Low energy Quantum Gravity from the Effective Average Action

Within the effective average action approach to quantum gravity, we recover the low energy effective action as derived in the effective field theory framework, by studying the flow of possibly non-local form factors that appear in the curvature expansion of the effective average action. We restrict to the one-loop flow where progress can be made with the aid of the non-local heat kernel expansion. We discuss the possible physical implications of the scale dependent low energy effective action through the analysis of the quantum corrections to the Newtonian potential.Comment: 24 pages, 1 figure; minor corrections, references adde

Statistical J/psi production and open charm enhancement in Pb+Pb collisions at CERN SPS

Production of open and hidden charm hadrons in heavy ion collisions is considered within the statistical coalescence model. Charmed quarks and antiquarks are assumed to be created at the initial stage of the reaction and their number is conserved during the evolution of the system. They are distributed among open and hidden charm hadrons at the hadronization stage in accordance with laws of statistical mechanics. The model is in excellent agreement with the experimental data on J/psi production in lead-lead collisions at CERN SPS and predicts strong enhancement of the open charm multiplicity over the standard extrapolation from nucleon-nucleon to nucleus-nucleus collisions. A possible mechanism of the charm enhancement is proposed.Comment: Presented at 6th International Conference on Strange Quarks in Matter, Frankfurt am Main, 2001. 4 pages, LaTeX, 1 PS-figur

Transition rate of the Unruh-DeWitt detector in curved spacetime

We examine the Unruh-DeWitt particle detector coupled to a scalar field in an arbitrary Hadamard state in four-dimensional curved spacetime. Using smooth switching functions to turn on and off the interaction, we obtain a regulator-free integral formula for the total excitation probability, and we show that an instantaneous transition rate can be recovered in a suitable limit. Previous results in Minkowski space are recovered as a special case. As applications, we consider an inertial detector in the Rindler vacuum and a detector at rest in a static Newtonian gravitational field. Gravitational corrections to decay rates in atomic physics laboratory experiments on the surface of the Earth are estimated to be suppressed by 42 orders of magnitude.Comment: 27 pages, 1 figure. v3: Typos corrected. Published versio

On the Deconfinement Phase Transition in the Resonance Gas

We obtain the constraints on the ruling parameters of the dense hadronic gas model at the critical temperature and propose the quasiuniversal ratios of the thermodynamic quantities. The possible appearence of thermodynamical instability in such a model is discussed.Comment: 7 pages, plain LaTeX, BI-TP 94/4

Hadron spectra from nuclear collisions

Leonidov A, Nardi M, Satz H. Hadron spectra from nuclear collisions. In: Nuclear Physics A. NUCLEAR PHYSICS A. Vol 610. ELSEVIER SCIENCE BV; 1996: C124-C131.We describe high energy nuclear collisions by a superposition of isotropically decaying thermal sources (''fireballs'') of freeze-out temperature T = 0.15 GeV. The longitudinal fireball superposition is taken as boost-invariant, in a rapidity range determined by the average energy loss of nucleons in p - p collisions. The transverse fireball motion is assumed to be due to random walk initial state collisions; it is determined by p - A data and then extrapolated to central A - B interactions. We thus obtain parameter-free predictions for the rapidity and transverse momentum spectra of hadrons produced in high energy nucleus-nucleus collisions. The results account fully for the observed broadening of transverse momentum distributions, so that single-particle spectra require neither collective flow nor temperature increase

Discontinuity Theorem for First Order Phase Transitions. Implications for QCD

A first order phase transition leading to deconfinement and chiral restoration is a likely possibility for QCD, at least in some region of the temperature-density plane. A signal for a unique transition is that the order parameters for such transitions (which can be understood in terms of symmetries only in limiting situations of very massive or massless quarks) are both discontinuous at the same critical temperature. We show that such a situation can be understood on a precise thermodynamical basis because of a general relation among discontinuities which holds for first order transitions. We derive the result by a generalization of the Clausius-Clapeyron equation and also through the effective action formalism. We illustrate the theorem in an elementary example.Comment: 10 pages, LATEX, UGVA-DPT 1992/12/79

Non-extensivity Parameter of Thermodynamical Model of Hadronic Interactions at LHC energies

The LHC measurements above SPS and Tevatron energies give the opportunity to test predictions of non-extensive thermodynamical picture of hadronic interaction to examine measured transverse momenta distributions for new interaction energy range. We determined Tsallis model non-extensivity parameter for the hadronization process before short-lived particles decayed and distort the initial p_t distribution. We have shown that it follows exactly smooth rise determined at lower energies below present LHC record. The shape of the q parameter energy dependence is consistent with expectations and the evidence of the asymptotic limit may be seen.Comment: 2 pages, 2 figure

Charmonium dissociation temperatures in lattice QCD with a finite volume technique

Dissociation temperatures of J/\psi, \psi', and \chi_c states play key roles in the sequential J/\psi suppression scenario for high energy heavy ion collisions. We report on a study of charmonium dissociation temperatures in quenched lattice QCD. On anisotropic lattices, we first subtract the effects of the constant mode in finite temperature meson correlators, which have lead to unphysical results in previous studies. We then extract ground and first exited state masses by diagonalizing correlation functions among different source and sink operators. To distinguish bound states from scattering states, we first compare the charmonium mass spectra under different spatial boundary conditions, and examine the shape and the volume-dependence of their Bethe-Salpeter wave functions. From these studies, we found so far no sign of scattering states up to about 2.3T_c.Comment: 4pages, 2figures, proceedings of Quark Matter 2008 (QM2008), Jaipur, India, Feb 4-10, 200