2,050 research outputs found
Generalized local and nonlocal master equations for some stochastic processes
In this paper, we present a study on generalized local and nonlocal equations for some stochastic processes. By considering the net flux change in a region determined by the transition probability, we derive the master equation to describe the evolution of the probability density function. Some examples, such as classical Fokker-Planck equations, models for Lévy process, and stochastic coagulation equations, are provided as illustrations. A particular application is a consistent derivation of coupled dynamical systems for spatially inhomogeneous stochastic coagulation processes
Non-Markovian Levy diffusion in nonhomogeneous media
We study the diffusion equation with a position-dependent, power-law
diffusion coefficient. The equation possesses the Riesz-Weyl fractional
operator and includes a memory kernel. It is solved in the diffusion limit of
small wave numbers. Two kernels are considered in detail: the exponential
kernel, for which the problem resolves itself to the telegrapher's equation,
and the power-law one. The resulting distributions have the form of the L\'evy
process for any kernel. The renormalized fractional moment is introduced to
compare different cases with respect to the diffusion properties of the system.Comment: 7 pages, 2 figure
Non-Markovian dynamics in open quantum systems
The dynamical behavior of open quantum systems plays a key role in many
applications of quantum mechanics, examples ranging from fundamental problems,
such as the environment-induced decay of quantum coherence and relaxation in
many-body systems, to applications in condensed matter theory, quantum
transport, quantum chemistry and quantum information. In close analogy to a
classical Markov process, the interaction of an open quantum system with a
noisy environment is often modelled by a dynamical semigroup with a generator
in Lindblad form, which describes a memoryless dynamics leading to an
irreversible loss of characteristic quantum features. However, in many
applications open systems exhibit pronounced memory effects and a revival of
genuine quantum properties such as quantum coherence and correlations. Here,
recent results on the rich non-Markovian quantum dynamics of open systems are
discussed, paying particular attention to the rigorous mathematical definition,
to the physical interpretation and classification, as well as to the
quantification of memory effects. The general theory is illustrated by a series
of examples. The analysis reveals that memory effects of the open system
dynamics reflect characteristic features of the environment which opens a new
perspective for applications, namely to exploit a small open system as a
quantum probe signifying nontrivial features of the environment it is
interacting with. This article further explores the various physical sources of
non-Markovian quantum dynamics, such as structured spectral densities, nonlocal
correlations between environmental degrees of freedom and correlations in the
initial system-environment state, in addition to developing schemes for their
local detection. Recent experiments on the detection, quantification and
control of non-Markovian quantum dynamics are also discussed.Comment: 26 pages, 10 figure
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