Hypothetical substance used in certain cosmological theories
Chaplygin gas,[1][2] which occurs in certain theories of cosmology, is a hypothetical substance that satisfies an exotic equation of state in the form
,
where is the pressure, is the density, with and a positive constant. The substance is named after Sergey Chaplygin.
In some models, generalized Chaplygin gas is considered, where is a parameter, which can take on values .