Bound state energies and phase shifts of a non-commutative well

Non-commutative quantum mechanics can be viewed as a quantum system represented in the space of Hilbert-Schmidt operators acting on non-commutative configuration space. Within this framework an unambiguous definition can be given for the non-commutative well. Using this approach we compute the bound state energies, phase shifts and scattering cross sections of the non- commutative well. As expected the results are very close to the commutative results when the well is large or the non-commutative parameter is small. However, the convergence is not uniform and phase shifts at certain energies exhibit a much stronger then expected dependence on the non-commutative parameter even at small values.Comment: 12 pages, 8 figure

Decreasing flood risk perception in Porto Alegre – Brazil and its influence on water resource management decisions

Porto Alegre is the capital and largest city in the Brazilian state of Rio Grande do Sul in Southern Brazil with approximately 1.5 million inhabitants. The city lies on the eastern bank of the Guaiba Lake, formed by the convergence of five rivers and leading to the Lagoa dos Patos, a giant freshwater lagoon navigable by even the largest of ships. This river junction has become an important alluvial port as well as a chief industrial and commercial centre. However, this strategic location resulted in severe damage because of its exposure to flooding from the river system, affecting the city in the years 1873, 1928, 1936, 1941 and 1967. In order to reduce flood risk, a complex system of levees and pump stations was implemented during 1960s and 1970s. Since its construction, not a single large flood event occurred. However, in recent years, the levees in the downtown region of Porto Alegre were severally criticized by city planners and population. Several projects have been proposed to demolish the Mauá Wall due to the false perception of lack of flood risk. Similar opinions and reactions against flood infrastructure have been observed in other cities in Brazil, such as Itajaí and Blumenau, with disastrous consequences. This paper illustrates how the perception of flood risk in Porto Alegre has changed over recent years as a result of flood infrastructure, and how such changes in perceptions can influence water management decisions

Noncommutative quantum mechanics as a gauge theory

The classical counterpart of noncommutative quantum mechanics is a constrained system containing only second class constraints. The embedding procedure formulated by Batalin, Fradkin and Tyutin (BFT) enables one to transform this system into an Abelian gauge theory exhibiting only first class constraints. The appropriateness of the BFT embedding, as implemented in this work, is verified by showing that there exists a one to one mapping linking the second class model with the gauge invariant sector of the gauge theory. As is known, the functional quantization of a gauge theory calls for the elimination of its gauge freedom. Then, we have at our disposal an infinite set of alternative descriptions for noncommutative quantum mechanics, one for each gauge. We study the relevant features of this infinite set of correspondences. The functional quantization of the gauge theory is explicitly performed for two gauges and the results compared with that corresponding to the second class system. Within the operator framework the gauge theory is quantized by using Dirac's method.Comment: Accepted for publication in Physical Review

Spectrum of the non-commutative spherical well

We give precise meaning to piecewise constant potentials in non-commutative quantum mechanics. In particular we discuss the infinite and finite non-commutative spherical well in two dimensions. Using this, bound-states and scattering can be discussed unambiguously. Here we focus on the infinite well and solve for the eigenvalues and eigenfunctions. We find that time reversal symmetry is broken by the non-commutativity. We show that in the commutative and thermodynamic limits the eigenstates and eigenfunctions of the commutative spherical well are recovered and time reversal symmetry is restored

On the true nature of renormalizability in Horava-Lifshitz gravity

We argue that the true nature of the renormalizability of Horava-Lifshitz gravity lies in the presence of higher order spatial derivatives and not in the anisotropic Lifshitz scaling of space and time. We discuss the possibility of constructing a higher order spatial derivatives model that has the same renormalization properties of Horava-Lifshitz gravity but that does not make use of the Lifshitz scaling. In addition, the state-of-the-art of the Lorentz symmetry restoration in Horava-Lifshitz-type theories of gravitation is reviewed.Comment: Latex file in Revtex style, 5 pages, no figures. v2: references added, version accepted for publication in Foundations of Physic

Petrographic, spectral and magnetic susceptibility study of hydrothermal alteration associated with Pb-Zn-Cu-Ag-Au polymetallic deposits in the Sierra de Comechingones,Córdoba (Argentina)

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOEn el basamento metamórfico de la Sierra de Comechingones, extensión más austral de las Sierras de Córdoba (Argentina), se emplaza un conjunto de vetas polimetálicas con Pb, Zn, Cu, Ag, Au asociadas con zonas de alteración hidrotermal, que constituyen el registro de una época metalogenética ocurrida hacia fines del Paleozoico. En este trabajo la aplicación de técnicas espectrales en la región del SWIR (infrarrojo de onda corta) y magnéticas, poco usual en Argentina para este estilo de mineralización, demostró ser una herramienta eficaz en el estudio de las zonas alteradas y de utilidad para establecer targets de prospección y/o exploración. La asociación sericitacuarzo es el principal producto de alteración hidrotermal de las rocas de caja migmáticas, se desarrolla en franjas estrechas pero continuas que siguen el rumbo principal de las estructuras mineralizadas y pueden alcanzar hasta 5 metros de potencia hacia los laterales. En sectores localizados, una asociación carbonática de siderita-calcita se desarrolla como consecuencia de la alteración de anfibolitas intercaladas dentro de la secuencia metamórfica.En los espectros de reflectancia, la posición del rasgo de absorción Al-OH indicó una variación composicional y procesos de sustitución iónica en las micas blancas de origen hidrotermal, desde micas potásicas (longitudes de onda cercanas a 2200 nm) a micas con menor contenido relativo de Al en el sitio octaédrico (longitudes de onda gt; a 2210 nm) tendientes a la variedad fengita. Estas variaciones y su distribución espacial están controladas fundamentalmente por tres factores: 1) temperatura del fluido hidrotermal, 2) pH y/o 3) relación Mg-Fe/Al dentro del sistema fluido-roca. Los índices de cristalinidad (IC) calculados a partir de los datos espectrales revelaron la predominancia de illitas de alta cristalinidad con un leve incremento de este parámetro hacia las zonas proximales a las vetas mineralizadas. Las interestratificaciones de illita/esmectita hacia las zonas distales de algunas estructuras, reflejan la disminución de la temperatura del fluido y pueden ser utilizadas como vectores hacia las mineralizaciones. Las asociaciones hidrotermales sericita-cuarzo y siderita-calcita están frecuentemente afectadas por los procesos de oxidación supergénica que condujeron a una conspicua precipitación de hematita-goethita dentro de las zonas alteradas. El estado de oxidación del Fe+3 en estos minerales es la principal causa de la disminución del parámetro de susceptibilidad magnética de las rocas hospedantes. Desde una perspectiva regional, estas zonas de alteración hidrotermal caracterizadas por una alta abundancia de micas blancas de moderada a alta cristalinidad (IC=1,21-3,92 e IK=0,21-0,23), composiciones variables entre potásicas y fengíticas (absorción del enlace Al-OH entre 2200 y 2215 nm) y asociadas con zonas de hematización y bajos valores de susceptibilidad magnética (< 0,2 x 10-3 SI), pueden considerase como potenciales targets para futuras etapas de prospección y/o exploración de vetas polimetálicas emplazadas en el ambiente metamórfico de las Sierras Pampeanas731118FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOsem informaçã