Research On LTB Universe And Its Related Issues

The discovery of the dimming of the Ia type supernovae in 1998 has provided the modern physics great opportunities and also big challenges, and has troubled the minds of almost every physicists. Lemaitre-Tolman-Bondi (LTB) cosmological model is an alternative explanation to the observational fact of SNeIa dimming, while without the invocation of the mysterious dark energy. In this thesis, we investigate the LTB universe and its related issues. This thesis has five chapters:The first chapter as an introduction mainly introduces the background of our research, including the observational foundations of modern cosmology, and accelerating expansion of the universe and the possible mechanisms to explain it. The motivations for introducing the inhomogeneous cosmological models have also been provided.In the second chapter, our main purpose is to explore, theoretically, the D-dimensional LTB universe. We have provided its metric, and deduce the one-Hubble-parameter Friedmann equation, the two-Hubble-parameter Friedmann equation and the generalized accelerating equation and continuity equation. Furthermore, we have given the null geodesic equations in D-dimensional LTB universe. Finally, we reformulate the basic equations of the LTB universe in redshift space.In the third chapter, we explore the other alternative methods to get the Friedmann equations. Firstly, we have deduce the one-Hubble-parameter Friedmann equation in the framework of Newtonian cosmology. Secondly, starting from the unified first law of thermodynamics, we have found the basic equations that dominate the evolution of the LTB universe, which is in agreement with the corresponding principle for closed systems put forward in this thesis. In the fourth chapter, we define the horizon of the LTB universe as trapping horizon, and give its corresponding Hawking temperature.In the last chapter, we summarize this thesis and look forward to the future.