Calculus of Variations and Geometric Measure Theory

R. Badal - M. Cicalese - L. De Luca - M. Ponsiglione

$\Gamma$-convergence analysis of a generalized $XY$ model: fractional vortices and string defects

created by ponsiglio on 09 Dec 2016
modified by cicalese on 21 Jan 2019


Published Paper

Inserted: 9 dec 2016
Last Updated: 21 jan 2019

Journal: Commun. Math. Phys.
Volume: 358
Number: 2
Pages: 705–739
Year: 2018


We propose and analyze a generalized two dimensional $XY$ model, whose interaction potential has $n$ weighted wells, describing corresponding symmetries of the system. As the lattice spacing vanishes, we derive by $\Gamma$-convergence the discrete-to-continuum limit of this model. In the energy regime we deal with, the asymptotic ground states exhibit fractional vortices, connected by string defects. The $\Gamma$-limit takes into account both contributions, through a renormalized energy, depending on the configuration of fractional vortices, and a surface energy, proportional to the length of the strings. Our model describes in a simple way several topological singularities arising in Physics and Materials Science. Among them, disclinations and string defects in liquid crystals, fractional vortices and domain walls in micromagnetics, partial dislocations and stacking faults in crystal plasticity.