@misc{oai:ir.soken.ac.jp:00004071,
author = {矢田, 雅哉 and ヤタ, マサヤ and YATA, Masaya},
month = {2016-02-26},
note = {The superstring theory has been considered as an important candidate for a fundamental theory. There exist five consistent superstring theory: type I, type IIA, type IIB, SO(32) heterotic and E8×E8 heterotic theories. Heterotic strings automatically include the SO(32) or E8×E8 gauge symmetries, so it can explain the origin of gauge symmetries. Since the E8×E8 gauge group is remarkable from the point of view of the GUTs, E8×E8 heterotic string has been considered to be the most promising theory for describing the physics beyond the Standard Model. On the other hand, type II strings are possible to include gauge symmetries by D-branes which are higher dimensional objects. The D-branes have many interesting properties and applications, so various studies have been considered. Although superstring theories possess lots of attractive features, there is no conclusive evidence that the string theories are fundamental theories. The Standard Model does not appear automatically in the superstring theory in the first place. Thus, we must consider the scenario or setup that links the superstring theories at high energy and the Standard Model or the GUTs at low energy. The salient issue is that the superstring theories are consistent only in 10D spacetime. Since the Standard Model (or the GUTs) is in 4D spacetime, we do something about the issue. Usually, the extra 6D space is regarded as an unknown compact manifold and the size of the manifold is assumed to be sufficiently small. The long standing study of superstring theory reveals that the internal 6D space structure relates the framework of the 4D low energy field theories, such as the family structure and gauge groups. Although various approaches have been pursued to construct realistic models, none of the approaches can achieve the success. In heterotic string theory, one of the primary tasks of the string compactification is to find a way to realize a model with less moduli.
In this thesis, we introduce a novel, interesting brane setup in heterotic string theory, where we use NS5-branes instead of D-branes. After the brief review of heterotic string theory and orbifold compactifications, we consider the system of two stacks of intersecting NS5-brane in E8×E8 heterotic string theory and investigate the localized zeromodes on the branes. Since the generalized spin connection is in SU(3) structure, the system preserves 4D N=1 SUSY and the unbroken gauge symmetry is E6. We perform an explicit computation of the Dirac zeromodes on two types of intersecting five-brane backgrounds, the domain wall-type and vortex type solutions, and confirm that three chiral zeromodes, two are in 27 and one is in ￣27 representations in E6, are localized on the brane in both types of solutions.
We also investigate the possibility of realizing warped compactifications in heterotic string theory. It is known that warped compactification needs being with some of negative tension branes. In type II string theories, such an object corresponds to orientifolds. In the other hand, such negative tension objects have not been found in heterotic string theory. We suggest a possible interpretation of the negative tension branes in heterotic theories as a T-dual of the asymptotic form of the Atiyah-Hitchin manifold. Since the asymptotic form of the Atiyah-Hitchin manifold agrees with the negative charge Taub-NUT metric and Taub-NUT solutions can be converted to smeared NS 5-brane solutions by T-duality, we can obtain negative tension five-branes in heterotic string theory. Furthermore, The Atiyah-Hitchin manifold has a bolt singularity, the negative tension five-branes behave as orientifold like objects. In order to compactify the extra 4D space, we consider the Gibbons-Hawking metric for a three-dimensional periodic array of multi-Taub-NUT centers which contain positive NUT charges but also negative NUT charges, where the negative charge Taub-NUT is regarded as the asymptotic form of the Atiyah-Hitchin metric. The array is converted by T-duality to a system of NS5-branes with the SU(2) structure, and further considered as a heterotic background by the standard embedding.
The one of advantages of the NS5-brane construction is that it is a non-zero flux theory. The three form flux is beneficial to moduli stabilization, even if it cannot stabilize completely in heterotic string theory. It is also noteworthy that the setup is the new way that achieves the warped compactification in heterotic string theory., 総研大甲第1592号},
title = {Toward the construction of realistic models from Superstrings},
year = {}
}