Collective motion occurs inevitably in a class of populations of globally coupled chaotic elements

We discovered numerically a scaling law obeyed by the amplitude of collective mo tion in large populations of chaotic elements. Our analysis strongly suggests that such populations generically exhibit collective motion in the presence of interaction, however weak it may be. A phase diagram for the collective motion, which is characterized by peculiar structures similar to Arnold tongues, is obtained.Comment: 6 pages, 9 Postscript figures, uses revtex.st

Thermodynamic Irreversibility from high-dimensional Hamiltonian Chaos

This paper discusses the thermodynamic irreversibility realized in high-dimensional Hamiltonian systems with a time-dependent parameter. A new quantity, the irreversible information loss, is defined from the Lyapunov analysis so as to characterize the thermodynamic irreversibility. It is proved that this new quantity satisfies an inequality associated with the second law of thermodynamics. Based on the assumption that these systems possess the mixing property and certain large deviation properties in the thermodynamic limit, it is argued reasonably that the most probable value of the irreversible information loss is equal to the change of the Boltzmann entropy in statistical mechanics, and that it is always a non-negative value. The consistency of our argument is confirmed by numerical experiments with the aid of the definition of a quantity we refer to as the excess information loss.Comment: LaTeX 43 pages (using ptptex macros) with 11 figure

A heat pump at a molecular scale controlled by a mechanical force

We show that a mesoscopic system such as Feynman's ratchet may operate as a heat pump, and clarify a underlying physical picture. We consider a system of a particle moving along an asymmetric periodic structure . When put into a contact with two distinct heat baths of equal temperature, the system transfers heat between two baths as the particle is dragged. We examine Onsager relation for the heat flow and the particle flow, and show that the reciprocity coefficient is a product of the characteristic heat and the diffusion constant of the particle. The characteristic heat is the heat transfer between the baths associated with a barrier-overcoming process. Because of the correlation between the heat flow and the particle flow, the system can work as a heat pump when the particle is dragged. This pump is particularly effective at molecular scales where the energy barrier is of the order of the thermal energy.Comment: 7 pages, 5 figures; revise

Labor Force Participation, Gender and Work in South Africa: What Can Time Use Data Reveal?

The utilization of time use data for exploring employment issues has received little attention in economic analysis. Using data from the 2000 South African national time use survey we argue that a gender-aware understanding of how men and women organize their daily life can help identify labor market and subsistence work that are missed in labor force surveys, thus complementing the information they provide. Further, information on the time spent in jobrelated search and household work provide insights on the interconnectedness of gender inequalities in the labor market and within the household. Our analysis of the time use patterns of 10,465 working age women and men, shows that a non-trivial proportion of men and women classified as either "not in the labor force" or "unemployed" actually engaged in subsistence, temporary and casual forms of employment. Secondly, we find that regardless of their labor force status, women's and men's hours of unpaid work donot vary greatly. These affect not only employment options of women but also their ability to look for work. Thirdly, time use data helps identify the salient characteristics of these individuals and the type of occupations they are engaged in.time allocation, gender, labor force participation, South Africa JEL Codes: E24, J22

Igneous and tectonic evolution of Venusian and terrestrial coronae

A great variety of tectonic and volcanic features have been documented on Venus. It is widely appreciated that there are close spatial associations among certain types of tectonic structures and some classes of volcanic flows and constructs. Coronae are endowed with a particularly rich variety of volcanism. It is thought that coupled tectonic and volcanic aspects of coronae are cogenetic manifestations of mantle plumes. An outstanding feature of most venusian coronae is their circular or elliptical shape defined by peripheral zones of fracturing and/or folding. Some coronae are composite, consisting of two or more small coronae within a larger enclosing corona, suggesting complex histories of structured diapirism analogous in some ways to salt dome tectonics. Coronae range widely in size, from smaller than 100 km to over 1000 km in diameter. Volcanic features associated with venusian coronae include lunar-like sinuous rilles, thin lava flows, cinder cone-like constructs, shield volcanos, and pancake domes. Several types of volcanic features are often situated within or near a single corona, in many instances including land-forms indicating effusions of both low- and high-viscosity lavas. In some cases stratigraphic evidence brackets emplacement of pancake domes during the period of tectonic development of the corona, thus supporting a close link between the igneous and tectonic histories of coronae. These associations suggest emplacement of huge diapirs and massive magmatic intrusions, thus producing the tectonic deformations defining these structures. Igneous differentiation of the intrusion could yield a range of lava compositions. Head and Wilson suggested a mechanism that would cause development of neutral buoyancy zones in the shallow subsurface of Venus, thereby tending to promote development of massive igneous intrusions