Derived Subgroups of Fixed Points in Profinite Groups

The main result of this paper is the following theorem. Let q be a prime, A an elementary abelian group of order q^3. Suppose that A acts as a coprime group of automorphisms on a profinite group G in such a manner that C_G(a)' is periodic for each nontrivial element a in A. Then G' is locally finite.Comment: To appear in Glasgow Mathematical Journal (2011). 11 page

Regularization of energy-momentum tensor correlators and parity-odd terms

We discuss the problem of regularizing correlators in conformal field theories. The only way to do it in coordinate space is to interpret them as distributions. Unfortunately except for the simplest cases we do not have tabulated mathematical results. The way out we pursue here is to go to momentum space and use Feynman diagram techniques and their regularization methods. We focus on the energy-momentum tensor correlators and, to gain insight, we compute and regularize 2-point functions in 2d with various techniques both in coordinate space and in momentum space, obtaining the same results. Then we do the same for 2-point functions in 4d. Finally we turn to 3-point function in 4d, and concentrate on the parity-odd part. We derive in particular the regularized trace and divergence of the energy-momentum tensor in a chiral fermion model. We discuss the problems related to the parity-odd trace anomaly.Comment: 40 pages, 1 figure. v2: minor changes and typos correcte

Variação sazonal na composição química de detritos foliares em zonas ripárias do Cerrado

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Biológicas, Departamento de Ecologia, Programa de Pós-Graduação em Ecologia, 2015.A matéria orgânica da vegetação ripária adjacente aos riachos de pequena ordem é a principal fonte de energia para o ecossistema aquático, sendo o detrito foliar o que tem maior contribuição biológica para os riachos, em termos de biomassa e nutrientes. Assim, a composição química do detrito foliar é um fator regulador da qualidade do detrito para os micro-organismos, vertebrados e invertebrados aquáticos, uma vez que a cadeia trófica desses ecossistemas é baseada em detritos. Além de influenciar a cadeia trófica, a qualidade do detrito também influencia outros processos ecológicos, como a decomposição e a ciclagem biogeoquímica, em riachos de cabeceira. O objetivo deste estudo foi avaliar as variações temporais na composição química dos detritos foliares que entram nos riachos do Cerrado, a partir da seguinte hipótese: os detritos foliares tem menor concentração de nitrogênio e fósforo na estação seca devido à reabsorção destes elementos pelas plantas no período de maior perda de folhas. Da mesma forma, espera-se que a razão C: N e C: P seja maior na época seca. O experimento foi realizado em três riachos de pequena ordem preservados em Brasília, DF. As coletas foram realizadas mensalmente durante 24 meses (entre setembro de 2010 e agosto de 2012). As espécies dos 11 primeiros meses foram identificadas, contudo os detritos dos 24 meses foram moídos misturados. Foram feitas análises químicas para quantificação de nutrientes (N e P), de polifenóis, fibras, lignina e celulose. A composição química dos detritos foliares foi comparada com a precipitação. Os resultados mostram que a composição química dos detritos está fortemente relacionada com o clima do Cerrado. Os detritos foliares são mais ricos em compostos secundários e estruturais na estação seca do que na estação chuvosa. Adicionalmente, a quantidade de nutrientes é menor na estação seca e a razão C:P e C:N é maior, corroborando nossa hipótese. Portanto a qualidade do detrito que cai na época seca é pior para os organismos detritívoros do que a que cai na estação chuvosa. Comparando os dados de nutrientes deste estudo com a cronologia da biota aquática da literatura, conclui-se que existe um padrão temporal da dinâmica nutricional, da colonização dos detritos por micro-organimos e da atividade de invertebrados detritívoros em relação à estacionalidade climática do Cerrado. Este padrão reflete nos processos ecológicos, como a decomposição, a ciclagem biogeoquímica e a disponibilidade de nutrientes no ecossistema ripário do Cerrado.The organic matter from riparian vegetation that bounds streams are the primary energy source to the aquatic ecosystem. Allochthonous leaf litter have a pronounced biological contribution to streams. The chemical composition of leaf litter plays an important role in leaf litter quality to the aquatic microorganisms, to the litter breakdown process and to the nutrient cycling, since the food webs from these systems are detritus based. The aim of this study was to assess temporal variation on leaf litter chemical composition from the Cerrado riparian vegetation. We hypothesized that leaf litter has lower concentration of nitrogen and phosphorus during the dry season because of nutrient resorption before leaf abscission. Therefore, the C:N and C:P ratios would be higher during the dry season. The study was carried out in three low order preserved streams in Brasília, Brazil. Samples were collected monthly during 24 months (between September of 2010 and august 2012). The 11 firsts months species were identified, however, all the 24 collected months were ground mixed. We measured nutrient (N and P), polyphenol, fiber, lignin and celluloses content. Thereafter we compared the leaf litter chemical composition with precipitation. The results shows that leaf litter chemical composition is narrowly related to the Cerrado climate. Leaf litter are more concentrated on secondary and structural compounds during the dry season than the rainy season. Nevertheless, nutrient content is lower during the dry season, and C:N and C:P ratios are higher, which confirms our hypothesis. Therefore, the leaf litter that falls on the dry season is of worse quality to the aquatic detritivores than the litterfall from the rainy season. Putting together our nutrient results with studies from literature about streams biota, we conclude that there is a relation between temporal pattern of nutritional dynamics, leaf colonization, the detritivorous invertebrates and seasonal climate from Cerrado. This pattern results on ecological processes such as decomposition rate, biogeochemical cycle and nutrient availability the Cerrado riparian ecosystem

Future reference in portuguese: the case for a volitive periphrasis

The aim of this paper is to investigate the occurrences of [querer + verb in infinitive] in Portuguese and its implications in comparison to [ir + verb in infinitive], two constructions that express futurity. Based on the notion exposed by Bybee and Pagliuca (1987) that the concept of desire is one of the most common lexical sources of future markers, we propose that there is an association between volition and futurity made by speakers of Portuguese. The study draws on theoretical underpinnings of Usage Based-Linguistics and Construction Grammar to explore uses of [querer + verb in the infinitive] by Portuguese speakers as a construction that indicates future reference. We argue that this construction licenses multiple uses that can be activated by the speaker during the communicative situation. This paper contributes to research on verbal periphrasis and future reference from a Construction Grammar point of view