Formation of Density Fluctuation and Spacetime structure in Extended Inflation Model

COBE发现了宇宙背景辐射的涨落，这在很大程度上支持了膨胀宇宙模型，因为光谱与该模型预测的光谱完全相同。然而，这一模型仍然存在一些理论问题。在目前的工作中，我们首先用Regge微积分方法研究了宇宙无毛猜想在什么条件下成立。在均匀模型和各向异性模型中，我们发现了对膨胀初始条件的一些约束，现在正在将这种方法推广到非均匀模型。其次，我们研究了真空相变在早期宇宙中可能形成的整体织构对密度涨落的产生。我们发现它具有非高斯涨落的幂函数谱。第三，我们研究了真空相变形成虫洞的条件及其演化。我们发现，在满足弱能量条件的情况下，膨胀宇宙中仍然可以存在可穿越的虫洞。这项研究是与M.长泽、Y.Furihata和K.Narahara合作完成的。

The Inflationary Universe Model was greatly supported by the discovery of the fluctuations in cosmic background radiation by COBE,since the spectrum was just the same one predicted by this model. This model, however, still have some theoretical problems. In the present work, first we investigated by what conditions cosmic no hair conjecture holds, by using Regge Calculus Method. We found some constraints on the initial condition for inflation in homogeneous and anisotropic model, and now are extending this method to inhomogeneous model. Second, we investigated generation of the density fluctuations by global texture which is expected to be formed in early universe by phase transition of vacuum. We found it has a power law spectrum with non Gaussian fluctuations. Third we investigated the condition of formation of wormholes by phase transition of vacuum, and their evolution. We found traversable wormholes can exist in expanding universe in spite that weak energy condition is satisfied. This research was done as collaboration with M.Nagasawa, Y.Furihata and K.Narahara.