New interactions in the dark sector mediated by dark energy

Cosmological observations have revealed the existence of a dark matter sector, which is commonly assumed to be made up of one particle species only. However, this sector might be more complicated than we currently believe: there might be more than one dark matter species (for example, two components of cold dark matter or a mixture of hot and cold dark matter) and there may be new interactions between these particles. In this paper we study the possibility of multiple dark matter species and interactions mediated by a dark energy field. We study both the background and the perturbation evolution in these scenarios. We find that the background evolution of a system of multiple dark matter particles (with constant couplings) mimics a single fluid with a time-varying coupling parameter. However, this is no longer true on the perturbative level. We study the case of attractive and repulsive forces as well as a mixture of cold and hot dark matter particles

Curupira

Portuguese: Vou falar um pouco da lenda do Curupira que é um personagem da Amazônia e ela diz assim, bom, minha avó fala que a avó dela contava para ela que a lenda nos conta que o Curupira é a defensor dos animais, sendo ele um dos mais populares personagens do folclore brasileiro. Então é isso, entendeu? Só que ela continua dizendo que o Curupira gosta de sentar na sombra das mangeiras para comer os frutos. Lá fica entretido deliciando cada manga mas percebendo que está sendo observado, logo sai correndo numa velocidade tão grande que a humana não consegue acompanhar. Não adianta correr atrás de um curupira. Eu: Como o Curupira defende a floresta? Israel: O Curupira, ele defende a mata, a fauna, a flora...eh, dos predadores tipo cortadores, destruidores demais, esse negócio todo entendeu, então ele só parece para as pessoas que vao fazer mal pra floresta. Assim minha avó contava que ela viu uma vez o Curupira também em vida quando ela tinha vinte anos aquele negócio todo que ela morava no interior Urucurituba. Mas esse mesmo a história do Curupira. [Dito depois de uma segunda lenda contada na mesma mensagem] Então essas duas lendas estou contando para você. Se alguém tiver dúvida aí, pode falar para vim em Manaus, em Amazonas, e eles podem ver que é real, o encontro das águas e histórias reais e os antigos contam bem melhor que eu. Estou só te contando o que minha avó contou para mim, entendeu? English Translation: Israel: I will talk a little about the legend of the Curupira that is a person from the Amazon and the legend says this, well, my grandma said that her grandpa told her this legend and told us that the Curupira is the defender of the animals, hime being one of the most popular people in Brazilian folklore. So it is this, understand? Only that my grandma continued saying that the Curupira likes to sit in the shade of the mango trees to eat the fruits. There it stays enjoying every mango but noticing that it is being observed, right away it leaves running at a velocity so fast that humans can’t follow. It’s no use running after a curupira. Me: How does the Curupira defend the forest? Israel: The Curupira, he defends the jungle, the animals, the plants…um, from the predators like those who cut down trees, people who destroy too much, this whole kind of thing understand, so he only appears for the people who will harm the forest. Like that my grandma said that saw a Curupira once in real life when she was twenty years old that whole thing when she lived in the interior of Urucurituba. But this is the story of the Curupira. [After another legend told in the same conversation he said this] So these two legends that I’m telling you. If anyone has doubt there, you can tell them to come to Manaus, to Amazonas, and they can see that it is real, the meeting of the waters and the real stories and the elderly tell them way better than me. I’m just telling you what my grandma told to me, understand

Speed of Sound in the Mass Varying Neutrinos Scenario

We discuss about the speed of sound squared in the Mass Varying Neutrinos scenario (MaVaNs). Recently, it was argued that the MaVaNs has a catastrophic instability which is the emergence of an imaginary speed of sound at the non-relativistic limit of neutrinos. As the result of this instability, the neutrino-acceleron fluid cannot act as the dark energy. However, it is found that the speed of sound squared in the neutrino-acceleron fluid could be positive in our model. We examine the speed of sound in two cases of the scalar potential. One is the small fractional power-law potential and another is the logarithmic one. The power-law potential model with the right-handed neutrinos gives a stable one.Comment: 17 pages, References added, minor modification

Phase transition in the fine structure constant

Within the context of mass-varying neutrinos, we construct a cosmological model that has a phase transition in the electromagnetic fine structure constant \alpha at a redshift of 0.5. The model accommodates hints of a time variable \alpha in quasar spectra and the nonobservance of such an effect at very low redshifts. It is consistent with limits from the recombination and primordial nucleosynthesis eras and is free of instabilities.Comment: 6 pages, 1 figure. Version to appear in PL

