{ "id": "2012.10116", "version": "v1", "published": "2020-12-18T09:17:36.000Z", "updated": "2020-12-18T09:17:36.000Z", "title": "Automorphisms of (Affine) SL(2,q)-Unitals", "authors": [ "Verena Möhler" ], "comment": "15 pages", "categories": [ "math.CO" ], "abstract": "$\\operatorname{SL}(2,q)$-unitals are unitals of order $q$ admitting a regular action of $\\operatorname{SL}(2,q)$ on the complement of some block. They can be obtained from affine $\\operatorname{SL}(2,q)$-unitals via parallelisms. We compute a sharp upper bound for automorphism groups of affine $\\operatorname{SL}(2,q)$-unitals and show that exactly two parallelisms are fixed by all automorphisms. In $\\operatorname{SL}(2,q)$-unitals obtained as closures of affine $\\operatorname{SL}(2,q)$-unitals via those two parallelisms, we show that there is one block fixed under the full automorphism group.", "revisions": [ { "version": "v1", "updated": "2020-12-18T09:17:36.000Z" } ], "analyses": { "subjects": [ "51A10", "05E18" ], "keywords": [ "full automorphism group", "parallelisms", "sharp upper bound", "regular action", "complement" ], "note": { "typesetting": "TeX", "pages": 15, "language": "en", "license": "arXiv", "status": "editable" } } }