269 research outputs found
Debye mass and heavy quark potential in a PNJL quark plasma
We calculate the Debye mass for the screening of the heavy quark potential in
a plasma of massless quarks coupled to the temporal gluon background governed
by the Polyakov loop potential within the PNJL model in RPA approximation. We
give a physical motivation for a recent phenomenological fit of lattice data by
applying the calculated Debye mass with its suppression in the confined phase
due to the Polyakov-loop to a description of the temperature dependence of the
singlet free energy for QCD with a heavy quark pair at infinite separation. We
compare the result to lattice data.Comment: 6 pages, 1 figure, contribution to Proceedings of the 6th
International Conference on "Critical Point and Onset of Deconfinement", to
appear in Phys. At. Nucl., vol. 7
QCD equation of state in a virial expansion
We describe recent three-flavor QCD lattice data for the pressure, speed of
soun d and interaction measure at nonzero temperature and vanishing chemical
potentia l within a virial expansion. For the deconfined phase we use a
phenomenological model which includes non-pert urbative effects from dimension
two gluon condensates that reproduce the free en ergy of quenched QCD very
well. The hadronic phase is parameterized by a generalized resonance-gas model.
Furthermore, we extend this approach to finite quark densities introducing an
ex plicit -dependence of the interaction. We calculate pressure,
quark-number density, entropy and energy density and compare to results of
lattice calculatio ns. We, additionally, investigate the structure of the phase
diagram by calculating the isobaric and isentropic lines as well as the
critical endpoint in the ()-plane.Comment: 9 pages, 11 figures. Submitted to Phys. Rev.
QGP Susceptibilities from PNJL Model
An improved version of the PNJL model is used to calculate various
thermodynamical quantities, {\it viz.}, quark number susceptibility, isospin
susceptibility, specific heat, speed of sound and conformal measure. Comparison
with Lattice data is found to be encouraging.Comment: 4 pages, 2 figures, poster presented at Quark Matter'0
Cosmological phase transitions in warped space: gravitational waves and collider signatures
We study the electroweak phase transition within a 5D warped model including
a scalar potential with an exponential behavior, and strong back-reaction over the metric,
in the infrared. By means of a novel treatment of the superpotential formalism, we explore
parameter regions that were previously inaccessible. We nd that for large enough values
of the t'Hooft parameter (e.g. N = 25) the holographic phase transition occurs, and it
can force the Higgs to undergo a rst order electroweak phase transition, suitable for
electroweak baryogenesis. The model exhibits gravitational waves and colliders signatures.
It typically predicts a stochastic gravitational wave background observable both at the
Laser Interferometer Space Antenna and at the Einstein Telescope. Moreover the radion
tends to be heavy enough such that it evades current constraints, but may show up in
future LHC runs.The work of EM is supported by the Spanish MINEICO under
Grant FPA2015-64041-C2-1-P and FIS2017-85053-C2-1-P, by the Junta de Andaluc a under
Grant FQM-225, by the Basque Government under Grant IT979-16, and by the Spanish
Consolider Ingenio 2010 Programme CPAN (CSD2007-00042). The research of EM is also
supported by the Ram on y Cajal Program of the Spanish MINEICO, and by the Universidad
del Pa s Vasco UPV/EHU, Bilbao, Spain, as a Visiting Professor. GN is supported
by the Swiss National Science Foundation (SNF) under grant 200020-168988. The work
of MQ is partly supported by Spanish MINEICO under Grant CICYT-FEDER-FPA2014-
55613-P and FPA2017-88915-P, by the Severo Ochoa Excellence Program of MINEICO
under Grant SEV-2016-0588, and by CNPq PVE fellowship project 405559/2013-5
Hadron Production in Ultra-relativistic Nuclear Collisions: Quarkyonic Matter and a Triple Point in the Phase Diagram of QCD
We argue that features of hadron production in relativistic nuclear
collisions, mainly at CERN-SPS energies, may be explained by the existence of
three forms of matter: Hadronic Matter, Quarkyonic Matter, and a Quark-Gluon
Plasma. We suggest that these meet at a triple point in the QCD phase diagram.
