The Standard Model of Cosmology

We mention the fundamentals in the theory of general relativity, i.e., the principles of equivalence and general covariance. Based on the facts that our universe is homogeneous and isotropic at large scales, we derive the Robertson-Walker metric and subsequently the Friedmann equation which governs the expansion of the universe. The equation is expressed in a convenient form in terms of density parameters. Next, we describe thermonuclear reaction rates utilized in astrophysics, which involve resonant and nonresonant reactions, photodisintegration, electron capture, and β-decay. We review the significance of standard Big Bang nucleosynthesis (SBBN) and summarize the current situation in the observed primordial abundance of light elements,4He, D, and 7Li. Comparing the calculated abundance of the elements with observed values, we determine a reasonable range for the baryon-to-photon ratio. Moreover, we examine the dependence of the produced amount of 4He on the measured lifetimes of neutrons. Finally, we consider the magnitude-redshift relation of type Ia supernovae (SNe Ia) as an independent probe to cosmological models.