitions occur simultaneously. The critical exponent of
the spin-glass susceptibility is estimated as ,
which makes an agreement with the experiments of the insulating and the
canonical spin-glass materials.Comment: 4 pages, 2 figure
Ordering of the Heisenberg Spin Glass in High Dimensions
Ordering of the Heisenberg spin glass with the nearest-neighbor Gaussian
coupling is investigated by equilibrium Monte Carlo simulations in four and
five dimensions. Ordering of the mean-field Heisenberg spin-glass is also
studied for comparison. Particular attention is paid to the nature of the
spin-glass and the chiral-glass orderings. Our numerical data suggest that, in
five dimensions, the model exhibits a single spin-glass transition at a finite
temperature, where the spin-glass order accompanying the simultaneous
chiral-glass order sets in. In four dimensions, by contrast, the model exhibits
a chiral-glass transition at a finite temperature, not accompanying the
standard spin-glass order. The critical region associated with the chiral-glass
transition, however, is very narrow, suggesting that dimension four is close to
the marginal dimensionality.Comment: 18 pages, 12 figure
Measuring our universe from galaxy redshift surveys
Galaxy redshift surveys have achieved significant progress over the last
couple of decades. Those surveys tell us in the most straightforward way what
our local universe looks like. While the galaxy distribution traces the bright
side of the universe, detailed quantitative analyses of the data have even
revealed the dark side of the universe dominated by non-baryonic dark matter as
well as more mysterious dark energy (or Einstein's cosmological constant). We
describe several methodologies of using galaxy redshift surveys as cosmological
probes, and then summarize the recent results from the existing surveys.
Finally we present our views on the future of redshift surveys in the era of
Precision Cosmology.Comment: 82 pages, 31 figures, invited review article published in Living
Reviews in Relativity, http://www.livingreviews.org/lrr-2004-
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