Jf. Escobar, CONFORMAL DEFORMATION OF A RIEMANNIAN METRIC TO A CONSTANT SCALAR CURVATURE METRIC WITH CONSTANT MEAN-CURVATURE ON THE BOUNDARY, Indiana University mathematics journal, 45(4), 1996, pp. 917-943
Let (M-n,g) be a compact Riemannian manifold with boundary and n great
er than or equal to 3. We show that for almost any (M-n,g) there exist
s a metric within the conformal class of g having constant scalar curv
ature on M and constant mean curvature on the boundary. The problem is
equivalent to finding a positive solution to a semilinear elliptic eq
uation with a non-linear boundary condition with critical Sobolev expo
nents in the interior and on the boundary.