{"title":"Volumes of Subset Minkowski Sums and the Lyusternik Region","authors":"Franck Barthe, Mokshay Madiman","doi":"10.1007/s00454-023-00606-w","DOIUrl":"https://doi.org/10.1007/s00454-023-00606-w","url":null,"abstract":"<p>We begin a systematic study of the region of possible values of the volumes of Minkowski subset sums of a collection of <i>M</i> compact sets in <span>(mathbb {R}^d)</span>, which we call the Lyusternik region, and make some first steps towards describing it. Our main result is that a fractional generalization of the Brunn–Minkowski–Lyusternik inequality conjectured by Bobkov et al. (in: Houdré et al. (eds) Concentration, functional inequalities and isoperimetry. Contemporary mathematics, American Mathematical Society, Providence, 2011) holds in dimension 1. Even though Fradelizi et al. (C R Acad Sci Paris Sér I Math 354(2):185–189, 2016) showed that it fails in general dimension, we show that a variant does hold in any dimension.</p>","PeriodicalId":50574,"journal":{"name":"Discrete & Computational Geometry","volume":"157 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138543760","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
James Davies, Tomasz Krawczyk, Rose McCarty, Bartosz Walczak
{"title":"Grounded L-Graphs Are Polynomially $$chi $$ -Bounded","authors":"James Davies, Tomasz Krawczyk, Rose McCarty, Bartosz Walczak","doi":"10.1007/s00454-023-00592-z","DOIUrl":"https://doi.org/10.1007/s00454-023-00592-z","url":null,"abstract":"<p>A <i>grounded L-graph</i> is the intersection graph of a collection of “L” shapes whose topmost points belong to a common horizontal line. We prove that every grounded L-graph with clique number <span>(omega )</span> has chromatic number at most <span>(17omega ^4)</span>. This improves the doubly-exponential bound of McGuinness and generalizes the recent result that the class of circle graphs is polynomially <span>(chi )</span>-bounded. We also survey <span>(chi )</span>-boundedness problems for grounded geometric intersection graphs and give a high-level overview of recent techniques to obtain polynomial bounds.</p>","PeriodicalId":50574,"journal":{"name":"Discrete & Computational Geometry","volume":"14 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138543213","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Some New Results on Geometric Transversals","authors":"Otfried Cheong, Xavier Goaoc, Andreas F. Holmsen","doi":"10.1007/s00454-023-00573-2","DOIUrl":"https://doi.org/10.1007/s00454-023-00573-2","url":null,"abstract":"<p>We investigate a number of questions, problems, and conjectures related to geometric transversal theory. Among our results we disprove a conjecture of Bárány and Kalai regarding weak <span>(varepsilon )</span>-nets for <i>k</i>-flats and convex sets in <span>(mathbb {R}^d)</span>, and we prove a conjecture of Arocha, Bracho, and Montejano regarding a colorful version of the Goodman–Pollack–Wenger transversal theorem. We also investigate the connected components of the space of line transversals to pairwise disjoint convex sets in <span>(mathbb {R}^3)</span>, and we extend a theorem of Karasev and Montejano regarding colorful intersections and <i>k</i>-transversals.</p>","PeriodicalId":50574,"journal":{"name":"Discrete & Computational Geometry","volume":"130 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138507782","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The Visible-Volume Function of a Set of Cameras is Continuous, Piecewise Rational, Locally Lipschitz, and Semi-Algebraic in All Dimensions","authors":"Jörg Rambau","doi":"10.1007/s00454-023-00541-w","DOIUrl":"https://doi.org/10.1007/s00454-023-00541-w","url":null,"abstract":"","PeriodicalId":50574,"journal":{"name":"Discrete & Computational Geometry","volume":"70 1","pages":"1038 - 1058"},"PeriodicalIF":0.8,"publicationDate":"2023-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43661006","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Delaunay and Regular Triangulations as Lexicographic Optimal Chains","authors":"D. Cohen-Steiner, A. Lieutier, J. Vuillamy","doi":"10.1007/s00454-023-00485-1","DOIUrl":"https://doi.org/10.1007/s00454-023-00485-1","url":null,"abstract":"","PeriodicalId":50574,"journal":{"name":"Discrete & Computational Geometry","volume":"70 1","pages":"1 - 50"},"PeriodicalIF":0.8,"publicationDate":"2023-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45486294","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}