766 research outputs found
Temperature Dependence of the QCD Coupling
We present a one-loop calculation of a gauge invariant QCD beta function.
Using both momentum and temperature renormalization group equations we
investigate the running coupling in the magnetic sector as a function of
temperature and momentum scale. At fixed momentum scale we find that, in
contrast to or QED, high-temperature QCD is strongly coupled,
even after renormalization group improvement. However, if the momentum scale is
changed simultaneously with temperature in a specified manner, the coupling
decreases. We also point out in what regime dimensional reduction occurs. Both
the cases smaller and larger than are discussed.Comment: 10 pages, LaTeX (5 postscript figures available),
ITFA-93-11,THU-93/0
Critical Temperature and Amplitude Ratios from a Finite-Temperature Renormalization Group
We study \l\f^4 theory using an environmentally friendly finite-temperature
renormalization group. We derive flow equations, using a fiducial temperature
as flow parameter, develop them perturbatively in an expansion free from
ultraviolet and infrared divergences, then integrate them numerically from zero
to temperatures above the critical temperature. The critical temperature, at
which the mass vanishes, is obtained by integrating the flow equations and is
determined as a function of the zero-temperature mass and coupling. We
calculate the field expectation value and minimum of the effective potential as
functions of temperature and derive some universal amplitude ratios which
connect the broken and symmetric phases of the theory. The latter are found to
be in good agreement with those of the three-dimensional Ising model obtained
from high- and low-temperature series expansions.Comment: 14 pages of LaTeX. Postscript figures available upon request form
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The Finite-Temperature Renormalization Group Applied to λϕ⁴ Theory and QCD
In this paper we apply the finite-temperature renormalization group from the point of view of “environmentally friendly” renormalization. We study both λϕ⁴ theory and the magnetic sector of QCD. At one loop level the complete temperature range of λϕ⁴ is successfully described in terms of the parameters of the zero temperature theory. We show also how the critical temperature can be calculated in terms of the latter. For the magnetic sector of QCD, in distinction to λϕ⁴, a one-loop finite temperature renormalization group improvement is not sufficient to
describe the high-temperature regime
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