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Piotr Garbaczewski

Publications and source records attributed to Piotr Garbaczewski.

51 records · Page 3Linked to original sources
arXiv2005

Comment on "Time-dependent entropy of simple quantum model systems"

In the above mentioned paper by J. Dunkel and S. A. Trigger [Phys. Rev. {\bf A 71}, 052102, (2005)] a hypothesis has been pursued that the loss of information associated with the quantum evolution of pure states, quantified in terms of an increase in time of so-called Leipnik's joint entropy, could be a rather general property shared by many quantum systems. This behavior has been confirmed for the unconfined model systems and properly tuned initial data (maximally classical states). We provide two particular examples which indicate a complexity of the quantum evolution. In the presence of a confining (harmonic) potential Leipnik's entropy may be non-increasing for maximally classical initial data. Another choice of initial data implies periodicity in time of the Leipnik entropy.

quant-ph↗
arXiv2005

A Subtlety of the Schrödinger Picture Dynamics

We address a mathematical and physical status of exotic (like e.g. fractal) wave packets and their quantum dynamics. To this end, we extend the formal meaning of the Schrödinger equation beyond the domain of the Hamiltonian. The dynamical importance of the finite mean energy condition is elucidated.

quant-ph↗
arXiv2005

Shannon versus Kullback-Leibler Entropies in Nonequilibrium Random Motion

We analyze dynamical properties of the Shannon information entropy of a continuous probability distribution, which is driven by a standard diffusion process. This entropy choice is confronted with another option, employing the conditional Kullback-Leibler entropy. Both entropies discriminate among various probability distributions, either statically or in the time domain. An asymptotic approach towards equilibrium is typically monotonic in terms of the Kullback entropy. The Shannon entropy time rate needs not to be positive and is a sensitive indicator of the power transfer processes (removal/supply) due to an active environment. In the case of Smoluchowski diffusions, the Kullback entropy time rate coincides with the Shannon entropy "production" rate.

cond-mat.stat-mech↗
arXiv2004

Dynamics of Uncertainty in Nonequilibrium Random Motion

Shannon information entropy is a natural measure of probability (de)localization and thus (un)predictability in various procedures of data analysis for model systems. We pay particular attention to links between the Shannon entropy and the related Fisher information notion, which jointly account for the shape and extension of continuous probability distributions. Classical, dynamical and random systems in general give rise to time-dependent probability densities and associated information measures. The induced dynamics of Shannon and Fisher functionals reveals an interplay among various characteristics of the considered diffusion-type systems: information, uncertainty and localization while put against mean energy and its balance.

cond-mat.stat-mech↗
arXiv2003

Random Dynamics, Entropy Production and Fisher Information

We analyze a specific role of probability density gradients in the theory of irreversible transport processes. The classic Fisher information and information entropy production concepts are found to be intrinsically entangled with the very notion of the Markovian diffusion process and that of the related (local) momentum conservation law.

cond-mat.stat-mech↗
arXiv2001

Signatures of Randomness in Quantum Chaos

We investigate toy dynamical models of energy-level repulsion in quantum eigenvalue sequences. We focus on parametric (with respect to a running coupling or "complexity" parameter) stochastic processes that are capable of relaxing towards a stationary regime (e. g. equilibrium, invariant asymptotic measure). In view of ergodic property, that makes them appropriate for the study of short-range fluctuations in any disordered, randomly-looking spectral sequence (as exemplified e. g. by empirical nearest-neighbor spacings histograms of various quantum systems). The pertinent Markov diffusion-type processes (with values in the space of spacings) share a general form of forward drifts $b(x) = {{N-1}\over {2x}} - x$, where $x>0$ stands for the spacing value. Here $N = 2,3,5$ correspond to the familiar (generic) random-matrix theory inspired cases, based on the exploitation of the Wigner surmise (usually regarded as an approximate formula). N=4 corresponds to the (non-generic) non-Hermitian Ginibre ensemble. The result appears to be exact in the context of $2\times 2$ random matrices and indicates a potential validity of other non-generic $N>5$ level repulsion laws.

cond-mat.stat-mech↗
arXiv2001

Parametric Dynamics of Level Spacings in Quantum Chaos

We identify parametric (radial) Bessel-Ornstein-Uhlenbeck stochastic processes as primitive dynamical models of energy level repulsion in irregular quantum systems. Familiar GOE, GUE, GSE and non-Hermitian Ginibre universality classes of spacing distributions arise as special cases in that formalism.

quant-ph↗
arXiv2000

Stochastic Models of Exotic Transport

Non-typical transport phenomena may arise when randomly driven particles remain in an active relationship with the environment instead of being passive. If we attribute to Brownian particles an ability to induce alterations of the environment on suitable space-time scales, those in turn must influence their further movement. In that case a general feedback mechanism needs to be respected. By resorting to a specific choice of the particle-bath coupling, an enhanced (super-diffusion) or non-dispersive diffusion-typ processes are found to exist in generically non-equilibrium contexts.

