Department of Mathematics, University of California, Berkeley, CA 94720;
Department of Mathematics, University of California, Davis, CA 95616.
Proc Natl Acad Sci U S A. 2018 Oct 23;115(43):10857-10860. doi: 10.1073/pnas.1718953115.
We define an integer invariant [Formula: see text] of a smooth, compact, closed 4-manifold X by minimizing a certain complexity of a trisection of X over all trisections. The good feature of [Formula: see text] is that when [Formula: see text] and X is a homology 4-sphere, then X is diffeomorphic to the 4-sphere. Naturally, L is hard to compute.
我们通过在所有三分叉中最小化 X 的三分叉复杂度来定义光滑、紧致、闭 4 流形 X 的整数不变量 [公式:见正文]。[公式:见正文] 的一个很好的特点是,当 [公式:见正文] 且 X 是一个同调 4-球体时,那么 X 与 4-球体同胚。自然地,L 很难计算。