Latest documents http://publikationen.ub.uni-frankfurt.de/index/index/ Fri, 29 Apr 2011 16:21:30 +0200 Fri, 29 Apr 2011 16:21:30 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/17195 We derive the equations of second order dissipative fluid dynamics from the relativistic Boltzmann equation following the method of W. Israel and J. M. Stewart [1]. We present a frame independent calculation of all first- and second-order terms and their coefficients using a linearised collision integral. Therefore, we restore all terms that were previously neglected in the original papers of W. Israel and J. M. Stewart. Barbara Betz; Gabriel Denicol; Tomoi Koide; Etele Molnár; Harri Niemi; Dirk-Hermann Rischke article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/17195 Fri, 29 Apr 2011 16:21:30 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/20405 To investigate the formation and the propagation of relativistic shock waves in viscous gluon matter we solve the relativistic Riemann problem using a microscopic parton cascade. We demonstrate the transition from ideal to viscous shock waves by varying the shear viscosity to entropy density ratio n/s. Furthermore we compare our results with those obtained by solving the relativistic causal dissipative fluid equations of Israel and Stewart (IS), in order to show the validity of the IS hydrodynamics. Employing the parton cascade we also investigate the formation of Mach shocks induced by a high-energy gluon traversing viscous gluon matter. For n/s = 0.08 a Mach cone structure is observed, whereas the signal smears out for n/s >=0.32. Ioannis Bouras; Etele Molnár; Harri Niemi; Zhe Xu; Andrej El; Oliver Fochler; Francesco Lauciello; Felix Reining; Christian Wesp; Carsten Greiner; Dirk-Hermann Rischke article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/20405 Thu, 02 Dec 2010 09:21:30 +0100 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/6505 We calculate low-energymeson decay processes and pion-pion scattering lengths in a two-flavour linear sigma model with global chiral symmetry, exploring the scenario in which the scalar mesons f0(600) and a0(980) are assumed to be ¯qq states. Denis Parganlija; Francesco Giacosa; Dirk-Hermann Rischke article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/6505 Mon, 11 May 2009 13:38:09 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/1602 We study the phase diagram of dense, locally neutral three-flavor quark matter within the framework of the Nambu--Jona-Lasinio model. In the analysis, dynamically generated quark masses are taken into account self-consistently. The phase diagram in the plane of temperature and quark chemical potential is presented. The results for two qualitatively different regimes, intermediate and strong diquark coupling strength, are presented. It is shown that the role of gapless phases diminishes with increasing diquark coupling strength. Stefan Bernhard Rüster; Verena Werth; Michael Buballa; Igor A. Shovkovy; Dirk-Hermann Rischke preprint http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/1602 Mon, 26 Feb 2007 09:05:37 +0100 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/1598 We study the effect of neutrino trapping on the phase diagram of dense, locally neutral three-flavor quark matter within the framework of a Nambu--Jona-Lasinio model. In the analysis, dynamically generated quark masses are taken into account self-consistently. The phase diagrams in the plane of temperature and quark chemical potential, as well as in the plane of temperature and lepton-number chemical potential are presented. We show that neutrino trapping favors two-flavor color superconductivity and disfavors the color-flavor-locked phase at intermediate densities of matter. At the same time, the location of the critical line separating the two-flavor color-superconducting phase and the normal phase of quark matter is little affected by the presence of neutrinos. The implications of these results for the evolution of protoneutron stars are briefly discussed. PACS numbers: 12.39.-x 12.38.Aw 26.60.+c Stefan Bernhard Rüster; Verena Werth; Michael Buballa; Igor A. Shovkovy; Dirk-Hermann Rischke preprint http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/1598 Mon, 26 Feb 2007 08:56:50 +0100 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/1597 We discuss the phase diagram of moderately dense, locally neutral three-flavor quark matter using the framework of an effective model of quantum chromodynamics with a local interaction. The phase diagrams in the plane of temperature and quark chemical potential as well as in the plane of temperature and lepton-number chemical potential are discussed. Stefan Bernhard Rüster; Verena Werth; Michael Buballa; Igor A. Shovkovy; Dirk-Hermann Rischke preprint http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/1597 Mon, 26 Feb 2007 08:50:33 +0100 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/1603 We study the phase diagram of dense, locally neutral three-flavor quark matter