1,721,320 research outputs found
Enhancement of stability of metastable states in the presence of L\'{e}vy noise
Full text linkThe barrier crossing event for superdiffusion in the form of symmetric
L\'{e}vy flights is investigated. We derive from the fractional Fokker-Planck
equation a general differential equation with the corresponding conditions
useful to calculate the mean residence time of a particle in a fixed interval
for an arbitrary smooth potential profile, in particular metastable, with a
sink and a L\'{e}vy noise with an arbitrary index . A closed expression
in quadrature of the nonlinear relaxation time for L\'{e}vy flights with the
index in cubic metastable potential is obtained. Enhancement of the
mean residence time in the metastable state, analytically derived, due to
L\'{e}vy noise is found.Comment: 7 pages, 3 figure
Pattern formation and spatial correlation induced by the noise in two competing species
Full text linkWe analyze the spatio-temporal patterns of two competing species in the presence of two white noise sources: an additive noise acting on the interaction parameter and a multiplicative noise which aects directly the dynamics of the species densities. We use a coupled map lattice (CML) with uniform initial conditions. We nd a nonmonotonic behavior both of the pattern formation and the density correlation as a function of the multiplicative noise intensity
New trends in nonequilibrium statistical mechanics: classical and quantum systems
No full textThe main aim of this special issue is to report recent advances and new trends in nonequilibrium statistical mechanics of classical and quantum systems, from both theoretical and experimental points of view, within an interdisciplinary context. In particular, the nonlinear relaxation processes in the dynamics of out-of-equilibrium systems and the role of the metastability and environmental noise will be overviewed. Three main areas of nonequilibrium statistical mechanics will be covered: slow relaxation phenomena and dissipative dynamics; long-range interactions and classical systems; quantum systems. New trends such as quantum thermodynamics and novel types of quantum phase transitions occurring in nonequilibrium steady states and topological phase transitions will be also highlighted
Open challenges in environmental data analysis and ecological complex system
Full text linkThis letter focuses on open challenges in the fields of environmental data analysis and ecological complex systems. It highlights relations between research problems in stochastic population dynamics, machine learning and big data research, and statistical physics. Recent and current developments in statistical modeling of spatiotemporal data and in population dynamics are briefly reviewed. The presentation emphasizes stochastic fluctuations, including their statistical representation, data-based estimation, prediction, and impact on the physics of the underlying systems. Guided by the common thread of stochasticity, a deeper and improved understanding of environmental processes and ecosystems can be achieved by forging stronger interdisciplinary connections between statistical physics, spatiotemporal data modeling, and ecology
Analysis of ecological shifts in the two-age structured population model with Allee effect and environmental noise
No full textWe study noise-induced transformations in the two-age structured population model with the Allee effect and environmental fluctuations. In this bistable model, ecological shifts are associated mathematically with random transitions between basins of coexisting attractors. The following phenomena are revealed and studied: (i) noise-induced extinction, (ii) stochastic regeneration, and (iii) excitement of random mixed-mode oscillations. Constructive abilities of the analytical method of confidence domains are demonstrated in the parametric study of these phenomena
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Josephson-junction-based axion detection through resonant activation
Full text linkWe discuss the resonant activation phenomenon on a Josephson junction due to the coupling of the Josephson system with axions. We show how such an effect can be exploited for axion detection. A nonmonotonic behavior, with a minimum, of the mean switching time from the superconducting to the resistive state versus the ratio of the axion energy and the Josephson plasma energy is found. We demonstrate how variations in switching times make it possible to detect the presence of the axion field. An experimental protocol for observing axions through their coupling with a Josephson system is proposed
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