Chaplygin gas

Chaplygin gas which occurs in certain theories of cosmology, is a hypothetical substance that satisfies an exotic equation of state in the form p = − A / ρ α where p is the pressure, ρ is the density, with α = 1 and A a positive constant. The substance is named after Sergey Chaplygin.

In some models, generalized Chaplygin gas is considered, where α is a parameter which can take on values 0 < α ≤ 1 .