Published online by Cambridge University Press: 20 November 2018
An unsettled conjecture of V. Bergelson and I. Håland proposes that if $(X,\,\mathcal{A},\,\mu ,\,T)$ is an invertible weak mixing measure preserving system, where $\mu (X)<\infty $, and if ${{p}_{1}},{{p}_{2}},...,{{p}_{k}}$ are generalized polynomials (functions built out of regular polynomials via iterated use of the greatest integer or floor function) having the property that no ${{p}_{i}}$, nor any ${{p}_{i}}-{{p}_{j,}}i\ne j$, is constant on a set of positive density, then for any measurable sets ${{A}_{0}},{{A}_{1}},...,{{A}_{K}}$, there exists a zero-density set $E\subset Z$ such that
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We formulate and prove a faithful version of this conjecture for mildly mixing systems and partially characterize, in the degree two case, the set of families $\left\{ {{p}_{1}},{{p}_{2}},\,.\,.\,.\,,\,{{p}_{k}} \right\}$ satisfying the hypotheses of this theorem.