%0 Report
%D 2018
%T Transmission conditions obtained by homogenisation
%A Gianni Dal Maso
%A Giovanni Franzina
%A Davide Zucco
%X We study the asymptotic behaviour of solutions to variational problems in perforated domains with Neumann boundary conditions. We consider perforations that in the limit concentrate on a smooth manifold. We characterise the limits of the solutions and show that they solve a variational problem with a transmission condition across the manifold. This is expressed through a measure on the manifold, vanishing on sets of capacity zero. Then, we prove that every such measure can be obtained by homogenising suitable perforations. Eventually, we provide an asymptotic formula for this measure by using some auxiliary minimum problems.
%G en
%U http://preprints.sissa.it/handle/1963/35310
%1 35618
%2 Mathematics
%4 1
%# MAT/05
%$ Submitted by Maria Pia Calandra (calapia@sissa.it) on 2018-03-19T09:23:08Z
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%0 Journal Article
%D 2016
%T Confinement of dislocations inside a crystal with a prescribed external strain
%A Ilaria Lucardesi
%A Marco Morandotti
%A Riccardo Scala
%A Davide Zucco
%X We study screw dislocations in an isotropic crystal undergoing antiplane shear. In the framework of linear elasticity, by fixing a suitable boundary condition for the strain (prescribed non-vanishing boundary integral), we manage to confine the dislocations inside the material. More precisely, in the presence of an external strain with circulation equal to n times the lattice spacing, it is energetically convenient to have n distinct dislocations lying inside the crystal. The novelty of introducing a Dirichlet boundary condition for the tangential strain is crucial to the confinement: it is well known that, if Neumann boundary conditions are imposed, the dislocations tend to migrate to the boundary. The results are achieved using PDE techniques and Ƭ-convergence theory, in the framework of the so-called core radius approach.
%G en
%U http://urania.sissa.it/xmlui/handle/1963/35247
%1 35558
%2 Mathematics
%$ Submitted by Maria Pia Calandra (calapia@sissa.it) on 2016-10-20T11:44:46Z
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%0 Report
%D 2015
%T Convex combinations of low eigenvalues, Fraenkel asymmetries and attainable sets
%A Dario Mazzoleni
%A Davide Zucco
%X We consider the problem of minimizing convex combinations of the first two eigenvalues of the Dirichlet-Laplacian among open set of $R^N$ of fixed measure. We show that, by purely elementary arguments, based on the minimality condition, it is possible to obtain informations on the geometry of the minimizers of convex combinations: we study, in particular, when these minimizers are no longer convex, and the optimality of balls. As an application of our results we study the boundary of the attainable set for the Dirichlet spectrum. Our techniques involve symmetry results à la Serrin, explicit constants in quantitative inequalities, as well as a purely geometrical problem: the minimization of the Fraenkel 2-asymmetry among convex sets of fixed measure.
%I SISSA
%G en
%U http://urania.sissa.it/xmlui/handle/1963/35140
%1 35378
%2 Mathematics
%4 1
%# MAT/05
%$ Submitted by Davide Zucco (dzucco@sissa.it) on 2015-12-03T12:26:59Z
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%0 Report
%D 2014
%T Where best to place a Dirichlet condition in an anisotropic membrane?
%A Paolo Tilli
%A Davide Zucco
%X We study a shape optimization problem for the first eigenvalue of an elliptic operator in divergence form, with non constant coefficients, over a fixed domain $\Omega$. Dirichlet conditions are imposed along $\partial\Omega$ and, in addition, along a set $\Sigma$ of prescribed length ($1$-dimensional Hausdorff measure). We look for the best shape and position for the supplementary Dirichlet region $\Sigma$ in order to maximize the first eigenvalue. We characterize the limit distribution of the optimal sets, as their prescribed length tends to infinity, via $\Gamma$-convergence.
%I SISSA
%G en_US
%U http://urania.sissa.it/xmlui/handle/1963/7481
%1 7592
%$ Submitted by dzucco@sissa.it (dzucco@sissa.it) on 2014-11-07T16:09:28Z
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%0 Journal Article
%D 2013
%T Asymptotics of the first Laplace eigenvalue with Dirichlet regions of prescribed length
%A Paolo Tilli
%A Davide Zucco
%X We consider the problem of maximizing the first eigenvalue of the $p$-Laplacian (possibly with nonconstant coefficients) over a fixed domain $\Omega$, with Dirichlet conditions along $\partial\Omega$ and along a supplementary set $\Sigma$, which is the unknown of the optimization problem. The set $\Sigma$, which plays the role of a supplementary stiffening rib for a membrane $\Omega$, is a compact connected set (e.g., a curve or a connected system of curves) that can be placed anywhere in $\overline{\Omega}$ and is subject to the constraint of an upper bound $L$ to its total length (one-dimensional Hausdorff measure). This upper bound prevents $\Sigma$ from spreading throughout $\Omega$ and makes the problem well-posed. We investigate the behavior of optimal sets $\Sigma_L$ as $L\to\infty$ via $\Gamma$-convergence, and we explicitly construct certain asymptotically optimal configurations. We also study the behavior as $p\to\infty$ with $L$ fixed, finding connections with maximum-distance problems related to the principal frequency of the $\infty$-Laplacian.
%I Society for Industrial and Applied Mathematics
%G en
%U http://urania.sissa.it/xmlui/handle/1963/35141
%1 35379
%2 Physics
%4 1
%# MAT/05
%$ Approved for entry into archive by Maria Pia Calandra (calapia@sissa.it) on 2015-12-09T16:12:39Z (GMT) No. of bitstreams: 0
%R 10.1137/130916825