12,504 research outputs found
Josephson Vortex States in Intermediate Fields
Motivated by recent resistance data in high superconductors in fields
{\it parallel} to the CuO layers, we address two issues on the Josephson-vortex
phase diagram, the appearances of structural transitions on the observed first
order transition (FOT) curve in intermediate fields and of a lower critical
point of the FOT line. It is found that some rotated pinned solids are more
stable than the ordinary rhombic pinned solids with vacant interlayer spacings
and that, due to the vertical portion in higher fields of the FOT line, the FOT
tends to be destroyed by creating a lower critical point.Comment: 12 pages, 3 figures. To appear in J.Phys.Soc.Jpn. 71, No.2 (February,
2002
Glass Transition of the Monodisperse Gaussian Core Model
We numerically study dynamical properties of the one-component Gaussian Core
Model in the supercooled states. We find that nucleation is suppressed as
density increases. Concomitantly the system exhibits glassy slow dynamics
characterized by the two-step and stretched exponential relaxation of the
density correlation as well as drastic increase of the relaxation time. It is
found that violation of the Stokes-Einstein relation is weaker and the
non-Gaussian parameter is smaller than typical model glass formers, implying
weaker dynamic heterogeneities. Besides, agreement of simulation data with the
prediction of mode-coupling theory is exceptionally good, indicating that the
nature of slow dynamics of this ultra-soft particle fluid is mean-field-like.
This fact may be understood as the consequences of multiple overlaps of the
constituent particles at high densities.Comment: 5 pages, 4 figure
Mode-Coupling Theory as a Mean-Field Description of the Glass Transition
Mode-coupling theory (MCT) is conjectured to be a mean-field description of
dynamics of the structural glass transition and the replica theory to be its
thermodynamic counterpart. However, the relationship between the two theories
remains controversial and quantitative comparison is lacking. In this Letter,
we investigate MCT for monatomic hard sphere fluids at arbitrary dimensions
above three and compare the results with replica theory. We find grave
discrepancies between the predictions of two theories. While MCT describes the
nonergodic parameter quantitatively better than the replica theory in three
dimension, it predicts a completely different dimension dependence of the
dynamical transition point. We find it to be due to the pathological behavior
of the nonergodic parameters derived from MCT, which exhibit negative tails in
real space at high dimensions.Comment: 5 pages, to appear in Phys. Rev. Lett.: Typos have been correcte
An Alternative Topological Field Theory of Generalized Complex Geometry
We propose a new topological field theory on generalized complex geometry in
two dimension using AKSZ formulation. Zucchini's model is model in the case
that the generalized complex structuredepends on only a symplectic structure.
Our new model is model in the case that the generalized complex structure
depends on only a complex structure.Comment: 29 pages, typos and references correcte
Evidence for realignment of the charge density wave state in ErTe and TmTe under uniaxial stress via elastocaloric and elastoresistivity measurements
We report the evolution of a charge density wave (CDW) state in the quasi-2D
rare-earth tritellurides (Te for =Er,Tm) as a function of in-plane
uniaxial stress. Measurements of the elastocaloric effect, resistivity, and
elastoresistivity allow us to demonstrate the importance of in-plane
antisymmetric strain on the CDW and to establish a phase diagram. We show that
modest tensile stress parallel to the in-plane -axis can reversibly switch
the direction of the ordering wavevector between the two in-plane directions.
This work establishes Te as a promising model system for the study of
strain-CDW interactions in a quasi-2D square lattice.Comment: 18 pages, 12 figure
Slow Dynamics of the High Density Gaussian Core Model
We numerically study crystal nucleation and glassy slow dynamics of the
one-component Gaussian core model (GCM) at high densities. The nucleation rate
at a fixed supersaturation is found to decrease as the density increases. At
very high densities, the nucleation is not observed at all in the time window
accessed by long molecular dynamics (MD) simulation. Concomitantly, the system
exhibits typical slow dynamics of the supercooled fluids near the glass
transition point. We compare the simulation results of the supercooled GCM with
the predictions of mode-coupling theory (MCT) and find that the agreement
between them is better than any other model glassformers studied numerically in
the past. Furthermore, we find that a violation of the Stokes-Einstein relation
is weaker and the non-Gaussian parameter is smaller than canonical
glassformers. Analysis of the probability distribution of the particle
displacement clearly reveals that the hopping effect is strongly suppressed in
the high density GCM. We conclude from these observations that the GCM is more
amenable to the mean-field picture of the glass transition than other models.
