Photon Euler equation
= Photon Euler equation
The dipole member of the photon Boltzmann hierarchy is the photon Euler equation. In Newtonian gauge and without collisions,
$$
\Theta_1'=\frac{k}{3}(\Theta_0+\Psi-2\Theta_2).
$$
= Photon Euler equation
The dipole member of the photon Boltzmann hierarchy is the photon Euler equation. In Newtonian gauge and without collisions,
$$
\Theta_1'=\frac{k}{3}(\Theta_0+\Psi-2\Theta_2).
$$