Continuum limits of Laplace operators on general lattices are considered, and it is
shown that these operators converge to elliptic operators on the Euclidean space in
the sense of the generalized norm resolvent convergence. We then study operators on
the hexagonal lattice, which does not apply the above general theory, but we can
show its Laplace operator converges to the continuous Laplace operator in
the continuum limit. We also study discrete operators on the square lattice
corresponding to second order strictly elliptic operators with variable coefficients,
and prove the generalized norm resolvent convergence in the continuum
limit.
Keywords
discrete Schrödinger operators, continuum limit, hexagonal
lattices, general lattices