Bela Lukacs

THERMODYNAMIC LENGTH, TIME, SPEED, AND OPTIMUM PATH TO MINIMIZE ENTROPY PRODUCTION

In addition to the Riemannian metricization of the thermodynamic state space, local relaxation times offer a natural time scale, too. Generalizing existing proposals, we relate a thermodynamic time scale to the standard kinetic coefficients of irreversible thermodynamics. The notion of thermodynamic speed is generalized to higher dimensions. Criteria for minimum entropy production in slow, slightly irreversible processes are discussed. Euler–Lagrange equations are derived for optimum thermodynamic control for fixed clock time period as well as for fixed thermodynamic time period. It is emphasized that the correct derivation of the principle of constant thermodynamic speed, proposed earlier by others, requires the entropy minimization at fixed thermodynamic time instead of clock‐time. Most remarkably, optimum paths are Riemannian geodesics which would not be the case had we used ordinary time. To interpret thermodynamic time, an easy‐to‐implement stepwise algorithm is constructed to realize control at cons...

An interpretable family of equations of state for dense hadronic matter

Abstract We present a new family of equations of state for hadronic matter which is consistent with nuclear matter properties at normal nuclear densities and at the high densities produced in heavy-ion collision. This description contains interacting nucleons with free masses and reasonable singleparticle distributions, thus allowing reliable hadrochemical calculations.

A NUT-like solution with fluid matter

Stationary solutions of the Einstein equation are investigated when the source is a rigidly rotating fluid. Using the three-dimensional spin coefficient method the angular dependence of the metric tensor can be analytically calculated if the eigenray congruence is geodesic and shear free. The nonstatic solutions of this class do not describe physically realistic bodies, but, instead, bodies with NUT-type geometry.

Strange particle production in the hadrochemical model

Abstract Strange particle production in heavy ion collisions is calculated in the framework of a hadrochemical model. It is compared with the results of cascade and fireball model calculations and experimental data. The importance of πN and πΔ collisions in producing kaons and hyperons is pointed out.

Lyapunov functional approach to raiative metrics

Lyapunovs second method is applied to the spherical radiative Robinson-Trautman vacuum space-times to prove that they asymptotically settle down to Schwarzschild space-time. This class of Robinson-Trautman metrics is characterized by the surfaceS being topologically a two-sphere, whereS is invariantly defined by the intersection of the hypersurfacesu=const andr=const. It is shown that ∝SK2dσ is a Lyapunov functional, whereK is the Gaussian curvature anddσ is the invariant measure onS. The critical point occurs atK=0 or, equivalently, at ð2K=0, which condition is shown to characterize Schwarzschild space-time.

Two-fluid hydrodynamics applied to the deconfinement transition in the fragmentation region in ultra-relativistic nuclear collisions

Abstract A two-fluid model is presented which describes the interpenetration of nuclei colliding at ultra-relativistic energies. The two fluids are coupled by friction resulting from hadron-hadron collisions. The model calculations predict the deconfinement transition in the baryon-rich fragmentation region. The degree of the conversion and the maximum temperature depend sensitively on the characteristic time for the rearrangement of nuclear matter into the quark-gluon plasma.

Dynamical aspects of the transition from nuclear matter to a quark-gluon plasma in heavy ion collisions☆

Abstract Taking into account a finite conversion rate the transition of nuclear matter to quark-gluon matter and vice versa is treated in a hydrodynamical model for heavy ion collisions. For fast conversion pure quark matter is formed for laboratory energies between 4 and 10 GeV per nucleon while below 4 GeV per nucleon matter stays in a mixed phase. Due to the large amount of latent heat the temperature does not exceed k T = 160 MeV.

Energy dependence of the production of pions, kaons and antikaons calculated in the hadrochemical model

Cross sections for production of pions, kaons and antikaons in heavy ion reactions are calculated in the framework of the hadrochemical model. For the reaction Ne on NaF satisfactory agreement to the measured data is reached in a wide range of energies. The importance of consecutive hadron-hadron collisions for the mass dependence is shown.

A note on helicity

We give a formal definition of the helicity operator for integral spin fields, which does not involve their momentum‐space decomposition. We base our discussion upon a representation of the Pauli–Lubanski operator in terms of the action on tensor fields by the Killing vectors associated with the generators of the Poincare group. This leads to an identification of the helicity operator with the duality operator defined by the space–time alternating tensor. Helicity eigenstates then correspond to self‐dual or anti‐self‐dual fields, in agreement with usage implicit in the literature. In addition, we discuss the relationship between helicity eigenstates, which are intrinsically nonclassical, and states of right or left circular polarization in classical electrodynamics

Inflation and compactification from Galaxy redshifts

The distribution of galaxies in the pencil-beam surveys of Broadhurstet al. which proved periodical across 8–10 consecutive steps in a flat dust model withq0=0.5 is found to reveal extended periodicity up to 16–17 phase-coherent steps, covering the total sample, in a flat, moderately inflationary model withq0=−0.5 (vacuum/dust ratio 2/1). In the latter model the vacuum component helps to reach the critical density and lengthens the expansion time-scale. It is shown that the explanation of the found periodicity as a consequence of space compactification as suggested by G. Paál twenty years ago in connection with apparent quasar periodicities is still possible.