Codimension-Two bifurcations for convection in binary fluid mixtures.

An amplitude equation is derived for thermal convection in a binary fluid mixture in a porous medium and in bulk, in the vicinity of the intersection point of the lines of stationary and oscillatory instabilities. Slow spatial modulations are included in the amplitude equation near this codimension-two bifurcation. The experimental realizability in binary fluid mixtures is discussed using data for specific systems like alcohol-water mixtures and normal fluid He-3-He-4 mixtures. Analogies are drawn to other physical systems which are easily accessible to experiment, like the convective instability in nematic liquid crystals in an external magnetic field.