Superstatistics from a different perspective

In this paper we elaborate on the recently proposed superstatistics formalism [C. Beck and E.G.D. Cohen, Physica A 322, 267 (2003)], used to interpret unconventional statistics. Their interpretation is that unconventional statistics in dynamical systems arise as weighted averages of the ordinary statistics obeyed by these systems over a statistical distribution of background configurations due to fluctuations intrinsic to the background. In this paper we suggest that the same picture can arise because of the intrinsic dynamics of the system. The dynamics of the system and the background, hence, concur together to determine the overall final statistics: differently evolving systems embedded within the same background can yield different statistical distributions. Some simple examples are provided; among them a toy model able to yield a power-law distribution. Also, some recent independent results are quoted, that appear to support this viewpoint.Comment: 10 pages. Final version to appear in Physica

Bayesian approach to superstatistics

The superstatistics approach recently introduced by Beck [C. Beck and E.G.D. Cohen, Physica A 322, 267 (2003)] is a formalism that aims to deal in a unifying way with a large variety of complex nonequilibrium systems, for which spatio-temporal fluctuations of one intensive variable (the "temperature" 1/b) are supposed to exist. The intuitive explanation provided by Beck for superstatistics is based on the ansatz that the system under consideration, during its evolution, travels within its phase space which is partitioned into cells. Within each cell, the system is described by ordinary Maxwell-Boltzmann statistical mechanics, i.e., its statistical distribution is the canonical one, but b varies from cell to cell, with its own probability density f(b). In this work we first address that the explicit inclusion of the density of states in this description is essential for its correctness. The correction is not relevant for developments of the theory, but points to the fact that its correct starting point, as well its meaning, must be found at a more basic level: the pure probability product rule involving the intensive variable b and its conjugate extensive one. The question therefore arises how to assign a meaning to these probabilities for each specific problem. We will see that it is easily answered through Bayesian analysis. This way, we are able to provide an interpretation for f(b), that was not fully elucidated till now.Comment: 13 pages. To be published in The European Physics Journal

Further study of the Over-Barrier Model to compute charge exchange processes

In this paper we study theoretically the process of electron capture between one-optical-electron atoms (e.g. hydrogenlike or alkali atoms) and ions at low-to-medium impact velocities ($v/v_e \approx 1$) working on a modification of an already developed classical In this work we present an improvement over the Over Barrier Model (OBM) described in a recent paper [F. Sattin, Phys. Rev. A {\bf 62}, 042711 (2000)]. We show that: i) one of the two free parameters there introduced actually comes out consistently from the starting assumptions underlying the model; ii) the modified model thus obtained is as much accurate as the former one. Furthermore, we show that OBMs are able to accurately predict some recent results of state selective electron capture, at odds with what previously supposed.Comment: RevTeX, 7 pages, 4 eps figures. To appear in Physical Review A (2001-september issue

SWKB for the Angular Momentum

In this paper we solve the eigenvalue problem of the angular momentum operator by using the supersymmetric semiclassical quantum mechanics (SWKB), and show that it gives the correct quantization already at the leading order.Comment: latex, 9 pages, no figures, to be published in Modern Physics Letters

Chaos in coplanar classical collisions with particles interacting through 1/r21/r^2 forces

The scattering among three particles interacting through $1/r^2$ forces, with opposite charges and widely different masses, is studied in a coplanar geometry. The present work shows that at low impact velocities the output of the collision presents typical fingerprints of chaos. The details of the process are investigated.Comment: ReVTeX (uses epsf), 8 pages, 5 figs. To be published as a Brief Report in Phys. Rev.