#10926: is_gamma0_equiv on Cusps in wrong
-----------------------------+----------------------------------------------
Reporter: wuthrich | Owner: craigcitro
Type: defect | Status: new
Priority: major | Milestone: sage-4.7
Component: modular forms | Keywords: cusps Gamma0
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Here is a simple counter-example.
{{{
sage: Cusp(1/2).is_gamma0_equiv(1/3,11,transformation=True)
(True, 8)
}}}
Accoring to the documentation there should be a matrix in Gamma_0(11)
sending 1/2 to 1/3 such that the upper left entry is 8. In fact all these
matrices are given by
{{{
[ -3 + 22m 2 - 11m ]
[ 11 + 66m 7 - 33m ]
}}}
for some integer m.
The problem is that the very last line in the code reduces modulo N.
But while we are at it; it would be better if the matrix is given back
rather than one of its coefficients.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10926>
Sage <http://www.sagemath.org>
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