as a function of the strange quark mass, the quark chemical potential, and the temperature, employing a general nine-parameter ansatz for the gap matrix. At zero temperature and small values of the strange quark mass, the ground state of matter corresponds to the color-flavor-locked (CFL) phase. At some critical value of the strange quark mass, this is replaced by the recently proposed gapless CFL (gCFL) phase. We also find several other phases, for instance, a metallic CFL (mCFL) phase, a so-called uSC phase where all colors of up quarks are paired, as well as the standard two-flavor color-superconducting (2SC) phase and the gapless 2SC (g2SC) phase. Stefan Bernhard Rüster; Igor A. Shovkovy; Dirk-Hermann Rischke preprint http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/1603 Mon, 26 Feb 2007 08:46:01 +0100 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/1604 We discuss gapless colour superconductivity for neutral quark matter in β equilibrium at zero as well as at nonzero temperature. Basic properties of gapless superconductors are reviewed. The current progress and the remaining problems in the understanding of the phase diagram of strange quark matter are discussed. Igor A. Shovkovy; Stefan Bernhard Rüster; Dirk-Hermann Rischke preprint http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/1604 Mon, 26 Feb 2007 08:40:12 +0100 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/1605 We compare quark stars made of color-superconducting quark matter to normal-conducting quark stars. We focus on the most simple color-superconducting system, a two-flavor color superconductor, and employ the Nambu-Jona-Lasinio (NJL) model to compute the gap parameter and the equation of state. By varying the strength of the four-fermion coupling of the NJL model, we study the mass and the radius of the quark star as a function of the value of the gap parameter. If the coupling constant exceeds a critical value, the gap parameter does not vanish even at zero density. For coupling constants below this critical value, mass and radius of a color-superconducting quark star change at most by ca. 20% compared to a star consisting of normal-conducting quark matter. For coupling constants above the critical value mass and radius may change by factors of two or more. Stefan Bernhard Rüster; Dirk-Hermann Rischke preprint http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/1605 Mon, 26 Feb 2007 08:31:20 +0100 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2673 We demonstrate that strangeness separates in the Gibbs-phase coexistence between a baryon-rich quark-gluon plasma and hadron matter, even at T=0. For finite temperatures this is due to the associated production of kaons (containing s¯ quarks) in the hadron phase while s quarks remain in the deconfined phase. The s-s¯ separation results in a strong enhancement of the s-quark abundance in the quark phase. This mechanism is further supported by cooling and net strangeness enrichment due to the prefreezeout evaporation of pions and K+, K0, which carry away entropy and anti- strangeness from the system. Metastable droplets (i.e., stable as far as weak interactions are not regarded) of strange-quark matter (‘‘strangelets’’) can thus be formed during the phase transition. Such cool, compact, long-lived clusters could be experimentally observed by their unusually small Z/A ratio (≤0.1–0.3). Even if the strange-quark-matter phase is not stable under strong interactions, it should be observable by the delayed correlated emission of several hyperons. This would serve as a unique signature for the transient formation of a quark-gluon plasma. Carsten Greiner; Dirk-Hermann Rischke; Horst Stöcker; Peter Koch article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2673 Tue, 06 Jun 2006 11:29:50 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2678 We investigate the hydrodynamical flow of nuclear matter in a conical-shock-wave scenario of a central, asymmetric heavy-ion collision. This work is motivated by a suggestion of Chapline and Granik that the creation of a deconfined phase of quarks and gluons behind the shock will appreciably increase the deflection angle of the matter flow. We employ several hadron matter equations of state recently suggested to solve the conical-shock-wave problem and compare the results with a calculation using the bag equation of state. We find that large differences in the deflection angle obtained in the rest frame of the shock vanish in the laboratory system. However, a signature for the deconfinement transition may be the transverse momentum of the matter flow, which is up to a factor of 2 larger for the quark-gluon plasma. Thus, an excitation function of the mean transverse momentum would show an increase at a certain bombarding energy, signaling the onset of the deconfinement transition. Dirk-Hermann Rischke; Horst Stöcker; Walter Greiner article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2678 Fri, 02 Jun 2006 15:14:59 