ABSTRACT
The phase of the early universe accelerated expansion is called cosmic inflation. The idea of cosmic inflation has been around for 40 years now. The main observational support for inflation is based on the fact that the observed primordial density perturbations exhibit acausal correlations. The increasing precision of cosmological observations suggests that inflation is simple; driven by a single degree of freedom. Modelling this as a scalar field, the inflaton field, and then most probably the inflaton slow-rolls down a plateau scalar potential. Modelling dark energy as a scalar field, this quintessential inflation is severely constrained by both inflation and quintessence physics. Rendering late dark energy dynamical introduces a new tuning problem, that of its initial conditions. If the attractor is such that the dark energy substance is led to eventual domination, then the attractor is called a tracker. Modified gravity is becoming a popular alternative to scalar fields to model both early and late dark energy.
