Statistical theory of finite Fermi systems with chaotic excited eigenstates

A theory of strongly interacting Fermi systems of a few particles is developed. At high excit at ion energies (a few times the single-parti cle level spacing) these systems are characterized by an extreme degree of complexity due to strong mixing of the shell-model-based many-part icle basis st at es by the residual two- body interaction. This regime can be described as many-body quantum chaos. Practically, it occurs when the excitation energy of the system is greater than a few single-particle level spacings near the Fermi energy. Physical examples of such systems are compound nuclei, heavy open shell atoms (e.g. rare earths) and multicharged ions, molecules, clusters and quantum dots in solids. The main quantity of the theory is the strength function which describes spreading of the eigenstates over many-part icle basis states (determinants) constructed using the shell-model orbital basis. A nonlinear equation for the strength function is derived, which enables one to describe the eigenstates without diagonalization of the Hamiltonian matrix. We show how to use this approach to calculate mean orbital occupation numbers and matrix elements between chaotic eigenstates and introduce typically statistical variable s such as t emperature in an isolated microscopic Fermi system of a few particles.

Men, Women and an Integrated History of the Russian Revolutionary Movement

Since its emergence as a discipline in the 1960s, women’s history has had a profound effect on the study of the past. Scholarship on women’s experiences of and contributions to the Russian revolutionary movement has increased exponentially since the publication of a number of biographies of Aleksandra Kollontai in the 1970s and 1980s and a comprehensive picture has emerged of women’s involvement in all the major revolutionary parties, as leading figures as well as rank and file activists. Despite this wealth of historical discovery, remarkably little has found its way into so-called ‘general’ histories of the revolution. An integrated history, which is the ultimate aim of women’s history, has yet to be produced for the Russian revolutionary movement, even though recent prosopographical studies of revolutionary women have made clear the numerous ways in which men and women cooperated and interacted on a daily basis in the underground. This article explores the nature of and reasons for this failure, makes a case for why incorporating women’s experiences into the grand narrative of the Russian revolution is important and discusses how this might be achieved.

Environmental context explains Levy and Brownian movement patterns of marine predators

An optimal search theory, the so-called Levy-flight foraging hypothesis(1), predicts that predators should adopt search strategies known as Levy flights where prey is sparse and distributed unpredictably, but that Brownian movement is sufficiently efficient for locating abundant prey(2-4). Empirical studies have generated controversy because the accuracy of statistical methods that have been used to identify Levy behaviour has recently been questioned(5,6). Consequently, whether foragers exhibit Levy flights in the wild remains unclear. Crucially, moreover, it has not been tested whether observed movement patterns across natural landscapes having different expected resource distributions conform to the theory's central predictions. Here we use maximum-likelihood methods to test for Levy patterns in relation to environmental gradients in the largest animal movement data set assembled for this purpose. Strong support was found for Levy search patterns across 14 species of open-ocean predatory fish (sharks, tuna, billfish and ocean sunfish), with some individuals switching between Levy and Brownian movement as they traversed different habitat types. We tested the spatial occurrence of these two principal patterns and found Levy behaviour to be associated with less productive waters (sparser prey) and Brownian movements to be associated with productive shelf or convergence-front habitats (abundant prey). These results are consistent with the Levy-flight foraging hypothesis(1,7), supporting the contention(8,9) that organism search strategies naturally evolved in such a way that they exploit optimal Levy patterns.

The effect of teachers trained in a fundamental movement skills programme on children’s self-perceptions and motor competence

Perceived and actual motor competence are hypothesized to have potential links to children and young people’s physical activity (PA) levels with a potential consequential link to long-term health. In this cross-sectional study, Harter’s (1985, Manual for the Self-perception Profile for Children. Denver, CO: University of Denver) Competency Motivation-based framework was used to explore whether a group of children taught, during curriculum time, by teachers trained in the Fundamental Movement Skills (FMS) programme, scored higher on self-perception and on core motor competencies when compared to children whose teachers had not been so trained. One hundred and seventy seven children aged 7–8 years participated in the study. One hundred and seven were taught by FMS-trained teachers (FMS) and the remaining 70 were taught by teachers not trained in the programme (non-FMS). The Harter Self-Perception Profile for Children assessed athletic competence, scholastic competence, global self-worth and social acceptance. Three core components of motor competence (body management, object control and locomotor skills) were assessed via child observation. The FMS group scored higher on all the self-perception domains (p < 0.05). Statistically significant differences were found between the schools on all of the motor tasks (p < 0.05). The relationships between motor performance and self-perception were generally weak and non-significant. Future research in schools and with teachers should explore the FMS programme’s effect on children’s motor competence via a longitudinal approach.