Quasiconvex functions on regular trees

Fuente: arXiv
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Auteurs principaux: Del Pezzo, Leandro M., Frevenza, Nicolas, Rossi, Julio D.
Format: Preprint
Publié: 2020
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author Del Pezzo, Leandro M.
Frevenza, Nicolas
Rossi, Julio D.
author_facet Del Pezzo, Leandro M.
Frevenza, Nicolas
Rossi, Julio D.
contents We introduce a definition of a quasiconvex function on an infinite directed regular tree that depends on what we understood by a segment on the tree. Our definition is based on thinking on segments as sub-trees with the root as the midpoint of the segment. A convex set in the tree is then a subset such that it contains every midpoint of every segment with terminal nodes in the set. Then a quasiconvex function is a real map on the tree such that every level set is a convex set. For this concept of quasiconvex functions on a tree, we show that given a continuous boundary datum there exists a unique quasiconvex envelope on the tree and we characterize the equation that this envelope satisfies. It turns out that this equation is a mean value property that involves a median among values of the function on successors of a given vertex. We also relate the quasiconvex envelope of a function defined inside the tree with the solution of an obstacle problem for this characteristic equation.
format Preprint
id arxiv_https___arxiv_org_abs_2006_11568
institution arXiv
publishDate 2020
record_format arxiv
spellingShingle Quasiconvex functions on regular trees
Del Pezzo, Leandro M.
Frevenza, Nicolas
Rossi, Julio D.
Analysis of PDEs
We introduce a definition of a quasiconvex function on an infinite directed regular tree that depends on what we understood by a segment on the tree. Our definition is based on thinking on segments as sub-trees with the root as the midpoint of the segment. A convex set in the tree is then a subset such that it contains every midpoint of every segment with terminal nodes in the set. Then a quasiconvex function is a real map on the tree such that every level set is a convex set. For this concept of quasiconvex functions on a tree, we show that given a continuous boundary datum there exists a unique quasiconvex envelope on the tree and we characterize the equation that this envelope satisfies. It turns out that this equation is a mean value property that involves a median among values of the function on successors of a given vertex. We also relate the quasiconvex envelope of a function defined inside the tree with the solution of an obstacle problem for this characteristic equation.
title Quasiconvex functions on regular trees
topic Analysis of PDEs
url https://arxiv.org/abs/2006.11568