We investigate dynamical stability of a single propeller-like shaped molecular cogwheel modelled as the fixed-axis rigid rotator. In the realistic situations, rotation of the finite-size cogwheel is subject to the environmentally-induced Brownian-motion effect that we describe by utilizing the quantum Caldeira-Leggett master equation. Assuming the initially narrow (classical-like) standard deviations for the angle and the angular momentum of the rotator, we investigate the dynamics of the first and second moments depending on the size, i.e. on the number of blades of both the free rotator as well as of the rotator in the external harmonic field. The larger the standard deviations, the less stable (i.e. less predictable) rotation. We detect the absence of the simple and straightforward rules for utilizing the rotator's stability. Instead, a number of the size-related criteria appear whose combinations may provide the optimal rules for the rotator dynamical stability and possibly control. In the realistic situations, the quantum-mechanical corrections, albeit individually small, may effectively prove non-negligible, and also revealing subtlety of the transition from the quantum to the classical dynamics of the rotator. As to the latter, we detect a strong size-dependence of the transition to the classical dynamics beyond the quantum decoherence process.
There is a solution to the problem of asymptotic completeness in many body
scattering theory that offers a specific view of the quantum unitary dynamics
which allows for the straightforward introduction of local time for every, at
least approximately closed, many-particle system. In this approach, Time
appears as a hidden classical parameter of the unitary dynamics of a
many-particle system. We show that a closed many-particle system can exhibit
behavior that is characteristic for open quantum systems and there is no need
for the "state collapse" or environmental influence. On the other hand, closed
few-particle systems bear high quantum coherence. This local time scheme
encompasses concepts including "emergent time", "relational time" as well as
the "hybrid system" models with possibly induced gravitational uncertainty of
time.Comment: Rewritten (including the title). This version accepted by the
Proceedings
It is shown that a choice of degrees of freedom of a bipartite continuous variable system determines amount of non-classical correlations (quantified by discord) in the system's state. Non-classical correlations (that include entanglement as a special kind of correlations) are ubiquitous for such systems. For a quantum state, if there are not non-classical correlations (quantum discord is zero) for one, there are in general non-classical correlations (quantum discord is non-zero) for another set of the composite system's degrees of freedom. The physical relevance of this 'quantum correlations relativity' is emphasized also in the more general context.
How to cite this paper: Jeknić-Dugić, J., Dugić, M., Francom, A. and Arsenijević, M. (2014)
Abstract Modern quantum theory introduces quantum structures (decompositions into subsystems) as a new discourse that is not fully comparable with the classical-physics counterpart. To this end, socalled Entanglement Relativity appears as a corollary of the universally valid quantum mechanicsthat can provide for a deeper and more elaborate description of the composite quantum systems. In this paper we employ this new concept to describe the hydrogen atom. We offer a consistent picture of the hydrogen atom as an open quantum system that naturally answers the following important questions: 1) how do the so called "quantum jumps" in atomic excitation and de-excitation occur? and 2) why does the classically and seemingly artificial "center-of-mass + relative degrees of freedom" structure appear as the primarily operable form in most of the experimental reality of atoms?
The composite systems can be non-uniquely decomposed into parts (subsystems). Not all decompositions (structures) of a composite system are equally physically relevant. In this paper we answer on theoretical ground why it may be so. We consider a pair of mutually un-coupled modes in the phase space representation that are subjected to the independent quantum amplitude damping channels. By investigating asymptotic dynamics of the degrees of freedom, we find that the environment is responsible for the structures non-equivalence. Only one structure is distinguished by both locality of the environmental influence on its subsystems and a classical-like description.
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