Meson decay in a corrected 30P3^P_0 model

Extensively applied to both light and heavy meson decay and standing as one of the most successful strong decay models is the $3^P_0$ model, in which $q\bar{q}$ pair production is the dominant mechanism. The pair production can be obtained from the non-relativistic limit of a microscopic interaction Hamiltonian involving Dirac quark fields. The evaluation of the decay amplitude can be performed by a diagrammatic technique for drawing quark lines. In this paper we use an alternative approach which consists in a mapping technique, the Fock-Tani formalism, in order to obtain an effective Hamiltonian starting from same microscopic interaction. An additional effect is manifest in this formalism associated to the extended nature of mesons: bound-state corrections. A corrected $3^P_0$ is obtained and applied, as an example, to $b_{1}\to\omega\pi$ and $a_{1}\to\rho\pi$ decays.Comment: 3 figures. To appear in Physical Review

Topological Approach to Microcanonical Thermodynamics and Phase Transition of Interacting Classical Spins

We propose a topological approach suitable to establish a connection between thermodynamics and topology in the microcanonical ensemble. Indeed, we report on results that point to the possibility of describing {\it interacting classical spin systems} in the thermodynamic limit, including the occurrence of a phase transition, using topology arguments only. Our approach relies on Morse theory, through the determination of the critical points of the potential energy, which is the proper Morse function. Our main finding is to show that, in the context of the studied classical models, the Euler characteristic $\chi(E)$ embeds the necessary features for a correct description of several magnetic thermodynamic quantities of the systems, such as the magnetization, correlation function, susceptibility, and critical temperature. Despite the classical nature of the studied models, such quantities are those that do not violate the laws of thermodynamics [with the proviso that Van der Waals loop states are mean field (MF) artifacts]. We also discuss the subtle connection between our approach using the Euler entropy, defined by the logarithm of the modulus of $\chi(E)$ per site, and that using the {\it Boltzmann} microcanonical entropy. Moreover, the results suggest that the loss of regularity in the Morse function is associated with the occurrence of unstable and metastable thermodynamic solutions in the MF case. The reliability of our approach is tested in two exactly soluble systems: the infinite-range and the short-range $XY$ models in the presence of a magnetic field. In particular, we confirm that the topological hypothesis holds for both the infinite-range ($T_c \neq 0$) and the short-range ($T_c = 0$) $XY$ models. Further studies are very desirable in order to clarify the extension of the validity of our proposal

Estabelecimento In Vitro de Erva-Mate (Ilex paraguariensis St. Hil.).

bitstream/item/31493/1/comunicado-215.pd

Levantamento de dados sobre produção e mercado de sementes forrageiras de clima temperado na região da Campanha do Rio Grande do Sul.

SIEPE

Alternativas de controle para redução de grãos ardidos na cultura do milho.

As podridões de espiga e grãos ardidos estão entre as principais doenças da cultura do milho. O presente trabalho teve como objetivo avaliar o efeito da resistência genética e densidade de plantio na incidência de grãos ardidos na cultura do milho. O experimento de resistência genética foi conduzido nas cidades de Indianópolis -MG e Guarda-Mor –MG. O experimento de densidade de plantio foi conduzido na cidade de Sete Lagoas –MG. Realizaram-se identificação e quantificação dos grãos ardidos das amostras de grãos colhidos nos experimentos. Foi realizado o Teste de Patologia de Sementes, através do método do papel de filtro umedecido, para identificação dos fungos associados à ocorrência de grãos ardidos. Foram identificadas cultivares com alto nível de resistência a grãos ardidos. O aumento da densidade de plantio resultou em aumento na incidência de grãos ardidos. De acordo com os resultados obtidos, conclui-se que a resistência genética é uma alternativa viável de controle de fungos que atacam as espigas, e o aumento na densidade de plantio influencia a incidência de grãos ardidos na cultura do milho