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 $$ p = -A/\rho^\alpha $$, where $$p$$ is the pressure, $$\rho$$ is the density, with $$\alpha = 1$$ and $$A$$ a positive constant. The substance is named after Sergey Chaplygin.

In some models, generalized Chaplygin gas is considered, where $$\alpha$$ is a parameter, which can take on values $$0 < \alpha \le 1$$.