Exact propagators for atom-laser interactions

A class of exact propagators describing the interaction of an $N$-level atom with a set of on-resonance $\delta$-lasers is obtained by means of the Laplace transform method. State-selective mirrors are described in the limit of strong lasers. The ladder, V and $\Lambda$ configurations for a three-level atom are discussed. For the two level case, the transient effects arising as result of the interaction between both a semi-infinite beam and a wavepacket with the on-resonance laser are examined.Comment: 13 pages, 6 figure

One-dimensional anyons with competing δ\delta-function and derivative δ\delta-function potentials

We propose an exactly solvable model of one-dimensional anyons with competing $\delta$-function and derivative $\delta$-function interaction potentials. The Bethe ansatz equations are derived in terms of the $N$-particle sector for the quantum anyonic field model of the generalized derivative nonlinear Schr\"{o}dinger equation. This more general anyon model exhibits richer physics than that of the recently studied one-dimensional model of $\delta$-function interacting anyons. We show that the anyonic signature is inextricably related to the velocities of the colliding particles and the pairwise dynamical interaction between particles.Comment: 9 pages, 2 figures, minor changes, references update

Avaliação de genótipos de soja de diferentes grupos de maturação e resistência aos percevejos.

bitstream/item/71814/1/ID-30968.pd

Inflation in Multidimensional Quantum Cosmology

We extend to multidimensional cosmology Vilenkin's prescription of tunnelling from nothing for the quantum origin of the observable Universe. Our model consists of a $D+4$-dimensional spacetime of topology ${\cal R}\times {\cal S}^3 \times{\cal S}^D$, with a scalar field (``chaotic inflaton'') for the matter component. Einstein gravity and Casimir compactification are assumed. The resulting minisuperspace is 3--dimensional. Patchwise we find an approximate analytic solution of the Wheeler--DeWitt equation through which we discuss the tunnelling picture and the probability of nucleation of the classical Universe with compactifying extra dimensions. Our conclusion is that the most likely initial conditions, although they do not lead to the compactification of the internal space, still yield (power-law) inflation for the outer space. The scenario is physically acceptable because the inner space growth is limited to $\sim 10^{11}$ in 100 e-foldings of inflation, starting from the Planck scale.Comment: RevTeX, 30 pages, 4 figures available via fax on request to [email protected], submitted to Phys. Rev.

Extended Hauser-Feshbach Method for Statistical Binary-Decay of Light-Mass Systems

An Extended Hauser-Feshbach Method (EHFM) is developed for light heavy-ion fusion reactions in order to provide a detailed analysis of all the possible decay channels by including explicitly the fusion-fission phase-space in the description of the cascade chain. The mass-asymmetric fission component is considered as a complex-fragment binary-decay which can be treated in the same way as the light-particle evaporation from the compound nucleus in statistical-model calculations. The method of the phase-space integrations for the binary-decay is an extension of the usual Hauser-Feshbach formalism to be applied to the mass-symmetric fission part. The EHFM calculations include ground-state binding energies and discrete levels in the low excitation-energy regions which are essential for an accurate evaluation of the phase-space integrations of the complex-fragment emission (fission). In the present calculations, EHFM is applied to the first-chance binary-decay by assuming that the second-chance fission decay is negligible. In a similar manner to the description of the fusion-evaporation process, the usual cascade calculation of light-particle emission from the highly excited complex fragments is applied. This complete calculation is then defined as EHFM+CASCADE. Calculated quantities such as charge-, mass- and kinetic-energy distributions are compared with inclusive and/or exclusive data for the $^{32}$S+$^{24}$Mg and $^{35}$Cl+$^{12}$C reactions which have been selected as typical examples. Finally, the missing charge distributions extracted from exclusive measurements are also successfully compared with the EHFM+CASCADE predictions.Comment: 34 pages, 6 Figures available upon request, Phys. Rev. C (to be published

Enhanced low-energy γ\gamma-decay strength of 70^{70}Ni and its robustness within the shell model

