Lifshitz-point critical behaviour to O(ϵ2){\boldsymbol{O(\epsilon^2)}}

We comment on a recent letter by L. C. de Albuquerque and M. M. Leite (J. Phys. A: Math. Gen. 34 (2001) L327-L332), in which results to second order in $\epsilon=4-d+\frac{m}{2}$ were presented for the critical exponents $\nu_{{\mathrm{L}}2}$, $\eta_{{\mathrm{L}}2}$ and $\gamma_{{\mathrm{L}}2}$ of d-dimensional systems at m-axial Lifshitz points. We point out that their results are at variance with ours. The discrepancy is due to their incorrect computation of momentum-space integrals. Their speculation that the field-theoretic renormalization group approach, if performed in position space, might give results different from when it is performed in momentum space is refuted.Comment: Latex file, uses the included iop stylefiles; Uses the texdraw package to generate included figure

Numerical simulations of two dimensional magnetic domain patterns

I show that a model for the interaction of magnetic domains that includes a short range ferromagnetic and a long range dipolar anti-ferromagnetic interaction reproduces very well many characteristic features of two-dimensional magnetic domain patterns. In particular bubble and stripe phases are obtained, along with polygonal and labyrinthine morphologies. In addition, two puzzling phenomena, namely the so called `memory effect' and the `topological melting' observed experimentally are also qualitatively described. Very similar phenomenology is found in the case in which the model is changed to be represented by the Swift-Hohenberg equation driven by an external orienting field.Comment: 8 pages, 8 figures. Version to appear in Phys. Rev.

Finite Size Effects in Thermal Field Theory

We consider a neutral self-interacting massive scalar field defined in a d-dimensional Euclidean space. Assuming thermal equilibrium, we discuss the one-loop perturbative renormalization of this theory in the presence of rigid boundary surfaces (two parallel hyperplanes), which break translational symmetry. In order to identify the singular parts of the one-loop two-point and four-point Schwinger functions, we use a combination of dimensional and zeta-function analytic regularization procedures. The infinities which occur in both the regularized one-loop two-point and four-point Schwinger functions fall into two distinct classes: local divergences that could be renormalized with the introduction of the usual bulk counterterms, and surface divergences that demand countertems concentrated on the boundaries. We present the detailed form of the surface divergences and discuss different strategies that one can assume to solve the problem of the surface divergences. We also briefly mention how to overcome the difficulties generated by infrared divergences in the case of Neumann-Neumann boundary conditions.Comment: 31 pages, latex, to appear in J. Math. Phy

Suplementação alimentar com resíduos da agroindústria em bubalinos na fase de crescimento.

bitstream/item/59257/1/CPATU-ComTec44.pd

Genotipagem de plantas de cupuaçuzeiro, obtidas de uma população contrastante para resistência a Moniliophthora perniciosa, para a identificação de QRL's.

O mapeamento molecular visando à identificação de locos quantitativos associados à resistência a patógenos é uma ferramenta que poderá ser muito útil ao programa de melhoramento do cupuaçuzeiro. O objetivo desta pesquisa foi realizar a primeira etapa para identificar locus controladores de resistência à vassoura de bruxa, efetuando a genotipagem de uma família cujos pais apresentavam resistência contrastante àquela enfermidade. Para a obtenção da progênie foram realizadas polinizações controladas entre os clones 174 (resistente) e 1074 (susceptível). Obtida a família com 200 indivíduos, foi feita a extração do DNA de tecido foliar, e o teste dos primers. Foram testados 31 primers microssatélites de cacaueiro e 42 de cupuaçuzeiro. Dos quais foram selecionados 16 primers, sendo 10 de cacau e 6 cupuaçuzeiro, que demonstraram boa amplificação e polimorfismo. Foi obtido um total de 36 alelos, com média de 2,25 alelos/loco, sendo 3 o máximo de alelos por loco. O fingerprint de cada indivíduo será utilizado para a elaboração dos mapas de ligação.PIBIC-2011