137 research outputs found
Model study of the sign problem in a mean-field approximation
We study the sign problem of the fermion determinant at nonzero baryon
chemical potential. For this purpose we apply a simple model derived from
Quantum Chromodynamics, in the limit of large chemical potential and mass. For
SU(2) color, there is no sign problem and the mean-field approximation is
similar to data from the lattice. For SU(3) color the sign problem is
unavoidable, even in a mean-field approximation. We apply a phase-reweighting
method, combined with the mean-field approximation, to estimate thermodynamic
quantities. We also investigate the mean-field free energy using a saddle-point
approximation.Comment: 7 pages, 2 figures, talk presented at the XXV International Symposium
on Lattice Field Theory, July 30 - August 4, 2007, Regensburg, German
Broken spacetime symmetries and elastic variables
We discuss spontaneous breaking of continuum symmetries, whose generators do
explicitly depend on the spacetime coordinates. We clarify the relation between
broken symmetries and elastic variables at both zero and finite temperatures,
and/or finite densities, and show the general counting rule that is
model-independently determined by the symmetry breaking pattern. We apply it to
three intriguing examples: rotational, conformal, and gauge symmetries.Comment: 6 pages, 1 figure; some discussions added in Sec. 4, published
versio
General formulae for dipole Wilson line correlators with the Color Glass Condensate
We present general formulae to compute Wilson line correlators with the Color
Glass Condensate described by the McLerran-Venugopalan model. We explicitly
construct a complete and non-orthogonal set of color-singlet bases and write
matrix elements down, so that the exponential of the matrix leads to the Wilson
line correlators. We further develop a systematic perturbative expansion of
dipole Wilson line correlators in terms of where is the color
number. As a phenomenological application we calculate the flow harmonics
in the dipole model and discuss the scaling.Comment: 19 pages, 4 figure
Counting rule for Nambu-Goldstone modes in nonrelativistic systems
The counting rule for Nambu-Goldstone modes is discussed using Mori's
projection operator method in nonrelativistic systems at zero and finite
temperatures. We show that the number of Nambu-Goldstone modes is equal to the
number of broken charges, Q_a, minus half the rank of the expectation value of
[Q_a,Q_b].Comment: 5 pages, no figures; typos corrected; some discussion added and
clarifie
Fermion Spectrum at Ultrasoft Region in a Hot QED/QCD Plasma
An spectrum of an electron (quark) with ultrasoft momentum (p g^2T) is
discussed at extremely high temperature in quantum electrodynamics
(chromodynamics) with a resummed perturbation theory. We establish the
existence of the pole suggested in the previous work of the electron (quark)
propagator at ultrasoft region, and find that its pole position is p_0=\mp
|p|/3-i\zeta, where \zeta is the damping rate which is of order g^2T ln 1/g,
and the expression of its residue. We also discuss whether the resummation
scheme preserves the gauge symmetry.Comment: 3 pages, 1 figure, presented by D. Satow at the 19th Particles and
Nuclei International Conference, PANIC 2011, MIT, Cambridge, MA (July 24-29,
2011
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