589 research outputs found
From confinement to new states of dense QCD matter
Transitions between centre sectors are related to confinement in pure
Yang-Mills theories. We study the impact of these transitions in QCD-like
theories for which centre symmetry is explicitly broken by the presence of
matter. For low temperatures, we provide numerical evidence that centre
transitions do occur with matter merely providing a bias towards the trivial
centre sector until centre symmetry is spontaneously broken at high
temperatures. The phenomenological consequences of these transitions for dense
hadron matter are illustrated in an SU(3) effective quark theory: centre
dressed quarks undergo condensation due to Bose-type statistics forming a
hitherto unknown state of dense but cold quark matter.Comment: 7 pages, 7 figures, talk presented at the International School of
Nuclear Physics "From Quarks and Gluons to Hadrons and Nuclei", 16-24 Sept
2011, Erice, Sicily, Ital
Singular gauge potentials and the gluon condensate at zero temperature
We consider a new cooling procedure which separates gluon degrees of freedom
from singular center vortices in SU(2) LGT in a gauge invariant way. Restricted
by a cooling scale fixing the residual SO(3) gluonic action
relative to the string tension, the procedure is RG invariant. In the limit
a pure Z(2) vortex texture is left. This {\it minimal} vortex
content does not contribute to the string tension. It reproduces, however, the
lowest glueball states. With an action density scaling like with ,
it defines a finite contribution to the action density at T=0 in the continuum
limit. We propose to interpret this a mass dimension 4 condensate related to
the gluon condensate. Similarly, this vortex texture is revealed in the Landau
gauge.Comment: 3 pages, 4 figures, Contribution to ''Lattice 2001'' (confinement) to
appear in the Proceedings (Nucl. Phys. B Proc. Suppl.
Chiral symmetry breaking in strongly coupled QED?
The coupled system of renormalized Dyson-Schwinger equations for the electron
self-energy and the photon propagator are supplied with the tree level vertex
as Ansatz for the renormalized three point function. The system is investigated
numerically. In the case of a massive electron, the theory is ``weakly
renormalizable'', i.e.\ cutoff independent for values of the cutoff below an
upper limit. In this regime of cutoff independence, the quenched approximation
yields good results for the electron self-energy. In the chiral limit, a
logarithmic cutoff dependence of the electron self-energy is found. The
question, whether a regime of cutoff independence with a spontaneously broken
chiral symmetry exists in strongly coupled QED, remains open.Comment: 13 pages, 5 figures, complete uu-file avaiable on reques
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