cond-mat.stat-mech↗
arXiv1999

Ornstein-Uhlenbeck-Cauchy Process

We combine earlier investigations of linear systems with Lévy fluctuations [Physica {\bf 113A}, 203, (1982)] with recent discussions of Lévy flights in external force fields [Phys.Rev. {\bf E 59},2736, (1999)]. We give a complete construction of the Ornstein-Uhlenbeck-Cauchy process as a fully computable model of an anomalous transport and a paradigm example of Doob's stable noise-supported Ornstein-Uhlenbeck process. Despite the nonexistence of all moments, we determine local characteristics (forward drift) of the process, generators of forward and backward dynamics, relevant (pseudodifferential) evolution equations. Finally we prove that this random dynamics is not only mixing (hence ergodic) but also exact. The induced nonstationary spatial process is proved to be Markovian and quite apart from its inherent discontinuity defines an associated velocity process in a probabilistic sense.

chao-dyn↗
arXiv1999

Stochastic modelling of nonlinear dynamical systems

We develop a general theory dealing with stochastic models for dynamical systems that are governed by various nonlinear, ordinary or partial differential, equations. In particular, we address the problem how flows in the random medium (related to driving velocity fields which are generically bound to obey suitable local conservation laws) can be reconciled with the notion of dispersion due to a Markovian diffusion process.

chao-dyn↗
arXiv1999

Noise perturbations in the Brownian motion and quantum dynamics

The third Newton law for mean velocity fields is utilised to generate anomalous (enhanced) or non-dispersive diffusion-type processes which, in particular, can be interpreted as a probabilistic counterpart of the Schrödinger picture quantum dynamics.

quant-ph↗
arXiv1998

Perturbations of Noise: The origins of Isothermal Flows

We make a detailed analysis of both phenomenological and analytic background for the "Brownian recoil principle" hypothesis (Phys. Rev. A 46, (1992), 4634). A corresponding theory of the isothermal Brownian motion of particle ensembles (Smoluchowski diffusion process approximation), gives account of the environmental recoil effects due to locally induced tiny heat flows. By means of local expectation values we elevate the individually negligible phenomena to a non-negligible (accumulated) recoil effect on the ensemble average. The main technical input is a consequent exploitation of the Hamilton-Jacobi equation as a natural substitute for the local momentum conservation law. Together with the continuity equation (alternatively, Fokker-Planck), it forms a closed system of partial differential equations which uniquely determines an associated Markovian diffusion process. The third Newton law in the mean is utilised to generate diffusion-type processes which are either anomalous (enhanced), or generically non-dispersive.

cond-mat↗
arXiv1996

Feynman-Kac Kernels in Markovian Representations of the Schroedinger Interpolating Dynamics

Probabilistic solutions of the so called Schrödinger boundary data problem provide for a unique Markovian interpolation between any two strictly positive probability densities designed to form the input-output statistics data for the process taking place in a finite-time interval. The key issue is to select the jointly continuous in all variables positive Feynman-Kac kernel, appropriate for the phenomenological (physical) situation. We extend the existing formulations of the problem to cases when the kernel is \it not \rm a fundamental solution of a parabolic equation, and prove the existence of a continuous Markov interpolation in this case. Next, we analyze the compatibility of this stochastic evolution with the original parabolic dynamics, while assumed to be governed by the temporally adjoint pair of (parabolic) partial differential equations, and prove that the pertinent random motion is a diffusion process. In particular, in conjunction with Born's statistical interpretation postulate in quantum theory, we consider stochastic processes which are compatible with the Schrödinger picture quantum evolution.

quant-ph↗
arXiv1996

Comment on "Why quantum mechanics cannot be formulated as a Markov process"

In the paper with the above title, D. T. Gillespie [Phys. Rev. A 49, 1607, (1994)] claims that the theory of Markov stochastic processes cannot provide an adequate mathematical framework for quantum mechanics. In conjunction with the specific quantum dynamics considered there, we give a general analysis of the associated dichotomic jump processes. If we assume that Gillespie's "measurement probabilities" \it are \rm the transition probabilities of a stochastic process, then the process must have an invariant (time independent) probability measure. Alternatively, if we demand the probability measure of the process to follow the quantally implemented (via the Born statistical postulate) evolution, then we arrive at the jump process which \it can \rm be interpreted as a Markov process if restricted to a suitable duration time. However, there is no corresponding Markov process consistent with the $Z_2$ event space assumption, if we require its existence for all times $t\in R_+$.

quant-ph↗