Finite Temperature Effective Potential for Gauge Models in de Sitter Space

The one-loop effective potential for gauge models in static de Sitter space at finite temperatures is computed by means of the $\zeta$--function method. We found a simple relation which links the effective potentials of gauge and scalar fields at all temperatures. In the de Sitter invariant and zero-temperature states the potential for the scalar electrodynamics is explicitly obtained, and its properties in these two vacua are compared. In this theory the two states are shown to behave similarly in the regimes of very large and very small radii a of the background space. For the gauge symmetry broken in the flat limit ($a \to \infty$) there is a critical value of a for which the symmetry is restored in both quantum states. Moreover, the phase transitions which occur at large or at small a are of the first or of the second order, respectively, regardless the vacuum considered. The analytical and numerical analysis of the critical parameters of the above theory is performed. We also established a class of models for which the kind of phase transition occurring depends on the choice of the vacuum.Comment: 23 pages, LaTeX, 5 figure.ep

Vestibulo-Ocular Reflex Modification after Virtual Environment Exposure

Immersion in an illusory world is possible by means of virtual reality (VR), where environmental perception is modi bff c1c ed by artificial sensorial stimulation. The application of VR for the assessment and rehabilitation of pathologies affecting the vestibular system, in terms of both diagnosis and care, could represent an interesting new line of research. Our perception of reality is in fact based on static and dynamic spatial information perceived by our senses. During head movements in a virtual environment the images on the display and the labyrinthine information relative to the head angular accelerations differ and therefore a visuo-vestibular conflict is present. It is known that mismatches between visual and labyrinthine information may modify the vestibulo-oculomotor reflex (VOR) gain. We studied the post-immersion modifications in 20 healthy subjects (mean age 25 years) exposed to a virtual environment for 20 min by wearing a head-mounted display. VOR gain and phase were measured by means of harmonic sinusoidal stimulation in the dark before, at the end of and 30 min after VR exposure. A VOR gain reduction was observed in all subjects at the end of VR exposure which disappeared after 30 min. Our data show that exposure to a virtual environment can induce a temporary modi bff c1c cation of the VOR gain. This bff c1c nding can be employed to enable an artificial, instrumental modification of the VOR gain and therefore opens up new perspectives in the assessment and rehabilitation of vestibular diseases

Avaliação do efeito do Baculovirus anticarsia sobre Podisus nigrispinus (DALLAS, 1851), predador da lagarta da soja Anticarsia gemmatalis (HUBNER, 1818).

Este trabalho tem como objetivo conhecer os efeitos da ingestão de lagartas da soja infectadas com B. anticarsia pelo predador Podisus nigrispinus, avaliando-se os parâmetros biológicos de cada inseto.bitstream/CNPMA/5854/1/baculovirus_anticarsia.pd

Natural coastal risks and the Coastal Zone Integrated Management

An analysis of the main natural risk factors of the Peninsula of Hicacos, on the coast center-west of Cuba is submitted. From an exhaustive bibliographic review, first it is presented a physical-geographical and socio-economic characterization of the peninsula of Hicacos, and on this basis are identified geological, geomorphological and hydrometeorological factors that determine natural hazards in the area under study. In particular an analysis of probabilities of extreme winds in the past 200 years associated with hurricanes, and the heights and periods of waves on the coast of the peninsula to different periods of return is materialize. Also it´s includes a brief analysis of the endogenous risks, and conclude that the hurricanes, the severe local storms and the frontal systems are the main natural dangers that affect the Peninsula. Finally the value of the MIZC for the study, prevision and confrontation of the natural risk is argued, and the positive experience of the application of that approach in the beach of Varadero.Se presenta un análisis de los principales factores de riesgos naturales de la Península de Hicacos, en la costa centro-occidental de Cuba. A partir de una revisión bibliográfica exhaustiva, se presenta primero una caracterización físico-geográfica y socio-económica de la península de Hicacos y sobre esta base se identifican los factores geológicos, geomorfológicos e hidrometeorológicos que condicionan los riesgos naturales en la zona objeto de estudio. En particular se realiza un análisis de probabilidades de los vientos extremos en los últimos 200 años asociados a los huracanes, y de las alturas y periodos del oleaje en el litoral de la península para diferentes periodos de retorno. Se incluye un breve análisis de los riesgos endógenos, y se concluye que son los huracanes, las tormentas locales severas y los frentes fríos los principales peligros naturales que afectan la a Península. Finalmente, se argumenta el valor del enfoque de MIZC para el estudio, previsión y enfrentamiento de los riesgos naturales, y se expone la positiva experiencia de aplicación de tal enfoque en la playa de Varadero.Ciencias Experimentale

Heat-kernel Coefficients and Spectra of the Vector Laplacians on Spherical Domains with Conical Singularities

The spherical domains $S^d_\beta$ with conical singularities are a convenient arena for studying the properties of tensor Laplacians on arbitrary manifolds with such a kind of singular points. In this paper the vector Laplacian on $S^d_\beta$ is considered and its spectrum is calculated exactly for any dimension $d$. This enables one to find the Schwinger-DeWitt coefficients of this operator by using the residues of the $\zeta$-function. In particular, the second coefficient, defining the conformal anomaly, is explicitly calculated on $S^d_\beta$ and its generalization to arbitrary manifolds is found. As an application of this result, the standard renormalization of the one-loop effective action of gauge fields is demonstrated to be sufficient to remove the ultraviolet divergences up to the first order in the conical deficit angle.Comment: plain LaTeX, 23 pp., revised version, a misprint in expressions (1.8) and (4.38) of the second heat coefficient for the vector Laplacian is corrected. No other change

Natural coastal risks and the Coastal Zone Integrated Management

An analysis of the main natural risk factors of the Peninsula of Hicacos, on the coast center-west of Cuba is submitted. From an exhaustive bibliographic review, first it is presented a physical-geographical and socio-economic characterization of the peninsula of Hicacos, and on this basis are identified geological, geomorphological and hydrometeorological factors that determine natural hazards in the area under study. In particular an analysis of probabilities of extreme winds in the past 200 years associated with hurricanes, and the heights and periods of waves on the coast of the peninsula to different periods of return is materialize. Also it´s includes a brief analysis of the endogenous risks, and conclude that the hurricanes, the severe local storms and the frontal systems are the main natural dangers that affect the Peninsula. Finally the value of the MIZC for the study, prevision and confrontation of the natural risk is argued, and the positive experience of the application of that approach in the beach of Varadero.Se presenta un análisis de los principales factores de riesgos naturales de la Península de Hicacos, en la costa centro-occidental de Cuba. A partir de una revisión bibliográfica exhaustiva, se presenta primero una caracterización físico-geográfica y socio-económica de la península de Hicacos y sobre esta base se identifican los factores geológicos, geomorfológicos e hidrometeorológicos que condicionan los riesgos naturales en la zona objeto de estudio. En particular se realiza un análisis de probabilidades de los vientos extremos en los últimos 200 años asociados a los huracanes, y de las alturas y periodos del oleaje en el litoral de la península para diferentes periodos de retorno. Se incluye un breve análisis de los riesgos endógenos, y se concluye que son los huracanes, las tormentas locales severas y los frentes fríos los principales peligros naturales que afectan la a Península. Finalmente, se argumenta el valor del enfoque de MIZC para el estudio, previsión y enfrentamiento de los riesgos naturales, y se expone la positiva experiencia de aplicación de tal enfoque en la playa de Varadero.Ciencias Experimentale