Sebastian Brandt, Yi-Jun Chang, Jan Grebík, Christoph Grunau, Václav Rozhoň, Zoltán Vidnyánszky
{"title":"ON HOMOMORPHISM GRAPHS","authors":"Sebastian Brandt, Yi-Jun Chang, Jan Grebík, Christoph Grunau, Václav Rozhoň, Zoltán Vidnyánszky","doi":"10.1017/fmp.2024.8","DOIUrl":null,"url":null,"abstract":"We introduce new types of examples of bounded degree acyclic Borel graphs and study their combinatorial properties in the context of descriptive combinatorics, using a generalization of the determinacy method of Marks [Mar16]. The motivation for the construction comes from the adaptation of this method to the <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S2050508624000088_inline1.png\"/> <jats:tex-math> $\\mathsf {LOCAL}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> model of distributed computing [BCG<jats:sup>+</jats:sup>21]. Our approach unifies the previous results in the area, as well as produces new ones. In particular, strengthening the main result of [TV21], we show that for <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S2050508624000088_inline2.png\"/> <jats:tex-math> $\\Delta>2$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>, it is impossible to give a simple characterization of acyclic <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S2050508624000088_inline3.png\"/> <jats:tex-math> $\\Delta $ </jats:tex-math> </jats:alternatives> </jats:inline-formula>-regular Borel graphs with Borel chromatic number at most <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S2050508624000088_inline4.png\"/> <jats:tex-math> $\\Delta $ </jats:tex-math> </jats:alternatives> </jats:inline-formula>: such graphs form a <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S2050508624000088_inline5.png\"/> <jats:tex-math> $\\mathbf {\\Sigma }^1_2$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>-complete set. This implies a strong failure of Brooks-like theorems in the Borel context.","PeriodicalId":2,"journal":{"name":"ACS Applied Bio Materials","volume":null,"pages":null},"PeriodicalIF":4.6000,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"ACS Applied Bio Materials","FirstCategoryId":"100","ListUrlMain":"https://doi.org/10.1017/fmp.2024.8","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATERIALS SCIENCE, BIOMATERIALS","Score":null,"Total":0}
引用次数: 0
Abstract
We introduce new types of examples of bounded degree acyclic Borel graphs and study their combinatorial properties in the context of descriptive combinatorics, using a generalization of the determinacy method of Marks [Mar16]. The motivation for the construction comes from the adaptation of this method to the $\mathsf {LOCAL}$ model of distributed computing [BCG+21]. Our approach unifies the previous results in the area, as well as produces new ones. In particular, strengthening the main result of [TV21], we show that for $\Delta>2$ , it is impossible to give a simple characterization of acyclic $\Delta $ -regular Borel graphs with Borel chromatic number at most $\Delta $ : such graphs form a $\mathbf {\Sigma }^1_2$ -complete set. This implies a strong failure of Brooks-like theorems in the Borel context.