There are many elaborations of standard cosmology either involving new features following from known physics or involving new physics. While no convincing evidence exists for any of the mas of this writing, they are all being actively sought. Explain how to generalize standard cosmology to accommodate these possibilities and to test for them, repeating calculations, where possible.
(a) Space curvature.

(b) Dark energy. Adopt an empirical equation of state with the parameter w being constant and slightly greater than −1.

(c) Additional neutrino flavors, including sterile neutrinos.

(d) Nonadiabatic and non-Gaussian initial fluctuations.