398 research outputs found
Magnetic Z(N) symmetry in hot QCD and the spatial Wilson loop
We discuss the relation between the deconfining phase transition in gauge
theories and the realization of the magnetic Z(N) symmetry. At low temperature
the Z(N) symmetry is spontaneously broken while above the phase transition it
is restored. This is intimately related to the change of behaviour of the
spatial 't Hooft loop discussed in hep-ph/9909516. We also point out that the
realization of the magnetic symmetry has bearing on the behaviour of the
spatial Wilson loop. We give a physical argument to the effect that at zero
temperature the spatial Wilson loop must have perimeter law behaviour in the
symmetric phase but area law behaviour in the spontaneously broken phase. At
high temperature the argument does not hold and the restoration of magnetic
Z(N) is consistent with area law for the Wilson loop.Comment: 30 pages, discussion of the Wilson loop at high temperature
completely revised, new references adde
The Higgs field and the ultraviolet behaviour of the vortex operator in 2+1 dimensions
We calculate the change in the ultraviolet behaviour of the vortex operator
due to the presence of dynamical Higgs field in both 2+1 dimensional QED and
the 2+1 dimensional Georgi-Glashow model. We find that in the QED case the
presence of the Higgs field leads at the one loop level to power like
correction to the propagator of the vortex operator. On the other hand, in the
Georgi-Glashow model, the adjoint Higgs at one loop has no affect on the vortex
propagator. Thus, as long as the mass of the Higgs field is much larger than
the gauge coupling constant, the ultraviolet behaviour of the vortex operator
in the Georgi-Glashow model is independent of the Higgs mass.Comment: 14 page
Gluon production and diffraction in the dipole picture
Using the eikonal approximation, we show that inclusive gluon production is
related to the scattering of a gluon-gluon dipole while diffractive gluon
production in DIS is related to a two- dipole scattering amplitude.
Hence diffractive photon dissociation cross-sections are observables that
provide potential information on dipole correlations, which represent an open
issue in high-energy QCD.Comment: 4 pages, 2 figures, Proceedings of the 10th International Baryons
Conference (Baryons04), Ecole Polytechnique, Palaiseau, France, October 25-29
200
Magnetic Z(N) symmetry in 2+1 dimensions
This review describes the role of magnetic symmetry in 2+1 dimensional gauge
theories. In confining theories without matter fields in fundamental
representation the magnetic symmetry is spontaneously broken. Under some mild
assumptions, the low-energy dynamics is determined universally by this
spontaneous breaking phenomenon. The degrees of freedom in the effective theory
are magnetic vortices. Their role in confining dynamics is similar to that
played by pions and sigma in the chiral symmetry breaking dynamics.
I give an explicit derivation of the effective theory in (2+1)-dimensional
weakly coupled confining models and argue that it remains qualitatively the
same in strongly coupled (2+1)-dimensional gluodynamics. Confinement in this
effective theory is a very simple classical statement about the long range
interaction between topological solitons, which follows (as a result of a
simple direct classical calculation) from the structure of the effective
Lagrangian. I show that if fundamentally charged dynamical fields are present
the magnetic symmetry becomes local rather than global. The modifications to
the effective low energy description in the case of heavy dynamical fundamental
matter are discussed. This effective lagrangian naturally yields a bag like
description of baryonic excitations. I also discuss the fate of the magnetic
symmetry in gauge theories with the Chern-Simons term
Charge and Magnetic Flux Correlations in Chern-Simons Theory with Fermions
Charge and magnetic flux bearing operators are introduced in Chern-Simons
theory both in its pure form and when it is coupled to fermions. The magnetic
flux creation operator turns out to be the Wilson line. The euclidean
correlation functions of these operators are shown to be local and are
evaluated exactly in the pure case and through an expansion in the inverse
fermion mass whenever these are present. Physical states only occur in the
presence of fermions and consist of composite charge-magnetic flux carrying
states which are in general anyonic. The large distance behavior of the
correlation functions indicates the condensation of charge and magnetic flux.Comment: Latex, 17 page
Critical Exponents of the Superconducting Phase Transition
We study the critical exponents of the superconducting phase transition in
the context of renormalization group theory starting from a dual formulation of
the Ginzburg-Landau theory. The dual formulation describes a loop gas of
Abrikosov flux tubes which proliferate when the critical temperature is
approached from below. In contrast to the Ginzburg-Landau theory, it has a
spontaneously broken global symmetry and possesses an infrared stable fixed
point. The exponents coincide with those of a superfluid with reversed
temperature axis.Comment: Postscript file. For related work see www adress
http://www.physik.fu-berlin.de/kleiner_re.html in our homepage
http://www.physik.fu-berlin.de/kleinert.htm
Small-x QCD effects in forward-jet and Mueller-Navelet jet production
We investigate small-x QCD effects in forward-jet production in deep
inelastic scattering in the kinematic regime where the virtuality of the photon
and the transverse momentum of the jet are two hard scales of about the same
magnitude. We show that the data from HERA published by the H1 and ZEUS
collaborations are well described by leading-logarithmic BFKL predictions.
Parametrizations containing saturation effects expected to be relevant at
higher energies also compare well to the present data. We extend our analysis
to Mueller-Navelet jets at the LHC and discuss to what extent this observable
could test these small-x effects and help distinguishing between the different
descriptions.Comment: 18 pages, 9 figures, minor changes, published versio
Aspects of Duality in Nodal Liquids
Starting from a microscopic t-J like model and a SU(2) spin-charge separation
ansatz, a relativistic continuum gauge lagrangian is obtained in the vicinity
of a nodal point of the Fermi surface. The excitations in the pseudogap phase
are described by topological excitations in the dual model which has a Z_2
global symmetry due to the effect of instantons. Confinement of spinon and
holons emerge from this picture. The adjoint and fundamental strings are
associated with stripes. As the spin gap decreases a local Z_2 symmetry
emerges.Comment: 15 pages revtex, no figure
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