Supersymmetry breaking and its implication to cosmology

在这项工作中，我在具有低能超对称的粒子物理模型的框架下研究了宇宙学。特别是，我特别关注1)宇宙密度涨落的起源，以及2)大爆炸核合成。在第一个主题中，我考虑了存在一些标量场（而不是暴胀场）的情况，这些标量场曾在早期统治过宇宙。如果这样一个标量场获得了原初的振幅涨落，它就可能成为目前宇宙密度涨落的起源。（这样的标量场被称为“曲率”场。）在超对称模型中有各种各样的候选曲率场。我考虑了右手标量中微子扮演曲率场角色的情况，以及在这种情况下可能出现的信号。我还讨论了超对称模型中所谓的d项暴胀模型的曲率情景的含义。关于第二个主题，我考虑了引力子的衰变对大爆炸核合成的影响，引力子是引力子的超级伴侣。我对引力子的衰变速率进行了详细的计算，获得了关于引力子衰变产物的精确信息。然后，研究了这些衰变产物对轻元素丰度的影响。我用这个计算得到了膨胀后再加热温度的一个非常可靠的上界。

In this work, I have studied cosmology in the framework of particle-physics models with low-energy supersymmetry. In particular, I have paid particular attention to 1) origin of the density fluctuation of the universe, and 2) big-bang nuclesynthesis.On the first topics, I have considered the case where there exists some scalar field (other than the inflaton) which once dominates the universe in the early epoch. If such a scalar field acquires primordial amplitude fluctuation, it may become the origin of the present density fluctuation of the universe. (Such a scalar field is called the "curvaton" field.) There are various candidates of the curvaton field in supersymmetric models. I have considered the case where the right-handed scalar neutrino plays the role of the curvaton field, and possible signals in such a case. I also discussed the implication of the curvaton scenario for the so-called D-term inflation model in supersymmetric model.On the second subject, I considered the effects of the decay of the gravitino, which is the superpartner of the graviton, on the big-bang nucleosynthesis. I have performed a detailed calculation of the decay rate of the gravitino and obtained a precise information about the decay products of the gravitino. Then, I have studied the effects of those decay products on the light-element abundances. I have obtained a very reliable upper bound on the reheating temperature after the inflation using this calculation.