##
**Generalized existence of isoperimetric regions in non-compact Riemannian manifolds and applications to the isoperimetric profile.**
*(English)*
Zbl 1297.49081

Let \((M,g)\) be a complete Riemannan manifold. Denote by \(V\) the canonical Riemannian measure induced on \(M\) by \(g\) and by \(A\) the \((n-1)\)-Hausdorff measure associated to the canonical Riemannian length space metric \(d\) of \(M\). The isoperimetric profile function \(I_M:[0,V(M)[\to [0,\infty[\) is defined by \(I_M(v)=\inf\{A(\partial \Omega):\Omega\in \tau_M, V(\Omega)=v\}\) for \(v\neq 0\) and \(I_M(0)=0\), where \(\tau_M\) denotes the set of relatively compact open subsets of \(M\) with smooth boundary. The author considers instead of \(\tau_M\) the subsets of finite perimeter. The main result of the present paper is Theorem 2 which provides a generalized existence result for isoperimetric regions in a noncompact Riemannian manifold satisfying the condition of bounded geometry. In the general case solutions do not exist in the original ambient manifold, but rather in the disjoint union of a finite number of pointed limit manifolds \(M_{1,\infty},\dots M_{N,\infty}\), obtained as limit of \(N\) sequences of pointed manifolds \((M,p_{ij},g)_j, i\in\{1,\dots,N\}\). After the proof of Theorem 2, one obtains a decomposition lemma for the thick part of a subsequence of an arbitrary minimizing sequence, which extracts exactly the structure of such sets, important for the study of the isometric profile.

Reviewer: Vasile Oproiu (Iaşi)

### MSC:

49Q20 | Variational problems in a geometric measure-theoretic setting |

49Q05 | Minimal surfaces and optimization |

53A10 | Minimal surfaces in differential geometry, surfaces with prescribed mean curvature |

58E99 | Variational problems in infinite-dimensional spaces |