{ "id": "1004.2517", "version": "v4", "published": "2010-04-14T22:18:08.000Z", "updated": "2011-06-16T20:57:19.000Z", "title": "Upper and lower bounds for normal derivatives of spectral clusters of Dirichlet Laplacian", "authors": [ "Xiangjin Xu" ], "comment": "14 pages, Rewrite section 6 (the appendix) and correct a mistake in section 6", "categories": [ "math.AP", "math.SP" ], "abstract": "In this paper, we prove the upper and lower bounds for normal derivatives of spectral clusters $u=\\chi_{\\lambda}^s f$ of Dirichlet Laplacian $\\Delta_M$, $$c_s \\lambda\\|u\\|_{L^2(M)} \\leq \\| \\partial_{\\nu}u \\|_{L^2(\\partial M)} \\leq C_s \\lambda \\|u\\|_{L^2(M)} $$ where the upper bound is true for any Riemannian manifold, and the lower bound is true for some small $0