4,443 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
Conformal Window of Gauge Theories with Four-Fermion Interactions and Ideal Walking
We investigate the effects of four-fermion interactions on the phase diagram
of strongly interacting theories for any representation as function of the
number of colors and flavors. We show that the conformal window, for any
representation, shrinks with respect to the case in which the four-fermion
interactions are neglected. The anomalous dimension of the mass increases
beyond the unity value at the lower boundary of the new conformal window. We
plot the new phase diagram which can be used, together with the information
about the anomalous dimension, to propose ideal models of walking technicolor.
We discover that when the extended technicolor sector, responsible for giving
masses to the standard model fermions, is sufficiently strongly coupled the
technicolor theory, in isolation, must have an infrared fixed point for the
full model to be phenomenologically viable. Using the new phase diagram we show
that the simplest one family and minimal walking technicolor models are the
archetypes of models of dynamical electroweak symmetry breaking. Our
predictions can be verified via first principle lattice simulations.Comment: RevTeX4, 22 pages, 16 figure
The equation of state at high temperatures from lattice QCD
We present results for the equation of state upto previously unreachable,
high temperatures. Since the temperature range is quite large, a comparison
with perturbation theory can be done directly.Comment: 7 pages, 5 figures, Lattice 200
The nature of the finite temperature QCD transition as a function of the quark masses
The finite temperature QCD transition for physical quark masses is a
crossover. For smaller quark masses a first-order phase transition is expected.
Using Symanzik improved gauge and stout improved fermion action for 2+1 flavour
staggered QCD we give estimates/bounds for the phase line separating the
first-order region from the crossover one. The calculations are carried out on
two different lattice spacings. Our conclusion for the critical mass is for and for lattices.Comment: Talk presented at the XXV International Symposium on Lattice Field
Theory, July 30 - August 4 2007, Regensburg, Germany. 7 pages, 6 figure
QCD phase diagram and charge fluctuations
We discuss the phase structure and fluctuations of conserved charges in two
flavor QCD. The importance of the density fluctuations to probe the existence
of the critical end point is summarized. The role of these fluctuations to
identify the first order phase transition in the presence of spinodal phase
separation is also discussed.Comment: 8 pages, 8 figures, plenary talk given at the 19th International
Conference on Ultrarelativistic Nucleus-Nucleus Collisions: Quark Matter 2006
(QM 2006), Shanghai, China, 14-20 Nov 200
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
The curvature of the QCD phase transition line
We determine the curvature of the phase transition line in the mu-T plane
through an analysis of various observables, including the Polyakov loop, the
quark number susceptibilities and the susceptibility of the chiral condensate.
The second derivative of these quantities with respect to mu was calculated.
The measurements were carried out on N_T = 4,6,8 and 10 lattices generated with
a Symanzik improved gauge and stout-link improved 2+1 flavour staggered fermion
action using physical quark masses.Comment: Talk presented at the XXVI International Symposium on Lattice Field
Theory, July 14 - 19, 2008, Williamsburg, Virginia, USA. 7 pages, 6 figure
Lattice SU(3) thermodynamics and the onset of perturbative behaviour
We present the equation of state (pressure, trace anomaly, energy density and
entropy density) of the SU(3) gauge theory from lattice field theory in an
unprecedented precision and temperature range. We control both finite size and
cut-off effects. The studied temperature window () stretches
from the glueball dominated system into the perturbative regime, which allows
us to discuss the range of validity of these approaches. From the critical
couplings on fine lattices we get T_c/\Lambdamsbar=1.26(7) and use this ratio
to express the perturbative free energy in units. We also determine the
preferred renormalization scale of the Hard Thermal Loop scheme and we fit the
unknown order perturbative coefficient at extreme high temperatures
. We furthermore quantify the nonperturbative contribution to the
trace anomaly using two simple functional forms.Comment: 7 pages, Contribution to the The XXVIII International Symposium on
Lattice Field Theory; June 14 - 19, 2010, Villasimius, Sardinia, Ital
- …