%0 Journal Article %T Spectral gap of segments of periodic waveguides %A Sylwia Kondej %A Ivan Veselic' %J Mathematics %D 2006 %I arXiv %R 10.1007/s11005-006-0111-5 %X We consider a periodic strip in the plane and the associated quantum waveguide with Dirichlet boundary conditions. We analyse finite segments of the waveguide consisting of $L$ periodicity cells, equipped with periodic boundary conditions at the ``new'' boundaries. Our main result is that the distance between the first and second eigenvalue of such a finite segment behaves like $L^{-2}$. %U http://arxiv.org/abs/math-ph/0608005v2