{ "id": "1702.02568", "version": "v1", "published": "2017-02-08T15:34:12.000Z", "updated": "2017-02-08T15:34:12.000Z", "title": "The automorphism groups of Johnson graphs revisited", "authors": [ "Morteza Mirafzal" ], "comment": "Research paper, submitted", "categories": [ "math.CO", "math.GR" ], "abstract": "The Johnson graph $J(n, i)$ is defined to the graph whose vertex set is the set of all $i$-element subsets of $\\{1, . . . , n \\}$, and two vertices are adjacent whenever the cardinality of their intersection is equal to $i$-1. In Ramras and Donovan [SIAM J. Discrete Math, 25(1): 267-270, 2011], it is proved that, if $ n \\neq 2i$ then the automorphism group of $J(n, i)$ is isomorphic with the group $Sym(n)$ and it is conjectured that if $n = 2i$, then the automorphism group of $J(n, i)$ is isomorphic with the group $ Sym(n) \\rtimes Sym(2)$. In this paper we will find these results by different methods. We will prove the conjecture in the affirmative.", "revisions": [ { "version": "v1", "updated": "2017-02-08T15:34:12.000Z" } ], "analyses": { "subjects": [ "05C25", "05C69", "94C15" ], "keywords": [ "automorphism group", "johnson graph", "isomorphic", "discrete math", "vertex set" ], "note": { "typesetting": "TeX", "pages": 0, "language": "en", "license": "arXiv", "status": "editable" } } }