Power-like loop corrections to gauge couplings are a generic feature of higher-dimensional field theories. In supersymmetric grand unified theories in d = 5 dimensions, such corrections arise only in the presence of a vacuum expectation value of the adjoint scalar of the gauge multiplet. We show that, using the analysis of the exact quantum effective action by Intriligator, Morrison and Seiberg...

We apply the method of zeta functions, together with the nμ-prescription for the temporal gauge, to evaluate the thermodynamic pressure in QCD at finite temperature T . Working in the imaginary-time formalism and employing a special version of the unified-gauge prescription, we show that the pure-gauge contribution to the pressure at two loops is given by P gauge 2 = −(g/144)NcNgT 4, where Nc a...

We present a simple extension of the minimal supersymmetric standard model which provides a unified picture of cosmological baryon asymmetry and dark matter. Our model introduces a gauge singlet field N and a color triplet field X which couple to the right-handed quark fields. The out-of-equilibrium decay of the Majorana fermion N mediated by the exchange of the scalar field X generates adequat...

In the standard model matter fields form complete representations of a grand unified group whereas Higgs fields belong to incomplete ‘split’ multiplets. This remarkable fact is naturally explained by ‘local grand unification’ in higher-dimensional extensions of the standard model. Here, the generations of matter fields are localized in regions of compact space which are endowed with a GUT gauge...

Standard (level one) heterotic string models with standard model gauge group predict the unification of SU(3) and SU(2) gauge couplings whereas the U(1) factor is unified modulo an unknown normalization factor k1. On the other hand the unification mass is known. I argue that this situation is quite analogous (though opposite) to that in SUSYGUTs in which the U(1) normalization is known (k1 = 5/...

We study the possibility of achieving low unification scale in a grand unification scheme based on the gauge group SU(16). Baryon number symmetry being an explicit local gauge symmetry here gauge boson mediated proton decay is absent . We present in detail a number of symmetry breaking patterns and the higgs field representations giving rise to the desired symmetry breakings and identify one ch...

Grand Unified Theories based on an E6 gauge group embed all Higgsand matter fields within one 27 dimensional fundamental representation. In addition each 27 contains a right handed neutrino, an NMSSM-like standard model singlet and a pair of exotic particles, that couple quarks to leptons. The extended particle content spoils simple gauge unification as in the MSSM. By embedding the SM into a P...

We present some results on the usefulness of upgraded Tevatron and LHC hadron colliders to test the idea of a strongly interacting sector as responsible for the electroweak symmetry breaking. The calculations are performed within an effective lagrangian description, called the BESS model 1 (BESS standing for Breaking Electroweak Symmetry Strongly), which provides for a rather general frame base...

I present two new renormalizable grand unified theories where the neutrino masses are generated through the type I and type III seesaw mechanisms. These theories can be considered as the simplest (SUSY) renormalizable grand unified theories based on the SU(5) gauge symmetry. Several phenomenological and cosmological aspects of these proposals are discussed. PACS. 12.10.Dm Unified theories and m...