119159824
Non-Gaussianity and gravitational wave background in curvaton with a double well potential
We study the density perturbation by a curvaton with a double well potential and give analytical expressions for the observables such as nonlinear parameters f{sub NL}, g{sub NL} and tensor-to-scalar ratio r{sub T} with emphasizing the differences from the simple quadratic potential. We show that the level of non-Gaussianity and the tensor-to-scalar ratio depends crucially on the reheating temperature as well as the curvaton self-coupling constant for a given initial amplitude of the curvaton. We find that for a large initial field the nonlinear parameters f{sub NL} can be 10-20 and the gravitational wave background also is observable in the Planck satellite.
7390821
Spectral running and non-Gaussianity from slow-roll inflation in generalized two-field models
Theories beyond the standard model such as string theory motivate low energy effective field theories with several scalar fields which are not only coupled through a potential but also through their kinetic terms. For such theories we derive the general formulae for the running of the spectral indices for the adiabatic, isocurvature and correlation spectra in the case of two-field inflation. We also compute the expected non-Gaussianity in such models for specific forms of the potentials. We find that the coupling has little impact on the level of non-Gaussianity during inflation.
42769057
Conditions for large non-Gaussianity in two-field slow-roll inflation
We study the level of primordial non-Gaussianity in slow-roll two-field inflation. Using an analytic formula for the non-linear parameter fNL in the case of a sum or product separable potential, we find that it is possible to generate significant non-Gaussianity even during slow-roll inflation with Gaussian perturbations at Hubble exit. In this paper we give the general conditions for obtaining large non-Gaussianity and calculate the level of fine-tuning required to obtain this. We present explicit models in which the non-Gaussianity at the end of inflation can exceed the current observational bound of .
118604242
Quasar polarization with two axionlike particles
Abstract Recently, it was shown, that the absence of circular polarization of visible light from quasars, severely constrains the interpretation of axion like particles (ALPs) as a solution for the generation of the linear polarization. Furthermore, the new observation of the linear polarization in the radio wavelength from quasars, similar to the earlier observation performed in the optical band, makes the ALPs scenario inconsistent with at least one of the two observations. In this study we extend this scenario, to two axion like particles, one scalar and another pseudoscalar. We find, that the effects from scalar and pseudoscalar cancel out each other, thereby suppressing the circular polarization, while preserving consistent linear polarization, as observed in both visible and radio waves bands.
14862395
Softness of brane-localized supersymmetry breaking on orbifolds
Abstract We consider the brane-localized supersymmetry breaking in 5D compactified on S 1 / Z 2 . In case of a bulk gaugino with arbitrary brane masses for its even and odd modes, we find the mass spectrum and the wave functions of gaugino. We show that the gaugino masses at the distant brane are soft in the usual sense in the effective field theory with zero modes of bulk gauge fields and they are also extremely soft in view of the one-loop finite mass of a brane scalar in the KK regularization.
119366917
Double suppression of FCNCs in supersymmetric models
A mechanism for double suppression of flavor-changing neutral currents (FCNCs) and CP violating phases in supersymmetric models is suggested. At M{sub SUSY} they are suppressed due to a nonabelian discrete flavor symmetry, and the infrared attractive force of gauge interactions in extra dimensions are used to suppress them at the compactification scale. We present a concrete model, which is a simple extension of S{sub 3} invariant minimal supersymmetric standard model, where only SU(2){sub L} and SU(3){sub C} gauge multiplets are assumed to propagate in the bulk. We find that a disorder of 2 orders of magnitude in soft supersymmetry breaking parameters above the compactification scale may be allowed to satisfy experimental constraints on FCNC processes and CP violating phenomena.
119243457
Non-Abelian Discrete Flavor Symmetries on Orbifolds
We study non-Abelian flavor symmetries on orbifolds, S1/Z2 and T2/Z3. Our extra dimensional models realize DN, Σ(2N2), Δ(3N2) and Δ(6N2) including A4 and S4. In addition, one can also realize their subgroups such as QN, T7, etc. The S3 flavor symmetry can be realized on both S1/Z2 and T2/Z3 orbifolds.
119250759
Flavor structure from magnetic fluxes and non-Abelian Wilson lines
We study the flavor structure of four-dimensional (4D) effective theories, which are derived from extra dimensional theories with magnetic fluxes and non-Abelian Wilson lines. We study zero-mode wave functions in generic case and compute Yukawa couplings as well as four-point couplings. In our models, we also discuss non-Abelian discrete flavor symmetries such as ${D}_{4}$, $\ensuremath{\Delta}(27)$, and $\ensuremath{\Delta}(54)$. The orbifold background is also studied.
199677054
Spectrum of Heterotic String on Orbifold
119260886
Cosmological moduli problem in large volume scenario and thermal inflation
We show that in a large volume scenario of type IIB string or F-theory compactifications, single thermal inflation provides only a partial solution to the cosmological problem of the light volume modulus. We then clarify the conditions for double thermal inflation, being a simple extension of the usual single thermal inflation scenario, to solve the cosmological moduli problem in the case of relatively light moduli masses. Using a specific example, we demonstrate that double thermal inflation can be realized in large volume scenario in a natural manner, and the problem of the light volume modulus can be solved for the whole relevant mass range. We also find that right amount of baryon asymmetry and dark matter can be obtained via a late-time Affleck-Dine mechanism and the decays of the visible sector NLSP to flatino LSP.
125848056
Gauge Unification via Stable Brane Recombination
We study the transition between parallel and intersecting branes on a torus. Spontaneous symmetry breaking of nonabelian gauge symmetry is understood as brane separation, and a more general intermediate deformation is discussed. We argue that there exists supersymmetry preserving transition and we can always have parallel branes as a final state. The transition is interpreted due to dynamics of the F‐ and D‐string junctions and their generalization to (F, Dp) bound states. The gauge group and coupling unification is achieved, also as a result of supersymmetry. From the tadpole cancelation condition, we naturally have some class of intersecting brane models as broken phases of Type I theory with SO(32) gauge group.