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Hans-Thomas Elze

Publications and source records attributed to Hans-Thomas Elze.

45 records · Page 3Linked to original sources
arXiv2003

Quantum features in statistical observations of "timeless" classical systems

We pursue the view that quantum theory may be an emergent structure related to large space-time scales. In particular, we consider classical Hamiltonian systems in which the intrinsic proper time evolution parameter is related through a probability distribution to the discrete physical time. This is motivated by studies of ``timeless'' reparametrization invariant models, where discrete physical time has recently been constructed based on coarse-graining local observables. Describing such deterministic classical systems with the help of path-integrals, primordial states can naturally be introduced which follow unitary quantum mechanical evolution in suitable limits.

gr-qc↗
arXiv2000

The Functional Derivation of Master Equations

Master equations describe the quantum dynamics of open systems interacting with an environment. They play an increasingly important role in understanding the emergence of semiclassical behavior and the generation of entropy, both being related to quantum decoherence. Presently we derive the exact master equation for a homogeneous scalar Higgs or inflaton like field coupled to an environment field represented by an infinite set of harmonic oscillators. Our aim is to demonstrate a derivation directly from the path integral representation of the density matrix propagator. Applications and generalizations of this result are discussed.

quant-ph↗
arXiv1999

Variational Principle for Relativistic Fluid Dynamics

The variational principle for the special and general relativistic hydrodynamics are discussed in view of its application to obtain approximate solutions to these problems. We show that effective Lagrangians can be obtained for suitable ansatz for the dynamical variables such as density profile of the system. As an example, the relativistic version of spherical droplet motion (Rayleigh-Plesset equation) is derived from a simple Lagrangian. For the general relativistic case the most general Lagrangian for spherically symmetric systems is given.

hep-ph↗
arXiv1997

Open Quantum Systems, Entropy and Chaos

Entropy generation in quantum sytems is tied to the existence of a nonclassical environment (heat bath or other) with which the system interacts. The continuous `measuring' of the open system by its environment induces decoherence of its wave function and entropy increase. Examples of nonrelativistic quantum Brownian motion and of interacting scalar fields illustrate these general concepts. It is shown that the Hartree-Fock approximation around the bare classical limit can lead to spurious semiquantum chaos, which may affect the determination of entropy production and thermalization also in other cases.

quant-ph↗
arXiv1995

On Quantum Field Brownian Motion, Decoherence and Semiquantum Chaos

Entropy production in quantum (field) systems requiring environment-induced decoherence is described in a Gaussian variational approximation. The new phenomenon of Semiquantum Chaos is reported. (Presented at the International Conference on Nonlinear Dynamics, Chaotic and Complex Systems, Zakopane (Poland), 7-12.11.95.)

quant-ph↗
arXiv1994

About Entropy and Thermalization - a Miniworkshop Perspective

We present a summary and perspective view of the Miniworkshop on ``{\it Entropy and Thermalization}'' in strong interactions (convener J. Rafelski), which was part of the NATO Advanced Research Workshop on ``{\it Hot Hadronic Matter}'' that took place in Divonne, 27 June to 1 July 1994. To appear in the Proceedings (Plenum Press).

hep-ph↗
arXiv1994

Vacuum-Induced Quantum Decoherence and the Entropy Puzzle

Or: ``How to generate an ensemble in a single event?'' Following recent work on entropy in strong interactions, I explain the concept of environment-induced quantum decoherence in elementary quantum mechanics. The classically chaotic inverted oscillator becomes partially decoherent already in the environment of a single other oscillator performing only vacuum fluctuations. One finds exponential entropy growth in the subsystem with a Lyapunov exponent, which approaches the classical one for weak coupling. Presented at the Workshops on ``Quantum Infrared Physics'', Paris, 6 - 10.6.94, and ``QCD 94'', Montpellier, 7 - 13.7.94. Invited talk at the NATO Adv. Res. Workshop on ``Hot Hadronic Matter'', Divonne, 27.6. - 1.7.94. To appear in the Proceedings.

hep-ph↗
arXiv1994

Entropy, Quantum Decoherence and Pointer States in Scalar ``Parton'' Fields

Entropy arises in strong interactions by a dynamical separation of ``partons'' from unobservable ``environment'' modes due to confinement. For interacting scalar fields we calculate the statistical entropy of the observable subsystem. Diagonalizing its functional density matrix yields field pointer states and their probabilities in terms of Wightman functions. It also indicates how to calculate a finite geometric entropy proportional to a surface area.

hep-th↗