[en] We give a complete analytical computation of three- and two-point loop integrals occurring in heavy particle theories, involving a velocity change, for arbitrary real values of the external masses and residual momenta. (orig.)

[en] We construct vacua of heterotic M-theory with general gauge bundles and five-branes. Some aspects of the resulting low-energy effective theories are discussed. (orig.)

[en] Using non-relativistic effective theories, new next-to-next-to-leading order (NNLO) QCD corrections to the total t anti t production cross section at the linear collider have been calculated recently. In this article the NNLO calculations of several groups are compared and the remaining uncertainties are discussed. The theoretical prospects for an accurate determination of top quark mass parameters are discussed in detail. An outlook on possible future improvements is given. (orig.)

[en] Using a manifestly gauge-invariant approach we show that the set of low-energy constants in the electroweak chiral Lagrangian currently used in the literature is redundant. In particular, by employing the equations of motion for the gauge fields, one can choose to remove two low-energy constants which contribute to the self-energies of the gauge-bosons. The relation of this result to the experimentally determined values for the oblique parameters S, T and U is discussed. We then evaluate the matching relation between gauge-invariant Green's functions in the full and the effective theory for the case of the standard model with a heavy Higgs boson and compare the results for the independent low-energy constants with those for a simple technicolor model. Since the pattern of the low-energy constants is very different in these two models it may be misleading to mimic any strongly interacting symmetry breaking sector by a heavy Higgs boson. From our investigation we conclude that current electroweak precision data do not really rule out such strongly interacting models. (orig.)

[en] In the framework of the minimal supersymmetric standard model we compute the one-loop effective action for the electroweak bosons obtained after integrating out the different sleptons, squarks, neutralinos and charginos, and present the result in terms of the physical sparticle masses. In addition we study the asymptotic behavior of the two-, three- and four-point Green's functions with external electroweak bosons in the limit where the physical sparticle masses are very large in comparison with the electroweak scale. We find that in this limit all the effects produced by the supersymmetric particles can either be absorbed in the standard model parameters and gauge boson wave functions, or else they are suppressed by inverse powers of the supersymmetric particle masses. This work, therefore, completes the proof of decoupling of the heavy supersymmetric particles from the standard ones in the electroweak boson effective action and in the sense of the Appelquist-Carazzone theorem; we started this proof in a previous work. From the point of view of effective field theories this work can be seen as a (partial) proof that the SM can indeed be obtained from the MSSM as the quantum low-energy effective theory of the latter when the SUSY spectra are much heavier than the electroweak scale. (orig.)