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Home > Vol 29, No 3 (2009)

Antonio Breda D'Azevedo¹ , Gareth Jones² , Roman Nedela³ and Martin Škoviera⁴

¹Universidade de Aveiro Departamento de Matematica 3810-193 Aveiro Portugal
²University of Southampton School of Mathematics Southampton SO17 1BJ UK
³Matej Bel University Department of Mathematics Banská Bystrica Slovakia
⁴Comenius University Department of Informatics 842 48 Bratislava Slovakia

Although the phenomenon of chirality appears in many investigations of maps and hypermaps, no detailed study of chirality seems to have been carried out. Chirality of maps and hypermaps is not merely a binary invariant but can be quantified by two new invariants-the chirality group and the chirality index, the latter being the size of the chirality group. A detailed investigation of the chirality groups of orientably regular maps and hypermaps will be the main objective of this paper. The most extreme type of chirality arises when the chirality group coincides with the monodromy group. Such hypermaps are called totally chiral. Examples of these are constructed by considering appropriate “asymmetric” pairs of generators of certain non-abelian simple groups. We also show that every finite abelian group is the chirality group of some hypermap, whereas many non-abelian groups, including symmetric and dihedral groups, cannot arise as chirality groups.

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