| Several theoretical and observational arguments suggest the existence of a nonzero cosmological constant $Lambda$. Since the presence of such constant would affect the growth of gravitational instabilities leading to the formation of large scale structures, detailed observations of these structures, combined with theoretical models, might enable us to determine, or rule out, the existence of the cosmological constant.;This thesis presents the results of a detailed study of the formation and evolution of large scale structures in Friedmann models composed of non-relativistic, pressureless matter and a nonzero cosmological constant. The main objective of this study was to determine how large scale structures are affected by the presence of the cosmological constant, and whether introducing a nonzero $Lambda$ in the model improves the fit to the observations. The results of this work enables us to decide which observational tests are most likely to yield a determination the value of $Lambda$.;The main approach consists of deriving relations among various quantities characterizing the large scale structures and the Friedmann background, and to study the dependence of these relations upon the value of the cosmological constant.;Analytical approximations are used in Chapters 2, 3, and 4. Linear perturbation theory for $Lambda$ models is rederived in Chapter 2, and a simple relation between the peculiar velocity field, the density parameter, and the cosmological constant is obtained. Chapter 3 describes in detail the properties of spherically symmetric systems in $Lambda not=$ 0 models. In Chapter 4, analytical expressions for the density enhancement inside halos for $Lambda$ = 0 and $Lambda not=$ 0 are derived. Numerical simulations of cosmic voids are presented in Chapter 5. The relation between density contrast, peculiar velocity field, initial perturbation, and the cosmological parameters is discussed in great detail. Chapter 6 presents N-body simulations of galaxy clustering in $Lambda not=$ 0 models. The dependence of the two-point correlation function upon the cosmological constant is discussed. Summary and conclusions are given in Chapter 7. All results lead to the conclusion that studying the large scale structures is unlikely to provide definitive information on the value of the cosmological constant. |
