Fundamental Tone, Concentration of Density, and Conformal Degeneration on Surfaces

http://dx.doi.org/10.4153/CJM-2009-029-1
Canad. J. Math. 61(2009), 548-565

  Published:2009-06-01
 Printed: Jun 2009

We study the effect of two types of degeneration of a Riemannian metric on the first eigenvalue of the Laplace operator on surfaces. In both cases we prove that the first eigenvalue of the round sphere is an optimal asymptotic upper bound. The first type of degeneration is concentration of the density to a point within a conformal class. The second is degeneration of the conformal class to the boundary of the moduli space on the torus and on the Klein bottle. In the latter, we follow the outline proposed by N. Nadirashvili in 1996.