postinflation

Postinflation is a term used in both economics and cosmology to denote the period after a phase of rapid expansion or price-level increase has ended. In economics, it refers to the phase following the successful reduction of inflation to low, stable levels and the normalization of inflation expectations. In cosmology, it describes the era after cosmic inflation ends and the universe transitions to a hot, radiation-dominated state through reheating.

In economic usage, a postinflation environment is characterized by price stability, credible monetary policy, and anchored inflation expectations. Real interest rates typically adjust as the central bank seeks to maintain sustainable growth without reigniting inflation. Wages and consumer prices gradually align with productivity gains, and investment and long-run growth may recover as uncertainty declines. Policy challenges include avoiding the double-edged effects of too-high real rates, which can slow growth, and ensuring that gains in price stability are durable and broadly shared. Disinflation, or a slow decline in inflation, may precede a true postinflation regime, and external shocks or supply constraints can test the durability of stability.

In cosmology, the postinflationary epoch follows the end of the inflationary expansion in the early universe. The inflaton field’s energy is converted into standard-model particles during reheating, setting the stage for the hot Big Bang. The universe then enters a radiation-dominated phase, followed by matter domination and later structure formation. Observational evidence, including the cosmic microwave background and light element abundances, underpins this sequence.

See also: inflation, disinflation, monetary policy, reheating, cosmic microwave background, Big Bang nucleosynthesis.