Energy transfer dynamics and thermalization of two oscillators interacting via chaos

We consider the classical dynamics of two particles moving in harmonic potential wells and interacting with the same external environment (HE), consisting of N non-interacting chaotic systems. The parameters are set so that when either particle is separately placed in contact with the environment, a dissipative behavior is observed. When both particles are simultaneously in contact with HE an indirect coupling between them is observed only if the particles are in near resonance. We study the equilibrium properties of the system considering ensemble averages for the case N=1 and single trajectory dynamics for N large. In both cases, the particles and the environment reach an equilibrium configuration at long times, but only for large N a temperature can be assigned to the system.Comment: 8 pages, 6 figure

Kondo effect in transport through molecules adsorbed on metal surfaces: from Fano dips to Kondo peaks

The Kondo effect observed in recent STM experiments on transport through CoPc and TBrPP-Co molecules adsorbed on Au(111) and Cu(111) surfaces, respectively, is discussed within the framework of a simple model (Phys. Rev. Lett. {\bf 97}, 076806 (2006)). It is shown that, in the Kondo regime and by varying the adequate model parameters, it is possible to produce a crossover from a conductance Kondo peak (CoPc) to a conductance Fano dip (TBrPP-Co). In the case of TBrPP-Co/Cu(111) we show that the model reproduces the changes in the shape of the Fano dip, the raising of the Kondo temperature and shifting to higher energies of the dip minimum when the number of nearest neighbors molecules is lowered. These features are in line with experimental observations indicating that our simple model contains the essential physics underlying the transport properties of such complex molecules.Comment: 4 pages, 3 figures, submitted to PR

Relación entre los factores de circulación atmosférica regional y de la cupla océano - atmósfera con los derrames extremos de los ríos San Juan y Mendoza

Dada la crisis hídrica que soporta Cuyo en la actualidad, agudizada desde 2010, resulta fundamental investigar la variabilidad temporal de los derrames anuales de los ríos de los Andes Áridos, que dependen esencialmente de la provisión de agua proveniente de un régimen nival de alta montaña, con el fin de identificar sus tendencias decrecientes y caracterizar sus periodos extremos; por ser los más perjudiciales para las actividades socioeconómicas. Los autores estudiaron la estructura temporal de los derrames de dichos ríos verificando diferencias marcadas entre ambos durante los eventos extremos, tanto excesos como sequías, ocasionados principalmente por la influencia de las temperaturas superficiales del mar en el área "Niño" 3+4, estado del Anticiclón del Pacífico Sur y Oscilación Decadal Pacífica, entre otros, pertenecientes a la circulación regional. Por lo que en este artículo pretenden encontrar el origen dinámico de esas diferencias.Given the water crisis currently supports Cuyo, intensified since 2010, it is essential to investigate the temporal variability of annual runoff from the Arid Andes rivers, in order to identify their declining secular trends and further characterize the extreme periods; since these happen to be the most harmful to the socio-economic activities. Despite its negative effects they were minimized since 1980 by the existence of dams. Both are the main factor of economic development: intensive farming practiced in the great oasis of Mendoza and San Juan, which depends essentially of provision of water from these rivers. They have a snowy regime related to the Arid Andes. The authors studied the temporal structure of runoff verifying these rivers had differences during extreme events, both excesses as well as drought caused mainly by the influence of sea surface temperatures in the "Niño" 3 + 4, the status of South Pacific Anticyclone and Pacific Decadal Oscillation and other factors belong to regional circulation. The aim of this article is to find the dynamical origin of these differences.Fil: Poblete, Arnobio G.. Universidad Nacional de San JuanFil: Aguiar, Laura A.. Universidad Nacional de San Jua

Comment on the Adiabatic Condition

The experimental observation of effects due to Berry's phase in quantum systems is certainly one of the most impressive demonstrations of the correctness of the superposition principle in quantum mechanics. Since Berry's original paper in 1984, the spin 1/2 coupled with rotating external magnetic field has been one of the most studied models where those phases appear. We also consider a special case of this soluble model. A detailed analysis of the coupled differential equations and comparison with exact results teach us why the usual procedure (of neglecting nondiagonal terms) is mathematically sound.Comment: 9 page

Stochastic Quantization of Real-Time Thermal Field Theory

We use the stochastic quantization method to obtain the free scalar propagator of a finite temperature field theory formulated in Minkowski spacetime. First we use the Markovian stochastic quantization approach to present the two-point function of the theory. Second, we assume a Langevin equation with a memory kernel and Einstein's relations with colored noise. The convergence of the stochastic processes in the asymptotic limit of the Markov parameter of these Markovian and non-Markovian Langevin equations for a free scalar theory is obtained. Our formalism can be the starting point to discuss systems at finite temperature out of equilibrium

Using the Sound Card as a Timer

Experiments in mechanics can often be timed by the sounds they produce. In such cases, digital audio recordings provide a simple way of measuring time intervals with an accuracy comparable to that of photogate timers. We illustrate this with an experiment in the physics of sports: to measure the speed of a hard-kicked soccer ball.Comment: 3 pages, 4 figures, Late