 Cosmic inflation

Cosmic inflation is a proposed early period of accelerating expansion of the universe. In general relativity, a homogeneous component with sufficiently negative pressure can drive this behaviour. In units $c=1$, the Friedmann acceleration equation gives acceleration when the total source satisfies $\rho +3P<0$. A slowly evolving canonical scalar field can meet this condition when its potential energy dominates its kinetic energy.

During acceleration the comoving Hubble radius decreases. Perturbations can move from scales smaller than the Hubble radius to larger scales, linking the early dynamics with later Cosmic microwave background anisotropy and structure formation. Different inflaton potentials predict different fluctuation spectra and correlations, so inflation is a class of models with testable assumptions. Ending acceleration and producing a hot particle bath also require an explanation through a graceful exit from inflation and reheating.^[ref]