283 research outputs found
Systematic study of autocorrelation time in pure SU(3) lattice gauge theory
Results of our autocorrelation measurement performed on Fujitsu AP1000 are
reported. We analyze (i) typical autocorrelation time, (ii) optimal mixing
ratio between overrelaxation and pseudo-heatbath and (iii) critical behavior of
autocorrelation time around cross-over region with high statistic in wide range
of for pure SU(3) lattice gauge theory on , and
lattices. For the mixing ratio K, small value (3-7) looks optimal in the
confined region, and reduces the integrated autocorrelation time by a factor
2-4 compared to the pseudo-heatbath. On the other hand in the deconfined phase,
correlation times are short, and overrelaxation does not seem to matter For a
fixed value of K(=9 in this paper), the dynamical exponent of overrelaxation is
consistent with 2 Autocorrelation measurement of the topological charge on
lattice at = 6.0 is also briefly mentioned.Comment: 3 pages of A4 format including 7-figure
Non-perturbative determination of anisotropy coefficients and pressure gap at the deconfining transition of QCD
We propose a new non-perturbative method to compute derivatives of gauge
coupling constants with respect to anisotropic lattice spacings (anisotropy
coefficients). Our method is based on a precise measurement of the finite
temperature deconfining transition curve in the lattice coupling parameter
space extended to anisotropic lattices by applying the spectral density method.
We determine the anisotropy coefficients for the cases of SU(2) and SU(3) gauge
theories. A longstanding problem, when one uses the perturbative anisotropy
coefficients, is a non-vanishing pressure gap at the deconfining transition
point in the SU(3) gauge theory. Using our non-perturbative anisotropy
coefficients, we find that this problem is completely resolved.Comment: LATTICE98(hightemp
Autocorrelation in Updating Pure SU(3) Lattice Gauge Theory by the use of Overrelaxed Algorithms
We measure the sweep-to-sweep autocorrelations of blocked loops below and
above the deconfinement transition for SU(3) on a lattice using
20000-140000 Monte-Carlo updating sweeps. A divergence of the autocorrelation
time toward the critical is seen at high blocking levels. The peak is
near = 6.33 where we observe 440 210 for the autocorrelation time
of Wilson loop on blocked lattice. The mixing of 7 Brown-Woch
overrelaxation steps followed by one pseudo-heat-bath step appears optimal to
reduce the autocorrelation time below the critical . Above the critical
, however, no clear difference between these two algorithms can be seen
and the system decorrelates rather fast.Comment: 4 pages of A4 format including 6-figure
Non-perturbative determination of anisotropy coefficients in lattice gauge theories
We propose a new non-perturbative method to compute derivatives of gauge
coupling constants with respect to anisotropic lattice spacings (anisotropy
coefficients), which are required in an evaluation of thermodynamic quantities
from numerical simulations on the lattice. Our method is based on a precise
measurement of the finite temperature deconfining transition curve in the
lattice coupling parameter space extended to anisotropic lattices by applying
the spectral density method. We test the method for the cases of SU(2) and
SU(3) gauge theories at the deconfining transition point on lattices with the
lattice size in the time direction -- 6. In both cases, there is a
clear discrepancy between our results and perturbative values. A longstanding
problem, when one uses the perturbative anisotropy coefficients, is a
non-vanishing pressure gap at the deconfining transition point in the SU(3)
gauge theory. Using our non-perturbative anisotropy coefficients, we find that
this problem is completely resolved: we obtain and
on and 6 lattices, respectively.Comment: 24pages,7figures,5table
Scaling Study of Pure Gauge Lattice QCD by Monte Carlo Renormalization Group Method
The scaling behavior of pure gauge SU(3) in the region is
examined by a Monte Carlo Renormalization Group analysis. The coupling shifts
induced by factor 2 blocking are measured both on 32 and 16 lattices
with high statistics. A systematic deviation from naive 2-loop scaling is
clearly seen. The mean field and effective coupling constant schemes explain
part, but not all of the deviation. It can be accounted for by a suitable
change of coupling constant, including a correction term in the
2-loop lattice -function. Based on this improvement,
is estimated to be from the analysis of the string tension .Comment: 4 pages of A4 format including 7-postscript figure
Hadron Properties just before Deconfinement
We have investigated hadron screening masses, the chiral condensate, and the
pion decay constant close to the deconfinement phase transition in the confined
phase of QCD. The simulations were done in the quenched approximation, on a
lattice of size \mbox{}. We examined temperatures ranging from
0.75\tc up to 0.92\tc. We see no sign of a temperature dependence in the
chiral condensate or the meson properties, but some temperature dependence for
the nucleon screening mass is not excluded.Comment: Postscript file, uuencoded compresse
Scaling Properties of the Energy Density in SU(2) Lattice Gauge Theory
The lattice data for the energy density of gauge theory are
calculated with \nop~derivatives of the coupling constants. These derivatives
are obtained from two sources : i) a parametrization of the \nop~beta function
in accord with the measured critical temperature and values and
ii) a \nop~calculation of the presssure. We then perform a detailed finite size
scaling analysis of the energy density near . It is shown that at the
critical temperature the energy density is scaling as a function of with
the corresponding Ising model critical exponents. The value of
in the continuum limit is estimated to be 0.256(23). In
the high temperature regime the energy density is approaching its weak coupling
limit from below, at it has reached only about of the
limit.Comment: 15 pages + 9 figures, BI-TP 94/3
Identificação molecular de Bartonella henselae em paciente com SIDA soronegativo para doença da arranhadura do gato no Rio de Janeiro, Brasil
Bartonella henselae is associated with a wide spectrum of clinical manifestations, including cat scratch disease, endocarditis and meningoencephalitis, in immunocompetent and immunocompromised patients. We report the first molecularly confirmed case of B. henselae infection in an AIDS patient in state of Rio de Janeiro, Brazil. Although DNA sequence of B. henselae has been detected by polymerase chain reaction in a lymph node biopsy, acute and convalescent sera were nonreactive.Bartonella henselae estĂĄ associada a um amplo espectro de manifestaçÔes clĂnicas, incluindo a doença da arranhadura de gato, endocardite, e meningoencefalite, em pacientes imunocompetentes e imunocomprometidos. Relatamos o primeiro caso confirmado por mĂ©todo molecular de B. henselae em um paciente com SIDA no estado do Rio de Janeiro, Brasil. Apesar da sequĂȘncia de DNA de B. henselae ser detectada pela reação em cadeia da polimerase em uma biĂłpsia do linfonodo, soros das fases aguda e convalescente foram nĂŁo reativos
De novo mutations in PURA are associated with hypotonia and developmental delay
PURA is the leading candidate gene responsible for the developmental phenotype in the 5q31.3 microdeletion syndrome. De novo mutations in PURA were recently reported in 15 individuals with developmental features similar to the 5q31.3 microdeletion syndrome. Here we describe six unrelated children who were identified by clinical whole-exome sequencing (WES) to have novel de novo variants in PURA with a similar phenotype of hypotonia and developmental delay and frequently associated with seizures. The protein Puralpha (encoded by PURA) is involved in neuronal proliferation, dendrite maturation, and the transport of mRNA to translation sites during neuronal development. Mutations in PURA may alter normal brain development and impair neuronal function, leading to developmental delay and the seizures observed in patients with mutations in PURA
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