Tetsutaro Higaki

Moduli stabilization, F-term uplifting and soft supersymmetry breaking terms

We study moduli stabilization with F-term uplifting. As a source of uplifting F-term, we consider spontaneous supersymmetry breaking models, e.g. the Polonyi model and the Intriligator-Seiberg-Shih model. We analyze potential minima by requiring almost vanishing vacuum energy and evaluate the size of modulus F-term. We also study soft SUSY-breaking terms. In our scenario, the mirage mediation is dominant in gaugino masses. Scalar masses can be comparable with gaugino masses or much heavier, depending on couplings with spontaneous supersymmetry breaking sector.

More about F-term uplifting

We study moduli stabilization and a realization of de Sitter vacua in generalized F-term uplifting scenarios of the Kachru-Kallosh-Linde-Trivedi-type anti-de Sitter vacuum, where the uplifting sector X directly couples to the light Kaehler modulus T in the superpotential through, e.g., stringy instanton effects. F-term uplifting can be achieved by a spontaneous supersymmetry breaking sector, e.g., the Polonyi model, the ORaifeartaigh model, and the Intriligator-Seiberg-Shih model. Several models with the X-T mixing are examined, and qualitative features in most models even with such mixing are almost the same as those in the Kachru-Kallosh-Linde-Trivedi scenario. One of the quantitative changes, which are relevant to the phenomenology, is a larger hierarchy between the modulus mass m{sub T} and the gravitino mass m{sub 3/2}, i.e., m{sub T}/m{sub 3/2}=O(a{sup 2}), where a{approx}4{pi}{sup 2}. In spite of such a large mass, the modulus F term is suppressed not like F{sup T}=O(m{sub 3/2}/a{sup 2}), but like F{sup T}=O(m{sub 3/2}/a) for ln(M{sub Pl}/m{sub 3/2}){approx}a, because of an enhancement factor coming from the X-T mixing. Then we typically find a mirage-mediation pattern of gaugino masses of O(m{sub 3/2}/a), while the scalar masses would be generically of O(m{sub 3/2})

Kachru-Kallosh-Linde-Trivedi-type models with moduli-mixing superpotential

We study KKLT type models with moduli-mixing superpotential. In several string models, gauge kinetic functions are written as linear combinations of two or more moduli fields. Their gluino condensation generates moduli-mixing superpotential. We assume one of moduli fields is frozen already around the string scale. It is found that Kahler modulus can be stabilized at a realistic value without tuning 3-form fluxes because of gluino condensation on (non-)magnetized D-brane. Furthermore, we do not need to highly tune parameters in order to realize a weak gauge coupling and a large hierarchy between the gravitino mass and the Planck scale, when there exists non-perturbative effects on D3-brane. SUSY breaking patterns in our models have a rich structure. Also, some of our models have cosmologically important implications, e.g., on the overshooting problem and the destabilization problem due to finite temperature effects as well as the gravitino problem and the moduli problem.

Flavor structure and coupling selection rule from intersecting D-branes

We study flavor structure and the coupling selection rule in intersecting D-brane configurations on T{sup 2}xT{sup 2}xT{sup 2} as well as its orbifold/orientifold compactifications. We formulate the selection rule for Yukawa couplings and its extensions to generic n-point couplings. We investigate the possible flavor structure, which can appear from intersecting D-brane configuration. Then, we show there is a certain rule among intersecting numbers for states corresponding to allowed Yukawa couplings, and also it is found that their couplings are determined by discrete Abelian symmetries. Our studies on the flavor structure and the coupling selection rule in this class of models show that there is no solution to derive realistic Yukawa matrices only from stringy 3-point couplings at the tree-level within the framework of the minimal matter content of the supersymmetric standard model.

Remark on integrating out heavy moduli in flux compactification

We study two steps of moduli stabilization in type IIB flux compactification with gaugino condensations. We consider the condition that one can integrate out heavy moduli first with light moduli remaining. We give appendix, where detail study is carried out for potential minima of the model with a six dimensional compact space with h{sub 1,1}=h{sub 2,1}=1, including the model, whose respective moduli with h{sub 1,1},h{sub 2,1}{ne}1 are identified.

Moduli-mixing racetrack model

Abstract We study supersymmetric models with double gaugino condensations in the hidden sector, where the gauge couplings depend on two light moduli of superstring theory. We perform a detailed analysis of this class of model and show that there is no stable supersymmetric minimum with finite vacuum values of moduli fields. Instead, we find that the supersymmetry breaking occurs with moduli stabilized and negative vacuum energy. That yields moduli-dominated soft supersymmetry breaking terms. To realize slightly positive (or vanishing) vacuum energy, we add uplifting potential. We discuss uplifting does not change qualitatively the vacuum expectation values of moduli and the above feature of supersymmetry breaking.

Dynamically sequestered F-term uplifting in extra dimension

We study moduli stabilization, the dynamical supersymmetry (SUSY) breaking, the uplifting of SUSY anti-de Sitter (AdS) vacuum and the sequestering of hidden sector in a five-dimensional supergravity model, where all modes of the visible sector and the hidden sector are originated from bulk fields. We clarify couplings between the visible and hidden sectors. The expressions for the visible sector soft SUSY breaking terms as well as the hidden sector potential are shown explicitly in our model. The sequestering is achieved dynamically by a wavefunction localization in extra dimension. We find that the tree-level soft scalar mass and the A-term can be suppressed at a SUSY breaking Minkowski minimum where the radius modulus is stabilized, while gaugino masses would be a mirage type.

Anomalous U(1) D-term contribution in type i string models

We study the D-term contribution for anomalous

Wave-Function Profile and SUSY Breaking in 5D Model with Fayet-Iliopoulos Terms

U(1)

Twisted moduli stabilization in type I string models

symmetries in type I string models and derive a general formula for the D-term contribution, assuming that the dominant source of supersymmetry breaking is given by the F terms of the dilaton, (overall) moduli, or twisted moduli fields. On the basis of the formula, we also point out that there are several features different from the case of heterotic string models. The differences originate from the different forms of the Kahler potential between twisted moduli fields in type I string models and the dilaton field in heterotic string models.