Cooperation in neural systems: Bridging complexity and periodicity

Cooperation in neural systems: Bridging complexity and periodicity

Date: November 29, 2012
Creator: Zare, Marzieh & Grigolini, Paolo
Description: This article discusses cooperation in neural systems. Abstract: Inverse power law distributions are generally interpreted as a manifestation of complexity, and waiting time distributions with power index μ < 2 reflect the occurrence of ergodicity-breaking renewal events. In this paper we show how to combine these properties with the apparently foreign clocklike nature of biological processes. We use a two-dimensional regular network of leaky integrate-and-fire neurons, each of which is linked to its four nearest neighbors, to show that both complexity and periodicity are generated by locality breakdown: Links of increasing strength have the effect of turning local interactions into long-range interactions, thereby generating time complexity followed by time periodicity. Increasing the density of neuron firings reduces the influence of periodicity, thus creating a cooperation-induced renewal condition that is distinctly non-Poissonian.
Contributing Partner: UNT College of Arts and Sciences
Scaling Detection in Time Series: Diffusion Entropy Analysis

Scaling Detection in Time Series: Diffusion Entropy Analysis

Date: September 25, 2002
Creator: Scafetta, Nicola & Grigolini, Paolo
Description: This article discusses scaling detection in time series. The methods currently used to determine the scaling exponent of a complex dynamic process described by a time series are based on the numerical evaluation of variance. This means that all of them can be safely applied only to the case where ordinary statistical properties hold true even if strange kinetics are involved. The authors illustrate a method of statistical analysis based on the Shannon entropy of the diffusion process generated by the time series, called diffusion entropy analysis (DEA). The authors adopt artificial Gauss and Lévy time series, as prototypes of ordinary and anomalous statistics, respectively, and the authors analyze them with the DEA and four ordinary methods of analysis, some of which are very popular. The authors show that the DEA determines the correct scaling exponent even when the statistical properties, as well as the dynamic properties, are anomalous. The other four methods produce correct results in the Gauss case but fail to detect the correct scaling in the case of Lévy statistics.
Contributing Partner: UNT College of Arts and Sciences
Quantum Entanglement and Entropy

Quantum Entanglement and Entropy

Date: August 20, 2001
Creator: Giraldi, Filippo & Grigolini, Paolo
Description: This article discusses quantum entanglement and entropy. Entanglement is the fundamental quantum property behind the now popular field of quantum transport of information. This quantum property is incompatible with the separation of a single system into two uncorrelated subsystems. Consequently, it does not require the use of an additive form of entropy. The authors discuss the problem of the choice of the most convenient entropy indicator, focusing their attention on a system of two qubits, and on a special set, denoted by ℑ. This set contains both the maximally and partially entangled states that are described by density matrices diagonal in the Bell basis set. The authors select this set for the main purpose of making their work of analysis more straightforward. As a matter of fact, the authors find that in general the conventional von Neumann entropy is not a monotonic function of the entanglement strength. This means that the von Neumann entropy is not a reliable indicator of the departure from the condition of maximum entanglement. The authors study the behavior of a form of nonadditive entropy, made popular by the 1988 work by Tsallis [J. Stat. Phys. 52, 479 (1988)]. The authors show that in the set ...
Contributing Partner: UNT College of Arts and Sciences
Networking of psychophysics, psychology, and neurophysiology

Networking of psychophysics, psychology, and neurophysiology

Date: November 5, 2012
Creator: West, Bruce J. & Grigolini, Paolo
Description: This article focuses on dynamic networking and dynamic networks in complex research on psychophysics, psychology, and neurophysiology. It states that new ways were suggested by dynamic networking and dynamic networks to transfer information utilizing the long-distance communication through local cooperative interaction. It says that the fluctuations in brain and social dynamics reveal the emergence of complex behavior when analyzed with advanced methods of fractal statistical analysis.
Contributing Partner: UNT College of Arts and Sciences
Sun-Climate Complexity Linking

Sun-Climate Complexity Linking

Date: February 29, 2008
Creator: West, Bruce J. & Grigolini, Paolo
Description: This article discusses sun-climate complexity linking. It is known that Earth's short-term temperature anomalies share the same complexity index μ as solar flares. The authors show that this property is not accidental and is a consequence of the phenomenon of information transfer based on the crucial role of non-Poisson renewal events in complex networks.
Contributing Partner: UNT College of Arts and Sciences
Non-Markovian Nonstationary Completely Positive Open-Quantum-System Dynamics

