1,721,321 research outputs found
A non-Boltzmannian behaviour of the energy distribution for quasi-stationary regimes of the Fermi-Pasta-Ulam β system
No full textIn a recent paper [M. Leo, R.A. Leo, P. Tempesta, C. Tsallis, Physical Review E 85 (2012) 031149], the existence of quasi-stationary states for the Fermi-Pasta-Ulam β system has been shown numerically, by analyzing the stability properties of the N/4-mode exact nonlinear solution. Here we study the energy distribution of the modes N/4, N/3 and N/2, when they are unstable, as a function of N and of the initial excitation energy. We observe that the classical Boltzmann weight is repaced by a different weight, expressed by a q-exponential function
On the high-energy stability of the non linear modal solutions for the Fermi-Pasta-Ulam beta system
No full textThermostatistics in the neighbourhoodof the pi-mode solution for theFermi–Pasta–Ulam beta system: fromweak to strong chaos
Full text linkWe consider a π-mode solution of the Fermi–Pasta–Ulam β system.
By perturbing it, we study the system as a function of the energy density from a
regime where the solution is stable to a regime where it is unstable, first weakly
and then strongly chaotic. We introduce, as an indicator of stochasticity, the
ratio ρ (when it is defined) between the second and the first moment of a given
probability distribution. We will show numerically that the transition between
weak and strong chaos can be interpreted as the symmetry breaking of a set
of suitable dynamical variables. Moreover, we show that in the region of weak
chaos there is numerical evidence that the thermostatistic is governed by the
Tsallis distribution
Finding frequent items in parallel
No full textWe present a deterministic parallel algorithm for the k-majority problem, that can be used to find in parallel frequent items, i.e. those whose multiplicity is greater than a given threshold, and is therefore useful to process iceberg queries and in many other different contexts of applied mathematics and information theory. The algorithm can be used both in the online (stream) context and in the offline setting, the difference being that in the former case we are restricted to a single scan of the input elements, so that verifying the frequent items that have been determined is not allowed (e.g. network traffic streams passing through internet routers), while in the latter a parallel scan of the input can be used to determine the actual k-majority elements. To the best of our knowledge, this is the first parallel algorithm solving the proposed problem
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
Non-Maxwellian behavior and quasistationary regimes near the modal solutions of the Fermi-Pasta-Ulam \beta system
No full textVariations 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
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