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We investigate the average sizes of the $n$ largest fragments in nuclear multifragmentation events near the critical point of the nuclear matter phase diagram. We perform analytic calculations employing Poisson statistics as well as Monte Carlo simulations of the percolation type. We find that previous claims of manifestations of Zipf's Law in the rank-ordered fragment size distributions are not born out in our result, neither in finite nor infinite systems. Instead, we find that Zipf-Mandelbrot distributions are needed to describe the results, and we show how one can derive them in the infinite size limit. However, we agree with previous authors that the investigation of rank-ordered fragment size distributions is an alternative way to look for the critical point in the nuclear matter diagram., Comment: 8 pages, 11 figures, submitted to PRC

The derivation of the Maxwell equations is reproduced whereby magnetic charges are included. This ansatz yields the results: 1) Longitudinal Ampere forces in a differential magnetostatic force law are improbable. Otherwise an electric current would generate magnetic charges. 2) Simple magnetic and electric induced polarization phenomena are completely analogous and are described by a Laplace equation. 3) Magnetic charges are the topological defects of a magnetic spin field similar like electric charges are the topological defects of an electric field. The magnetic charges should be interconnected with an elastic or inertial field which compensates the torque field generated by the magnetic moments of the anisotropic distributed spins. 4) Permanent magnetic fields can be understood to be caused by magnetic charges. Consequently, a moving permanent magnet represents a magnetic current which generates an electric field. 5) The electromagnetic tensors of energy and momentum have some additional terms which are written down generally. 6) Nonlinear electro-thermodynamic systems may violate the second law of thermodynamics. This is illustrated by an electric cycle with a data storing FET invented by Yusa & Sakaki., Comment: 60 pages, Acrobat Reader 4.0 or higher; small additions: p.26 -quantum mechanics interpreations of monopoles included; p.57 -a hint how to explain the Searl effect; p.10: - errors in proof removed; otherwise many cosmetic improvements

The isospin and strangeness dimensions of the Equation of State are explored. RIA and the SIS200 accelerator at GSI will allow to explore these regions in compressed baryonic matter. $^{132}$Sn+$^{132}$Sn and $^{100}$Sn+$^{100}$Sn collisions as well as the excitation functions of $K/\pi$, $\Lambda/\pi$ and the centrality dependence of charmonium suppression from the UrQMD and HSD transport models are presented and compared to data. Unambiguous proof for the creation of a 'novel phase of matter' from strangeness and charm yields is not in sight., Comment: Proceedings of the ISPUN 02. 8 pp, 6 figs

A percolation model of nuclear fragmentation is used to interpret 10.2 GeV/c p+197Au multi-fragmentation data. Emphasis is put on finding signatures of a continuous nuclear matter phase transition in finite nuclear systems. Based on model calculations, corrections accounting for physical constraints of the fragment detection and sequential decay processes are derived. Strong circumstantial evidence for a continuous phase transition is found, and the values of two critical exponents, sigma = 0.5+-0.1 and tau = 2.35+-0.05, are extracted from the data. A critical temperature of T_c = 8.3+-0.2 MeV is found., Comment: 5 pages, 4 figures, submitted to Phys. Rev. Lett

The field-dependent equilibrium thermodynamics is derived with two methods: either by using the potential formalism either by the statistical method. Therefore, Pontrjagin's extremum principle of control theory is applied to an extended ensemble average. This approach allows to derive the grand partition function of thermodynamics as a result of a control problem with the Hamilton energy. Furthermore, the maximum entropy principle follows and the second law in a modified form. The derivation can predict second law violations if cycles with irreversibilities in varying potential fields are included into consideration. This conclusion is supported indirectly by experimental data from literature. The upper maximum gain efficiency of a cycle with a known polymer solution as dielectrics was estimated to less than 1 promille per cycle. Note added in proof 28th October 2003: Comparing this preprint work with an analogous ferrofluidic system discrepancies are is found which show that the concrete model proposed here in section 4 is insufficient to settle the question. A way to solve the problem is proposed., Comment: 42 pages in PDF, Acrobat 4.0, 5.0, 14 figures, note added in proof regarding the calculations of section 4

