Conformal upper bounds for the first eigenvalue of the p-Laplacian

Let M be a compact, connected, m-dimensional manifold without boundary and p>1. For 1<p\leq m, we prove that the first eigenvalue \lambda_{1,p} of the p-Laplacian is bounded on each conformal class of Riemannian metrics of volume one on M. For p>m, we show that any conformal class of Riemannian metrics on M contains metrics of volume one with \lambda_{1,p} arbitrarily large. As a consequence, we obtain that in two dimensions \lambda_{1,p} is uniformly bounded on the space of Riemannian metrics of volume one if 1<p\leq 2, respectively unbounded if p>2.