Bahri invariants for fractional Nirenberg-type flows

Abstract

This paper is concerned with prescribing the fractional Q-curvature on the unit sphere mathbb {S}^{n} endowed with its standard conformal structure g_0, nge 4. Since the associated variational problem is noncompact, we approach this issue with techniques passed by Abbas Bahri, as the well known theory of critical points at infinity, as well as some lesser known topological invariants that appear here as criteria for existence results.