Multiple correlation sequences not approximable by nilsequences
Abstract We show that there is a measure-preserving system $(X,\mathscr {B}, \mu , T)$ together with functions $F_0, F_1, F_2 \in L^{\infty }(\mu )$ such that the correlation sequence $C_{F_0, F_1, F_2}(n) = \int _X F_0 \cdot T^n F_1 \cdot T^{2n} F_2 \, d\mu $ is not an approximate integral combination of $2$ -step nilsequences.
2016 ◽
Vol 38
(4)
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pp. 1525-1542
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2016 ◽
Vol 38
(1)
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pp. 81-142
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2015 ◽
Vol 202
(2)
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pp. 875-892
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2013 ◽
Vol 35
(1)
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pp. 176-191
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Keyword(s):
1983 ◽
Vol 26
(1)
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pp. 2-9
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