Non-perturbative unification in the light of LEP results

We consider an alternative to conventional GUTs originally proposed by Maiani, Parisi and Petronzio, where owing to the existence of extra fermion generations at some intermediate scale, the gauge couplings become large at high energies. We first comment on how the non- supersymmetric version of this scenario is ruled out; we then consider the two-loop evolution of the couplings in the supersymmetric extension of this scenario, and check whether such a scenario is feasible in the light of the precies values of couplings now available from LEP.Comment: Latex file 7 pages+1 fig. (ps file appended after the latex file), CERN-TH.6913/9

Comment on SU(16) grand unification

In a recent paper on SU(16) grand unification, because of the presence of intermediate-energy gauge groups containing products of U(1) factors which are not orthogonal among themselves, the renormalization-group treatment has a few small errors. I correct it. I emphasize that one should not switch gauge couplings at the various thresholds. It is easier, and it avoids errors, to use throughout the gauge couplings of the standard model, and compute at each threshold, in the usual way, the extra contributions to the beta functions from the extra non-decoupled fields. I also point out that the SU(16) grand unification theory, due to the large number of scalars present in it, is not asymptotically free. It becomes a strong-coupling theory at energies only slightly larger than the unification scale.Comment: 5 latex pages, 2 tables, no figure

Proton Decay and Related Processes in Unified Models with Gauged Baryon Number:

In unification models based on SU(15) or SU(16), baryon number is part of the gauge symmetry, broken spontaneously. In such models, we discuss various scenarios of important baryon number violating processes like proton decay and neutron-antineutron oscillation. Our analysis depends on the effective operator method, and covers many variations of symmetry breaking, including different intermediate groups and different Higgs boson content. We discuss processes mediated by gauge bosons and Higgs bosons parallely. We show how accidental global or discrete symmetries present in the full gauge invariant Lagrangian restrict baryon number violating processes in these models. In all cases, we find that baryon number violating interactions are sufficiently suppressed to allow grand unification at energies much lower than the usual $10^{16}$ GeV.Comment: (32 pages LATEX) [DOE-ER\,40757-022, CPP-93-22] {Small changes made and two references added. This version will appear in Phys. Rev. D

Effects of an intermediate scale in SUSY grand unification

We discuss the production of lepton flavor violation and EDMs and the viability of the $b-\tau$ unification hypothesis in SUSY grand unification with an intermediate gauge symmetry breaking scale.Comment: 3 pages (Latex, esprc2.sty used), talk given at 4th International Conference on Supersymmetry (SUSY '96, College Park, MD, May 29 - June 1, 1996

Constrained analytical interrelations in neutrino mixing

Hermitian squared mass matrices of charged leptons and light neutrinos in the flavor basis are studied under general additive lowest order perturbations away from the tribimaximal (TBM) limit in which a weak basis with mass diagonal charged leptons is chosen. Simple analytical expressions are found for the three measurable TBM-deviants in terms of perturbation parameters appearing in the neutrino and charged lepton eigenstates in the flavor basis. Taking unnatural cancellations to be absent and charged lepton perturbation parameters to be small, interrelations are derived among masses, mixing angles and the amount of CP-violation.Comment: To be published in the Springer Proceedings in the Physics Series under the heading of the XXI DAE-BRNS Symposium (Guwahati, India