Hence in the primal counter space there is strain and stress, analysis of which gives the ideal gas law. Their difference phi is a measure of the strain. A constant volume tetrahedron is taken as the basis, just as a triangle was taken for gases. The affine stress gradient is summed vectorially at the vertices, but the result is considerably more complicated than for the chord law . These tetrahedra are only stable when regular, but the equilibrium is dynamic as the residual stresses are not zero, but in a sensitive balance, giving the fluid its sensitivity.
Surfaces are thus the principal source of imbalance.
This behaviour may refer to vorticity. The reason is that they have zero volume and are thus singular for special affine geometry. Again a surface is most significant for such cases. Thus the behaviour of a volume of liquid is based on the constant volume property of special affine linkages coupled with the action of affine stress.