Investigation of cosmological phenomena by using generalized uncertainty principle

In this thesis, generalized uncertainty principle was studied. Firstly, generalized uncertainty principle modified van der Waals black hole solution was obtained. Thermodynamic properties and phase transition of modified solution were investigated. Also, phase transition in P-V plane was studied. Taking into account generalized uncertainty principle, it was shown that there is a physically meaningful phase transition. Secondly, using the modified entropy-area relation from DSR-GUP, modified Friedmann equations were obtained from the first law of thermodynamics at apparent horizon. A minimum apparent horizon, which has the potential to remove the Big Bang singularity, was found. Also, deceleration parameter was studied for the all eras of the Universe. The generalized second law of thermodynamics is satisfied for the all eras of the Universe. Finally, Shapiro time delay, gravitational redshift, and geodetic precession were investigated for generalized uncertainty principle modified Schwarzschild metric. Using observational and experimental results, uppper bounds of generalized uncertainty principle dimensionless parameter were obtained. These bounds compared with other bounds in the literature.