Dark Energy and the Cosmological Constant

One of the unknowns about dark energy, the illusive substance driving the observed acceleration of the universe, is what it is composed of? Is it a genuine cosmological constant of the observed energy density, or is it something else like an evolving scalar field (Quintessence) or something that is arising from a modification of Einstein's General theory of relativity on large scales?

This has come into stark question recently with the apparent tension arising in local and global measurements of the Hubble parameter today. One possible explanation is that we could be seeing evidence of early dynamical dark energy at a redshift linked to the region between matter radiation equality and recombination. Using a combination of analytical approaches to dark energy evolution through dynamical systems, and a complementary approach using genetic machine learning techniques to reconstruct the best fitting dark energy equation of state, we aim to say something more definitive than is currently possible about the nature of dark energy in the universe.