Specific enthalpy per particle
= Specific enthalpy per particle
{title2=$\epsilon=(\rho+p)/n$}
For <number density> $n$, rest-frame <energy density> $\rho$ and <pressure> $p$, the enthalpy per particle is $\epsilon=(\rho+p)/n$. In an isentropic <barotropic fluid>, $d\rho=\epsilon\,dn$ and $dp=n\,d\epsilon$. It differs from enthalpy per unit mass by the particle mass when that mass is fixed. Using $\epsilon$ as thermodynamic variable gives $n=p'(\epsilon)$ and $\rho=\epsilon p'(\epsilon)-p(\epsilon)$.