1,924 research outputs found
The Center symmetry and its spontaneous breakdown at high temperatures
We examine the role of the center Z(N) of the gauge group SU(N) in gauge
theories. In this pedagogical article, we discuss, among other topics, the
center symmetry and confinement and deconfinement in gauge theories and
associated finite-temperature phase transitions. We also look at universal
properties of domain walls separating distinct confined and deconfined bulk
phases, including a description of how QCD color-flux strings can end on
color-neutral domain walls, and unusual finite-volume dependence in which
quarks in deconfined bulk phase seem to be "confined".Comment: LaTex, 35 pages, 6 figures, uses sprocl.sty. To be published in the
Festschrift in honor of B.L. Ioffe, "At the Frontier of Particle Physics/
Handbook of QCD", edited by M. Shifma
The Thermodynamics of Quarks and Gluons
This is an introduction to the study of strongly interacting matter. We
survey its different possible states and discuss the transition from hadronic
matter to a plasma of deconfined quarks and gluons. Following this, we
summarize the results provided by lattice QCD finite temperature and density,
and then investigate the nature of the deconfinement transition. Finally we
give a schematic overview of possible ways to study the properties of the
quark-gluon plasma.Comment: 19 pages, 21 figures; lecture given at the QGP Winter School,
Jaipur/India, Feb.1-3, 2008; to appear in Springer Lecture Notes in Physic
Confinement and the center of the gauge group
The question of the role of the center of the gauge group in the phenomenon
of confinement in Yang-Mills theory is addressed. The investigation is
performed from the most general perspective of considering all possible choices
for the gauge symmetry group. In this context, an interesting role is played by
G(2) Yang-Mills theory: the simplest pure gauge theory with a trivial center
and without 't Hooft flux vortices. Numerical simulations show the presence of
a first order finite temperature deconfinement phase transition in G(2)
Yang-Mills theory in (3+1) dimensions. Interestingly, the G(2) gauge symmetry
can be broken to an SU(3) subgroup by the Higgs mechanism. We investigate the
relation between the deconfinement phase transition in G(2) and SU(3)
Yang-Mills theories by numerical simulations in the G(2) gauge-Higgs system.Comment: Plenary talk at 23rd International Symposium on Lattice Field Theory:
Lattice 2005, Trinity College, Dublin, Ireland, 25-30 Jul 200
An effective chiral Hadron-Quark Equation of State
We construct an effective model for the QCD equation of state, taking into
account chiral symmetry restoration as well as the deconfinement phase
transition. The correct asymptotic degrees of freedom at the high and low
temperature limits are included (quarks hadrons). The model
shows a rapid crossover for both order parameters, as is expected from lattice
calculations. We then compare the thermodynamic properties of the model at
which turn out to be in qualitative agreement with lattice data,
while apparent quantitative differences can be attributed to hadronic
contributions and excluded volume corrections. Furthermore we discuss the
effects of a repulsive vector type quark interaction at finite baryon number
densities on the resulting phase diagram of the model. Our current model is
able to reproduce a first-order liquid gas phase transition as expected, but
does not show any signs of a first order deconfinement or chiral phase
transition. Both transitions rather appear as a very wide crossover in which
heavily medium modified hadron coexist with free quarks.Comment: 19 pages, 13 figures Version accepted by J. Phys.
Colour deconfinement in hot and dense matter
We first introduce the conceptual basis of critical behaviour in strongly
interacting matter, with colour deconfinement as QCD analog of the
insulator-conductor transition and chiral symmetry restoration as special case
of the associated shift in the mass of the constituents. Next we summarize
quark-gluon plasma formation in finite temperature lattice QCD. We consider the
underlying symmetries and their spontaneous breaking/restoration in the
transition, as well as the resulting changes in thermodynamic behaviour.
Finally, we turn to the experimental study of strongly interacting matter by
high energy nuclear collisions, using charmonium production to probe the
confinement status of the produced primordial medium. Recent results from Pb-Pb
collisions at CERN may provide first evidence for colour deconfinement.Comment: 11 pages tex, uses macro-hs.tex, 10 figures; talk given at CRIS '96,
First Catania Relativistic Ion Studies, Acicastello, Italy, May 27 - 31,
1996; to appear in the Proceeding
Strangeness Production in Nuclear Matter and Expansion Dynamics
Thermodynamical properties of hot and dense nuclear matter are analyzed and
compared for different equation of state (EoS). It is argued that the softest
point of the equation of state and the strangeness separation on the phase
boundary can manifest themselves in observables. The influence of the EoS and
the order of the phase transition on the expansion dynamics of nuclear matter
and strangeness excitation function is analyzed. It is shown that bulk
properties of strangeness production in A-A collisions depend only weakly on
the particular form of the EoS. The predictions of different models are related
with experimental data on strangeness production.Comment: 38 page
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