Dilepton and Photon Emission Rates from a Hadronic Gas III

We extend our early analyses of the dilepton and photon emission rates from a hadronic gas to account for strange mesons using a density expansion. The emission rates are reduced to vacuum correlation functions using three-flavor chiral reduction formulas, and the latters are assessed in terms of empirical data. Using a fire-ball, we compare our results to the low and intermediate mass dilepton data available from CERN. Our results suggest that a baryon free hadronic gas does not account for the excess of low mass dielectrons observed at CERES but do well in accounting for the intermediate dimuons at HELIOS. The same observations apply to the recent low and high $p_t$ dielectron rates from CERES.Comment: 12 pages LaTeX, 11 eps figure

Two-loop effective potential for a general renormalizable theory and softly broken supersymmetry

I compute the two-loop effective potential in the Landau gauge for a general renormalizable field theory in four dimensions. Results are presented for the \bar{MS} renormalization scheme based on dimensional regularization, and for the \bar{DR} and \bar{DR}' schemes based on regularization by dimensional reduction. The last of these is appropriate for models with softly broken supersymmetry, such as the Minimal Supersymmetric Standard Model. I find the parameter redefinition which relates the \bar{DR} and \bar{DR}' schemes at two-loop order. I also discuss the renormalization group invariance of the two-loop effective potential, and compute the anomalous dimensions for scalars and the beta function for the vacuum energy at two-loop order in softly broken supersymmetry. Several illustrative examples and consistency checks are included.Comment: 38 pages. Typos in equations (3.5), (3.11), and (6.3) are fixed. Explicit claim of renormalization group invariance in the general case of softly-broken supersymmetry is added. Additional discussion of cases of multiple simple or U(1) groups. Equations in Appendix B rewritten in a more useful for

Iterative algorithms for total variation-like reconstructions in seismic tomography

A qualitative comparison of total variation like penalties (total variation, Huber variant of total variation, total generalized variation, ...) is made in the context of global seismic tomography. Both penalized and constrained formulations of seismic recovery problems are treated. A number of simple iterative recovery algorithms applicable to these problems are described. The convergence speed of these algorithms is compared numerically in this setting. For the constrained formulation a new algorithm is proposed and its convergence is proven.Comment: 28 pages, 8 figures. Corrected sign errors in formula (25

The renormalization group and spontaneous compactification of a higher-dimensional scalar field theory in curved spacetime

The renormalization group (RG) is used to study the asymptotically free $\phi_6^3$-theory in curved spacetime. Several forms of the RG equations for the effective potential are formulated. By solving these equations we obtain the one-loop effective potential as well as its explicit forms in the case of strong gravitational fields and strong scalar fields. Using zeta function techniques, the one-loop and corresponding RG improved vacuum energies are found for the Kaluza-Klein backgrounds $R^4\times S^1\times S^1$ and $R^4\times S^2$. They are given in terms of exponentially convergent series, appropriate for numerical calculations. A study of these vacuum energies as a function of compactification lengths and other couplings shows that spontaneous compactification can be qualitatively different when the RG improved energy is used.Comment: LaTeX, 15 pages, 4 figure

Chiral symmetry breaking in gauged NJL{\bf NJL} model in curved spacetime

Using the renormalization group (RG) approach and the equivalency between the class of gauge-Higgs-Yukawa models and the gauged Nambu-Jona-Lasinio (NJL) model, we study the gauged NJL model in curved space-time. The behaviour of the scalar-gravitational coupling constant $\xi(t)$ in both theories is discussed. The RG improved effective potential of gauged NJL model in curved spacetime is found. The curvature at which chiral symmetry in the gauged NJL model is broken is obtained explicitly in a remarkably simple form. The powerful RG improved effective potential formalizm leads to the same results as ladder Schwinger-Dyson equations which have not been formulated yet in curved spacetime what opens new possibilities in the study of GUTs and NJL-like models in curved spacetime

Projeções de superfície 3D no plano para análise de interfaces proteicas através do Sting.

Análise, de forma visual, de como algumas grandezas físico-químico estão presentes na interface proteica. A proteína é mostrada em 3 dimensões(3D). Cada região da cadeia proteic é colorida com uma cor diferente, representando a variaçao de características físico-químicas na cadeiaAcesso em 28 maio 2008

Aspectos computacionais da análise da co-evolução de aminoácidos que pertencem a uma proteína qualquer.

O software Sting é um software voltado para a Bioinformática e, d eforma geral, faz análise de estrutura de proteínas e mostra de forma especializada qualquer proteína cuja estrutura está em arquivos .pdf, que contém dados sobre proteínas, podendo ser acessados em Research Collaboratory for Structural Bionformatics.bitstream/CNPTIA/11392/1/ct77.pdfAcesso em: 28 maio 2008

Scattering in Soliton Models and the Bosonic Exchange description

We argue that the description of meson-nucleon dynamics based on the boson-exchange approach, is compatible with the description of the nucleon as a soliton in the nonrelativistic limit. Our arguments are based on an analysis of the meson-soliton form factor and the exact meson-soliton and soliton-soliton scattering amplitudes in the Sine-Gordon model.Comment: 16 page