Lifts of projective congruence groups, II
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We continue and complete our previous paper ``Lifts of projective congruence groups'' concerning the question of whether there exist noncongruence subgroups of that are projectively equivalent to one of the groups or . A complete answer to this question is obtained: In case of such noncongruence subgroups exist precisely if and we additionally have either that or that is divisible by an odd prime congruent to modulo . In case of these noncongruence subgroups exist precisely if .
As in our previous paper the main motivation for this question is the fact that the above noncongruence subgroups represent a fairly accessible and explicitly constructible reservoir of examples of noncongruence subgroups of that can serve as the basis for experimentation with modular forms on noncongruence subgroups.
Original language | English |
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Journal | Proceedings of the American Mathematical Society |
Volume | 142 |
Issue number | 11 |
Pages (from-to) | 3761-3770 |
Number of pages | 10 |
ISSN | 0002-9939 |
DOIs | |
Publication status | Published - 2014 |
ID: 122608744