Notes
We are unaware of a standard term for this structure and have decided on this name in analogy with the definition of semialgebra, which requires a finite disjoint union rather than a countable one. Note that the conditions for being a \(\sigma\)-algebra are stronger than those for being an algebra, while the conditions for being a semi-\(\sigma\)-algebra are weaker than those for being a semialgebra.
References
I. I. Piatetskii-Shapiro, Izv. Akad. Nauk SSSR Ser. Mat. 15 (1), 47 (1951).
A. G. Postnikov, Trudy Mat. Inst. Steklov 82 (1966).
N. G. Moshchevitin and I. D. Shkredov Math. Notes 73 (3–4), 539 (2003).
A. G. Postnikov, Trudy Mat. Inst. Steklov 57 (1960).
S. Akiyama, H. Kaneko, and D. H. Kim, Generic Point Equivalence and Pisot Numbers, in Ergodic Theory and Dynamical Systems (2019), pp. 1–12.
S. Nandakumar, S. Pulari, P. Vishnoi, and G. Viswanathan, An Analogue of Pillai’s Theorem for Continued Fraction Normality and an Application to Subsequences, arXiv: arXiv:1909.03431 (2019).
J. Vandehey Compos. Math. 153 (2), 274 (2017).
I. D. Shkredov J. Math. Sci. 182 (4), 567 (2012).
V. I. Bogachev Measure Theory (Springer, 2007), Vol. II.
Acknowledgments
The authors wish to thank N. G. Moshchevitin, I. D. Shkredov, and J. Vandehey for helpful discussions about the hotspot lemma, as well as the referee for helpful edits.
Funding
This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under grant no. DGE-1656466. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
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Airey, D., Mance, B. Hotspot Lemmas for Noncompact Spaces. Math Notes 108, 434–439 (2020). https://doi.org/10.1134/S0001434620090126
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DOI: https://doi.org/10.1134/S0001434620090126