Stability of Valuations and Koll\'ar Components
  We prove that among all Koll\'ar components obtained by plt blow ups of a klt singularity $o \in (X, D)$, there is at most one that is (log-)K-semistable. We achieve this by showing that if such a Koll\'ar component exists, it uniquely minimizes the normalized volume function introduced in [Li15a] among all divisorial valuations. Conversely, we show any divisorial minimizer of the normalized volume function yields a K-semistable Koll\'ar component. We also prove that for any klt singularity, the infimum of the normalized function is always approximated by the normalized volumes of Koll\'ar components. 
Chi Li and Chenyang Xu
math.AG math.AC math.DG