man div_div (3): -grad div operator

SYNOPSIS

form (const space V, const space& V, "div_div");

Assembly the form associated to the grad(div(.)) operator on the finite element space V:

                 /
                 |
        a(u,v) = | div(u) div(v) dx
                 |
                 / Omega

This form is usefull when considering elasticity problem.

Here is an example of the vector-valued form:

        geo omega ("square");
        space V (omega, "P2", "vector");
        form  a (V, V, "div_div");