A linear analysis of the stability of strong shocks and the evolution and distribution of materials in a cold dark matter dominated universe

In the first part of the dissertation, the analysis of rippling instability for strong decelerating shock waves is given. The results show that the shocks are overstable for the values of the adiabatic index close to one and most overstable for the wavelength comparable to the thickness of shells behind the shocks. Also the stability of isothermal shock waves has been studied by approximating the dynamical evolution of high density regions behind the shock waves. The results predict that isothermal blast shocks are overstable for post-shock density contrasts greater than ∼10 and isothermal wind-driven shocks are overstable for density contrasts greater than ∼25. In the second part of the dissertation, calculations using fluid codes have been done for three cosmological problems. Firstly, nonlinear gravitational clustering in a universe dominated by a coherently oscillating scalar field, which is a candidate of the cold dark matter, has been studied. The results show a marginal agreement with the observations. Secondly, the evolution of the intergalactic medium has been calculated in a universe dominated by a cold dark matter. The gravitational force has been calculated by interpolating the initial gravitational potential, and galaxies have formed only if the baryonic mater density is high. The results have been discussed. Finally, the evolution and distribution of the intergalactic medium, as well as the dark matter and galaxies, have been studied in a universe dominated by a cold dark matter. The results show a pattern of galaxy formation with peak at the redshift z ∼ 9 and the distributions of the IGM and galaxies which are not incompatible with the observations