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2684 Dirk-Hermann Rischke; B. L. Friman; B. M. Waldhauser; Horst Stöcker; Walter Greiner article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2684 Fri, 02 Jun 2006 14:40:22 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2703 The authors formulate a phenomenological extension of the mean-field theory approach and define a class of thermodynamically self-consistent equations of state for nuclear matter. A new equation of state of this class is suggested and examined in detail. Mark I. Gorenstein; Dirk-Hermann Rischke; Horst Stöcker; Walter Greiner; Kyrill A. Bugaev article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2703 Fri, 26 May 2006 14:59:04 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2704 We study dilepton production from a quark-gluon plasma of given energy density at finite quark chemical potential μ and find that the dilepton production rate is a strongly decreasing function of μ. Therefore, the signal to background ratio of dileptons from a plasma created in a heavy-ion collision may decrease significantly. Adrian Dumitru; Dirk-Hermann Rischke; Th. Schönfeld; L. A. Winckelmann; Horst Stöcker; Walter Greiner article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2704 Wed, 24 May 2006 11:15:13 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2957 We calculate thermal photon and neutral pion spectra in ultrarelativistic heavy-ion collisions in the framework of three-fluid hydrodynamics. Both spectra are quite sensitive to the equation of state used. In particular, within our model, recent data for S + Au at 200 AGeV can only be understood if a scenario with a phase transition (possibly to a quark-gluon plasma) is assumed. Results for Au+Au at 11 AGeV and Pb + Pb at 160 AGeV are also presented. Adrian Dumitru; Ulrich Katscher; Joachim A. Maruhn; Horst Stöcker; Walter Greiner; Dirk-Hermann Rischke preprint http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2957 Wed, 22 Feb 2006 16:50:36 +0100 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2944 The rapidity distribution of thermal photons produced in Pb+Pb collisions at CERN-SPS energies is calculated within scaling and three- fluid hydrodynamics. It is shown that these scenarios lead to very different rapidity spectra. A measurement of the rapidity dependence of photon radiation can give cleaner insight into the reaction dynamics than pion spectra, especially into the rapidity dependence of the temperature. Adrian Dumitru; Ulrich Katscher; Joachim A. Maruhn; Horst Stöcker; Walter Greiner; Dirk-Hermann Rischke preprint http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2944 Fri, 10 Feb 2006 16:36:22 +0100 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3008 To describe ultrarelativistic heavy-ion collisions we construct a three-fluid hydrodynamical model. In contrast to one-fluid hydrodynamics, it accounts for the finite stopping power of nuclear matter, i.e. for nonequilibrium e ects in the early stage of the reaction. Within this model, we study baryon dynamics in the BNL-AGS energy range. For the system Au+Au we find that kinetic equilibrium between projectile and target nucleons is established only after a time teq CM H 5 fm/c C 2RAu/³CM. Observables which are sensitive to the early stage of the collision (like e.g. nucleon flow) therefore di er considerably from those calculated in the one-fluid model. Jörg Brachmann; Adrian Dumitru; Joachim A. Maruhn; Horst Stöcker; Walter Greiner; Dirk-Hermann Rischke preprint http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3008 Tue, 17 Jan 2006 09:57:57 +0100 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3389 It is shown that in ideal relativistic hydrodynamics a phase transition from hadron to quark and gluon degrees of freedom in the nuclear matter equation of state leads to a minimum in the excitation function of the transverse collective flow. Dirk-Hermann Rischke; Yaris Pürsün; Joachim A. Maruhn; Horst Stöcker; Walter Greiner preprint http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3389 Mon, 31 Oct 2005 09:33:59 +0100 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/4821 Report-no: UFTP-492/1999 Journal-ref: Phys.Rev. C61 (2000) 024909 We investigate flow in semi-peripheral nuclear collisions at AGS and SPS energies within macroscopic as well as microscopic transport models. The hot and dense zone assumes the shape of an ellipsoid which is tilted by an angle Theta with respect to the beam axis. If matter is close to the softest point of the equation of state, this ellipsoid expands predominantly orthogonal to the direction given by Theta. This antiflow component is responsible for the previously predicted reduction of the directed transverse momentum around the softest point of the equation of state. Jörg Brachmann; Sven Soff; Adrian Dumitru; Horst Stöcker; Joachim A. Maruhn; Walter Greiner; Dirk-Hermann Rischke preprint http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/4821 Wed, 13 Apr 2005 15:17:14 +0200