The minimum index of a non-congruence subgroup of SL2 over an arithmetic domain. II: the rank zero cases

• Autores: A. W. Mason, Andreas Schweizer
• Localización: Journal of the London Mathematical Society, ISSN 0024-6107, Vol. 71, Nº 1, 2005, págs. 53-68
• Idioma: inglés
• DOI: 10.1112/s0024610704006027
• Texto completo no disponible (Saber más ...)
• Resumen

  • Let be a function field of genus with a finite constant field . Choose a place of of degree and let be the arithmetic Dedekind domain consisting of all elements of that are integral outside . An explicit formula is given (in terms of , and ) for the minimum index of a non-congruence subgroup in SL. It turns out that this index is always equal to the minimum index of an arbitrary proper subgroup in SL. The minimum index of a normal non-congruence subgroup is also determined.