What are Capra-Convex Sets?

Fuente: arXiv
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Main Authors: Chancelier, Jean-Philippe, de Lara, Michel, Franc, Adrien Le, Rakotomandimby, Seta
Format: Preprint
Published: 2025
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author Chancelier, Jean-Philippe
de Lara, Michel
Franc, Adrien Le
Rakotomandimby, Seta
author_facet Chancelier, Jean-Philippe
de Lara, Michel
Franc, Adrien Le
Rakotomandimby, Seta
contents This paper focuses on a specific form of abstract convexity known as Capra-convexity, where a constant along primal rays (Capra) coupling replaces the scalar product used in standard convex analysis to define generalized Fenchel conjugacies. A key motivating result is that the ${\ell}$0 pseudonorm - which counts the number of nonzero components in a vector - is equal to its Capra-biconjugate. This implies that ${\ell}$0 is a Capra-convex function, highlighting potential applications in statistics and machine learning, particularly for enforcing sparsity in models. Building on prior work characterizing the Capra-subdifferential of ${\ell}$0 and the role of source norms in defining the Capra-coupling, the paper provides a characterization of Capra-convex sets.
format Preprint
id arxiv_https___arxiv_org_abs_2509_06392
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle What are Capra-Convex Sets?
Chancelier, Jean-Philippe
de Lara, Michel
Franc, Adrien Le
Rakotomandimby, Seta
Optimization and Control
This paper focuses on a specific form of abstract convexity known as Capra-convexity, where a constant along primal rays (Capra) coupling replaces the scalar product used in standard convex analysis to define generalized Fenchel conjugacies. A key motivating result is that the ${\ell}$0 pseudonorm - which counts the number of nonzero components in a vector - is equal to its Capra-biconjugate. This implies that ${\ell}$0 is a Capra-convex function, highlighting potential applications in statistics and machine learning, particularly for enforcing sparsity in models. Building on prior work characterizing the Capra-subdifferential of ${\ell}$0 and the role of source norms in defining the Capra-coupling, the paper provides a characterization of Capra-convex sets.
title What are Capra-Convex Sets?
topic Optimization and Control
url https://arxiv.org/abs/2509.06392