Some of the features explained, both qualitatively and semi-quantitatively,
include the curve for the decoupling of chemical equilibrium, along with the
non-monotonic behavior of strange particle multiplicity ratios at center of
mass energies near 10 GeV. If the transition(s) between the three phases are
merely crossover(s), the triple point is only approximate.Comment: 28 pages, 9 figures; submitted to Nucl. Phys. A; v2 to eliminate
obsolete figs. inadvertently attached at the end of the paper; v3: final
version accepted for publicatio
Goldstones in Diphotons
We study the conditions for a new scalar resonance to be observed first in
diphotons at the LHC Run-2. We focus on scenarios where the scalar arises
either from an internal or spacetime symmetry broken spontaneously, for which
the mass is naturally below the cutoff and the low-energy interactions are
fixed by the couplings to the broken currents, UV anomalies, and selection
rules. We discuss the recent excess in diphoton resonance searches observed by
ATLAS and CMS at 750 GeV, and explore its compatibility with other searches at
Run-1 and its interpretation as Goldstone bosons in supersymmetry and composite
Higgs models. We show that two candidates naturally emerge: a Goldstone boson
from an internal symmetry with electromagnetic anomalies, and the scalar
partner of the Goldstone of supersymmetry breaking: the sgoldstino. The dilaton
from conformal symmetry breaking is instead disfavoured by present data, in its
minimal natural realization.Comment: 18 pages + refs, 2 figures. v2: typos corrected, references added,
discussions extended and three new plots. Conclusion unchanged. v3: published
versio
Two-color QCD via dimensional reduction
We study the thermodynamics of two-color QCD at high temperature and/or
density using a dimensionally reduced superrenormalizable effective theory,
formulated in terms of a coarse grained Wilson line. In the absence of quarks,
the theory is required to respect the Z(2) center symmetry, while the effects
of quarks of arbitrary masses and chemical potentials are introduced via soft
Z(2) breaking operators. Perturbative matching of the effective theory
parameters to the full theory is carried out explicitly, and it is argued how
the new theory can be used to explore the phase diagram of two-color QCD.Comment: 17 pages, 1 eps figure, jheppub style; v2: minor update, references
added, published versio
Trace Anomaly and Quasi-Particles in Finite Temperature SU(N) Gauge Theory
We consider deconfined matter in SU(N) gauge theory as an ideal gas of
transversely polarized quasi-particle modes having a temperature-dependent mass
m(T). Just above the transition temperature, the mass is assumed to be
determined by the critical behavior of the energy density and the screening
length in the medium. At high temperature, it becomes proportional to T as the
only remaining scale. The resulting (trace anomaly based) interaction measure
Delta=(e - 3P)/T^4 and energy density are found to agree well with finite
temperature SU(3) lattice calculations.Comment: 13 pages, 13 figures; references added for version
Hydrodynamics of a 5D Einstein-dilaton black hole solution and the corresponding BPS state
We apply the potential reconstruction approach to generate a series of
asymptotically AdS (aAdS) black hole solutions, with a self-interacting bulk
scalar field. Based on the method, we reproduce the pure AdS solution as a
consistency check and we also generate a simple analytic 5D black hole
solution. We then study various aspects of this solution, such as temperature,
entropy density and conserved charges. Furthermore, we study the hydrodynamics
of this black hole solution in the framework of fluid/gravity duality, e.g. the
ratio of the shear viscosity to the entropy density. In a degenerate case of
the 5D black hole solution, we find that the c function decreases monotonically
from UV to IR as expected. Finally, we investigate the stability of the
degenerate solution by studying the bosonic functional energy of the gravity
and the Witten-Nester energy . We confirm that the degenerate solution
is a BPS domain wall solution. The corresponding superpotential and the
solution of the killing spinor equation are found explicitly.Comment: V2: 23 pages, no figure, minor changes, typos corrected, new
references and comments added, version accepted by JHE
Thermodynamics of the PNJL model
QCD thermodynamics is investigated by means of the Polyakov-loop-extended
Nambu Jona-Lasinio (PNJL) model, in which quarks couple simultaneously to the
chiral condensate and to a background temporal gauge field representing
Polyakov loop dynamics. The behaviour of the Polyakov loop as a function of
temperature is obtained by minimizing the thermodynamic potential of the
system. A Taylor series expansion of the pressure is performed. Pressure
difference and quark number density are then evaluated up to sixth order in
quark chemical potential, and compared to the corresponding lattice data. The
validity of the Taylor expansion is discussed within our model, through a
comparison between the full results and the truncated ones.Comment: 6 pages, 5 figures, Talk given at the Workshop for Young Scientists
on the Physics of Ultrarelativistic Nucleus-Nucleus Collisions (Hot Quarks
2006), Villasimius, Italy, 15-20 May 200
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