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Journal of Convex Analysis 32 (2025), No. 4, 989--1022 Copyright Heldermann Verlag 2025 Convex Analysis in Groups and Semigroups and Applications to Separation and Optimization Jun Li Key Laboratory of Optimization Theory, School of Mathematics and Information, China West Normal University, Nanchong, P. R. China junli@cwnu.edu.cn Giandomenico Mastroeni Department of Computer Science, University of Pisa, Italy gmastroeni@di.unipi.it The aim of this paper is to investigate some fundamental properties of convex sets, cones, and functions in groups and semigroups. In particular, we introduce the concept of quasi core of a convex set, which allows us to provide separation theorems between convex sets in groups where at least one of them has nonempty quasi core. We also analyze optimization problems defined on groups and semigroups and provide saddle point necessary or sufficient optimality conditions by considering suitable Lagrangian functions associated with the given problem. Keywords: Convex sets, convex functions, groups, semigroups, separation, optimization problems. MSC: 46N10, 90C48. [ Fulltext-pdf (226 KB)] for subscribers only. |