ASPECTS OF UNIFORMITY IN RECURRENCE
ASPECTS OF UNIFORMITY IN RECURRENCE
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重复性的一致性方面
DOI:
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发表时间:
2000
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通讯作者:
Franiçois Parreau
中科院分区:
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作者:
V. Bergelson;B. Host;R. McCutcheon;Franiçois Parreau
We analyze and cite applications of various, loosely related notions of uni- formity inherent to the phenomenon of (multiple) recurrence in ergodic theory. An assort- ment of results are obtained, among them sharpenings of two theorems due to Bourgain. The first of these, which in the original guarantees existence of sets {x,x +h,x +h 2 } in subsetsE of positive measure in the unit interval, with lower bounds onh depending only onm(E), is expanded to the case of arbitrary finite polynomial configurations in subsets of positive measure in cubes of R n . The second is a direct computation of a lower bound, uniform ina andb and depending only on f, for f(x)f(x +at)f(x +bt)dxdt, where 0 �f � 1 is a function on the 1-torus. Our methodology parallels that of Bourgain, who originally considered the casea = 1,b = 2.