The asymptotically flat scalar-flat Yamabe problem with boundary

TL;DR

This paper addresses the existence of asymptotically flat scalar-flat metrics on non-compact manifolds with boundary, extending classical results to cases with boundary mean curvature conditions using elliptic PDE techniques.

Contribution

It establishes the existence of conformally equivalent scalar-flat metrics with prescribed boundary mean curvature on asymptotically flat manifolds, extending prior compact case results.

Findings

Existence of scalar-flat metrics matching given boundary data

Solution of elliptic PDE with critical exponent using sub- and supersolutions

Positive Sobolev quotient assumption is crucial

Abstract

We consider two cases of the asymptotically flat scalar-flat Yamabe problem on a non-compact manifold with boundary, in dimension $n\geq3$. First, following arguments of Cantor and Brill in the compact case, we show that given an asymptotically flat metric $g$, there is a conformally equivalent asymptotically flat scalar-flat metric that agrees with $g$ on the boundary. We then replace the metric boundary condition with a condition on the mean curvature: Given a function $f$ on the boundary that is not too large, we show that there is an asymptotically flat scalar-flat metric, conformally equivalent to $g$ whose boundary mean curvature is given by $f$. The latter case involves solving an elliptic PDE with critical exponent using the method of sub- and supersolutions. Both results require the usual assumption that the Sobolev quotient is positive.