Topological low-temperature limit of Z(2) spin-gauge theory in three dimensions

We study Z(2) lattice gauge theory on triangulations of a compact 3-manifold. We reformulate the theory algebraically, describing it in terms of the structure constants of a bidimensional vector space H equipped with algebra and coalgebra structures, and prove that in the low-temperature limit H reduces to a Hopf Algebra, in which case the theory becomes equivalent to a topological field theory. The degeneracy of the ground state is shown to be a topological invariant. This fact is used to compute the zeroth- and first-order terms in the low-temperature expansion of Z for arbitrary triangulations. In finite temperatures, the algebraic reformulation gives rise to new duality relations among classical spin models, related to changes of basis of H.Comment: 10 pages, no figure

New forms of land grabbing due to the bioeconomy. The case of Brazil

The present study discusses new forms of land grabbing related to biofuel production in the light of bioeconomic development. With a specific focus on Brazil, this article debates whether biofuel production is associated with (i) an expansion of agricultural land use-regarded as a process of unsustainable crop intensification or (ii) an increase in crop yield, driven by technical innovation with stable land use-intended as a form of sustainable intensification. We conclude that, in the case of Brazil, the current bioeconomy cannot be assumed to be environmentally sustainable. Starting from Brazil's experience, the (apparent and latent) relationship between bioeconomy and land grabbing requires a refined investigation in both wealthier and emerging economies, with the aim of proposing effective strategies to achieve truly sustainable development in the primary sector

Fluctuating Dimension in a Discrete Model for Quantum Gravity Based on the Spectral Principle

The spectral principle of Connes and Chamseddine is used as a starting point to define a discrete model for Euclidean quantum gravity. Instead of summing over ordinary geometries, we consider the sum over generalized geometries where topology, metric and dimension can fluctuate. The model describes the geometry of spaces with a countable number $n$ of points, and is related to the Gaussian unitary ensemble of Hermitian matrices. We show that this simple model has two phases. The expectation value $$, the average number of points in the universe, is finite in one phase and diverges in the other. We compute the critical point as well as the critical exponent of$$. Moreover, the space-time dimension $\delta$ is a dynamical observable in our model, and plays the role of an order parameter. The computation of $$ is discussed and an upper bound is found, $< 2$.Comment: 10 pages, no figures. Third version: This new version emphasizes the spectral principle rather than the spectral action. Title has been changed accordingly. We also reformulated the computation of the dimension, and added a new reference. To appear in Physical Review Letter

Dirac operator on the q-deformed Fuzzy sphere and Its spectrum

The q-deformed fuzzy sphere $S_{qF}^2(N)$ is the algebra of $(N+1)\times(N+1)$ dim. matrices, covariant with respect to the adjoint action of \uq and in the limit $q\to 1$, it reduces to the fuzzy sphere $S_{F}^2(N)$. We construct the Dirac operator on the q-deformed fuzzy sphere-$S_{qF}^{2}(N)$ using the spinor modules of \uq. We explicitly obtain the zero modes and also calculate the spectrum for this Dirac operator. Using this Dirac operator, we construct the \uq invariant action for the spinor fields on $S_{qF}^{2}(N)$ which are regularised and have only finite modes. We analyse the spectrum for both $q$ being root of unity and real, showing interesting features like its novel degeneracy. We also study various limits of the parameter space (q, N) and recover the known spectrum in both fuzzy and commutative sphere.Comment: 19 pages, 6 figures, more references adde

Estimativa do índice de desconforto térmico em Mossoró-RN.

O objetivo deste trabalho foi analisar o índice de desconforto térmico humano (ID) para o município de Mossoró-RN

BR - 5110 - Solimões: o milho de várzea do Amazonas.

BR - 5110 - Solimoes, variedade selecionada e adaptada para as condicoes de varzea no Amazonas. Sao descritas, alem das caracteristicas agronomicas da variedade, as recomendacoes tecnicas para o seu plantio em area de varzea no Amazonas.bitstream/CPAA-2009-09/2730/1/Com_Tec_9.pd

Multivariate analyses to establish reference values for soils in Médio Paraíba, state of Rio de Janeiro, Brazil.

