Lorentz-Violating Regulator Gauge Fields as the Origin of Dynamical Flavour Oscillations

We show how a mass mixing matrix can be generated dynamically, for two massless fermion flavours coupled to a Lorentz invariance violating (LIV) gauge field. The LIV features play the role of a regulator for the gap equations, and the non-analytic dependence of the dynamical masses, as functions of the gauge coupling, allows to consider the limit where the LIV gauge field eventually decouples from the fermions. Lorentz invariance is then recovered, to describe the oscillation between two free fermion flavours, and we check that the finite dynamical masses are the only effects of the original LIV theory. We also discuss briefly a connection of our results with the case of Majorana neutrinos in both, the standard model, where only left-handed (active) neutrinos are considered, and extensions thereof, with sterile right-handed neutrinos.Comment: 32 page

Quasi-relativistic fermions and dynamical flavour oscillations

We introduce new Lorentz-symmetry violating kinematics for a four-fermion interaction model, where dynamical mass generation is allowed, irrespectively of the strength of the coupling. In addition, these kinematics lead to a quasi-relativistic dispersion relation, in the sense that it is relativistic in both the infrared and the ultraviolet, but not in an intermediate regime, characterized by the mass $M$. For two fermions, we show that a flavour-mixing mass matrix is generated dynamically, and the Lorentz symmetric limit $M\to\infty$ leads to two free relativistic fermions, with flavour oscillations. This model, valid for either Dirac or Majorana fermions, can describe any set of phenomenological values for the eigen masses and the mixing angle.Comment: 18 pages, comments adde

Integral equations of scattering in one dimension

A self-contained discussion of integral equations of scattering is presented in the case of centrally-symmetric potentials in one dimension, which will facilitate the understanding of more complex scattering integral equations in two and three dimensions. The present discussion illustrates in a simple fashion the concept of partial-wave decomposition, Green's function, Lippmann-Schwinger integral equations of scattering for wave function and transition operator, optical theorem and unitarity relation. We illustrate the present approach with a Dirac delta potential.Comment: 12 pages, accepted in American Journal of Physic

Public information and IPO underpricing

We analyze the effect of public information on rational investors' incentives to reveal private information during the bookbuilding process and their demand for allocations in the IPO. Our model generates several new predictions. First, investors require more underpricing to truthfully reveal positive private information in bear markets than in bull markets (the incentive effect). Second, the fraction of positive private signals and of underpriced IPOs is increasing in market returns (the demand effect). Combined, these two effects can explain why IPO underpricing is positively related to pre-issue market returns, consistent with extant evidence. Using a sample of 5,000 U.S. IPOs from 1981-2008, we show that the empirical implications of the model are borne out in the data.Public information; partial adjustment; underpricing; IPOs; bookbuilding

Ovinos e caprinos: como atender a um mercado em alta.

bitstream/item/52667/1/Midia-Ovinos-e-caprinos-como-atender.pdfDisponível também em: http://www.cienciadoleite.com.br/ovinosecaprinos.htm

Manejo alimentar de caprinos e ovinos em pastejo no Nordeste do Brasil.

Caprinos e ovinos deslanados têm demonstrado um bom nível de adaptação ao ecossistema da caatinga. Enquanto os ovinos são selecionadores de volumosos, os caprinos são selecionadores intermediários, exibindo alto grau de flexibilidade alimentar, variando os seus hábitos de seleção de dieta de acordo com a época do ano, bem com em consonâncos com a qualidade e a disponibilidade de forragem. Contudo, a caatinga, por si só, é insuficiente para atender aos requerimentos energéticos e protéicos das duas espécies em pastejo, principalmente durante o período seco. Trabalhos conduzidos no semi-árido nordestino parecem indicar que, nos sítios ecológicos com potencial forrageiro, a manipulação da vegetação lenhosa é uma prática que resulta em incrementos substanciais na produção de forragem e, consequentemente, na produção animal. A escolha do método de manejo de pastagem, além de considerar respostas anteriormente obtidas na caatinga, deve levar em consideração o tipo de animal ou a combinação de animais que vão utilizar a área. O rebaixamento da caatinga, seguido do pastoreio combinado alternando caprinos e ovinos, constitui, provavelmente, a melhor opção de melhoramento e manejo de pastagens em extensas áreas do sertão. A suplementação alimentar pode ser buscada através da adoção de técnicas de conservação de forragens na própria fazenda, bem como por meio da utilização de bancos de proteína. Tendo em vista o desenvolvimento da fruticultura na região, resíduos da agroindústria podem constituir excelentes fontes de suplemento alimentar de qualidade e de baixo custo. Feeding management of grazing goats and sheep in northeastern Brazil. ABSTRACT - Goats and sheared sheep have demonstrated a good level of adaptation to the caatinga ecosystem. While sheep are voluminous selectors, goats are classified as intermediate selectors exhibiting a high degree of alimentary flexibility, varying their habits of diet selection with the time of year, as well as with the quality and availability of forage. Nevertheless, the caatinga alone is insufficient to meet the energy and protein requirements of both of these species in pasture, especially during the dry season. Studies done in semiarid Northeastern Brazil appear to indicate that, in ecological sites with forager potential, manipulation of woody vegetation can result in substancial increases in the production of ofrage and, consequently, in animal production. The choice of a pasturage management method, besides considering answers preciously obtained in the caatinga must also take into consideration degradation of the caatinga, followed by combined pasturage alternating sheep and goats, probably constitutes the best option for improvement and management of pasturage in extensive areas of Northeastern interior. Supplementary feeding can be done by adopting forage conservation techniques produced at the ranch itself, as well as by using protein banks. Due to the development of fruit industry in the region, byproducts residual of the agro-industry may constitute excellent sources of low-cost, high-quality supplemental feed for the animals

