186,373 research outputs found
Theory of transient response for arbitrarily strong driving fields
No full textA theory of the dynamical Kerr effect is developed for arbitrarily strong driving fields using a modification of the Mori equation of motion due to Grigolini et al. Using the multidimensional expansion of Grigolini and Ferrario the non-Markovian Mori equation may be written in Markov form. It is possible then to derive a macro–micro correlation theorem for the system by applying the method of Kivelson et al. In this way it is possible to bypass the linear response approximation of classical dielectric theory
Levy scaling: The diffusion entropy analysis applied to DNA sequences
No full textWe address the problem of the statistical analysis of a time series generated by complex dynamics with the diffusion entropy analysis (DEA) [N. Scafetta, P. Hamilton, and P. Grigolini, Fractals 9, 193 (2001)]. This method is based on the evaluation of the Shannon entropy of the diffusion process generated by the time series imagined as a physical source of fluctuations, rather than on the measurement of the variance of this diffusion process, as done with the traditional methods. We compare the DEA to the traditional methods of scaling detection and prove that the DEA is the only method that always yields the correct scaling value, if the scaling condition applies. Furthermore, DEA detects the real scaling of a time series without requiring any form of detrending. We show that the joint use of DEA and variance method allows to assess whether a time series is characterized by Lévy or Gauss statistics. We apply the DEA to the study of DNA sequences and prove that their large-time scales are characterized by Lévy statistics, regardless of whether they are coding or noncoding sequences. We show that the DEA is a reliable technique and, at the same time, we use it to confirm the validity of the dynamic approach to the DNA sequences, proposed in earlier work
Quantum jump as an objective process of nature
No full textWe study the time evolution of a linear superposition of two spatially separated wave packets, and we focus on the entanglement of the two distinct branches of the state vector with the environment. We focus in particular on the dynamics of a dissipative oscillator under the influence of objective processes of wave-function collapse, the continuous spontaneous localizations (CSL) recently proposed by Ghirardi et al. [G. C. Ghirardi, P. Pearle, and A. Rimini, Phys. Rev. A 42, 78 (1990)]. We prove that the entanglement of the system of interest with the environment induces an accumulation of spontaneous wave-function collapses denoted by us as the environment-enhanced CSL process. This process of CSL accumulation is triggered by the same mechanism of interaction between the quantum system and the environment as that responsible for relaxation and dissipation. In agreement with the predictions of a preceding paper of our group [D. Vitali, L. Tessieri, and P. Grigolini, Phys. Rev. A 50, 967 (1994)], the CSL processes are shown to produce negligible effects at the statistical level. However, if we assume the attitude stimulated by the recent literature on optical quantum jumps, which is forcing us to adopt individual-system pictures, we show that the single runs are characterized by processes of wave-function collapses occurring at times compatible in principle with the experimental observation
Emergence and Exploitation of Collective Intelligence of Groups
No full textThis dissertation deals with the emergence and exploitation of the collective intelligence of human groups. The first part of the work (chapter 2) aims to review the mechanisms beyond the swarming behaviors in natural systems, focusing on their properties, potentialities, and limitations, as well as providing the state of the art in the developing field of swarm robotics. In chapter 3, some of the most known biologically inspired optimization algorithms, are introduced, highlighting their variants, merits and drawbacks.
In chapter 4, the author introduces a new decision-making model (DMM), firstly proposed by Carbone and Giannoccaro (Carbone & Giannoccaro, 2015) for solving complex combinatorial problems, showing a detailed analysis of its features and potentialities.
In Chapter 5 an application of the DMM to the simulation of a management problem, easily adaptable to the simulation of any kind of social decision-making problems, is reported.
In chapter 6 the author introduces a novel optimization algorithm belonging to the class of swarm intelligence optimization methods. The proposed algorithm, referred as Human Group Optimization algorithm (HGO), is developed within the previously mentioned DMM (Carbone & Giannoccaro, 2015) and emulates the collective decision making process of human groups. To test the ability of the HGO algorithm, we compare its performance with those of the Simulated Annealing (SA), and Genetic Algorithm (GA) in solving NP-complete problems, consisting in finding the optimum on a fitness landscape, the latter generated within the Kauffman NK model of complexity.
Chapter 8 contains all the mathematical tools and the basic notions, necessary to a complete understanding of the models and procedures mentioned in the work
Scaling detection in time series: Diffusion entropy analysis
No full textThe 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. We 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). We adopt artificial Gauss and Lévy time series, as prototypes of ordinary and anomalous statistics, respectively, and we analyze them with the DEA and four ordinary methods of analysis, some of which are very popular. We 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
RESONANT ACTIVATION OF A BROWNIAN PARTICLE OUT OF A POTENTIAL WELL - REMARKS ON SOME RECENT THEORETICAL AND EXPERIMENTAL INVESTIGATIONS
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ON THE CONTRACTION OF FAST VARIABLES IN STOCHASTIC-PROCESSES - THE INFLUENCE OF PUMPING ON RELAXATION
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UNITARY POINT-OF-VIEW ON THE PUZZLING PROBLEM OF NONLINEAR-SYSTEMS DRIVEN BY COLORED NOISE
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