#9455: Dimensions of eigenspaces for the Atkin-Lehner operator acting on modular
forms
---------------------------------+---------------------------
       Reporter:  ljpk           |         Owner:  craigcitro
           Type:  enhancement    |        Status:  new
       Priority:  minor          |     Milestone:  sage-5.11
      Component:  modular forms  |    Resolution:
       Keywords:                 |     Merged in:
        Authors:  ljpk           |     Reviewers:
Report Upstream:  N/A            |   Work issues:
         Branch:                 |  Dependencies:
       Stopgaps:                 |
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Description changed by chapoton:

Old description:

> This is a port of David Kohel's MAGMA code to compute dimensions of the
> eigenspaces for the Atkin-Lehner operators acting on spaces of cusp forms
> of weight 2 (see here for the original):
>
> http://echidna.maths.usyd.edu.au/echidna/dbs/atkin-lehner/index.html
>
> These methods do not rely on computing explicit bases of newforms,
> instead using formulae about the ramification points of the Atkin-Lehner
> operator.
>
> These functions use the class number method qfbclassno() from Pari/GP.
>
> NOTES: the functions for newforms are really slow right now (much slower
> than MAGMA).
>
> The public methods supplied here are:
>
> {{{def modular_genusX0(self,w):
> def atkin_lehner_eigenspace_dimensions(self):
> def new_subspace_dimensionX0(self):
> def atkin_lehner_new_eigenspace_dimension(self,w):
> def old_subspace_dimension(self,M,R,w):
> def atkin_lehner_new_eigenspace_dimensions(self):
> }}}
> Is this too many? the most important two are
> atkin_lehner_eigenspace_dimensions and
> atkin_lehner_new_eigenspace_dimension as those give the really important
> data about spaces of modular forms. We could make the others private if
> we wanted to and not lose (too) much.

New description:

 This is a port of David Kohel's MAGMA code to compute dimensions of the
 eigenspaces for the Atkin-Lehner operators acting on spaces of cusp forms
 of weight 2 (see here for the original):

 http://echidna.maths.usyd.edu.au/echidna/dbs/atkin-lehner/index.html

 These methods do not rely on computing explicit bases of newforms, instead
 using formulae about the ramification points of the Atkin-Lehner operator.

 These functions use the class number method qfbclassno() from Pari/GP.

 NOTES: the functions for newforms are really slow right now (much slower
 than MAGMA).

 The public methods supplied here are:

 {{{
 def modular_genusX0(self,w):
 def atkin_lehner_eigenspace_dimensions(self):
 def new_subspace_dimensionX0(self):
 def atkin_lehner_new_eigenspace_dimension(self,w):
 def old_subspace_dimension(self,M,R,w):
 def atkin_lehner_new_eigenspace_dimensions(self):
 }}}
 Is this too many? the most important two are
 atkin_lehner_eigenspace_dimensions and
 atkin_lehner_new_eigenspace_dimension as those give the really important
 data about spaces of modular forms. We could make the others private if we
 wanted to and not lose (too) much.

--

--
Ticket URL: <http://trac.sagemath.org/ticket/9455#comment:5>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica, 
and MATLAB

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