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Fri, 30 Jun 2006 11:21:52 +0200Fri, 30 Jun 2006 11:21:52 +0200Stability of massive objects in a new scalar-tensor theory
http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2480
We define a new scalar-tensor theory with an effective gravitational coupling constant depending on a scalar field. The coupling is such that the gravitational interaction decreases with the strength of the scalar field. We show that this is not sufficient to prevent the gravitational collapse of sufficiently massive dense objects.Gerd Schmidt; Walter Greiner; Ulrich Heinz; Berndt Müllerarticlehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2480Fri, 30 Jun 2006 11:21:52 +0200Electron-translation effects in heavy-ion scattering
http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2478
The origin and importance of electron-translation effects within a molecular description of electronic excitations in heavy-ion collisions is investigated. First, a fully consistent quantum-mechanical description of the scattering process is developed; the electrons are described by relativistic molecular orbitals, while the nuclear motion is approximated nonrelativistically. Leaving the quantum-mechanical level by using the semiclassical approximation for the nuclear motion, a set of coupled differential equations for the occupation amplitudes of the molecular orbitals is derived. In these coupled-channel equations the spurious asymptotic dynamical couplings are corrected for by additional matrix elements stemming from the electron translation. Hence, a molecular description of electronic excitations in heavy-ion scattering has been achieved, which is free from the spurious asymptotic couplings of the conventional perturbated stationary-state approach. The importance of electron-translation effects for continuum electrons and positrons is investigated. To this end an algorithm for the description of continuum electrons is proposed, which for the first time should allow for the calculation of angular distributions for δ electrons. Finally, the practical consequences of electron-translation effects are studied by calculating the corrected coupling matrix elements for the Pb-Cm system and comparing the corresponding K-vacancy probabilities with conventional calculations. We critically discuss conventional methods for cutting off the coupling matrix elements in coupled-channel calculations.Ulrich Heinz; Walter Greiner; Berndt Müllerarticlehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2478Fri, 30 Jun 2006 11:07:06 +0200Possibility of detecting density isomers in high-density nuclear mach shock waves
http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2581
Up to now no experimentally feasible method for detecting abnormal nuclear states has been known. We propose to observe them in high-energy heavy-ion collisions through the disappearance of, or irregularities in, high-density nuclear Mach shock phenomena.Jürgen Hofmann; Horst Stöcker; Ulrich Heinz; Werner Scheid; Walter Greinerarticlehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2581Tue, 20 Jun 2006 10:50:41 +0200Comment on 'Strangeness enhancement in p+A and S+A interactions at energies near 200 A GeV"
http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3763
We argue that the recent analysis of strangeness production in nuclear collisions at 200 A GeV/c performed by Topor Pop et al. is flawed. The conclusions are based on an erroneous interpretation of the data and the numerical model results. The term "strangeness enhancement" is used in a misleading way.Marek Gazdzicki; Ulrich Heinzpreprinthttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3763Tue, 04 Oct 2005 08:51:17 +0200