Geographical variation in genetic structure of an Atlantic Coastal Forest frog reveals regional differences in habitat stability

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Wakes in dilatonic current-carrying cosmic strings

In this work, we present the gravitational field generated by a cosmic string carrying a timelike current in the scalar-tensor gravities. The mechanism of formation and evolution of wakes is fully investigated in this framework. We show explicitly that the inclusion of electromagnetic properties for the string induces logarithmic divergences in the accretion problem.

Four-point amplitude from open superstring field theory

An open superstring field theory action has been proposed which does not suffer from contact term divergences. In this paper, we compute the on-shell four-point tree amplitude fi om this action using the Giddings map. After including contributions from the quartic term in the action, the resulting amplitude agrees with the first-quantized prescription. (C) 2000 Elsevier B.V. B.V. All rights reserved.

Quark condensates and high density quark matter

We consider a Coulomb gauge quark model which includes an explicit construct for a nontrivial vacuum structure in QCD. The dynamics is described by a Hamiltonain that contains a linearly rising confining potential and longitudinal and transverse Coulomb-type interactions. The Coulomb potential gives rise to ultraviolate divergences which are non-perturbatively renormalized by adding appropriate counter terms to the Hamiltonian. The equation of state for u and d quark matter at zero temperature is derived in the Hartree-Fock approximation.

Linear relations between N >= 4 supergravity and subleading-color SYM amplitudes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

On KLT and SYM-supergravity relations from 5-point 1-loop amplitudes

We derive a new non-singular tree-level KLT relation for the n = 5-point amplitudes, with manifest 2(n-2)! symmetry, using information from one-loop amplitudes and IR divergences, and speculate how one might extend it to higher n-point functions. We show that the subleading-color N = 4 SYM 5-point amplitude has leading IR divergence of 1/epsilon, which is essential for the applications of this paper. We also propose a relation between the subleading-color N = 4 SYM and N = 8 supergravity 1-loop 5-point amplitudes, valid for the IR divergences and possibly for the whole amplitudes, using techniques similar to those used in our derivation of the new KLT relation.

Twistor and polytope interpretations for subleading color one-loop amplitudes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effective potential in curved space and cut-off regularizations

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Predictive formulation of the Nambu-Jona-Lasinio model

A novel strategy to handle divergences typical of perturbative calculations is implemented for the Nambu-Jona-Lasinio model and its phenomenological consequences investigated. The central idea of the method is to avoid the critical step involved in the regularization process, namely, the explicit evaluation of divergent integrals. This goal is achieved by assuming a regularization distribution in an implicit way and making use, in intermediary steps, only of very general properties of such regularization. The finite parts are separated from the divergent ones and integrated free from effects of the regularization. The divergent parts are organized in terms of standard objects, which are independent of the ( arbitrary) momenta running in internal lines of loop graphs. Through the analysis of symmetry relations, a set of properties for the divergent objects are identified, which we denominate consistency relations, reducing the number of divergent objects to only a few. The calculational strategy eliminates unphysical dependencies of the arbitrary choices for the routing of internal momenta, leading to ambiguity-free, and symmetry-preserving physical amplitudes. We show that the imposition of scale properties for the basic divergent objects leads to a critical condition for the constituent quark mass such that the remaining arbitrariness is removed. The model becomes predictive in the sense that its phenomenological consequences do not depend on possible choices made in intermediary steps. Numerical results are obtained for physical quantities at the one-loop level for the pion and sigma masses and pion-quark and sigma-quark coupling constants.

Applications of Subleading-Color Amplitudes in N=4 SYM Theory

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Superspace approach to the renormalization of the O'Raifeartaigh model up to the second order in the linear delta expansion parameter

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Raciocínio moral na tomada de decisões em relação a questões sociocientíficas: o exemplo do melhoramento genético humano

Nos últimos anos, os avanços nas Ciências Biológicas têm levado a sociedade a discutir diversas questões no campo da moral e da ética. Questões como engenharia genética, clonagem e pesquisas com células-tronco são questões chamadas de sociocientíficas por estarem na interface entre a ciência e a sociedade. Nesse trabalho buscamos entender como estudantes de Ensino Médio percebem e interpretam questões relacionadas à manipulação genética em seres humanos. Houve divisão de opiniões em relação à eugenia negativa, que se destina a remover características desfavoráveis das pessoas; mas a eugenia positiva, que busca melhoramento de características estéticas, foi rejeitada por todos os estudantes. As variações nas opiniões em relação ao assunto tratado podem ser, em grande medida, devidas às representações sociais dos estudantes.

When decisions on homologous structures cause ambiguous taxa relationships: the Neomorphinae (Aves, Cuculidae) example

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Lattice discretization in quantum scattering

The utility of lattice discretization technique is demonstrated for solving nonrelativistic quantum scattering problems and specially for the treatment of ultraviolet divergences in these problems with some potentials singular at the origin in two- and three-space dimensions. This shows that the lattice discretization technique could be a useful tool for the numerical solution of scattering problems in general. The approach is illustrated in the case of the Dirac delta function potential.

UNIFORMLY ACCELERATED FINITE-TIME DETECTORS

The behavior of uniformly accelerated detectors in the Minkowski and Rindler vacua is analyzed when the detector is coupled to a scalar field during a finite amount of time T. We point out that the logarithmic ultraviolet divergences reported in the literature are due to the instantaneous switching of the detector. We explicitly show this by considering a detector switched on and off continuously. The usual Planckian spectrum for the excitation probability is recovered in the limit T --> infinity.