arXiv subjects

H. -Th. Elze

Publications and source records attributed to H. -Th. Elze.

11 recordsLinked to original sources

arXiv2002

Time without time: a stochastic clock model

We study a classical reparametrization-invariant system, in which ``time'' is not a priori defined. It consists of a nonrelativistic particle moving in five dimensions, two of which are compactified to form a torus. There, assuming a suitable potential, the internal motion is ergodic or more strongly irregular. We consider quasi-local observables which measure the system's ``change'' in a coarse-grained way. Based on this, we construct a statistical timelike parameter, particularly with the help of maximum entropy method and Fisher-Rao information metric. The emergent reparametrization-invariant ``time'' does not run smoothly but is simply related to the proper time on the average. For sufficiently low energy, the external motion is then described by a unitary quantum mechanical evolution in accordance with the Schrödinger equation.

gr-qc↗

arXiv2002

Relativistic Quantum Transport Theory

Relativistic quantum transport theory has begun to play an important role in the space-time description of matter under extreme conditions of high energy density in out-of-equilibrium situations. The following introductory lectures on some of its basic concepts and methods comprise the sections: 1. Introduction; 2. Aims of transport theory (classical); 3. Quantum mechanical distribution functions - the density matrix and the Wigner function; 4. Transport theory for quantum fields; 5. Particle production by classical fields; 6. Fluid dynamics of relativistic quantum dust.

hep-ph↗

arXiv2002

Fluid Dynamics of Relativistic Quantum Dust

The microscopic transport equations for free fields are solved using the Schwinger function. Thus, for general initial conditions, the evolution of the energy-momentum tensor is obtained, incorporating the quantum effects exactly. The result for relativistic fermions differs from classical hydrodynamics, which is illustrated for Landau and Bjorken type initial conditions in this model of exploding primordial matter. Free fermions behave like classical dust concerning hydrodynamic observables. However, quantum effects which are present in the initial state are preserved.

hep-ph↗

arXiv2001

Entropy Production in Relativistic Hydrodynamics

The entropy production occurring in relativistic hydrodynamical systems such as the quark-gluon plasma (QGP) formed in high-energy nuclear collisions is explored. We study mechanisms which change the composition of the fluid, i.e. particle production and/or chemical reactions, along with chemo- and thermo-diffusion. These effects complement the conventional dissipative effects of shear viscosity, bulk viscosity, and heat conductivity.

hep-ph↗

arXiv2001

Collective Modes in Neutrino `Beam' Electron-Positron Plasma Interactions

We derive semiclassical neutrino-electron transport equations in the collisionless (Vlasov) limit from the coupled Dirac equations, incorporating the charged and neutral weak current-current as well as electromagnetic interactions. A corresponding linear response theory is derived. In particular, we calculate the response functions for a variety of beam-plasma geometries, which are of interest in a supernova scenario. We apply this to the study of plasmons and to a new class of collective {\it pharon} resonance modes, which are characterized by $ω< q$. We find that the growth rates of the unstable modes correspond to a strongly temperature ($\propto T_ν^2T_e^3$) and linearly momentum dependent e-folding length of about $10^{10}$ km under typical conditions for Type II supernovae. This appears to rule out such long-wavelength collective modes as an efficient means of depositing neutrino energy into the plasma sphere.

astro-ph↗

arXiv1998

Interfering QCD/QED Vacuum Polarization

Vacuum polarization mediated by quark loops is susceptible to external electromagnetic fields as well as to the QCD vacuum structure. Employing the stochastic vacuum model, we calculate the modification of the one-loop Euler-Heisenberg effective action due to stochastic color fields with the Fock-Schwinger technique. Our results indicate nonperturbative light quark contributions of the same order of magnitude as the usual QED terms. Various theoretical and experimental implications are discussed in this progress report.

hep-ph↗

arXiv1998

Variational Approach to Hydrodynamics - from QGP to General Relativity

We derive the special and general relativistic hydrodynamic equations of motion for ideal fluids from a variational principle. Our approach allows to find approximate solutions, whenever physically motivated trial functions can be used. Illustrating this, a Rayleigh-Plesset type equation for the relativistic motion of a spherical (QGP) droplet is obtained. Also the corresponding general relativistic effective Lagrangian for spherically symmetric systems is presented.

hep-ph↗

arXiv1998

Sonoluminescing Gas Bubbles

We draw attention to the fact that the popular but unproven hypothesis of shock-driven sonoluminescence is incompatible with the reported synchronicity of the single bubble sonoluminescence (SBSL) phenomenon. Moreover, it is not a necessary requirement, since we show that the sub-shock dynamic heating in gas bubble cavitation can lead to conditions required to generate intense 100ps light pulses. To wit we study the dynamics of the interior of a cavitating gas bubble subject to conditions suitable for sonoluminescence. We explore quantitatively the transfer of energy from the sound wave to the bubble interior, the frequency of atomic collisions in the bubble, the limits of quasi-stability of the non-linear bubble oscillations driven by an acoustical field, and obtain the implied reaction time scales.

cond-mat.soft↗

arXiv1997

The Sound of Sonoluminescence

We consider an air bubble in water under conditions of single bubble sonoluminescence (SBSL) and evaluate the emitted sound field nonperturbatively for subsonic gas-liquid interface motion. Sound emission being the dominant damping mechanism, we also implement the nonperturbative sound damping in the Rayleigh-Plesset equation for the interface motion. We evaluate numerically the sound pulse emitted during bubble collapse and compare the nonperturbative and perturbative results, showing that the usual perturbative description leads to an overestimate of the maximal surface velocity and maximal sound pressure. The radius vs. time relation for a full SBSL cycle remains deceptively unaffected.

cond-mat.soft↗

arXiv1995

Semiquantum Chaos in the Double-Well

The new phenomenon of semiquantum chaos is analyzed in a classically regular double-well oscillator model. Here it arises from a doubling of the number of effectively classical degrees of freedom, which are nonlinearly coupled in a Gaussian variational approximation (TDHF) to full quantum mechanics. The resulting first-order nondissipative autonomous flow system shows energy dependent transitions between regular behavior and semiquantum chaos, which we monitor by Poincaré sections and a suitable frequency correlation function related to the density matrix. We discuss the general importance of this new form of deterministic chaos and point out the necessity to study open (dissipative) quantum systems, in order to observe it experimentally.

chao-dyn↗

arXiv1994

Towards a Field Theoretical Description of Multiparticle Production in High Energy Collisions

We present an effective field theory of multiparticle correlations based on analogy with Ginzburg-Landau theory of superconductivity. With the assumption that the field represents particle density fluctuations, and in the case of gaussian-type effective action we find that there are no higer-order correlations, in agreement with the recent observations in high energy heavy-ion collisions. We predict that three-dimensional two-particle correlations have Yukawa form. We also present our results for the two-dimensional and one-dimensional two-particle correlations (i.e. cumulants) as projections of our theory to lower dimensions.

hep-ph↗