Neutron-capture reactions on very neutron-rich nuclei are essential for heavy-element nucleosynthesis through the rapid neutron-capture process, now shown to take place in neutron-star merger events. For these exotic nuclei, radiative neutron capture is extremely sensitive to their $\gamma$-emission probability at very low $\gamma$ energies. In this work, we present measurements of the $\gamma$-decay strength of $^{70}$Ni over the wide range $1.3 \leq E_{\gamma} \leq 8$ MeV. A significant enhancement is found in the $\gamma$-decay strength for transitions with $E_\gamma < 3$ MeV. At present, this is the most neutron-rich nucleus displaying this feature, proving that this phenomenon is not restricted to stable nuclei. We have performed $E1$-strength calculations within the quasiparticle time-blocking approximation, which describe our data above $E_\gamma \simeq 5$ MeV very well. Moreover, large-scale shell-model calculations indicate an $M1$ nature of the low-energy $\gamma$ strength. This turns out to be remarkably robust with respect to the choice of interaction, truncation and model space, and we predict its presence in the whole isotopic chain, in particular the neutron-rich $^{72,74,76}\mathrm{Ni}$.Comment: 9 pages, 9 figure

Interacting Modified Variable Chaplygin Gas in Non-flat Universe

A unified model of dark energy and matter is presented using the modified variable Chaplygin gas for interacting dark energy in a non-flat universe. The two entities interact with each other non-gravitationally which involves a coupling constant. Due to dynamic interaction, the variation in this constant arises that henceforth changes the equations of state of these quantities. We have derived the effective equations of state corresponding to matter and dark energy in this interacting model. Moreover, the case of phantom energy is deduced by putting constraints on the parameters involved.Comment: 9 pages; Accepted for publication in European Physical Journal

Dietary transition in native populations of Northern Tierra del Fuego during the Salesian missionary period: an isotopic approach

La misión salesiana La Candelaria funcionó de 1893 a 1928 en el norte de Tierra del Fuego, aunque su cementerio fue usado hasta 1948. Las fuentes históricas sugieren que los nativos que la habitaron sufrieron fuertes cambios en su dieta con respecto a los cazadoresrecolectores de la zona. El cambio estaría caracterizado por un gran incremento en el consumo de harina, arroz, papas y azúcar, que remplazan al guanaco como fuente principal de alimento. Nuestro objetivo es evaluar la transición alimentaria de los habitantes de la misión a través del análisis de isótopos estables de carbono y nitrógeno sobre huesos (colágeno, apatita) y dientes (dentina, esmalte) de 23 individuos exhumados del cementerio. Los valores de δ15N en colágeno (δ15Nc) y de δ13C tanto en colágeno (δ13Cc) como en apatita (δ13Ca) de individuos del cementerio resultaron más bajos que los valores publicados para la región para períodos pre-contacto. Dentro del cementerio, los valores de δ15Nc y de δ13Ca resultaron más bajos que los de δ15Nd (dentina) y de δ13Ce (esmalte), pero no hubo diferencias entre valores de δ13Cc y δ13Cd. Los valores de δ15Nd y δ13Cd resultaron significativamente más bajos que los valores de colágeno para períodos pre-contacto. Estos resultados son consistentes con la hipótesis planteada por las fuentes históricas y sugieren un desequilibrio en la dieta, con una mayor proporción de carbohidratos y una menor proporción de proteínas animales en los habitantes de la misión con relación a los cazadores-recolectores de Tierra del Fuego de períodos pre-contacto.The Salesian mission La Candelaria was run from 1893 to 1928 in the north of Tierra del Fuego, but its cemetery was in use until 1948. Historical sources suggest that the natives living there underwent marked dietary changes with respect to the hunter-gatherers of the area. The change can be characterized by a large increase in the consumption of flour, rice, potatoes, and sugar, in replacement of guanaco, as their main food source. Our objective is to evaluate the dietary transition experienced by the inhabitants of the mission through the analysis of stable isotopes of carbon and nitrogen on bones (collagen, apatite) and teeth (dentin, enamel) of 23 individuals exhumed from the cemetery. The δ15N values in collagen (δ15Nc), and δ13C values both in collagen (δ13Cc) and in apatite (δ13Ca) of samples from the cemetery were lower than the values published for the region in pre-contact periods. Within the cemetery, the δ15Nc, δ13Cc and δ13Ca values were lower than those of δ15Nd (dentin) and δ13Ce (enamel), but there were no differences between δ13Cc and δ13Cd values. The δ15Nd and δ13Cd values were significantly lower than the isotope values of collagen for pre-contact periods. The results are consistent with the hypothesis raised by historical sources and suggest an imbalance in the diet, with a higher proportion of carbohydrates and a lower proportion of animal proteins in the inhabitants of the mission in comparison with the hunter-gatherers of Tierra del Fuego of pre-contact periods.Asociación de Antropología Biológica de la República Argentin

