正上密度回归点集的若干性质
Some properties of positive upper density recurrence points

令X为紧致度量空间，f:X→X为连续映射，讨论正上密度回归点与支撑点的关系，并证明当正上密度回归点集稠密时，可迁系统等价于E系统.
Let X be a compact metric space and f:X→X a continuous onto maps. This paper discusses the relationships of the positive upper Banach density recurrence point and the support point，and proves that a topologically transitivity system is equivalent to a E-system when the set of positive upper Banach density recurrence points is dense