89 research outputs found
Two loop renormalisation of the magnetic coupling in hot QCD and spatial Wilson loop
With the known two loop renormalisation of the magnetic coupling, the 4D
results of the spatial Wilson loop are compared to the prediction from the
magnetostatic sector.Comment: 5 pages. To appear in the proceedings of 6th Conference on Strong and
Electroweak Matter 2004 (SEWM04), Helsinki, Finland, 16-19 Jun 200
Cubic order for spatial 't Hooft loop in hot QCD
Spatial 't Hooft loops of strength k measure the qualitative change in the
behaviour of electric colour flux in confined and deconfined phase of SU(N)
gauge theory. They show an area law in the deconfined phase, known analytically
to two loop order with a ``k-scaling'' law k(N-k).
In this paper we compute the O(g^3) correction to the tension.
It is due to neutral gluon fields that get their mass through interaction
with the wall. The simple k-scaling is lost in cubic order.
The generic problem of non-convexity shows up in this order.
The result for large N is explicitely given.Comment: 5 pages, appears in the proceedings of SEWM200
Spatial 't Hooft loop to cubic order in hot QCD II
In this paper we provide an exact formula for the area law of the 't Hooft
loop for any SU(N) gauge group to cubic order in hot gauge theory.
The correction is very small for all temperatures above , in stark
contrast to the cubic correction to the pressure. The gradient approximation in
a previous paper, only valid for large N, is in excellent agreement with the
present, exact evalution. Comparison to lattice data is good. Casimir scaling
is violated by a small amount not yet resolved by the precision of lattice
data.Comment: 21 pages, 5 figures, submitted to Nucl. Phys. B. Minor changes mad
Quasi particles in hot QCD
We show at very high temperature how the behaviour of the spatial 't Hooft
loop in the QCD plasma is simply related to the chromo electric flux of the
gluons. This simple picture is vindicated by a systematic quasi classical
approach. The spatial Wilson loop 's behaviour is computed by a similar nearly
free plasma of magnetic quasiparticles. This model predicts unambiguously
ratios of multiply charged Wilson loops. Recent simulations confirm these
predictions accurately.Comment: 3 pages. Talk given at Lattice200
Radiative corrections to the pressure and the one-loop polarization tensor of massless modes in SU(2) Yang-Mills thermodynamics
We compute the one-loop polarization tensor for the on-shell, massless
mode in a thermalized SU(2) Yang-Mills theory being in its deconfining phase.
Postulating that SU(2), we discuss
's effect on the low-momentum part of the black-body spectrum at
temperatures where K.
A table-top experiment is proposed to test the above postulate. As an
application, we point out a possible connection with the stability of dilute,
cold, and old innergalactic atomic hydrogen clouds. We also compute the
two-loop correction to the pressure arising from the instantaneous massless
mode in unitary-Coulomb gauge, which formerly was neglected, and present
improved estimates for subdominant corrections.Comment: 25 pages, 17 figs, v4: consequences of a modification of the
evolution equation for the effectice coupling implemented, no qualitative
change of the physic
Two loop renormalization of the magnetic coupling in hot QCD
Well above the critical temperature hot QCD is described by 3d electrostatic
QCD with gauge coupling and Debye mass . We integrate out the Debye
scales to two loop accuracy and find for the gauge coupling in the resulting
magnetostatic action .Comment: 5 pages, 1 figure. Cosmetic changes. To be published in Phys. Lett.
Two loop renormalization of the magnetic coupling and non-perturbative sector in hot QCD
The goal of this paper is two-fold. The first aim is to present a detailed
version of the computation of the two-loop renormalization of the magnetic
coupling in hot QCD. The second is to compare with lattice simulations the
string tension of a spatial Wilson loop using the result of our two-loop
computationComment: 32 page
Spatial 't Hooft loop to cubic order in hot QCD
Spatial 't Hooft loops of strength k measure the qualitative change in the
behaviour of electric colour flux in confined and deconfined phase of SU (N)
gauge theory. They show an area law in the deconfined phase, known analytica
lly to two loop order with a ``k-scaling'' law k(N-k). In this paper we comput
e the O(g^3) correction to the tension. It is due to neutral gluon fields that
get their mass through interaction with the wall. The simple k-scaling is lost
in cubic order. The generic problem of non-convexity shows up in this order an
d the cure is provided. The result for large N is explicitely given. We show
tha t nonperturbative effects appear at O(g^5).Comment: 22 pages. Apart from a discussion on the renormalization effect of
the Polyakov loop to cubic order only cosmetic changes with respect to the
earlier hep-ph/021229
Domain Walls and Metastable Vacua in Hot Orientifold Field Theories
We consider "Orientifold field theories", namely SU(N) gauge theories with
Dirac fermions in the two-index representation at high temperature. When N is
even these theories exhibit a spontaneously broken Z2 centre symmetry. We study
aspects of the domain wall that interpolates between the two vacua of the
theory. In particular we calculate its tension to two-loop order. We compare
its tension to the corresponding domain wall in a SU(N) gauge theory with
adjoint fermions and find an agreement at large-N, as expected from planar
equivalence between the two theories. Moreover, we provide a non-perturbative
proof for the coincidence of the tensions at large-N. We also discuss the
vacuum structure of the theory when the fermion is given a large mass and argue
that there exist N-2 metastable vacua. We calculate the lifetime of those vacua
in the thin wall approximation.Comment: 29 pages, 4 figures. v2: minor changes in the introduction section.
to appear in JHE
't Hooft and Wilson loop ratios in the QCD plasma
The spatial 't Hooft loop measuring the electric flux and the spatial
Wilsonloop measuring the magnetic flux are analyzed in hot SU(N) gauge theory.
Both display area laws. On one hand the tension of the 't Hooft loop is
perturbatively calculable, in the same sense as the pressure. We show that the
O(g^3) contribution is absent. The ratio of multi-charged 't Hooft loops have a
remarkably simple dependence on the charge, true up to, but not including,
O(g^4). This dependence follows also from a simple model of free screened
colour charges. On the other hand the surface tension of the Wilsonloop is
non-perturbative. But in a model of screened free monopoles at very high
temperature the known area law follows. The density of these monopoles starts
to contribute to O(g^6) to the pressure. The ratio of the multicharged Wilson
loops is calculable and identical to that of the 't Hooft loops.Comment: 28 pages, 8 figure
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