A method to treat a N-component percolation model as effective one component model is presented by introducing a scaled control variable $p_{+}$. In Monte Carlo simulations on $16^{3}$, $32^{3}$, $64^{3}$ and $128^{3}$ simple cubic lattices the percolation threshold in terms of $p_{+}$ is determined for N=2. Phase transitions are reported in two limits for the bond existence probabilities $p_{=}$ and $p_{\neq}$. In the same limits, empirical formulas for the percolation threshold $p_{+}^{c}$ as function of one component-concentration, $f_{b}$, are proposed. In the limit $p_{=} = 0$ a new site percolation threshold, $f_{b}^{c} \simeq 0.145$, is reported., Comment: RevTeX, 5 pages, 5 eps-figures

We confirm the importance of standard medium effects (hadronic rescattering) in heavy-ion collisions by using a pQCD-based model to investigate the dilepton spectra from Pb+Au collisions at 158 GeV/nucleon., Comment: 10 pages RevTex, incl. 2 postscript figures, submitted to Phys. Rev. C

We use a simple QCD-based model to study particle production in S+Au collisions at 200 GeV/n. A requisite consistency is met for the hadronic observables (pi0 and pi- spectra) while pursuing estimates for e+e- production. Since radiative decays of initially produced hadrons has accounted for only a portion of the observed dileptons at the CERN SPS, we search for additional mechanisms. By including contributions from prompt secondary hadronic scatterings, pi rho -> pi e+e-, and adding to pi+ pi- annihilation and hadronic decays, the ``excess'' dilepton signal can possibly be interpreted., Comment: 14 pages of LaTex and 5 postscript figures submitted Phys Rev D

We investigate the stochastic Direct Simulation Monte Carlo method (DSMC) for numerically solving the collision-term in heavy-ion transport theories of the Boltzmann-Uehling-Uhlenbeck (BUU) type. The first major modification we consider is changes in the collision rates due to excluded volume and shadowing/screening effects (Enskog theory). The second effect studied by us is the inclusion of an additional advection term. These modifications ensure a non-vanishing second virial and change the equation of state for the scattering process from that of an ideal gas to that of a hard-sphere gas. We analyse the effect of these modifications on the calculated value of directed nuclear collective flow in heavy ion collisions, and find that the flow slightly increases., Comment: 12 pages, REVTeX, figures available in PostScript from the authors upon request

Transport models have successfully described many aspects of intermediate energy heavy-ion collision dynamics. As the energies increase in these models to the ultrarelativistic regime, Lorentz covariance and causality are not strictly respected. The standard argument is that such effects are not important to final results; but they have not been seriously considered at high energies. We point out how and why these happen, how serious of a problem they may be and suggest ways of reducing or eliminating the undesirable effects., Comment: RevTeX, 23 pages, 9 (uuencoded) figures; to appear in Phys. Rev C

We consider the dependence of collective flow on the nuclear surface thickness in a Boltzmann--Uehling--Uhlenbeck transport model of heavy ion collisions. Well defined surfaces are introduced by giving test particles a Gaussian density profile of constant width. Zeros of the flow excitation function are as much influenced by the surface thickness as the nuclear equation of state, and the dependence of this effect is understood in terms of a simple potential scattering model. Realistic calculations must also take into account medium effects for the nucleon--nucleon cross section, and impact parameter averaging. We find that balance energy scales with the mass number as $A^{-y}$, where $y$ has a numerical value between 0.35 and 0.5, depending on the assumptions about the in-medium nucleon-nucleon cross section., Comment: 11 pages (LaTeX), 7 figures (not included), MSUCL-884, WSU-NP-93-1