Motivated by recent cosmological observations of a possibly unsuppressed primordial tensor component $r$ of inflationary perturbations, we reanalyse in detail the 5D conformal SUGRA originated natural inflation model of Ref. [1]. The model is a super
symmetric variant of 5D extra natural inflation, also based on a shift symmetry, and leads to the potential of natural inflation. Coupling the bulk fields generating the inflaton potential via a gauge coupling to the inflaton with brane SM states we necessarily obtain a very slow gauge inflaton decay rate and a very low reheating temperature $T_rstackrel{<}{_sim }{cal O}(100)$~GeV. Analysis of the required number of e-foldings (from the CMB observations) leads to values of $n_s$ in the lower range of present Planck 2015 results. Some related theoretical issues of the construction, along with phenomenological and cosmological implications, are also discussed.
Supersymmetric SU(5) GUT augmented with anomaly free U(1)_F flavor symmetry is presented. Very economical field content and U(1)_F charge assignment are obtained by specific construction. In particular, three families of 10+5* chiral matter, along th
e SU(5) singlet states (some of which serve as right handed neutrinos) are obtained. Appealing texture zero Yukawa matrices provide natural understanding of hierarchies between charged fermion masses and mixings. The model predicts inverted hierarchical neutrino mass scenario with interesting implications.
We propose a new mechanism for generating small neutrino masses which predicts the relation m_ u ~ v^4/M^3, where v is the electroweak scale, rather than the conventional seesaw formula m_ u ~ v^2/M. Such a mass relation is obtained via effective dim
ension seven operators LLHH(H*H)/M^3, which arise when an isospin 3/2 Higgs multiplet Phi is introduced along with iso-triplet leptons. The masses of these particles are naturally in the TeV scale. The neutral member of Phi acquires an induced vacuum expectation value and generates neutrino masses, while its triply charged partner provides the smoking gun signal of this scenario. These triply charged bosons can be pair produced at the LHC and the Tevatron, with Phi^{+++} decaying into W^+l^+l^+ or W^+W^+W^+, possibly with displaced vertices. The leptonic decays of Phi^{+++} will help discriminate between normal and inverted hierarchies of neutrino masses. This scenario also allows for raising the standard Higgs boson mass to values in excess of 500 GeV.
We show that in supersymmetric models with gauged B-L symmetry, there is a new source for cosmological lepton asymmetry. The Higgs bosons responsible for B-L gauge symmetry breaking decay dominantly into right-handed sneutrinos tilde{N} and tilde{N}*
producing an asymmetry in tilde{N} over tilde{N}*. This can be fully converted into ordinary lepton asymmetry in the decays of tilde{N}. In simple models with gauged B-L symmetry we show that resonant/soft leptogenesis is naturally realized. Supersymmetry guarantees quasi-degenerate scalar states, while soft breaking of SUSY provides the needed CP violation. Acceptable values of baryon asymmetry are obtained without causing serious problems with gravitino abundance.
