923 research outputs found
Finite Temperature Phase Diagrams of Gauge Theories
We discuss finite temperature phase diagrams of SU(N) gauge theory with
massless fermions as a function of the number of fermion flavors. Inside the
conformal window we find a phase boundary separating two different conformal
phases. Below the conformal window we find different phase structures depending
on if the beta function of the theory has a first or higher order zero at the
lower boundary of the conformal window. We also outline how the associated
behaviors will help in distinguishing different types of theories using lattice
simulations.Comment: 5 pages, 5 figure
Freezeout of resonances and nuclear fragments at RHIC
We quantify the conditions at which ``composites'', the resonances and bound
states are produced at RHIC. Using Hubble-like model for late stages,
one can analytically solve the rate equations and also calculate the relevant
optical depth factors. We calculate also the modification of masse and
width, and predict a radiacal shape change of .Comment: 6 pages, proccedings of 19th Winter Workshop on Nuclear Dynamics,
Breckenridge, Colorado, February 200
QCD phases at high density and instantons
The talk is an introduction into diquark condensation phenomena which occur
in QCD at high energy density. They are driven by instantons and
instanton-antiinstanton pairs (or ``molecules''), which generate attraction in
some qq channels. A number of phases is possible, with or without restoration
of chiral symmetry: the work is not finished and we do not yet know which take
place in real QCD. We also emphasize that specific diquark correlations play a
significant role in baryon structure, in particular making that of a nucleon
very different of a (or other member of a decuplet). This ``small
'' scenario based on comparison to QCD with two colors is contrasted with
the ``large '' one.Comment: invited talk at "QCD at finite baryon density", Bielefeld, 199
On the Origin of the "Ridge" phenomenon induced by Jets in Heavy Ion Collisions
We argue that "ridge" in 2-particle correlation function associated with hard
trigger at RHIC heavy ion collisions is naturally explained by an interrelation
of jet quenching and hydrodynamical transverse flow. The excess particles
forming the ridge are produced by QCD bremsstrahlung along the beam (and thus
have wide rapidity distribution) and then boosted by transverse flow.
Nontrivial correlation between directions of the jet and the radial flow is
provided by jet quenching: our straightforward and basically
parameter-independent calculation reproduces the angular shape, width and other
properties of the "ridge"
Anisotropy of photon production: Initial eccentricity or magnetic field
Recent measurements of the azimuthal anisotropy of direct photons in
heavy-ion collisions at the energies of RHIC show that it is of the same order
as the hadronic one. This finding appears to contradict the expected dominance
of photon production from a quark-gluon plasma at an early stage of a heavy-ion
collision. A possible explanation of the strong azimuthal anisotropy of the
photons, given recently, is based on the presence of a large magnetic field in
the early phase of a collision. In this letter, we propose a method to
experimentally measure the degree to which a magnetic field in heavy-ion
collisions is responsible for the observed anisotropy of photon production. The
experimental test proposed in this letter may potentially change our
understanding of the non-equilibrium stage and possible thermalization in
heavy-ion collisions.Comment: 4 pages, 3 figures; version accepted for publication: discussions
extended, MC calculations adde
Nonperturbative contributions to the QCD pressure
We summarize the most important arguments why a perturbative description of
finite-temperature QCD is unlikely to be possible and review various
well-established approaches to deal with this problem. Then, using a recently
proposed method, we investigate nonperturbative contributions to the QCD
pressure and other observables (like energy, anomaly and bulk viscosity)
obtained by imposing a functional cutoff at the Gribov horizon. Finally, we
discuss how such contributions fit into the picture of consecutive effective
theories, as proposed by Braaten and Nieto, and give an outline of the next
steps necessary to improve this type of calculation.Comment: 15 pages, 13 figures, uses xcolor.sty; in v2 quality of some figures
has been improved, discussion of other approaches has been extende
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