6,215 research outputs found
QCD phase diagram and the critical point
The recent progress in understanding the QCD phase diagram and the physics of
the QCD critical point is reviewed.Comment: 18 pages, 11 figures, for proceedings of "Finite Density QCD at
Nara", July 200
Excited hadrons as a signal for quark-gluon plasma formation
At the quark-hadron transition, when quarks get confined to hadrons, certain
orbitally excited states, namely those which have excitation energies above the
respective states of the same order as the transition temperature
, may form easily because of thermal velocities of quarks at the
transition temperature. We propose that the ratio of multiplicities of such
excited states to the respective states can serve as an almost model
independent signal for the quark-gluon plasma formation in relativistic
heavy-ion collisions. For example, the ratio of multiplicities of
and when plotted
with respect to the center of mass energy of the collision (or vs.
centrality/number of participants), should show a jump at the value of
beyond which the QGP formation occurs. This should happen
irrespective of the shape of the overall plot of vs. . Recent
data from RHIC on vs. N for large values of
N may be indicative of such a behavior, though there are large error
bars. We give a list of several other such candidate hadronic states.Comment: 19 pages, RevTex, no figures, minor change
Lattice QCD at finite temperature and density
QCD at finite temperature and density is becoming increasingly important for
various experimental programmes, ranging from heavy ion physics to
astro-particle physics. The non-perturbative nature of non-abelian quantum
field theories at finite temperature leaves lattice QCD as the only tool by
which we may hope to come to reliable predictions from first principles. This
requires careful extrapolations to the thermodynamic, chiral and continuum
limits in order to eliminate systematic effects introduced by the
discretization procedure. After an introduction to lattice QCD at finite
temperature and density, its possibilities and current systematic limitations,
a review of present numerical results is given. In particular, plasma
properties such as the equation of state, screening masses, static quark free
energies and spectral functions are discussed, as well as the critical
temperature and the QCD phase structure at zero and finite density.Comment: 32 pages, typos corrected, reference added. Lectures given at 45.
Internationale Universitatswochen fur Theoretische Physik: (Schladming Winter
School on Theoretical Physics): Conceptual and Numerical Challenges in
Femto-Scale and Peta-Scale Physics, Schladming, Styria, Austria, 24 Feb - 3
Mar 200
A slowly rotating perfect fluid body in an ambient vacuum
A global model of a slowly rotating perfect fluid ball in general relativity
is presented. To second order in the rotation parameter, the junction surface
is an ellipsoidal cylinder. The interior is given by a limiting case of the
Wahlquist solution, and the vacuum region is not asymptotically flat. The
impossibility of joining an asymptotically flat vacuum region has been shown in
a preceding work.Comment: 7 pages, published versio
Comparison of lunar rocks and meteorites: Implications to histories of the moon and parent meteorite bodies
A number of similarities between lunar and meteoritic rocks are reported and suggest that the comparison is essential for a clear understanding of meteorites as probes of the early history of the solar systems: (1) Monomict and polymict breccias occur in lunar rocks, as well as in achondritic and chondritic meteorites, having resulted from complex and repeated impact processes. (2) Chondrules are present in lunar, as well as in a few achondritic and most chondritic meteorites. It is pointed out that because chondrules may form in several different ways and in different environments, a distinction between the different modes of origin and an estimate of their relative abundance is important if their significance as sources of information on the early history of the solar system is to be clearly understood. (3) Lithic fragments are very useful in attempts to understand the pre- and post-impact history of lunar and meteoritic breccias. They vary from little modified (relative to the apparent original texture), to partly or completely melted and recrystallized lithic fragments
Wilson Loops in string duals of Walking and Flavored Systems
We consider the VEV of Wilson loop operators by studying the behavior of
string probes in solutions of Type IIB string theory generated by Nc D5 branes
wrapped on an internal manifold. In particular, we focus on solutions to the
background equations that are dual to field theories with a walking gauge
coupling as well as for flavored systems. We present in detail our walking
solution and emphasize various general aspects of the procedure to study Wilson
loops using string duals. We discuss the special features that the strings show
when probing the region associated with the walking of the field theory
coupling.Comment: 28 pages. Various figures. Version to be published
Strange Particles and Neutron Stars - Experiments at Gsi
Experiments on strangeness production in nucleus-nucleus collisions at SIS
energies address fundamental aspects of modern nuclear physics: the
determination of the nuclear equation-of-state at high baryon densities and the
properties of hadrons in dense nuclear matter. Experimental data and
theoretical results will be reviewed. Future experiments at the FAIR
accelerator aim at the exploration of the QCD phase diagram at highest baryon
densities.Comment: %Invited talk given at the International Invited talk given at the
International Symposium on Heavy Ion Physics (ISHIP 2006) April 3-6 2006,
FIAS, Frankfurt, Germany Frankfurt, German
Spontaneous symmetry breaking in a two-doublet lattice Higgs model
An SU(2) lattice gauge theory with two doublets of complex scalar fields is
considered. All continuous symmetries are identified and, using the
nonperturbative methods of lattice field theory, the phase diagram is mapped
out by direct numerical simulation. Two-doublet models contain phase
transitions that separate qualitatively distinct regions of the parameter
space. In some regions global symmetries are spontaneously broken. For some
special choices of the model parameters, the symmetry-breaking order parameter
is calculated. The pattern of symmetry breaking is verified further through
observation of Goldstone bosons.Comment: 24 pages, 13 figures, references added, published versio
- …