Study of a quantum inhomogeneous universe

点击翻译按钮获取中文摘要

In order to understand the quantum origin of inhomogeneous structures of the universe, the relation between quantum fluctuations of the spacetime metric and those of matter fields has been investigated in this project. (1)Quantum fluctuations in the power-law inflationary universe It was shown that the infrared quantum fluctuations in a power-law inflation model are more unstable than those in exponential inflation. Using this instability, the baryon spectrum in a unified model with majoron is found to be exactly what one needs for the minimal isocurvature scenario of the structure formation. Further, the probability distribution is found to be highly non-Gaussian on small scales but is Gaussian on large scales. (2)Quantum tunneling in the early universe To understand quantum tunneling in the universe, it is important to analyze the effect of dissipative environment, as well as to know the role of gravity. As a first step, a canonical formulation of quantum tunneling with dissipation was given and it was shown that dissipative interactions may not necessarily suppress the tunneling rate. Then, false vacuum decay under the presence of gravity was investigated and it was found that the existence of gravitational modes changes the previous naive picture significantly.