Abstract. In this work, we show how suitable generalizations of the integer transfinite diameter of some compact sets in C give very good bounds for coefficients of polynomials with small Mahler measure. By this way, we give the list of all monic irreducible primitive polynomials of Z[X] of degree at most 36 with Mahler measure less than 1. 324... and of degree 38 and 40 with Mahler measure less than 1. 31.

The discretization by finite element methods of a new variational formulation of crack problems is considered. The new formulation, called the smooth domain method, is derived for crack problems in the case of an elastic membrane. Inequality type boundary conditions are prescribed at the crack faces. The resulting model takes the form of a unilateral contact problem on the crack. We study and implement various mixed finite element methods for the numerical approximation of the model. A priori error estimates are derived, and results of computations are provided. The convergence rates obtained from the numerical simulations are in agreement with the theoretical estimates.

We consider a general formulation for shape optimization problems involving the eigenvalues of the Laplace operator. Both the cases of Dirichlet and Neumann conditions on the free boundary are studied. We survey the most recent results concerning the existence of optimal domains, and list some conjectures and open problems. Some open problems are supported by efficient numerical computations.

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We study the Neumann-Laplacian eigenvalue problem in domains with multiple cracks. We derive a mixed variational formulation which holds on the whole geometric domain (including the cracks) and implement efficient finite element discretizations for the computation of eigenvalues. Optimal error estimates are given and several numerical examples are presented, confirming the efficiency of the method. As applications, we numerically investigate the behavior of the low eigenvalues in domains with a high number of cracks.