Abstract
\({\mathrm{M}}^\natural \)-concave functions form a class of discrete concave functions in discrete convex analysis, and are defined by a certain exchange axiom. We show in this paper that \({\mathrm{M}}^\natural \)-concave functions can be characterized by a combination of two simpler exchange properties. It is also shown that for a function defined on an integral polymatroid, a much simpler exchange axiom characterizes \({\mathrm{M}}^\natural \)-concavity. These results have some significant implications in discrete convex analysis.
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Notes
The definition of an integral polymatroid will be given in Sect. 2.
\(\mathbb {B}\) stands for Binary, referring to functions on \(\{0,1\}^n\).
In [3] the concept of well-layered map is defined for more general set functions for which the effective domain can be a proper subset of \(2^N\). We here restrict our attention to the case of \(\mathrm{dom_{\mathbb {B}}\,}f = 2^N\) for simplicity of description.
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The authors thank Yu Yokoi and the anonymous referees for their valuable comments on the manuscript.
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This work was supported by The Mitsubishi Foundation, CREST, JST, Grant number JPMJCR14D2, Japan, and JSPS KAKENHI Grant numbers 26280004, 15K00030, 15H00848.
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Murota, K., Shioura, A. Simpler exchange axioms for M-concave functions on generalized polymatroids. Japan J. Indust. Appl. Math. 35, 235–259 (2018). https://doi.org/10.1007/s13160-017-0285-5
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DOI: https://doi.org/10.1007/s13160-017-0285-5