A Study of Birkhoff Orthogonal Sets in Smooth Banach Spaces

Referring to the definition of orthogonal set in inner product space,the concept of Birkhoff orthogonal set is introduced in finite-dimensional real Banach spaces,and the problem of whether there exists a Birkhoff orthogonal set whose number of elements exceeds the space dimension is studied in s...

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Main Authors: WANG Xiaomei, JI Donghai
Format: Article
Language:Chinese
Published: Harbin University of Science and Technology Publications 2024-02-01
Series:Journal of Harbin University of Science and Technology
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Online Access:https://hlgxb.hrbust.edu.cn/#/digest?ArticleID=2304
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author WANG Xiaomei
JI Donghai
author_facet WANG Xiaomei
JI Donghai
author_sort WANG Xiaomei
collection DOAJ
description Referring to the definition of orthogonal set in inner product space,the concept of Birkhoff orthogonal set is introduced in finite-dimensional real Banach spaces,and the problem of whether there exists a Birkhoff orthogonal set whose number of elements exceeds the space dimension is studied in smooth Banach spaces.It is proved that there is no Birkhoff orthogonal set whose number of elements exceeds the space dimension in two-dimensional smooth Banach spaces. In a smooth Banach space with more than three dimensions,there is no Birkhoff orthogonal set with more elements than the space dimension and all the elements are left ( right) symmetric points.It is also proved that if there is a Birkhoff orthogonal set A = { x1 ,x2 ,… , xn,xn + 1 } in an n-dimensional ( n ≥3)smooth Banach space,and then A must not satisfy the following two conditions: ( 1) for each xm ∈A,there exists xm 丄B xi ( Yi≠m) ; ( 2) for each xm ∈A,there exists xi 丄B xm ( Yi≠m) .
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publisher Harbin University of Science and Technology Publications
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spelling doaj-art-92bd0a7bf77a4913af6dce94ece7366b2025-07-14T10:11:15ZzhoHarbin University of Science and Technology PublicationsJournal of Harbin University of Science and Technology1007-26832024-02-01290114314910.15938/j.jhust.2024.01.016A Study of Birkhoff Orthogonal Sets in Smooth Banach SpacesWANG Xiaomei0JI Donghai1College of Science,Harbin University of Science and Technology,Harbin 150080,ChinaCollege of Science,Harbin University of Science and Technology,Harbin 150080,China Referring to the definition of orthogonal set in inner product space,the concept of Birkhoff orthogonal set is introduced in finite-dimensional real Banach spaces,and the problem of whether there exists a Birkhoff orthogonal set whose number of elements exceeds the space dimension is studied in smooth Banach spaces.It is proved that there is no Birkhoff orthogonal set whose number of elements exceeds the space dimension in two-dimensional smooth Banach spaces. In a smooth Banach space with more than three dimensions,there is no Birkhoff orthogonal set with more elements than the space dimension and all the elements are left ( right) symmetric points.It is also proved that if there is a Birkhoff orthogonal set A = { x1 ,x2 ,… , xn,xn + 1 } in an n-dimensional ( n ≥3)smooth Banach space,and then A must not satisfy the following two conditions: ( 1) for each xm ∈A,there exists xm 丄B xi ( Yi≠m) ; ( 2) for each xm ∈A,there exists xi 丄B xm ( Yi≠m) .https://hlgxb.hrbust.edu.cn/#/digest?ArticleID=2304banach spacebirkhoff orthogonalitybirkhoff orthogonal setsmoothness
spellingShingle WANG Xiaomei
JI Donghai
A Study of Birkhoff Orthogonal Sets in Smooth Banach Spaces
Journal of Harbin University of Science and Technology
banach space
birkhoff orthogonality
birkhoff orthogonal set
smoothness
title A Study of Birkhoff Orthogonal Sets in Smooth Banach Spaces
title_full A Study of Birkhoff Orthogonal Sets in Smooth Banach Spaces
title_fullStr A Study of Birkhoff Orthogonal Sets in Smooth Banach Spaces
title_full_unstemmed A Study of Birkhoff Orthogonal Sets in Smooth Banach Spaces
title_short A Study of Birkhoff Orthogonal Sets in Smooth Banach Spaces
title_sort study of birkhoff orthogonal sets in smooth banach spaces
topic banach space
birkhoff orthogonality
birkhoff orthogonal set
smoothness
url https://hlgxb.hrbust.edu.cn/#/digest?ArticleID=2304
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AT jidonghai astudyofbirkhofforthogonalsetsinsmoothbanachspaces
AT wangxiaomei studyofbirkhofforthogonalsetsinsmoothbanachspaces
AT jidonghai studyofbirkhofforthogonalsetsinsmoothbanachspaces