Abstract
The followingsandwich problem is considered: Given two real-valued functionsg:X→ℝ,h:Y→ℝ defined on subsetsX, Y ⊆ S of a preordered abelian monoids (S, +, 0, ≺), does there exist a real-valued ≺ additive functionf:S→ℝ such thatg≤f|X andf|Y≤h? We study several necessary conditions for the existence of such a functionf, some of which are also sufficient.
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Communicated by Karl H. Hofmann
The results of this paper formed part of the author's doctoral dissertation [11] at Technische Hochschule Darmstadt. The author would like to thank his supervisor, Professor Dr. J. Kindler, for his help and guidance and Professor Dr. K. H. Hofmann and Professor Dr. K. Keimel for useful suggestions and comments.
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Plappert, P. A sandwich theorem for monotone additive functions. Semigroup Forum 51, 347–355 (1995). https://doi.org/10.1007/BF02573643
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DOI: https://doi.org/10.1007/BF02573643