Natural inflation with and without modulations in type IIB string theory

We propose a mechanism for the natural inflation with and without modulation in the framework of type IIB string theory on toroidal orientifold or orbifold. We explicitly construct the stabilization potential of complex structure, dilaton and K\"ahler moduli, where one of the imaginary component of complex structure moduli becomes light which is identified as the inflaton. The inflaton potential is generated by the gaugino-condensation term which receives the one-loop threshold corrections determined by the field value of complex structure moduli and the axion decay constant of inflaton is enhanced by the inverse of one-loop factor. We also find the threshold corrections can also induce the modulations to the original scalar potential for the natural inflation. Depending on these modulations, we can predict several sizes of tensor-to-scalar ratio as well as the other cosmological observables reported by WMAP, Planck and/or BICEP2 collaborations.Comment: 18 pages, 4 figures, Typos corrected, references and comments adde

Wavefunctions and Yukawa Couplings on Resolutions of T2/ZNT^2/\mathbb{Z}_N Orbifolds

We propose matter wavefunctions on resolutions of $T^2/\mathbb{Z}_N$ singularities with constant magnetic fluxes. In the blow-down limit, the obtained wavefunctions of chiral zero-modes result in those on the magnetized $T^2/\mathbb{Z}_N$ orbifold models, but the wavefunctions of $\mathbb{Z}_N$-invariant zero-modes receive the blow-up effects around fixed points of $T^2/\mathbb{Z}_N$ orbifolds. Such blow-up effects change the selection rules and Yukawa couplings among the chiral zero-modes as well as the modular symmetry, in contrast to those on the magnetized $T^2/\mathbb{Z}_N$ orbifold models.Comment: 19 pages, 2 figures, v2: published versio

Optimal Sharing Rules in Repeated Partnerships

We study a simple model of repeated partnerships with noisy outcomes. Two partners first choose a sharing rule, under which they start their repeated interaction. We characterize the sharing rule which supports the most efficient equilibrium, and show that it suffices to consider two particular sharing rules. One is an asymmetric sharing rule, which induces only a more productive partner to work. It is optimal for impatient or less productive partners. The other treats them more evenly, and prevails for more productive and patient partners. Those results indicate how technological parameters and patience determine the role of a more productive partner. If the partners become more productive or more patient, the productive partner ceases to be a residual claimant and sacrifices his own share, in order to foster teamwork.

Realistic three-generation models from SO(32) heterotic string theory

We search for realistic supersymmetric standard-like models from SO(32) heterotic string theory on factorizable tori with multiple magnetic fluxes. Three chiral ganerations of quarks and leptons are derived from the adjoint and vector representations of SO(12) gauge groups embedded in SO(32) adjoint representation. Massless spectra of our models also include Higgs fields, which have desired Yukawa couplings to quarks and leptons at the tree-level.Comment: 29 pages, Typos corrected, references added, and Sec. 3.3 is adde

Supersymmetry preserving and breaking degenerate vacua, and radiative moduli stabilization

We propose a new type of moduli stabilization scenario where the supersymmetric and supersymmetry-breaking minima are degenerate at the leading level. The inclusion of the loop-corrections originating from the matter fields resolves this degeneracy of vacua. Light axions are predicted in one of our models.Comment: 18 pages, 14 figure