unstable: for example, the world lines of the dust particles in the Gödel solution have vanishing shear, expansion, and acceleration, but constant vorticity just balancing a constant Raychuadhuri scalar due to nonzero vacuum energy ("cosmological constant").
Schrödinger equation | Nernst equation | Monge–Ampère equation | Boltzmann equation | Tapan Raychaudhuri | Diophantine equation | Ordinary differential equation | ordinary differential equation | Young–Laplace equation | Wave equation | wave equation | Vlasov equation | Tait equation | Smoluchowski coagulation equation | Sauerbrey equation | Redlich–Kwong equation of state | Ramanujan–Nagell equation | Quadratic equation | Prony equation | Pell's equation | Mathieu's equation | Marchenko equation | Majorana's equation | Linear equation | linear equation | Liénard equation | Kepler's equation | Kaup–Kupershmidt equation | Ishimori equation | Hyperbolic partial differential equation |