∂2⁡𝒦∂⁡u2+∂2⁡𝒦∂⁡v2+∂2⁡𝒦∂⁡w2+2⁢γ-1u⁢∂⁡𝒦∂⁡u+2⁢δ-1v⁢∂⁡𝒦∂⁡v+2⁢ϵ-1w⁢∂⁡𝒦∂⁡w=0.