“…The existence theory (in the less-diffusivity case) has been for instance developed in [55,15,1,50,20,51], while stability of hydrodynamic equilibria is studied in [25,74,65,26]. We also refer to the so-called temperature patch (or front) problem adressed in [21,33,16]. Note that there is no diffusivity in the transport equation on the density, which makes the mathematical analysis much more challenging than the thermal diffusion case.…”