Equivalence between the real time Feynman histories and the quantum shutter approaches for the "passage time" in tunneling

We show the equivalence of the functions $G_{\rm p}(t)$ and $|\Psi(d,t)|^2$ for the ``passage time'' in tunneling. The former, obtained within the framework of the real time Feynman histories approach to the tunneling time problem, using the Gell-Mann and Hartle's decoherence functional, and the latter involving an exact analytical solution to the time-dependent Schr\"{o}dinger equation for cutoff initial waves

Reply to the Comment on "Resonant Spectra and the Time Evolution of the Survival and Nonescape Probabilities"

In our paper [Phys. Rev. Lett. 74, 337 (1995)], we derived an exact expression for the survival and nonescape probabilities as an expansion in terms of resonant states. It was shown that these quantities exhibit at long times a different behavior. Although both decay as a power law, they have different exponents. In this paper we show that, contrary to the claim in the Comment of R. M. Cavalcanti (quant-ph/9704023), the nonescape probability decay for long times as an inverse power law.Comment: 1 page, RevTex file, to appear in Phys. Rev. Let

Delay time and tunneling transient phenomena

Analytic solutions to the time-dependent Schr\"odinger equation for cutoff wave initial conditions are used to investigate the time evolution of the transmitted probability density for tunneling. For a broad range of values of the potential barrier opacity $\alpha$, we find that the probability density exhibits two evolving structures. One refers to the propagation of a {\it forerunner} related to a {\it time domain resonance} [Phys. Rev. A {\bf 64}, 0121907 (2001)], while the other consists of a semiclassical propagating wavefront. We find a regime where the {\it forerunners} are absent, corresponding to positive {\it time delays}, and show that this regime is characterized by opacities $\alpha < \alpha_c$. The critical opacity $\alpha_c$ is derived from the analytical expression for the {\it delay time}, that reflects a link between transient effects in tunneling and the {\it delay time}Comment: To be published in Physical Review

Transient tunneling effects of resonance doublets in triple barrier systems

Transient tunneling effects in triple barrier systems are investigated by considering a time-dependent solution to the Schr\"{o}dinger equation with a cutoff wave initial condition. We derive a two-level formula for incidence energies $E$ near the first resonance doublet of the system. Based on that expression we find that the probability density along the internal region of the potential, is governed by three oscillation frequencies: one of them refers to the well known Bohr frequency, given in terms of the first and second resonance energies of the doublet, and the two others, represent a coupling with the incidence energy $E$. This allows to manipulate the above frequencies to control the tunneling transient behavior of the probability density in the short-time regim

La recepción de la obra de William Collins: “Ode to Evening”

Trabajo que se ocupa de uno de los poetas más relevantes del siglo XVIII en Inglaterra, William Collins, que ha estado durante muchos años considerado como un poeta menor, aunque ya él Doctor Jonson en su Lives of the English Poets llamara la atención sobre él (“He wrote now and then odes and other poems, and did something, however little”), del que posteriormente se ha reconocido la importancia de sus Odas, y en concreto la “Ode to Evening”, considerada como una de las mejores odas de la poesía inglesa.The present article focuses on one of the most relevant 18th century English poets, William Collins. Although he had been considered a minor poet for a long time, Doctor Johnson drew his contemporaries‟ attention to him in his Lives of the English Poets (“He wrote now and then odes and other poems, and did something, however little”). Later, he has been later recognised for his odes, especially the “Ode to Evening”, now considered one of the best English odes

Characteristics, production insentives and the availability to pay for ecological milk in Medellin

En este artículo se emplea valoración contingente para evaluar mejoras hipotéticas en la calidad ambiental de la leche, y se encuentra que es posible incentivar su producción, puesto que la disponibilidad a pagar de la demanda estimada en Medellín supera los precios de mercado y los costos de oportunidad de producir leche tradicional, en cuya producción se genera contaminación y degradación de tierras, y hay problemas de control y regulación por los organismos ambientales en Colombia. La lechería ecológica puede hacer parte de los mercados verdes y ser una opción de auto-regulación ambiental al encontrarse un mercado potencial por sus distintos atributos.In this article, contingent valuation is used to evaluate the hypothetical improvements of the environmental quality of milk. Results show that it is possible to encourage its production given that the willingness to pay of the estimated demand for Medellin exceeds market prices and the opportunity costs of producing traditional milk, which during its production generates soil pollution and degradation, and where the Colombian environmental regulation units have problems involving regulations and control. Organic dairy can be part of green markets and an option for environmental self-regulation when finding that potential market with as many attributes as this one.Neste artigo se emprega valoração contingente para avaliar melhoras hipotéticas na qualidade ambiental do leite, e se encontra que é possível incentivar sua produção, já que a que a disponibilidade a pagar da demanda estimada em Medellín supera ospreços de mercado e os custos de oportunidade de produzir leite tradicional, em cuja produção se gera contaminação e degradação de terras, e há problemas de controle e regulação pelos organismos ambientais na Colômbia. A leitaria ecológica pode fazer parte dos mercados verdes e ser uma opção de auto regulação ambiental ao encontrarse um mercado potencial por seus diferentes atributos