{"title":"Mutual incidence matrix of two balanced incomplete block designs","authors":"Alexander Shramchenko, Vasilisa Shramchenko","doi":"10.1002/jcd.21949","DOIUrl":null,"url":null,"abstract":"<p>We propose to consider a mutual incidence matrix <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>M</mi>\n </mrow>\n </mrow>\n <annotation> $M$</annotation>\n </semantics></math> of two balanced incomplete block designs built on the same finite set. In the simplest case, this matrix reduces to the standard incidence matrix of one block design. We find all eigenvalues of the matrices <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>M</mi>\n \n <msup>\n <mi>M</mi>\n \n <mi>T</mi>\n </msup>\n </mrow>\n </mrow>\n <annotation> $M{M}^{T}$</annotation>\n </semantics></math> and <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <msup>\n <mi>M</mi>\n \n <mi>T</mi>\n </msup>\n \n <mi>M</mi>\n </mrow>\n </mrow>\n <annotation> ${M}^{T}M$</annotation>\n </semantics></math> and their eigenspaces.</p>","PeriodicalId":15389,"journal":{"name":"Journal of Combinatorial Designs","volume":"32 10","pages":"579-590"},"PeriodicalIF":0.5000,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jcd.21949","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Combinatorial Designs","FirstCategoryId":"100","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1002/jcd.21949","RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"MATHEMATICS","Score":null,"Total":0}
引用次数: 0
Abstract
We propose to consider a mutual incidence matrix of two balanced incomplete block designs built on the same finite set. In the simplest case, this matrix reduces to the standard incidence matrix of one block design. We find all eigenvalues of the matrices and and their eigenspaces.
期刊介绍:
The Journal of Combinatorial Designs is an international journal devoted to the timely publication of the most influential papers in the area of combinatorial design theory. All topics in design theory, and in which design theory has important applications, are covered, including:
block designs, t-designs, pairwise balanced designs and group divisible designs
Latin squares, quasigroups, and related algebras
computational methods in design theory
construction methods
applications in computer science, experimental design theory, and coding theory
graph decompositions, factorizations, and design-theoretic techniques in graph theory and extremal combinatorics
finite geometry and its relation with design theory.
algebraic aspects of design theory.
Researchers and scientists can depend on the Journal of Combinatorial Designs for the most recent developments in this rapidly growing field, and to provide a forum for both theoretical research and applications. All papers appearing in the Journal of Combinatorial Designs are carefully peer refereed.