Dislocations are topological singularities in crystals, which may be described
by lines to which a lattice-valued vector, called Burgers vector, is associated.
They may be identified with divergence-free matrix-valued measures
supported on curves or with 1-currents with multiplicity in a lattice.
In the modeling of dislocations one is thus often lead to energies concentrated
on lines, where the integrand depends on the orientation and on the Burgers
vector of the dislocation.