A theoretical density-functional study has been carried out to analyze the exchange coupling in the chains of CuGeO3 using discrete models. The results show a good agreement with the experimental exchange coupling constant ~J! together with a strong dependence of J with the Cu-O-Cu angle. The calculation of the J values for a distorted model indicates a larger degree of dimerization than those ...

The current status of measurements of the strong coupling constant from different reactions is reviewed. Including new results presented at the 1996 ICHEP conference, a global average αs(MZ) = 0.118± 0.003 is obtained. Plenary talk given at the XXVIII International Conference on High Energy Physics Warsaw, July 25–31, 1996.

We show that in 3-3-1 models there exist a natural relation among the SU(3)L coupling constant g, the electroweak mixing angle θW , the mass of the W , and one of the vacuum expectation values, which implies that those models can be realized at low energy scales and, in particular, even at the electroweak scale. So that, being that symmetries realized in Nature, new physics may be really just a...

The current status of the QCD coupling constant S and experimental and theoretical studies of hadronic jets are reviewed.

SUSY effects on various flavor changing neutral current processes are discussed in the minimal supergravity model and the SU(5) grand unified theory with righthanded neutrino supermultiplets. In particular, in the latter case the neutrino Yukawa coupling constants can be a source of the flavor mixing in the right-handeddown-type-squark sector. It is shown that due to this mixing the time-depend...

The Standard Model [1] contains one neutral scalar Higgs boson, which is a remnant of the mechanism that breaks the SU(2) × U(1) symmetry and generates the W and Z boson masses. The Higgs couples to quarks and leptons of mass m f with a strength gm f /2M W. Its coupling to W and Z bosons is of strength g, where g is the coupling constant of the SU(2) gauge theory. The branching ratio of the Hig...

Hadronic decays of the τ lepton provide a clean source to study hadron dynamics in an energy regime dominated by resonances, with the interesting information captured in the spectral functions. Recent results on exclusive channels are reviewed. Inclusive spectral functions are the basis for QCD analyses, delivering an accurate determination of the strong coupling constant and quantitative infor...

Introduction Conclusions References

The problem of the vacuum energy decay is studied for both signs of the cosmological constant, through the analysis of the vacuum survival amplitude, defined in terms of the conformal time, z, by Aðz; z0Þ hvac zjvac z0i. Transition amplitudes are computed for finite time span, Z z0 z, and their late time behavior (directly related to the putative decay width of the state), and the transients ar...