Plasticity in current-driven vortex lattices

We present a theoretical analysis of recent experiments on current-driven vortex dynamics in the Corbino disk geometry. This geometry introduces controlled spatial gradients in the driving force and allows the study of the onset of plasticity and tearing in clean vortex lattices. We describe plastic slip in terms of the stress-driven unbinding of dislocation pairs, which in turn contribute to the relaxation of the shear, yielding a nonlinear response. The steady state density of free dislocations induced by the applied stress is calculated as a function of the applied current and temperature. A criterion for the onset of plasticity at a radial location $r$ in the disk yields a temperature-dependent critical current that is in qualitative agreement with experiments.Comment: 11 pages, 4 figure

Action Curves and Clockwork Geniuses

Earlier analyses of the generation and spread of innovation led me to look into the generator and scatterer, man. Applying the same analytic techniques as are used for examining societal structures, I found that man is highly ordered and regulated. His output therefore can be simply described and, to an extent, predicted. This generalizes the principle that the biological paradigm can be extended to social behavior

The Car in a System Context. The Last 80 Years and the Next 20

The car is examined as a world system, concentrating on numbers and behavior and abstracting from most of technical details. Three parameter logistics appear to fit well the penetration of cars in various areas, and show a remarkable relationship between time of introduction and rate of penetration, Innovation and publicity do not show as tools for aggressive behavior, but more as homeostatic channels, Also safety appears under societal control. The position of Japan in the game is sketched, with medium term forecasts

Spontaneous patterns in coherently driven polariton microcavities

We consider a polariton microcavity resonantly driven by two external lasers which simultaneously pump both lower and upper polariton branches at normal incidence. In this setup, we study the occurrence of instabilities of the pump-only solutions towards the spontaneous formation of patterns. Their appearance is a consequence of the spontaneous symmetry breaking of translational and rotational invariance due to interaction induced parametric scattering. We observe the evolution between diverse patterns which can be classified as single-pump, where parametric scattering occurs at the same energy as one of the pumps, and as two-pump, where scattering occurs at a different energy. For two-pump instabilities, stripe and chequerboard patterns become the dominant steady-state solutions because cubic parametric scattering processes are forbidden. This contrasts with the single-pump case, where hexagonal patterns are the most common arrangements. We study the possibility of controlling the evolution between different patterns. Our results are obtained within a linear stability analysis and are confirmed by finite size full numerical calculations.Comment: 15 pages, 9 figure

On Progress and Providence

Long term forecasting requires a deep knowledge of the secular mechanisms operating inside a society. A brief historical analysis given here reports on the flow and convergence of the basic concepts and attitudes leading to the blossom of Western science and technology in the last two centuries

Renewable Energies in a Historical Context

The question of renewable energy is first re-defined in the appropriate physical context. The question of primary energies use and substitution is re-defined in the appropriate socio-economic (cultural) context. The conclusion is that for the next future (50 years), the most likely use of renewable energies is in special niches, where they can provide unique services and are not in an all-out conquest of the global energy market

On 10^12: A Check on Earth Carrying Capacity for Man

Much has been said about the carrying capacity of the planet Earth, and with most contradictory results, as the arguments have too often been used in the service of prejudices. In this essay we have made a static cross-section of a world very heavily populated by present standards; examined with a system view the level of basic necessities plus luxuries for this population; and indicated the technology to satisfy them. Where problems of a global level appeared, a geo-engineering solution has been sketched. The result of this analysis is that from a technological point of view a trillion people can live beautifully on the Earth, for an unlimited time, without exhausting any primary resource and without overloading the environment. The global view of the problems and of their solutions makes the difference, and shows that most of the physical limits to growth stem from an inappropriate frame of reference

Energy Systems - The Broader Context

Energy and energy systems are fashionable subjects, and this has generated a lot of papers, apparently beyond the carrying capacity of the subjacent methodology. In this written version of a presentation at the Third Energy Status Report, various examples serve to show the highly unsatisfactory situation, pointing especially to the internal contradiction of results. Some hints are given about the potential of an analysis based on information theory and the negentropy concept, and about the signifigance of a search for precise methods of forecasting

Innovation: A Vigorous River with High Banks

In this paper, prepared for the Beijing International Conference on Science and Technology Policy and Research Management, Dr. Cesare Marchetti explains that economics is basically an expression of culture rather than a mere assembly of money, managers, and machines, and argues that economic decisions should always be weighted and selected in a cultural context if they are to have a lasting and constructive effect. He shows that the introduction of new technologies in the western world seems to demonstrate the same behavior as a biological species filling an ecological niche, and that this leads to long waves, or cycles, of innovation. Finally, he considers the implications of these results for technology development in China