1,559 research outputs found
The locality of the fourth root of staggered fermion determinant in the interacting case
The fourth root approximation in LQCD simulations with dynamical staggered
fermions requires justification. We test its validity numerically in the
interacting theory in a renormalization group framework.Comment: 6 pages, Talk presented at Lattice 2005 (Machines and Algorithms
Stochastic analysis of different rough surfaces
This paper shows in detail the application of a new stochastic approach for
the characterization of surface height profiles, which is based on the theory
of Markov processes. With this analysis we achieve a characterization of the
scale dependent complexity of surface roughness by means of a Fokker-Planck or
Langevin equation, providing the complete stochastic information of multiscale
joint probabilities. The method is applied to several surfaces with different
properties, for the purpose of showing the utility of this method in more
details. In particular we show the evidence of Markov properties, and we
estimate the parameters of the Fokker-Planck equation by pure, parameter-free
data analysis. The resulting Fokker-Planck equations are verified by numerical
reconstruction of conditional probability density functions. The results are
compared with those from the analysis of multi-affine and extended multi-affine
scaling properties which is often used for surface topographies. The different
surface structures analysed here show in details advantages and disadvantages
of these methods.Comment: Minor text changes to be identical with the published versio
On different cascade-speeds for longitudinal and transverse velocity increments
We address the problem of differences between longitudinal and transverse
velocity increments in isotropic small scale turbulence. The relationship of
these two quantities is analyzed experimentally by means of stochastic
Markovian processes leading to a phenomenological Fokker- Planck equation from
which a generalization of the Karman equation is derived. From these results, a
simple relationship between longitudinal and transverse structure functions is
found which explains the difference in the scaling properties of these two
structure functions.Comment: 4 pages, 5 figures, now with corrected postscrip
Star-shaped Local Density of States around Vortices in a Type II Superconductor
The electronic structure of vortices in a type II superconductor is analyzed
within the quasi-classical Eilenberger framework. The possible origin of a
sixfold ``star'' shape of the local density of states, observed by scanning
tunneling microscope experiments on NbSe, is examined in the light of the
three effects; the anisotropic pairing, the vortex lattice, and the anisotropic
density of states at the Fermi surface. Outstanding features of split parallel
rays of this star are well explained in terms of an anisotropic -wave
pairing. This reveals a rich internal electronic structure associated with a
vortex core.Comment: 4 pages, REVTeX, 3 figures available upon reques
The Equation of State for QCD with 2+1 Flavors of Quarks
We report results for the interaction measure, pressure and energy density
for nonzero temperature QCD with 2+1 flavors of improved staggered quarks. In
our simulations we use a Symanzik improved gauge action and the Asqtad
improved staggered quark action for lattices with temporal extent and
6. The heavy quark mass is fixed at approximately the physical strange
quark mass and the two degenerate light quarks have masses or
. The calculation of the thermodynamic observables employs the integral
method where energy density and pressure are obtained by integration over the
interaction measure.Comment: 6 pages, 1 figure, 3 tables, contribution to the XXIIIrd
International Symposium on Lattice Field Theory, 25-30 July 2005, Trinity
College, Dublin, Irelan
More evidence of localization in the low-lying Dirac spectrum
We have extended our computation of the inverse participation ratio of
low-lying (asqtad) Dirac eigenvectors in quenched SU(3). The scaling dimension
of the confining manifold is clearer and very near 3. We have also computed the
2-point correlator which further characterizes the localization.Comment: presented at Lattice2005(Topology and Confinement), Dublin, July
25-30, 2005, 6 pages, 3 figures, to appear in Proceedings of Scienc
Update on pi and K Physics
We present an update of the MILC studies of the physics of light
pseudoscalars using improved staggered fermions. New runs at lighter quark
mass, as well as increased statistics for older sets, are enabling us to
improve the results for decay constants in full QCD. In addition, we have
analyzed quenched runs at two different lattice spacings. This makes possible a
test of the applicability of staggered chiral perturbation theory in a
different context.Comment: presented at Lattice2005(Hadron Spectrum), Dublin, July 25-30, 2005,
6 pages, 4 figures, to appear in Proceedings of Scienc
Local density of states in the vortex lattice in a type II superconductor
Local density of states (LDOS) in the triangular vortex lattice is
investigated based on the quasi-classical Eilenberger theory. We consider the
case of an isotropic s-wave superconductor with the material parameter
appropriate to NbSe_2. At a weak magnetic field, the spatial variation of the
LDOS shows cylindrical structure around a vortex core. On the other hand, at a
high field where the core regions substantially overlap each other, the LDOS is
sixfold star-shaped structure due to the vortex lattice effect. The orientation
of the star coincides with the experimental data of the scanning tunneling
microscopy. That is, the ray of the star extends toward the nearest-neighbor
(next nearest-neighbor) vortex direction at higher (lower) energy.Comment: 10 pages, RevTex, 32 figure
On the universality of small scale turbulence
The proposed universality of small scale turbulence is investigated for a set
of measurements in a cryogenic free jet with a variation of the Reynolds number
(Re) from 8500 to 10^6. The traditional analysis of the statistics of velocity
increments by means of structure functions or probability density functions is
replaced by a new method which is based on the theory of stochastic Markovian
processes. It gives access to a more complete characterization by means of
joint probabilities of finding velocity increments at several scales. Based on
this more precise method our results call in question the concept of
universality.Comment: 4 pages, 4 figure
Charmed meson decay constants in three-flavor lattice QCD
We present the first lattice QCD calculation with realistic sea quark content
of the D^+ meson decay constant f_{D^+}. We use the MILC Collaboration's
publicly available ensembles of lattice gauge fields, which have a quark sea
with two flavors (up and down) much lighter than a third (strange). We obtain
f_{D^+} = 201 +/- 3 +/- 17 MeV, where the errors are statistical and a
combination of systematic errors. We also obtain f_{D_s} = 249 +/- 3 +/- 16 MeV
for the D_s meson.Comment: note added on recent CLEO measurement; PRL versio
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