Evolution Of The Universe And The Structure

In this master dissertation, under the fundamental frame of general relativity, we study the tachyon inflation, D-stars in the spacetime with a nonzero cosmological constant and it's observable effects by using some modern mathematical methods such as differential equation and qualitative analysis.Firstly, in order to make a theoretical preparation for tachyon cosmology and D-star, we briefly review the standard hot big bang cosmology with inflation.Then, based on above review, we propose an analytical tachyon inflation model driven by scalar field with Bom-Infeld-type Lagrangian. We find it's an analytical model if we choose an exponential potential. We compute it's power spectrum and find that it can explain the evolution of universe.At last, we discuss the structure of D-stars in the spacetime with a nonzero cosmological constant .The metric and effective mass formula of D-stars have been educed. There is a factor which depends on the breaking scale in the formula of angle of deflection of timelike and spacelike test particles in this kind of cold stars .It is a possible observational effect for astrophysics. Qualitative analysis of dynamic system indicates that planetary structure can be formed from this kind of cold stars.