0610011v2

related topics
{time, decoherence, evolution}
{energy, gaussian, time}
{temperature, thermal, energy}
{classical, space, random}
{field, particle, equation}
{equation, function, exp}
{group, space, representation}
{cos, sin, state}
{level, atom, field}
{time, wave, function}
{measurement, state, measurements}

Variational Principle for Mixed Classical-Quantum Systems

M. Grigorescu

abstract: An extended variational principle providing the equations of motion for a system consisting of interacting classical, quasiclassical and quantum components is presented, and applied to the model of bilinear coupling. The relevant dynamical variables are expressed in the form of a quantum state vector which includes the action of the classical subsystem in its phase factor. It is shown that the statistical ensemble of Brownian state vectors for a quantum particle in a classical thermal environment can be described by a density matrix evolving according to a nonlinear quantum Fokker-Planck equation. Exact solutions of this equation are obtained for a two-level system in the limit of high temperatures, considering both stationary and nonstationary initial states. A treatment of the common time shared by the quantum system and its classical environment, as a collective variable rather than as a parameter, is presented in the Appendix.

oai_identifier:
oai:arXiv.org:quant-ph/0610011
categories:
quant-ph cond-mat.stat-mech gr-qc
comments:
16 pages, LaTex; added Figure 2 and Figure 3
doi:
10.1139/P07-107
arxiv_id:
quant-ph/0610011
journal_ref:
Can. J. Phys. 85 (2007) 1023-1034
created:
2006-10-02
updated:
2007-06-28

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