Quality Reference Values (QRVs) for potentially toxic elements are obtained from background levels in soils. However, this determination from mean values or percentiles is not appropriate given the variability in the natural distribution of these elements in soils. Therefore, the objective of this study was to propose a new methodology to establish the QRVs, using the Médio Paraíba region (RJ, Brazil) as an example, from groups of soils defined based on the pseudo-total levels of B, Ba, Co, Cr, Cu, Ni, Pb, and Zn through the use of multivariate analyses and discriminant functions. A total of 40 points, collected at depths of 0-20 and 20-40 cm, were used for the determination of pseudo-total contents, according to the EPA 3051A methodology. The samples were separated into three groups to better represent the variability of the soils of the region. The classification functions were obtained based on the variables Mn, Fe, and Mg. In general, the groups G1 and G2 presented lower values than the ones obtained when the sample universe was used, whereas G3 presented higher values. The QRVs obtained from the soil groups presented substantial differences that translate into advantages for the management of the contaminated areas of the region. Valores de Referência de Qualidade (VRQ) para elementos potencialmente tóxicos são obtidos através dos teores naturais nos solos. No entanto, esta determinação a partir de valores médios ou de percentis não é adequada, diante da variabilidade existente na distribuição natural desses elementos nos solos. Diante disso, o objetivo do estudo foi propor uma nova metodologia de estabelecimento dos VRQs, usando como exemplo a Região do Médio Paraíba - RJ, a partir de grupos de solos definidos com base nos teores pseudo-totais de B, Ba, Co, Cr, Cu, Ni, Pb e Zn, mediante a utilização de análises multivariadas e de funções discriminantes. Foram utilizados 40 pontos, coletados nas profundidades 0-20 e 20-40 cm, para a determinação dos teores pseudo-totais, conforme a metodologia EPA 3051A. As amostras foram separadas em três grupos, para melhor representar a variabilidade existente nos solos da região. As funções de classificação foram obtidas com base nas variáveis Mn, Fe e Mg. Em geral, os grupos G1 e G2 apresentaram valores inferiores, em relação aos obtidos quando se utilizou o universo amostral. Enquanto que, G3 apresentou valores superiores. Os VRQs obtidos a partir de grupos de solos apresentaram diferenças substanciais que traduzem vantagens para o gerenciamento de áreas contaminadas da região

Geotechnical characterization of Vertisols from Bahia State, Brazil.

Despite the existence of vertic soils with predominance of kaolinite is reported around the world, there are few studies shown the influence of this clay mineral in their geotechnical characteristics. The work aimed to perform a geotechnical characterization of Vertisols from Bahia, Brazil, besides understanding the influence of physical, chemical and mineralogical properties on the geotechnical behavior. Three Vertisols were collected in Juazeiro city, in a semi-arid region, one kaolinitic Vertisol and two smectite Vertisols. Other three Vertsols were collected in Recôncavo region, all presented clay mineralogy with codominance of smectite and kaolinite (Sm-K). A geotechnical characterization was carried out in their diagnostic horizons, determining properties such as granulometric curve, clay activity, linear expansion coefficient, compaction capacity, cohesion (c?), and internal friction angle (&#981;) of saturated soils. We observed that the clay content was the attribute that most influenced the geotechnical characteristics. All soils showed expansion potential above 0.01, considered as very high. The kaolinitic Vertisol showed the lowest clay activity. However, the clay content of 68% contributed to this soil to present an expansion potential similar to the smectite Vertisol with clay content of 35%. The major values of soil compaction were observed for the kaolinitic Vertisol, which presented greater reduction of void ratio and higher density as a function of moisture increase. For this soil, the optimal moisture content (OMC) and maximum dry density (MDD) were 22% and 1.65 g cm-3, respectively. The other soils presented OMC between 18-41% and MDD between 1.75-1.24 g cm-3. These smectite-soils, MDD decreased with increasing of OMC. All soils had low c? values, which is expected for high clay content soils. The c? values increased with increasing of kaolinite and decreased with increasing of clay content. The kaolinite Vertisol showed c? of 0.19 kgf cm-2. The c? values to Sm-K Vertisols ranged between 0.05-0.11 kgf cm-2. As for smectite-soil, c? values ranged between 0.02-0.03 kgf cm-2. Low &#981; values were observed for all soils, which indicates low shear resistance. In its turn, &#981; was more influenced by granulometry, in which higher levels of sand and gravel provided higher &#981;, independently of the type of clay. Vertisols with different mineralogy present different geotechnical characteristics. Keywords: Smectite; kaolinite; expansive soil

Qualitative Characteristics of Meat from Lambs Fed Hydrolyzed Sugarcane

We used 24 Ile de France lambs, weighing between 15 and 32 kg (BW). Treatments were supplemented with concentrate: "in nature" sugarcane (IN), sugarcane hydrolyzed using 0.6% calcium oxide (CaO) under aerobic condition (AER), and sugarcane hydrolyzed using 0.6% CaO under anaerobic condition (ANA), constituting a completely randomized design with eight repetitions per treatment. Lambs were housed in individual stalls and fed into the through, allowing 10% of leftovers. Lambs were slaughtered when body weight reached 32 kg. The following parameters were determined on Longissimus lumborum muscle of hot and cold carcasses: pH and color, 45 minutes and 24 hours after slaughtering. Qualitative analysis of the meat were performed in the loins, water-holding capacity (WHC), cooking loss (CL), and shear force (SF). We used a completely randomized design with three treatments and eight repetitions. Means were compared by Tukey test at 5% significance. A higher value for redness (a*) 45 minutes after slaughter (10.48) was found for lambs fed sugarcane hydrolyzed under anaerobic conditions. The other qualitative characteristics of meat were not affected by treatments (P >0.05). The comparison of meat quality resulting from the treatments shows that it is possible to feed in nature sugarcane to lambs, thus waiving hydrolyses process and the spending with alkalizing agent