Relativistic Astrophysics Based on Brane Cosmologyブレイン宇宙モデルに基づく相対論的宇宙物理学

弦理论中出现的“膜”概念，彻底改变了人们对早期宇宙和强引力现象的看法。它也改变了Kaluza和Klein对高维的传统看法，即膜的存在使得大的额外维度成为可能和可见。Randall和Sundrum提出了新的膜模型，给出了新的紧化机制类型。特别是第二个模型，因为它给出了高维世界中没有紧化的牛顿引力，而成为宇宙学家关注的焦点。这个模型提供了一个与传统的Kaluza-Klein紧化完全不同的方面。因此，许多相对主义者和宇宙学家正在研究它，以寻找新的世界观。在这种情况下，基于膜引力理论分析宇宙模型和强引力现象（如黑洞或引力坍缩）是非常重要的。在这个研究项目中，我们在两位杰出的年轻教授（David Wands和David Langlois）的帮助下，研究了膜世界的新观点。为了澄清膜引力的性质，我们研究了热释宇宙学模型中的膜碰撞，这可能是标准暴胀情景的一种替代方案，以及导致宇宙大爆炸的再加热机制。我们还分析了一些由弦理论量子修正而来的具有更高曲率项的有效理论，讨论了它们的宇宙学模型，并提出了新的暴胀情景。

The idea of "brane", which appeared in string theory, changes completely the view of the early universe and strong gravitational phenomena. It also changes the view of higher dimensions from the conventional old idea by Kaluza and Klein, i.e., the existence of a brane makes a large extra dimension possible and visible. Furthermore new brane models proposed by Randall and Sundrum give new types of compactification mechanism. Especially, the second model has become the focus of cosmologist's attention because it gives the Newtonian gravity in higher dimensional world without compactification. This model provides definitely a different aspect from the conventional Kaluza-Klein compactification. Hence many relativists and cosmologists are studying it to look for new world view. Under such a circumstance, it is very important to analyze cosmological models and strong gravitational phenomena such as a black hole or gravitational collapse based on this brane gravitational theory. In this research project, we study new view of the brane world with the help of two prominent young professors (David Wands and David Langlois).In order to clarify the properties of brane gravity, we have studied brane collision in the ekpyrotic cosmological model, which could be an alternative of the standard inflation scenario, and the reheating mechanism, which leads the universe to a big bang. We have also analyzed some effective theories with higher curvature terms, which come from quantum correction of string theory discussed their cosmological models, and proposed new inflationary scenario.