A Process for Improving Course Quality based on Mid-Semester Feedback

Proceedings of: First International Conference on Reforming Education, Quality of Teaching and Technology-Enhanced Learning: Learning Technologies, Quality of Education, Educational Systems, Evaluation, Pedagogies (TECH-EDUCATION 2010). Athens, Greece, May 19-21, 2010.Quality control mechanisms are becoming more important in higher educational institutions. Student evaluation of teaching is typically used to obtain feedback from students about a learning experience but its effect in the course may take too long. Fast feedback mechanisms, in exchange, look at obtaining feedback in order to apply corrective measures quickly. In this paper a process is described to obtain feedback from the students about a course, analyze the received results, and identify the most significant aspects. The process has been applied to a course and led to some adjustments that had immediate impact on the course.The authors are truly indebted to Miguel Valero for his guidance during the design of this process. Work partially funded by the Learn3 project, “Plan Nacional de I+D+I TIN2008-05163/TSI”, the Best Practice Network ICOPER (Grant No. ECP-2007-EDU-417007), the Flexo Project “Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica” (Ref. TSI-020301-2008-19), and the “Emadrid: Investigación y desarrollo de tecnologías para el e-learning en la Comunidad de Madrid” project (S2009/TIC-1650).Publicad

Land, cane and coconuts : papers on the rural economy of Fiji

The three papers contained in this volume are the outcome of research into various aspects of employment generation and income distribution in Fiji agriculture, undertaken in 1982 and 1983. The papers were originally prepared as Working Papers for the Fiji Employment and Development Mission, which submitted its final report to the Fiji Government in 1984. Revised versions are published together here in order to make available to a wider readership the result of the research

The diversity of Class II transposable elements in mammalian genomes has arisen from ancestral phylogenetic splits during ancient waves of proliferation through the genome

DNA transposons make up three percent of the human genome, roughly the same percentage as genes. However, due to their inactivity, they are often ignored in favour of the more abundant, active, retroelements. Despite this relative ignominy, there are a number of interesting questions to be asked of these transposon families. One particular question relates to the timing of proliferation and inactivation of elements in a family. Does an ongoing process of turnover occur, or is the process more akin to a life cycle for the family, with elements proliferating rapidly before deactivation at a later date? We answer this question by tracing back to the most recent common ancestor of each modern transposon family, using two different methods. The first method identifies the most recent common ancestor of the species in which a family of transposon fossils can still be found, which we assume will have existed soon after the true origin date of the transposon family. The second method uses molecular dating techniques to predict the age of the most recent common ancestor element from which all elements found in a modern genome are descended. Independent data from five pairs of species are used in the molecular dating analysis: Human- Chimpanzee, Human-Orangutan, Dog-Panda, Dog-Cat and Cow-Pig. Orthologous pairs of elements from host species pairs are included, and the divergence dates of these species are used to constrain the analysis. We discover that, in general, the times to element common ancestry, for a given family, are the same for the different species pairs, suggesting that there has been no order-specific process of turnover. Furthermore, for most families, the ages of the common ancestor of the host species and of that of the elements are similar, suggesting a life cycle model for the proliferation of transposons. Where these two ages differ, in families found only in Primates and Rodentia, for example, we find that the host species date is later than that of the common ancestor of the elements, implying that there may be large deletions of elements from host species, examples of which were found in their ancestors

Re-Focusing - Building a Future for Entrepreneurial Education & Learning

The field of entrepreneurship has struggled with fundamental questions concerning the subject’s nature and purpose. To whom and to what means are educational and training agendas ultimately directed? Such questions have become of central importance to policy makers, practitioners and academics alike. There are suggestions that university business schools should engage more critically with the lived experiences of practising entrepreneurs through alternative pedagogical approaches and methods, seeking to account for and highlighting the social, political and moral aspects of entrepreneurial practice. In the UK, where funding in higher education has become increasingly dependent on student fees, there are renewed pressures to educate students for entrepreneurial practice as opposed to educating them about the nature and effects of entrepreneurship. Government and EU policies are calling on business schools to develop and enhance entrepreneurial growth and skill sets, to make their education and training programmes more proactive in providing innovative educational practices which help and facilitate life experiences and experiential learning. This paper makes the case for critical frameworks to be applied so that complex social processes become a source of learning for educators and entrepreneurs and so that innovative pedagogical approaches can be developed in terms both of context (curriculum design) and process (delivery methods)

Mass-Varying Neutrinos from a Variable Cosmological Constant

We consider, in a completely model-independent way, the transfer of energy between the components of the dark energy sector consisting of the cosmological constant (CC) and that of relic neutrinos. We show that such a cosmological setup may promote neutrinos to mass-varying particles, thus resembling a recently proposed scenario of Fardon, Nelson, and Weiner (FNW), but now without introducing any acceleronlike scalar fields. Although a formal similarity of the FNW scenario with the variable CC one can be easily established, one nevertheless finds different laws for neutrino mass variation in each scenario. We show that as long as the neutrino number density dilutes canonically, only a very slow variation of the neutrino mass is possible. For neutrino masses to vary significantly (as in the FNW scenario), a considerable deviation from the canonical dilution of the neutrino number density is also needed. We note that the present `coincidence' between the dark energy density and the neutrino energy density can be obtained in our scenario even for static neutrino masses.Comment: 8 pages, minor corrections, two references added, to apear in JCA