# Compactness of asymptotically hyperbolic Einstein 4-manifolds

# Compactness of asymptotically hyperbolic Einstein 4-manifolds

**Online Talk **

Let $X^4$ be a differentiable 4-manifold with the boundary $M^3 = \partial X^4$ . Given a conformal class $(M, [h])$ of Riemannian metric $h$ on $M$, we try to ﬁnd ”conformal ﬁlling in” an asymptotically hyperbolic Einstein $g_+$ on $X$ such that $r^2 g_+|_M = h$ for some deﬁning function $r$ on $X$. The study of complete AH Einstein manifolds has become very active due to the AdS/CFT correspondence in string theory.

In this talk, instead of addressing the existence problem of a conformal ﬁlling in, we discuss the compactness problem, that is, how the compactness of the sequence of conformal inﬁnity metrics leads to the compactness result of the compactiﬁed ﬁlling in AHE manifolds under the suitable assumptions on the topology of X and some conformal invariants. We brieﬂy survey some known results then report recent joint work in progress with Alice Chang. Some applications will be discussed