Novos cenários para o agronegócio de caprinos e ovinos.

bitstream/item/52838/1/Midia-Novos-cenarios.pdfDisponível também em: ; , 20 dez. 2007

A produção de ovinos em regiões tropicais e realmente viável?

bitstream/item/51976/1/Midia-A-producao-de-ovinos.pd

Plano de acção para a sustentabilidade energética do concelho de Aveiro

Mestrado em Sistemas Energéticos SustentáveisFace ao actual paradigma energético ser baseado em combustíveis fósseis e cerca de 75% da população europeia viver em cidades, urge a adopção de políticas à escala municipal que revertam a actual tendência insustentável. Nesse sentido a União Europeia criou o Pacto de Autarcas que visa em adoptar um compromisso em que os signatários têm como objectivo diminuir em 20% as suas emissões de CO2 até 2020. Desse modo, o concelho de Aveiro em parceria com a Universidade de Aveiro produziu um Plano de Acção para a Sustentabilidade Energética que se vê reflectido no presente trabalho. Da matriz energética elaborada, tendo em conta o ano de referência de 2005, inventariou-se que o consumo era de 2616GWh e uma emissão de CO2 associada de 712304tCO2. Face estudo compreendido entre 2000 e 2005, projectaram-se os consumos e emissões até 2020 que visam valores na ordem dos 4850GWh e 1069558tCO2. Com base no diagnóstico elaborado propôs-se um conjunto de acções assentes na mobilidade, edifícios, eficiência energética, energias renováveis, governação, sensibilização e formação que visam reduzir em 20% o consumo e as emissões de CO2 em 2020, ou seja, para valores na ordem 3880GWh e 855646tCO2 respectivamente. Conclui-se que o planeamento energético num município é muito importante, indo além da simples protecção ambiental, dado que ao aumentar a eficiência energética do concelho, aumenta também a competitividade económica e, por consequência, torna-se mais atractivo aos investimentos externos, aumentando assim o emprego e o bem-estar social.In order of the current energy paradigm is based on fossil fuels and about 75% of the European population lives in cities, urge the adoption of policies to municipalities to reverse the current unsustainable trend. In this sense the EU has created the Covenant of Mayors which aims to adopt a compromise in which the parties aim to reduce by 20% its CO2 emissions by 2020. Thus, the Municipality of Aveiro in partnership with the University of Aveiro has produced a Sustainable Energy Action Plan that is reflected in this work. From the energy matrix produced, taking into account the reference year of 2005, it was inventoried the energy consumption of 2616GWh and the CO2 emissions of 712304tCO2. Taking in account a study between 2000 and 2005, is projected consumption and emissions by 2020 aimed at values of around 4850GWh and 1069558tCO2. Based on the diagnosis given, it was proposed a set of actions based on mobility, buildings, energy efficiency, renewable energy, governance, sensitizing and training aimed at reducing 20% consumption and CO2 emissions in 2020, for values in order 3880GWh and 855646tCO2 respectively. We conclude that the energy planning in a municipality is very important, going beyond simple environmental protection, since by increasing the energy efficiency of the municipality, also increases the economic competitiveness and, therefore, becomes more attractive to foreign investment, increasing as employment and social welfare