118666767
Relativistic diffusion and heavy-ion collisions
We study first- and second-order theories of relativistic diffusion coupled to hydrodynamics under the approximation, valid at midrapidity in the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC), that conserved number densities are much smaller than the entropy density. We identify experimentally accessible quantities of interest and show that the first- and second-order theories may lead to radically different evolutions of these quantities. In the first-order theory the memory of the initial state is almost completely washed out, whereas in the second-order theory it is possible that freeze-out occurs at a time when transient dynamics is still on and the memory of the initial state remains. There are observational consequences that we touch upon. In the first-order theory, and for initial conditions when the second-order theory mimics the first-order theory, one may be able to put a bound on the diffusion constant.
122166973
The phase diagram of QCD: methods and logic of the comparison of experiments and theory
Abstract A small review of the phase diagram of QCD is presented. This is followed by a discussion of the conditions under which experimental data on the fluctuations of conserved quantities in heavy-ion collisions can be treated in the grand canonical ensemble. A robust method for detecting the presence of a nearby critical point in experiments is given. There is a short discussion of the need for non-Gaussian error analysis.
119431013
A precise determination of T_c in QCD from scaling
Existing lattice data on the QCD phase transition are analyzed in renormalized perturbation theory. In quenched QCD it is found that T_c scales for lattices with only 3 time slices, and that T_c/Lambda_msbar=1.15 \pm 0.05. A preliminary estimate in QCD with two flavours of dynamical quarks shows that this ratio depends on the quark mass. For realistic quark masses we estimate T_c/Lambda_msbar=0.49 \pm 0.02. We also investigate the equation of state in quenched QCD at 1-loop order in renormalised perturbation theory.
123004962
Flavour degrees of freedom and the transition temperature in QCD
We study the finite temperature transition in QCD with four flavours of dynamical quarks. Our simulation is performed on an 8×16 3 lattice for quarks of mass ma=0.01. At the coupling β c =5.15, we find long-lived metastable states, as well as an abrupt change in the entropy density, suggesting a first order phase transition. Using presently available results from corresponding calculations of the hadron masses and the chiral condensate, this gives us a transition temperature T c ≅100 MeV, which is a factor two lower than the transition temperature found in quenched QCD.
121387686
Hybrid Monte Carlo simulations of a two-dimensional gauge theory
Through a study of the dynamics of the two-dimensional U(1) pure gauge theory we find exponential slowing down in barrier penetration problems. We verify that the dynamical critical exponent in HMC can be tuned exactly to 1, and that normal and gauge fixed updates have equal cost.
17443615
Lattice QCD for RHIC
I briefly introduce the methods by which lattice QCD predictions for RHIC are obtained. Next I deal with lattice determinations of strangeness production and event-to-event fluctuations of conserved quantities. I also present a new diagrammatic method for computing derivatives with respect to chemical potentials, and conclude with discussions of some tests of thermal perturbation theory which follow.
119711961
Aspects of deuteron production in relativistic heavy ion collisions
One criticism of the thermodynamic model for deuteron production has been that it may not be possible for deuterons to exist inside the fireball. We give arguments why deuterons can exist inside the fireball, although they cannot exist in cold nuclear matter at normal density. We redefine the Berkeley coalescence model and show that with this redefinition, the coalescence model is rather close to the thermodynamic prescription. We show that this redefined coalescence model is equivalent to the quantum mechanical sudden approximation model considered by Kapusta. We construct the grand canonical partition function for interacting fermions up to the second virial coefficient and show that the redefined coalescence model and the simple thermodynamic model are two limits of a more complete theory.
123577959
Quark Quark and Quark - Anti-quark Potentials
16048302
On free 4D Abelian 2-form and anomalous 2D Abelian 1-form gauge theories
We demonstrate a few striking similarities and some glaring differences between (i) the free four- (3+1)-dimensional (4D) Abelian 2-form gauge theory, and (ii) the anomalous two- (1+1)-dimensional (2D) Abelian 1-form gauge theory, within the framework of Becchi–Rouet–Stora–Tyutin (BRST) formalism. We demonstrate that the Lagrangian densities of the above two theories transform in a similar fashion under a set of symmetry transformations even though they are endowed with a drastically different variety of constraint structures. With the help of our understanding of the 4D Abelian 2-form gauge theory, we prove that the gauge-invariant version of the anomalous 2D Abelian 1-form gauge theory is a new field-theoretic model for the Hodge theory where all the de Rham cohomological operators of differential geometry find their physical realizations in the language of proper symmetry transformations. The corresponding conserved charges obey an algebra that is reminiscent of the algebra of the cohomological operators. We briefly comment on the consistency of the 2D anomalous 1-form gauge theory in the language of restrictions on the harmonic state of the (anti-) BRST and (anti-) co-BRST invariant version of the above 2D theory.
93793271
Radial Flow has little effect on clusterization at intermediate energies
The lattice gas model was extended to incorporate the effect of radial flow. Contrary to popular belief, radial flow has little effect on the clusterization process in intermediate energy heavy-ion collisions except adding an ordered motion to the particles in the fragmentation source. We compared the results from the lattice gas model with and without radial flow to experimental data. We found that charge yields from central collisions are not significantly affected by inclusion of any reasonable radial flow.
120261109
Predicting the number of deuterons from cascade calculations of relativistic heavy ion collisions
Formulas are presented which are useful for predicting the number of deuterons from cascade calculations of relativistic heavy ion collisions.