“…If we represents the membrane as the graph of a nonnegative function u : Ω → R, this function minimizes the functional (here g > 0 is the gravitational constant), see Figure 6. The existence and uniqueness of a minimizer for (2.3) follows by standard techniques in the calculus of variations, see for instance [16,Section 2]. Then, computing the Euler-Lagrange equations for the minimizer u, one can prove that u satisfies the equation ∆u = g χ {u>0} , see for instance [16,Section 3].…”