#16883: Modular forms for the theta subgroup (as part of Hecke triangle groups)
-------------------------------------+-------------------------------------
       Reporter:  jj                 |        Owner:
           Type:  enhancement        |       Status:  needs_review
       Priority:  minor              |    Milestone:  sage-6.4
      Component:  modular forms      |   Resolution:
       Keywords:  theta subgroup     |    Merged in:
  modular forms hecke triangle       |    Reviewers:
        Authors:  Jonas Jermann      |  Work issues:
Report Upstream:  N/A                |       Commit:
         Branch:  u/jj/theta_group   |  13ea3d8ecceea61173b0a8308ccafabe2769b208
   Dependencies:  #16839             |     Stopgaps:
-------------------------------------+-------------------------------------
Description changed by jj:

Old description:

> Complete support for modular forms for the Hecke triangle group
> corresponding to n=infinity
> (the theta subgroup) with corresponding + further doctests/documentation.
>
> The situation is slightly different since there are now two cusps with
> two corresponding generators.
>
> In particular the limit of the generator f_rho tends to 1 and the
> generator
> for n=infinity is instead E4 which is the limit of f_rho^n.
>
> Note that only functions which are meromorphic and meromorphic at the
> cusps are considerd.
> E.g. E4 is the 8th power of theta, but smaller powers are no longer
> meromorphic at -1.
> Also note that limits of functions/coefficients as n tends to infinity
> are usually given by
> the corresponding function in the theta subgroup.
>
> Additionally the ticket adds support for experimental rationalization of
> series
> and a refactoring of code which in particular provides more robust
> numerical
> Fourier expansions.
>
> The ticket also fixes a mistake from #16839 and has some other small
> changes.

New description:

 Complete support for modular forms for the Hecke triangle group
 corresponding to n=infinity
 (the theta subgroup) with corresponding + further doctests/documentation.

 The situation is slightly different since there are now two cusps with
 two corresponding generators.

 In particular the limit of the generator f_rho tends to 1 and the
 generator
 for n=infinity is instead E4 which is the limit of f_rho^n.

 Note that only functions which are meromorphic and meromorphic at the
 cusps are considerd.
 E.g. E4 is the 8th power of theta, but smaller powers are no longer
 meromorphic at -1.
 Also note that limits of functions/coefficients as n tends to infinity are
 usually given by
 the corresponding function in the theta subgroup.

 Additionally the ticket adds support for experimental rationalization of
 series,
 refactoring of code which in particular provides more robust numerical
 Fourier expansions
 and Eisenstein series of arbitrary weight for n=3,4,6.

 The ticket also fixes a mistake from #16839 and has some other small
 changes.

--

--
Ticket URL: <http://trac.sagemath.org/ticket/16883#comment:14>
Sage <http://www.sagemath.org>
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