643 research outputs found
HTL quasiparticle picture of the thermodynamics of QCD
Starting from a nonperturbative expression for entropy and density obtained
from -derivable two-loop approximations to the thermodynamic potential, a
quasiparticle model for the thermodynamics of QCD can be developed which
incorporates the physics of hard thermal loops and leads to a reorganization of
the otherwise ill-behaved thermal perturbation theory through order
. Some details of this reorganization are discussed and the
differences to simpler quasiparticle models highlighted. A comparison with
available lattice data shows remarkable agreement down to temperatures of .Comment: Talk given at the International Conference on Statistical QCD,
Bielefeld, Germany, August 26--30, 2001. 10 pages LATEX, 7 figure
Anomalous specific heat in ultradegenerate QED and QCD
We discuss the origin of the anomalous behavior of the
low-temperature entropy and specific heat in ultradegenerate QED and QCD and
report on a recent calculation which is complete to leading order in the
coupling and which contains an infinite series of anomalous terms involving
also fractional powers in . This result involves dynamical hard-dense-loop
resummation and interpolates between Debye screening effects at larger
temperatures and non-Fermi-liquid behavior from only dynamically screened
magnetic fields at low temperature.Comment: 5 pages, 3 figures, contribution to the Proceedings of Strong and
Electroweak Matter 2004 (SEWM04), Helsinki, Finland, 16-19 Jun 200
Frozen ghosts in thermal gauge field theory
We review an alternative formulation of gauge field theories at finite
temperature where unphysical degrees of freedom of gauge fields and the
Faddeev-Popov ghosts are kept at zero temperature.Comment: 6 page
No saturation of the quantum Bogomolnyi bound by two-dimensional supersymmetric solitons
We reanalyse the question whether the quantum Bogomolnyi bound is saturated
in the two-dimensional supersymmetric kink and sine-Gordon models. Our starting
point is the usual expression for the one-loop correction to the mass of a
soliton in terms of sums over zero-point energies. To regulate these sums, most
authors put the system in a box with suitable boundary conditions, and impose
an ultraviolet cut-off. We distinguish between an energy cut-off and a mode
number cut-off, and show that they lead to different results. We claim that
only the mode cut-off yields correct results, and only if one considers exactly
the same number of bosonic and fermionic modes in the total sum over
bound-state and zero-point energies. To substantiate this claim, we show that
in the sine-Gordon model only the mode cut-off yields a result for the quantum
soliton mass that is consistent with the exact result for the spectrum as
obtained by Dashen et al. from quantising the so-called breather solution. In
the supersymmetric case, our conclusion is that contrary to previous claims the
quantum Bogomolnyi bound is not saturated in any of the two-dimensional models
considered.Comment: 23 pages, LATe
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