Taizan Watari

Proton decay, yukawa couplings and underlying gauge symmetry in string theory

In string theory, massless particles often originate from a symmetry breaking of a large gauge symmetry G to its subgroup H. The absence of dimension-4 proton decay in supersymmetric theories suggests that ({bar D},L) are different from {bar H}({bar 5}) in their origins. In this article, we consider a possibility that they come from different irreducible components in g/h. Requiring that all the Yukawa coupling constants of quarks and leptons be generated from the super Yang-Mills interactions of G, we found in the context of Georgi-Glashow H = SU(5) unification that the minimal choice of G is E{sub 7} and E{sub 8} is the only alternative. This idea is systematically implemented in Heterotic String, M theory and F theory, confirming the absence of dimension 4 proton decay operators. Not only H = SU(5) but also G constrain operators of effective field theories, providing non-trivial information.

Electroweak supersymmetry with an approximate U(1) Peccei-Quinn symmetry

A predictive framework for supersymmetry at the TeV scale is presented, which incorporates the Ciafaloni-Pomarol mechanism for the dynamical determination of the \mu parameter of the MSSM. It is replaced by (\lambda S), where S is a singlet field, and the axion becomes a heavy pseudoscalar, G, by adding a mass, m_G, by hand. The explicit breaking of Peccei-Quinn (PQ) symmetry is assumed to be sufficiently weak at the TeV scale that the only observable consequence is the mass m_G. Three models for the explicit PQ breaking are given; but the utility of this framework is that the predictions for all physics at the electroweak scale are independent of the particular model for PQ breaking. Our framework leads to a theory similar to the MSSM, except that \mu is predicted by the Ciafaloni-Pomarol relation, and there are light, weakly-coupled states in the spectrum. The production and cascade decay of superpartners at colliders occurs as in the MSSM, except that there is one extra stage of the cascade chain, with the next-to-LSP decaying to its superpartner and \tilde{s}, dramatically altering the collider signatures for supersymmetry. The framework is compatible with terrestrial experiments and astrophysical observations for a wide range of m_G and . If G is as light as possible, 300 keV < m_G < 3 MeV, it can have interesting effects on the radiation energy density during the cosmological eras of nucleosynthesis and acoustic oscillation, leading to predictions for N_{\nu BBN} and N_{\nu CMB}

Landscape predictions for the Higgs boson and top quark masses

If the standard model is valid up to scales near the Planck mass, and if the cosmological constant and Higgs mass parameters scan on a landscape of vacua, it is well-known that the observed orders of magnitude of these quantities can be understood from environmental selection for large scale structure and atoms. If in addition the Higgs quartic coupling scans, with a probability distribution peaked at low values, environmental selection for a phase having a scale of electroweak symmetry breaking much less than the Planck scale leads to a most probable Higgs mass of 115 GeV. While fluctuations below this are negligible, the upward fluctuation is

Product-group unification in type IIB string theory

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Taming the Runaway Problem of Inflationary Landscapes

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GUT phase transition and hybrid inflation

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Simultaneous solutions of the strong CP and μ problems

measures the strength of the peaking of the a priori distribution of the quartic coupling. There is an additional

A stable proton without R-parity: Implications for the LSP

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Super- and CP-symmetric QCD in higher dimensions

uncertainty from calculable higher loop effects, and also sensitivity to the experimental values of

Density perturbations and the cosmological constant from inflationary landscapes

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