Generalized nonuniform dichotomies and local stable manifolds

We establish the existence of local stable manifolds for semiflows generated by nonlinear perturbations of nonautonomous ordinary linear differential equations in Banach spaces, assuming the existence of a general type of nonuniform dichotomy for the evolution operator that contains the nonuniform exponential and polynomial dichotomies as a very particular case. The family of dichotomies considered allow situations for which the classical Lyapunov exponents are zero. Additionally, we give new examples of application of our stable manifold theorem and study the behavior of the dynamics under perturbations.Comment: 18 pages. New version with minor corrections and an additional theorem and an additional exampl

A Curvature Principle for the interaction between universes

We propose a Curvature Principle to describe the dynamics of interacting universes in a multi-universe scenario and show, in the context of a simplified model, how interaction drives the cosmological constant of one of the universes toward a vanishingly small value. We also conjecture on how the proposed Curvature Principle suggests a solution for the entropy paradox of a universe where the cosmological constant vanishes.Comment: Essay selected for an honorable mention by the Gravity Research Foundation, 2007. Plain latex, 8 page

On Higgs and sphaleron effects during the leptogenesis era

We discuss the effects of various processes that can be active during the leptogenesis era, and present the Boltzmann equations that take them into account appropriately. A non-vanishing Higgs number asymmetry is always present, enhancing the washout of the lepton asymmetry. This is the main new effect when leptogenesis takes place at $T>10^{12}$ GeV, reducing the final baryon asymmetry and tightening the leptogenesis bound on the neutrino masses. If leptogenesis occurs at lower temperatures, electroweak sphalerons partially transfer the lepton asymmetry to a baryonic one, while Yukawa interactions and QCD sphalerons partially transfer the asymmetries of the left-handed fields to the right-handed ones, suppressing the washout processes. Depending on the specific temperature range in which leptogenesis occurs, the final baryon asymmetry can be enhanced or suppressed by factors of order 20%--40% with respect to the case when these effects are altogether ignored.Comment: one reference adde

Culpability and Willingness to Pay to Reduce Negative Externalities: A Contingent Valuation and Experimental Economics Study

Financial Economics,

Recurrent Parotiditis the First Manifestation of Systemic Lupus Erythematosus

Neste artigo apresenta-se o caso clínico de uma doente de 45 anos de idade com tumefacção recorrente das parótidas, que, após quatro anos de evolução, é internada por febre vespertina, sudorese nocturna, toracalgia esquerda com padrão pleurítico, derrame pleural esquerdo, poliartrite e poliartralgia simétricas (padrão inflamatório) dos punhos, articulações interfalângicas proximais das mãos, joelhos e tibiotársicas, acompanhadas de rigidez matinal. Este quadro tinha dois meses de evolução e, após investigação, foi comprovado o diagnóstico de Lúpus Eritematoso Sistémico

Protecção contra a traça da oliveira, Prays oleae Bern. em olivicultura biológica.

Com uma área correspondente a mais de 30% da área certificada em agricultura biológica em Portugal, o olival e também, no país, uma das culturas com maior potencial de crescimento segundo este modo de produção. Tal potencial só poderá no entanto, concretizar-se desde que sejam dispensados a cultura as cuidados adequados, nomeadamente ao nível da protecção contra pragas e doenças, como forma de garantir uma produção rentável, num mercado cada vez mais competitivo. Entre as pragas da oliveira que deverão ser alvo de medidas de protecção, destaca-se, pela gravidade dos prejuízos que pode ocasionar, a traça-da-oliveira, Prays aleae (Bern.), espécie que, desenvolvendo três gerações anuais, ataca sucessivamente, folhas, flores e frutos. Na presente comunicação analisam-se as principais estratégias de protecção disponíveis contra esta praga em olivicultura biológica, assim como os progressos em curso no sentido do desenvolvimento de novas estratégias. Refere-se, por um lado, a importância da valorização da acção da fauna auxiliar indígena e da luta microbiológica por meio de Bacillus turingiensis (Berliner). Par outro lado analisam-se as possibilidades do tratamento biológico com tricogramas e crisópideos, assim como da luta por confusão sexual

Quintessence Model and Observational Constraints

The recent observations of type Ia supernovae strongly support that the universe is accelerating now and decelerated in the recent past. By assuming a general relation between the quintessence potential and the quintessence kinetic energy, a general relation is found between the quintessence energy density and the scale factor. The potential includes both the hyperbolic and the double exponential potentials. A detailed analysis of the transition from the deceleration phase to the acceleration phase is then performed. We show that the current constraints on the transition time, the equation of state and the energy density of the quintessence field are satisfied in the model.Comment: update references,add acknowledgements and correct some errors, accepted for publication in class. and quant. gra

Instabilities in neutrino-plasma density waves

One examines the interaction and possible resonances between supernova neutrinos and electron plasma waves. The neutrino phase space distribution and its boundary regions are analyzed in detail. It is shown that the boundary regions are too wide to produce non-linear resonant effects. The growth or damping rates induced by neutrinos are always proportional to the neutrino flux and $G_{{\rm F}}^{2}$.Comment: 9 pages, a few words modified to match PRD publicatio