Non-Markovian Nonstationary Completely Positive Open-Quantum-System Dynamics

Date: August 4, 2009
Creator: Budini, Adrián A. & Grigolini, Paolo
Description: This article discusses non-Markovian nonstationary completely positive open-quantum-system dynamics. By modeling the interaction of a system with an environment through a renewal approach, the authors demonstrate that completely positive non-Markovian dynamics may develop some unexplored nonstandard statistical properties. The renewal approach is defined by a set of disruptive events, consisting in the action of a completely positive superoperator over the system density matrix. The random time intervals between events are described by an arbitrary waiting-time distribution. The authors show that, in contrast to the Markovian case, if one performs a system preparation (measurement) at an arbitrary time, the subsequent evolution of the density-matrix evolution is modified. The nonstationary character refers to the absence of an asymptotic master equation even when the preparation is performed at arbitrary long times. In spite this property, the authors demonstrate that operator expectation values and operators correlations have the same dynamical structure, establishing the validity of a nonstationary quantum regression hypothesis. The nonstationary property of the dynamics is also analyzed through the response of the system to an external weak perturbation.
Contributing Partner: UNT College of Arts and Sciences
The Markov approximation revisited: inconsistency of the standard quantum Brownian motion model

The Markov approximation revisited: inconsistency of the standard quantum Brownian motion model

Date: February 1999
Creator: Rocco, A. (Andrea) & Grigolini, Paolo
Description: This article discusses the Markov approximation. Abstract: We revisit the Markov approximation necessary to derive ordinary Brownian motion from a model widely adopted in literature for this specific purpose. We show that this leads to internal inconsistencies, thereby implying that further search for a more satisfactory model is required.
Contributing Partner: UNT College of Arts and Sciences
Canonical and noncanonical equilibrium distribution

Canonical and noncanonical equilibrium distribution

Date: 2001
Creator: Annunziato, Mario; Grigolini, Paolo & West, Bruce J.
Description: This article discusses canonical and noncanonical equilibrium distribution. Abstract: We address the problem of the dynamical foundation of noncanonical equilibrium. We consider, as a source of divergence from ordinary statistical mechanics, the breakdown of the condition of time scale separation between microscopic and macroscopic dynamics. We show that this breakdown has the effect of producing a significant deviation from the canonical prescription. We also show that, while the canonical equilibrium can be reached with no apparent dependence on dynamics, the specific form of noncanonical equilibrium is, in fact, determined by dynamics. We consider the special case where the thermal reservoir driving the system of interest to equilibrium is a generator of intermittent fluctuations. We assess the form of the noncanonical equilibrium reached by the system in this case. Using both theoretical and numerical arguments we demonstrate that Lévy statistics are the best description of the dynamics and that the Lévy distribution is the correct basin of attraction. We show that the correct path to noncanonical equilibrium by means of strictly thermodynamic arguments has not yet been found, and that further research has to be done to establish a connection between dynamics and thermodynamics.
Contributing Partner: UNT College of Arts and Sciences
Absorption and Emission in the Non-Poissonian Case

Absorption and Emission in the Non-Poissonian Case

Date: July 28, 2004
Creator: Aquino, Gerardo; Palatella, Luigi & Grigolini, Paolo
Description: This article discusses absorption and emission in the Non-Poissonian Case. Abstract: This Letter addresses the challenging problems posed to the Kubo-Anderson (KA) theory by the discovery of intermittent resonant fluorescence with a nonexponential distribution of waiting times. We show how to extend the KA theory from aged to aging systems, aging for a very extended time period or even forever, being a crucial consequence of non-Poisson statistics.
Contributing Partner: UNT College of Arts and Sciences
Anomalous diffusion associated with nonlinear fractional derivative Fokker-Planck-like equation: Exact time-dependent solutions

Anomalous diffusion associated with nonlinear fractional derivative Fokker-Planck-like equation: Exact time-dependent solutions

Date: August 2000
Creator: Bologna, Mauro; Tsallis, Constantino & Grigolini, Paolo
Description: This article discusses anomalous diffusion associated with nonlinear fractional derivative Fokker-Planck-like equation. Abstract: We consider the d=1 nonlinear Fokker-Planck-like equation with fractional derivatives (∂/∂t)P(x,t) = D(∂ƴ/∂xƴ)[P(x,t]v. Exact time-dependent solutions are found for v = (2 - y)/(1 + y)(-∞ < y ⩽ 2). By considering the long-distance asymptotic behavior of these solutions, a connection is established, namely, q = (y + 3)/(Y + 1)(0 < y ⩽ 2), with the solutions optimizing the nonextensive entropy characterized by index q. Interestingly enough, this relation coincides with the only already known for Lévy-like superdiffusion (i.e., v = 1 and 0 < y ⩽ 2). Finally, for (y,v) = (2,0) the authors obtain q=5/3, which differs from the value q = 2 corresponding to the y = 2 solutions available in the literature (v < 1 porous medium equation), thus exhibiting nonuniform convergence.
Contributing Partner: UNT College of Arts and Sciences
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