Superstring Theory and Low-Energy Physics

超弦理论是最有前途的统一理论。在这一理论中，时空维度应该大于4，这样才能使该理论在量子水平上保持一致。通过紧化后的四维有效理论，超维空间动态地成为共形不变的压缩流形。在该理论中，流形的拓扑和几何结构与规范对称性、物质场及其耦合等低能有效理论的各种性质密切相关。因此，弄清紧致流形的结构与低能有效理论之间的关系至关重要。在这个提出的共形不变流形的自发形变中，我们研究了Calabi-Yau超弦的可行的有效理论。我们研究了有效理论的特征，并期待在弱电标度下出现新的现象。找到了既能保证质子稳定性，又能实现规范耦合统一的现实解决方案。我们指出了R宇称在TeV尺度自发破缺的可能性。计算了Chargino和中性子的质谱图，并预测其中最轻的质量将小于弱玻色子质量。此外，我们还讨论了调味剂的代数和结构。在超对称模型所期望的双希格斯双重态模型中，发现带电的希格斯贡献可以给B介子无特征衰变的分支分数带来相当大的增强。我们研究了量子手性孤子与矢量介子耦合的稳定性。

Superstring theory is the most promising unified theory. In this theory the space-time dimension should be more than four so that the theory becomes consistent at quantum level. Four-dimensional effective theory is derived after the compactification through which the extra-dimensional space becomes a conformal invariant comactified manifold dynamically. In this theory topological and geometrical structure of the manifold is closely related to various properties of the low-energy effective theory such as gauge symmetries, matter fields and their couplings. Therefore, it is of critical importance to clarify the relation between the structure of compactified manifold and low-energy effective theory. In this proposed spontaneous deformation of conformal invariant manifold and using this mechanism we investigated viable effective theory from calabi-Yau superstring. We studied characteristic features of the effective theory and expected new phennomena at the electroweak scale.1. We found realistic solutions in which the proton stability is guaranteed and the unification of gauge couplings is realized.2. We pointed out the possibility that R-parity is spontaneously broken at TeV scale. Chargino and neutralino mass spectra are calculated and the lightest masses among them are predicted to be less than weak boson masses. Furthemore, we discussed the generation number and the structure of flavor mixing.3. In the two-Higgs-doublet model expected from the supersymmetric model, it is found that the charged Higgs contribution can give a sizable enhancement to the branching fractions of B-meson charamless decay.4. We studied the stability of quantum chiral solitions coupled with the vector mesons.