#19774: Full support for modular forms for the Theta subgroup
-------------------------------------+-------------------------------------
       Reporter:  jj                 |        Owner:
           Type:  enhancement        |       Status:  needs_review
       Priority:  major              |    Milestone:  sage-7.0
      Component:  modular forms      |   Resolution:
       Keywords:  modular forms      |    Merged in:
  theta subgroup half-integer        |    Reviewers:
  weight                             |  Work issues:
        Authors:  Jonas Jermann      |       Commit:
Report Upstream:  N/A                |  b3508cba62e714ccaea1cdaba6d22dd5855eb172
         Branch:  u/jj/theta_space   |     Stopgaps:
   Dependencies:  #17909             |
-------------------------------------+-------------------------------------
Changes (by jj):

 * status:  new => needs_review


Old description:

> The current implementation of modular forms for the Theta subgroup only
> allows modular forms with integer orders at the cusp -1.
> With this ticket all forms are supported, also forms with fractional
> order at the cusp -1.
> In particular this includes the theta function / half-integer weight
> forms.
>
> Also note that there is a correspondence between modular forms for the
> Theta subgroup
> and modular forms for Gamma0(4). So in essence this ticket provides
> support for
> classical half-integer weight modular forms (for Gamma0(4)) for all kind
> of analytic types:
> cuspidal, holomorphic, weakly holomorphic, meromorphic and also quasi
> forms,
> as ring or module elements and with a lot of powerful methods.
>
> The ticket depends on the branch u/jj/rankin_cohen_bracket (#17909).
>
> The ticket is basically implemented but some more testing/documentations
> are required.

New description:

 The current implementation of modular forms for the Theta subgroup only
 allows modular forms with integer orders at the cusp -1.
 With this ticket all forms are supported, also forms with fractional order
 at the cusp -1.
 In particular this includes the theta function / half-integer weight
 forms.

 Also note that there is a correspondence between modular forms for the
 Theta subgroup
 and modular forms for Gamma0(4). So in essence this ticket provides
 support for
 classical half-integer weight modular forms (for Gamma0(4)) for all kind
 of analytic types:
 cuspidal, holomorphic, weakly holomorphic, meromorphic and also quasi
 forms,
 as ring or module elements and with a lot of powerful methods.

 The ticket depends on the branch u/jj/rankin_cohen_bracket (#17909).

 The ticket is essentially implemented.

 Possible additional ideas:
 - Kohnen plus spaces
 - Eisenstein series
 - basis/detection of forms for the direct sum for ep=1 and ep=-1
   (which corresponds to the Modularform space for Gamma0(4)).

--

--
Ticket URL: <http://trac.sagemath.org/ticket/19774#comment:3>
Sage <http://www.sagemath.org>
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