518 research outputs found
Equation of state in 2+1 flavor QCD with improved Wilson quarks by the fixed scale approach
We study the equation of state in 2+1 flavor QCD with nonperturbatively
improved Wilson quarks coupled with the RG-improved Iwasaki glue. We apply the
-integration method to nonperturbatively calculate the equation of state by
the fixed-scale approach. With the fixed-scale approach, we can purely vary the
temperature on a line of constant physics without changing the system size and
renormalization constants. Unlike the conventional fixed- approach, it is
easy to keep scaling violations small at low temperature in the fixed scale
approach. We study 2+1 flavor QCD at light quark mass corresponding to
, while the strange quark mass is chosen around the
physical point. Although the light quark masses are heavier than the physical
values yet, our equation of state is roughly consistent with recent results
with highly improved staggered quarks at large .Comment: 14 pages, 12 figures, v2: Table I and Figure 3 are corrected,
reference updated. Main discussions and conclusions are unchanged, v3:
version to appear in PRD, v4: reference adde
Three-dimensional physics and the pressure of hot QCD
We update Monte Carlo simulations of the three-dimensional SU(3) + adjoint
Higgs theory, by extrapolating carefully to the infinite volume and continuum
limits, in order to estimate the contribution of the infrared modes to the
pressure of hot QCD. The sum of infrared contributions beyond the known 4-loop
order turns out to be a smooth function, of a reasonable magnitude and specific
sign. Unfortunately, adding this function to the known 4-loop terms does not
improve the match to four-dimensional lattice data, in spite of the fact that
other quantities, such as correlation lengths, spatial string tension, or quark
number susceptibilities, work well within the same setup. We outline possible
ways to reduce the mismatch.Comment: 14 page
DIRECTION OF ISOMETRIC BALLISTIC FORCE IS RELATED TO ANTAGONISTIC MUSCULE DISCHARGE
The purpose of this study was to investigate the relationship between electromyographic (EMG) activities of human thigh muscles (vastus medialis, vastus lateralis, rectus femoris, biceps femoris and semitendinosus) and the direction of knee extension force during ramp and ballistic contractions. Four subjects exerted isometric knee extension forces at a target force level of 40% of maximum voluntary contraction (MVC) at various speeds. Variations of EMG amplitudes of all thigh muscles during ballistic contraction were much larger than those during ramp contractions. Only biceps femoris was related to the direction of force. These results suggest that EMG activity of biceps femoris muscle is an important factor for deciding direction of isometric ballistic knee extension force
Finite temperature phase transition of two-flavor QCD with an improved Wilson quark action
We study the phase structure of QCD at finite temperatures with two flavors
of dynamical quarks on a lattice with the size , using a renormalization group improved gauge action and a clover improved
Wilson quark action. The simulations are made along the lines of constant
physics determined in terms of at zero-temperature. We
show preliminary results for the spatial string tension in the high temperature
phase.Comment: 7 pages, 7 figures, talk presented at Lattice 2006 (high temperature
and density
Static quark free energies at finite temperature with two flavors of improved Wilson quarks
Polyakov loop correlations at finite temperature in two-flavor QCD are
studied in lattice simulations with the RG-improved gluon action and the
clover-improved Wilson quark action. From the simulations on a
lattice, we extract the free energies, the effective running coupling and the Debye screening mass for various color channels of
heavy quark--quark and quark--anti-quark pairs above the critical temperature.
The free energies are well approximated by the screened Coulomb form with the
appropriate Casimir factors. The magnitude and the temperature dependence of
the Debye mass are compared to those of the next-to-leading order thermal
perturbation theory and to a phenomenological formula given in terms of . Also we made a comparison between our results with the Wilson quark
and those with the staggered quark previously reported.Comment: 7 pages, 9 figures, talk given at Lattice 2006 (high temperature and
density
MOTOR UNIT FIRINGS DURING VOLUNTARY ISOMETRIC RAMP AND BALLISTIC CONTRACTIONS IN HUMAN VASTUS MEDIALIS MUSCLE
Intra-muscular electromyographic (EMG) signals in vastus medialis muscle were decomposed into their constituent motor unit action potential trains using a specially designed quadrifilar wire electrode during voluntary isometric ramp and ballistic contractions. Five male adults participated in our experiments as subjects and performed ramp trapezoidal, ramp triangular, and ballistic contractions. By using a newly developed wire electrode, intra-muscular EMG signals were successfully decomposed into the individual motor unit action potential trains. The firing behaviors analyzed by the decomposition technique were consistent with previous studies on small muscles. This new quadrifilar wire electrode is potentially a useful tool for detecting intra-muscular electromyographic signals in large limb muscles such as the vastus medialis
Application of fixed scale approach to static quark free energies in quenched and 2+1 flavor lattice QCD with improved Wilson quark action
Free energies between static quarks and Debye screening masses in the
quark-gluon plasma are studied on the basis of Polyakov-line correlations in
lattice simulations of 2+1 flavors QCD with the renormalization-group improved
gluon action and the -improved Wilson quark action. We perform
simulations at (0.74) for light (strange) flavors
with lattice sizes of with --12. We adopt the
fixed-scale approach, where temperature can be varied without changing the
spatial volume and renormalization factor. We find that, at short distance, the
free energies of static quarks in color-singlet channel converge to the
static-quark potential evaluated from the Wilson-loop at zero-temperature, in
accordance with the expected insensitivity of short distance physics to the
temperature. At long distance, the free energies of static quarks approach to
twice the single-quark free energies, implying that the interaction between
static quarks is fully screened. The screening properties can be well described
by the screened Coulomb form with appropriate Casimir factor at high
temperature. We also discuss a limitation of the fixed-scale approach at high
temperature.Comment: 16 pages, 14 figure
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