Energy conservation for inhomogeneous incompressible and compressible Euler equations

Energy conservations are studied for inhomogeneous incompressible and compressible Euler equations with general pressure law in a torus or a bounded domain. We provide sufficient conditions for a weak solution to conserve the energy. By exploiting a suitable test function, the spatial regularity for the density is only required to be of order $2\mathrm{/}3$ in the incompressible case, and of order $1\mathrm{/}3$ in the compressible case. When the density is constant, we recover the existing results for classical incompressible Euler equation.