In
physical cosmology
Physical cosmology is a branch of cosmology concerned with the study of cosmological models. A cosmological model, or simply cosmology, provides a description of the largest-scale structures and dynamics of the universe and allows study of fu ...
, warm inflation is one of two dynamical realizations of
cosmological inflation. The other is the standard scenario,
sometimes called cold inflation.
In warm inflation radiation production occurs concurrently with inflationary expansion. This is consistent with the conditions necessary for inflation as given by the
Friedmann equations
The Friedmann equations, also known as the Friedmann–Lemaître (FL) equations, are a set of equations in physical cosmology that govern cosmic expansion in homogeneous and isotropic models of the universe within the context of general relativi ...
of
general relativity
General relativity, also known as the general theory of relativity, and as Einstein's theory of gravity, is the differential geometry, geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of grav ...
, which simply require that the
vacuum energy
Vacuum energy is an underlying background energy that exists in space throughout the entire universe. The vacuum energy is a special case of zero-point energy that relates to the quantum vacuum.
The effects of vacuum energy can be experiment ...
density dominates the energy content of the universe at time of inflation, and so does not prohibit some radiation to be present. As such the most general picture of inflation would include a radiation energy density component. The presence of radiation during inflation implies the inflationary phase could smoothly end into a
radiation-dominated era without a distinctively separate reheating phase,
thus providing a solution to the
graceful exit problem of inflation.
References
{{Reflist
Particle physics
Inflation (cosmology)