269 research outputs found
Effective potential analysis for 5D SU(2) gauge theories at finite temperature and radius
We calculate the one loop effective potential for a 5D SU(2) gauge field
theory at finite temperature and radius R=1/M. This calculation is
performed, for the first time, in the case of background fields with two
constant components (directed towards the compact extra dimension
with radius R) and (directed towards the compact Euclidean time
with radius ). This model possesses two discrete symmetries known as
Z_{M}(2) and Z_{T}(2). The corresponding phase diagram is presented in Ref. 4.
However the arguments which lead to this diagram are mainly qualitative. We
present a detailed analysis, from our point of view, for this phase diagram,
and we support our arguments performing lattice simulations for a simple
phenomenological model with two scalar fields interacting through the
previously calculated potential.Comment: 18 pages, 7 figures ; typos correcte
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
Z(N) wall junctions: Monopole fossils in hot QCD
We point out that the effective action of hot Yang--Mills theories has
semi-classical solutions, which are naturally identified with monopole world
lines, ``frozen'' into the short imaginary time dimension. The solutions look
like wall junctions: lines along which N electric Z(N) domain walls come
together. They are instrumental in reconciling explicit perturbative
calculations at high temperature with the magnetic Z(N) symmetry.Comment: 10 pages, Late
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
'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
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
Monopoles, vortices and confinement in SU(3) gauge theory
We compute, in SU(3) pure gauge theory, the vacuum expectation value (vev) of
the operator which creates a vortex wrapping the lattice through periodic
boundary conditions (dual Polyakov line). The technique used is the same
already tested in the SU(2) case. The dual Polyakov line proves to be a good
disorder parameter for confinement, and has a similar behaviour to the monopole
condensate. The new features which characterise the construction of the
disorder operator in SU(3) are emphasised.Comment: 8 pages, 4 eps figures, typed with elsart.cl
The interaction between center monopoles in SU(2) Yang-Mills
We study the potential between a static center monopole and antimonopole in
4d SU(2) Yang-Mills theory. Using a new numerical method, we show that the 't
Hooft loop is a dual order parameter with respect to the Wilson loop, for the
deconfinement phase transition. We observe a 3d Ising-like critical behaviour
for the dual string tension related to the spatial 't Hooft loop as a function
of the temperature.Comment: Lattice2000(Topology and Vacuum), 4 pages, 3 figure
Properties of the deconfining phase transition in SU(N) gauge theories
We extend our earlier investigation of the finite temperature deconfinement
transition in SU(N) gauge theories, with the emphasis on what happens as N->oo.
We calculate the latent heat in the continuum limit, and find the expected
quadratic in N behaviour at large N. We confirm that the phase transition,
which is second order for SU(2) and weakly first order for SU(3), becomes
robustly first order for N>3 and strengthens as N increases. As an aside, we
explain why the SU(2) specific heat shows no sign of any peak as T is varied
across what is supposedly a second order phase transition. We calculate the
effective string tension and electric gluon masses at T=Tc confirming the
discontinuous nature of the transition for N>2. We explicitly show that the
large-N `spatial' string tension does not vary with T for T<Tc and that it is
discontinuous at T=Tc. For T>Tc it increases as T-squared to a good
approximation, and the k-string tension ratios closely satisfy Casimir Scaling.
Within very small errors, we find a single Tc at which all the k-strings
deconfine, i.e. a step-by-step breaking of the relevant centre symmetry does
not occur. We calculate the interface tension but are unable to distinguish
between linear or quadratic in N variations, each of which can lead to a
striking but different N=oo deconfinement scenario. We remark on the location
of the bulk phase transition, which bounds the range of our large-N
calculations on the strong coupling side, and within whose hysteresis some of
our larger-N calculations are performed.Comment: 50 pages, 14 figure
- …