Dietary transition in native populations of Northern Tierra del Fuego during the Salesian missionary period: an isotopic approach

La misión salesiana La Candelaria funcionó de 1893 a 1928 en el norte de Tierra del Fuego, aunque su cementerio fue usado hasta 1948. Las fuentes históricas sugieren que los nativos que la habitaron sufrieron fuertes cambios en su dieta con respecto a los cazadoresrecolectores de la zona. El cambio estaría caracterizado por un gran incremento en el consumo de harina, arroz, papas y azúcar, que remplazan al guanaco como fuente principal de alimento. Nuestro objetivo es evaluar la transición alimentaria de los habitantes de la misión a través del análisis de isótopos estables de carbono y nitrógeno sobre huesos (colágeno, apatita) y dientes (dentina, esmalte) de 23 individuos exhumados del cementerio. Los valores de δ15N en colágeno (δ15Nc) y de δ13C tanto en colágeno (δ13Cc) como en apatita (δ13Ca) de individuos del cementerio resultaron más bajos que los valores publicados para la región para períodos pre-contacto. Dentro del cementerio, los valores de δ15Nc y de δ13Ca resultaron más bajos que los de δ15Nd (dentina) y de δ13Ce (esmalte), pero no hubo diferencias entre valores de δ13Cc y δ13Cd. Los valores de δ15Nd y δ13Cd resultaron significativamente más bajos que los valores de colágeno para períodos pre-contacto. Estos resultados son consistentes con la hipótesis planteada por las fuentes históricas y sugieren un desequilibrio en la dieta, con una mayor proporción de carbohidratos y una menor proporción de proteínas animales en los habitantes de la misión con relación a los cazadores-recolectores de Tierra del Fuego de períodos pre-contacto.The Salesian mission La Candelaria was run from 1893 to 1928 in the north of Tierra del Fuego, but its cemetery was in use until 1948. Historical sources suggest that the natives living there underwent marked dietary changes with respect to the hunter-gatherers of the area. The change can be characterized by a large increase in the consumption of flour, rice, potatoes, and sugar, in replacement of guanaco, as their main food source. Our objective is to evaluate the dietary transition experienced by the inhabitants of the mission through the analysis of stable isotopes of carbon and nitrogen on bones (collagen, apatite) and teeth (dentin, enamel) of 23 individuals exhumed from the cemetery. The δ15N values in collagen (δ15Nc), and δ13C values both in collagen (δ13Cc) and in apatite (δ13Ca) of samples from the cemetery were lower than the values published for the region in pre-contact periods. Within the cemetery, the δ15Nc, δ13Cc and δ13Ca values were lower than those of δ15Nd (dentin) and δ13Ce (enamel), but there were no differences between δ13Cc and δ13Cd values. The δ15Nd and δ13Cd values were significantly lower than the isotope values of collagen for pre-contact periods. The results are consistent with the hypothesis raised by historical sources and suggest an imbalance in the diet, with a higher proportion of carbohydrates and a lower proportion of animal proteins in the inhabitants of the mission in comparison with the hunter-gatherers of Tierra del Fuego of pre-contact periods.Asociación de Antropología Biológica de la República Argentin

Interacting Kasner-type cosmologies

It is well known that Kasner-type cosmologies provide a useful framework for analyzing the three-dimensional anisotropic expansion because of the simplification of the anisotropic dynamics. In this paper relativistic multi-fluid Kasner-type scenarios are studied. We first consider the general case of a superposition of two ideal cosmic fluids, as well as the particular cases of non-interacting and interacting ones, by introducing a phenomenological coupling function $q(t)$. For two-fluid cosmological scenarios there exist only cosmological scaling solutions, while for three-fluid configurations there exist not only cosmological scaling ones, but also more general solutions. In the case of triply interacting cosmic fluids we can have energy transfer from two fluids to a third one, or energy transfer from one cosmic fluid to the other two. It is shown that by requiring the positivity of energy densities there always is a matter component which violates the dominant energy condition in this kind of anisotropic cosmological scenarios.Comment: Accepted for publication in Astrophysics &Space Science, 8 page