Critical behaviour of the compactified λϕ4\lambda \phi^4 theory

We investigate the critical behaviour of the $N$-component Euclidean $\lambda \phi^4$ model at leading order in $\frac{1}{N}$-expansion. We consider it in three situations: confined between two parallel planes a distance $L$ apart from one another, confined to an infinitely long cylinder having a square cross-section of area $A$ and to a cubic box of volume $V$. Taking the mass term in the form $m_{0}^2=\alpha(T - T_{0})$, we retrieve Ginzburg-Landau models which are supposed to describe samples of a material undergoing a phase transition, respectively in the form of a film, a wire and of a grain, whose bulk transition temperature ($T_{0}$) is known. We obtain equations for the critical temperature as functions of $L$ (film), $A$ (wire), $V$ (grain) and of $T_{0}$, and determine the limiting sizes sustaining the transition.Comment: 12 pages, no figure

Reação à antracnose de variedades tradicionais de feijão-comum coletadas no Estado do Paraná.

O objetivo do trabalho foi testar variedades tradicionais coletadas em regiões produtores de feijão-comum no Estado do Paraná quanto à resistência à antracnose.CONAF

Tratamentos pré-germinativos em sementes de pata-de-vaca.

Resumo

Nesting Induced Precursor Effects: a Renormalization Group Approach

We develop a controlled weak coupling renormalization group (RG) approach to itinerant electrons. Within this formalism we rederive the phase diagram for two-dimensional (2D) non-nested systems. Then we study how nesting modifies this phase diagram. We show that competition between p-p and p-h channels, leads to the manifestation of unstable precursor fixed points in the RG flow. This effect should be experimentally measurable, and may be relevant for an explanation of pseudogaps in the high temperature superconductors (HTC), as a crossover phenomenon.Comment: 4 pages, 4 figures, 1 tabl

J/Psi suppression in colliding nuclei: statistical model analysis

We consider the $J/\Psi$ suppression at a high energy heavy ion collision. An ideal gas of massive hadrons in thermal and chemical equilibrium is formed in the central region. The finite-size gas expands longitudinally in accordance with Bjorken law. The transverse expansion in a form of the rarefaction wave is taken into account. We show that $J/\Psi$ suppression in such an environment, when combined with the disintegration in nuclear matter, gives correct evaluation of NA38 and NA50 data in a broad range of initial energy densities.Comment: 14 pages, 13 figures. Accepted for publication in Phys. Rev.

New possibilities for the gauging of chiral bosons

We study a new mechanism for the electromagnetic gauging of chiral bosons showing that new possibilities emerge for the interacting theory of chiral scalars. We introduce a chirally coupled gauge field necessary to mod out the degree of freedom that obstructs gauge invariance in a system of two opposite chiral bosons soldering them together.Comment: 11 pages, Latex. Accepted for publication in Physical Review

Caracterização morfológica dos acessos de feijão comum (Phaseolus vulgaris).

A diversidade genética é a responsável por essa segurança e estabilidade de produção. A coleta, caracterização e manutenção desses acessos disponibilizará aos programas de melhoramento genes responsáveis por características desejáveis na obtenção de novas cultivares.Apresentação oral - graduação