Lucas Aragão, Maurício Collares, João Pedro Marciano, Taísa Martins, Robert Morris
{"title":"A lower bound for set-coloring Ramsey numbers.","authors":"Lucas Aragão, Maurício Collares, João Pedro Marciano, Taísa Martins, Robert Morris","doi":"10.1002/rsa.21173","DOIUrl":null,"url":null,"abstract":"<p><p>The set-coloring Ramsey number <math><mrow><mrow><msub><mrow><mi>R</mi></mrow><mrow><mi>r</mi><mo>,</mo><mi>s</mi></mrow></msub><mo>(</mo><mi>k</mi><mo>)</mo></mrow></mrow></math> is defined to be the minimum <math><mrow><mrow><mi>n</mi></mrow></mrow></math> such that if each edge of the complete graph <math><mrow><mrow><msub><mrow><mi>K</mi></mrow><mrow><mi>n</mi></mrow></msub></mrow></mrow></math> is assigned a set of <math><mrow><mrow><mi>s</mi></mrow></mrow></math> colors from <math><mrow><mrow><mo>{</mo><mn>1</mn><mo>,</mo><mi>…</mi><mo>,</mo><mi>r</mi><mo>}</mo></mrow></mrow></math>, then one of the colors contains a monochromatic clique of size <math><mrow><mrow><mi>k</mi></mrow></mrow></math>. The case <math><mrow><mrow><mi>s</mi><mo>=</mo><mn>1</mn></mrow></mrow></math> is the usual <math><mrow><mrow><mi>r</mi></mrow></mrow></math>-color Ramsey number, and the case <math><mrow><mrow><mi>s</mi><mo>=</mo><mi>r</mi><mo>-</mo><mn>1</mn></mrow></mrow></math> was studied by Erdős, Hajnal and Rado in 1965, and by Erdős and Szemerédi in 1972. The first significant results for general <math><mrow><mrow><mi>s</mi></mrow></mrow></math> were obtained only recently, by Conlon, Fox, He, Mubayi, Suk and Verstraëte, who showed that <math><mrow><mrow><msub><mrow><mi>R</mi></mrow><mrow><mi>r</mi><mo>,</mo><mi>s</mi></mrow></msub><mo>(</mo><mi>k</mi><mo>)</mo><mo>=</mo><msup><mrow><mn>2</mn></mrow><mrow><mi>Θ</mi><mo>(</mo><mi>k</mi><mi>r</mi><mo>)</mo></mrow></msup></mrow></mrow></math> if <math><mrow><mrow><mi>s</mi><mo>/</mo><mi>r</mi></mrow></mrow></math> is bounded away from 0 and 1. In the range <math><mrow><mrow><mi>s</mi><mo>=</mo><mi>r</mi><mo>-</mo><mi>o</mi><mo>(</mo><mi>r</mi><mo>)</mo></mrow></mrow></math>, however, their upper and lower bounds diverge significantly. In this note we introduce a new (random) coloring, and use it to determine <math><mrow><mrow><msub><mrow><mi>R</mi></mrow><mrow><mi>r</mi><mo>,</mo><mi>s</mi></mrow></msub><mo>(</mo><mi>k</mi><mo>)</mo></mrow></mrow></math> up to polylogarithmic factors in the exponent for essentially all <math><mrow><mrow><mi>r</mi></mrow></mrow></math>, <math><mrow><mrow><mi>s</mi></mrow></mrow></math>, and <math><mrow><mrow><mi>k</mi></mrow></mrow></math>.</p>","PeriodicalId":54523,"journal":{"name":"Random Structures & Algorithms","volume":null,"pages":null},"PeriodicalIF":0.9000,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10952192/pdf/","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Random Structures & Algorithms","FirstCategoryId":"100","ListUrlMain":"https://doi.org/10.1002/rsa.21173","RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2023/8/3 0:00:00","PubModel":"Epub","JCR":"Q4","JCRName":"COMPUTER SCIENCE, SOFTWARE ENGINEERING","Score":null,"Total":0}
引用次数: 0
Abstract
The set-coloring Ramsey number is defined to be the minimum such that if each edge of the complete graph is assigned a set of colors from , then one of the colors contains a monochromatic clique of size . The case is the usual -color Ramsey number, and the case was studied by Erdős, Hajnal and Rado in 1965, and by Erdős and Szemerédi in 1972. The first significant results for general were obtained only recently, by Conlon, Fox, He, Mubayi, Suk and Verstraëte, who showed that if is bounded away from 0 and 1. In the range , however, their upper and lower bounds diverge significantly. In this note we introduce a new (random) coloring, and use it to determine up to polylogarithmic factors in the exponent for essentially all , , and .
期刊介绍:
It is the aim of this journal to meet two main objectives: to cover the latest research on discrete random structures, and to present applications of such research to problems in combinatorics and computer science. The goal is to provide a natural home for a significant body of current research, and a useful forum for ideas on future studies in randomness.
Results concerning random graphs, hypergraphs, matroids, trees, mappings, permutations, matrices, sets and orders, as well as stochastic graph processes and networks are presented with particular emphasis on the use of probabilistic methods in combinatorics as developed by Paul Erdõs. The journal focuses on probabilistic algorithms, average case analysis of deterministic algorithms, and applications of probabilistic methods to cryptography, data structures, searching and sorting. The journal also devotes space to such areas of probability theory as percolation, random walks and combinatorial aspects of probability.