Noether symmetry approach in pure gravity with variable G and Lambda

Abstract

We find exact cosmological solutions when the Newton parameter and the cosmological term are dynamically evolving in a renormalization-group improved Hamiltonian approach. In our derivation we use the Noether symmetry approach, leading to an interesting variable transformation which yields exact and general integration of the cosmological equations. The functional dependence of Lambda on G is determined by the method itself, therefore generalizing previous results on symmetry principles in cosmology. We find new functional relations between Lambda and G, jointly with power-law inflation for pure gravity.