Event-by-Event Fluctuations in Ultrarelativistic Heavy-Ion Collisions

Motivated by forthcoming experiments at RHIC and LHC, we study event-by-event fluctuations in ultrarelativistic heavy-ion collisions in participant nucleon as well as thermal models. The calculated physical observables, including multiplicity, kaon to pion ratios, and transverse momenta agree well with recent NA49 data at the SPS, and indicate that such studies do not yet reveal the presence of new physics. Finally, we present a simple model of how a first order phase transition can be signaled by very large fluctuations.Comment: final version, 4 pages, to appear in Phys. Lett.

Neutron stars and quark matter

Recent observations of neutron star masses close to the maximum predicted by nucleonic equations of state begin to challenge our understanding of dense matter in neutron stars, and constrain the possible presence of quark matter in their deep interiors.Comment: To be published in the proceedings of Quark Confinement and the Hadron Spectrum VII, Sept. 2006, Ponta Delgada, Azores. 7 pages, 3 figures, aipro

RHIC: From dreams to beams in two decades

This talk traces the history of RHIC over the last two decades, reviewing the scientific motivations underlying its design, and the challenges and opportunities the machine presents.Comment: To be published in Proceedings of Quark Matter '01. 10 pages, 1 figur

Condensate density and superfluid mass density of a dilute Bose gas near the condensation transition

We derive, through analysis of the structure of diagrammatic perturbation theory, the scaling behavior of the condensate and superfluid mass density of a dilute Bose gas just below the condensation transition. Sufficiently below the critical temperature, $T_c$, the system is governed by the mean field (Bogoliubov) description of the particle excitations. Close to $T_c$, however, mean field breaks down and the system undergoes a second order phase transition, rather than the first order transition predicted in Bogoliubov theory. Both condensation and superfluidity occur at the same critical temperature, $T_c$ and have similar scaling functions below $T_c$, but different finite size scaling at $T_c$ to leading order in the system size. Through a simple self-consistent two loop calculation we derive the critical exponent for the condensate fraction, $2\beta\simeq 0.66$.Comment: 4 page

Self-consistent approximations: application to a quasiparticle description of the thermodynamic properties of relativistic plasmas

We generalize the concept of conserving,\Phi-derivable, approximations to relativistic field theories. Treating the interaction field as a dynamical degree of freedom, we derive the thermodynamical potential in terms of fully dressed propagators, an approach which allows us to resolve the entropy of a relativistic plasma into contributions from its interacting elementary excitations. We illustrate the derivation for a hot QED plasma of massless particles. We also discuss how the self-consistency of the treatment manifests itself into relationships between the contributions from interaction and matter fields.Comment: 9 pages, 1 eps figure, to appear in "Progress in Nonequilibrium Green's functions.", M. Bonitz (Ed.), World Scientific, Singapore 200