This is attributed to the long-ranged nature of the interaction potential of
the GCM in the high density regime. Finally, the intermediate scattering
function at small wavevectors is found to decay much faster than its self part,
indicating that dynamics of the large-scale density fluctuations decouples with
the shorter-ranged caging motion.Comment: 15 pages, 13 figure
Electronic properties of metal-induced gap states formed at alkali-halide/metal interfaces
The spatial distribution and site- distribution of metal induced gap states
(MIGS) are studied by thickness dependent near edge x-ray absorption fine
structure (NEXAFS) and comparing the cation and anion edge NEXAFS. The
thickness dependent NEXAFS shows that the decay length of MIGS depends on
rather an alkali halide than a metal, and it is larger for alkali halides with
smaller band gap energy. By comparing the Cl edge and K edge NEXAFS for
KCl/Cu(001), MIGS are found to be states localizing at anion sites.Comment: 4 pages, to be published in Phys. Rev.
Numerical and Theoretical Study of a Monodisperse Hard-Sphere Glass Former
There exists a variety of theories of the glass transition and many more
numerical models. But because the models need built-in complexity to prevent
crystallization, comparisons with theory can be difficult. We study the
dynamics of a deeply supersaturated \emph{monodisperse} four-dimensional (4D)
hard-sphere fluid, which has no such complexity, but whose strong intrinsic
geometrical frustration inhibits crystallization, even when deeply
supersaturated. As an application, we compare its behavior to the mode-coupling
theory (MCT) of glass formation. We find MCT to describe this system better
than any other structural glass formers in lower dimensions. The reduction in
dynamical heterogeneity in 4D suggested by a milder violation of the
Stokes-Einstein relation could explain the agreement. These results are
consistent with a mean-field scenario of the glass transition.Comment: 5 pages, 3 figure
Two-Dimensional N=(2,2) Dilaton Supergravity from Graded Poisson-Sigma Models I: Complete Actions and Their Symmetries
The formalism of graded Poisson-sigma models allows the construction of
N=(2,2) dilaton supergravity in terms of a minimal number of fields. For the
gauged chiral U(1) symmetry the full action, involving all fermionic
contributions, is derived. The twisted chiral case follows by simple
redefinition of fields. The equivalence of our approach to the standard second
order one in terms of superfields is presented, although for the latter so far
only the bosonic part of the action seems to have been available in the
literature. It is shown how ungauged models can be obtained in a systematic way
and some relations to relevant literature in superstring theory are discussed.Comment: 26 p., LaTeX. v3: extended version, new title, new section on
ungauged model
A continental shelf upwelling event off Vancouver Island as revealed by satellite infrared imagery
A series of nine relatively cloud-free infrared satellite images, of the coastal ocean off Vancouver Island, reveals the evolution of sea-surface temperature patterns during a 16-day period of upwelling favorable winds in the summer of 1980. Early in the upwelling event, the cold water in the north was restricted to a narrow band, while in the south cold surface water extended out to the continental shelf break. This southern feature is believed to be an expression of a semipermanent, cold cyclonic eddy (Freeland and Denman, 1982). As upwelling continued, the cold water boundary propagated offshore at about 10 km/day eventually passing beyond the shelf break. Short-lived (2â3 days) meanders were observed in the northern front with length scales consistent with variations in local bottom topography and coastline irregularities. After wind reduction, the coldest band parted the coast and propagated offshore
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