8,354 research outputs found
Non-trivial Center Dominance in High Temperature QCD
We investigate the properties of quarks and gluons above the chiral phase
transition temperature using the RG improved gauge action and the Wilson
quark action with two degenerate quarks mainly on a lattice. In
the one-loop perturbation theory, the thermal ensemble is dominated by the
gauge configurations with effectively center twisted boundary
conditions, making the thermal expectation value of the spatial Polyakov loop
take a non-trivial center. This is in agreement with our lattice
simulation of high temperature QCD. We further observe that the temporal
propagator of massless quarks at extremely high temperature remarkably agrees with the temporal propagator of free
quarks with the twisted boundary condition for , but
differs from that with the trivial boundary condition. As we increase
the mass of quarks , we find that the thermal ensemble continues to be
dominated by the twisted gauge field configurations as long as and above that the trivial configurations come in. The
transition is essentially identical to what we found in the departure from the
conformal region in the zero-temperature many-flavor conformal QCD on a finite
lattice by increasing the mass of quarks. We argue that the behavior is
consistent with the renormalization group analysis at finite temperature.Comment: 16 pages, 9 figures; 4 tables, an appendix adde
IR fixed points in gauge Theories
We propose a novel RG method to specify the location of the IR fixed point in
lattice gauge theories and apply it to the gauge theories with
fundamental fermions. It is based on the scaling behavior of the propagator
through the RG analysis with a finite IR cut-off, which we cannot remove in the
conformal field theories in sharp contrast with the confining theories. The
method also enables us to estimate the anomalous mass dimension in the
continuum limit at the IR fixed point. We perform the program for and and indeed identify the location of the IR fixed points in all
cases.Comment: 7 pages, 7 figures, 1 table: the scale of the y axis in Figs..1-4
change; minor modifications as appear in PL
The Formation and Destruction of Molecular Clouds and Galactic Star Formation
We describe an overall picture of galactic-scale star formation. Recent
high-resolution magneto-hydrodynamical simulations of two-fluid dynamics with
cooling/heating and thermal conduction have shown that the formation of
molecular clouds requires multiple episodes of supersonic compression. This
finding enables us to create a scenario in which molecular clouds form in
interacting shells or bubbles on a galactic scale. First we estimate the
ensemble-averaged growth rate of molecular clouds over a timescale larger than
a million years. Next we perform radiation hydrodynamics simulations to
evaluate the destruction rate of magnetized molecular clouds by the stellar FUV
radiation. We also investigate the resultant star formation efficiency within a
cloud which amounts to a low value (a few percent) if we adopt the power-law
exponent -2.5 for the mass distribution of stars in the cloud. We finally
describe the time evolution of the mass function of molecular clouds over a
long timescale (>1Myr) and discuss the steady state exponent of the power-law
slope in various environments.Comment: 7 pages, 3 figures. Accepted for publication in Astronomy and
Astrophysic
Scaling Analysis of Improved Actions for Pure SU(3) Gauge Theory
We have explored the behaviour of some improved actions based on a
nonperturbative renormalization group (RG) analysis in coupling space. We
calculate the RG flow in two-coupling space (\boneone,\bonetwo) and examine
the restoration of rotational invariance and the scaling of physical quantities
.Comment: LATTICE98(improvement
Pole dynamics for the Flierl-Petviashvili equation and zonal flow
We use a systematic method which allows us to identify a class of exact
solutions of the Flierl-Petvishvili equation. The solutions are periodic and
have one dimensional geometry. We examine the physical properties and find that
these structures can have a significant effect on the zonal flow generation.Comment: Latex 40 pages, seven figures eps included. Effect of variation of
g_3 is studied. New references adde
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