Modular Abelian Varieties

Todo on March 16

• (craig) Newforms issue:

sage: f = CuspForms(37).newforms('a')[0]
sage: f.coefficients(10)
---------------------------------------------------------------------------
<type 'exceptions.TypeError'>             Traceback (most recent call last)
sage: f.coefficients([2..10])
---------------------------------------------------------------------------
<type 'exceptions.AttributeError'>        Traceback (most recent call last)
...
<type 'exceptions.AttributeError'>: 'Newform' object has no attribute '_compute'

• (william) This is completely wrong (the modabvar function on modular symbols assumes it's ambient!):

sage: m = ModularSymbols(37)[1]
sage: m.modular_abelian_variety()
Jacobian of the modular curve associated to the congruence subgroup Gamma0(37)

• (william) Move functions out of abvar_modsym_factor into abvar and delete that file.
• (william) Torsion subgroups:
  • Refactor base class
  • Get implementation to work with defining data being (lattice, abvar); compute generators.
  • Quotients by finite subgroup
• (william) Decomposition:
  • three types:
    • ungrouped as simple abvars (default)
    • groups abvars
    • over End(A)
    • deprecate hecke_decomposition
  • label function
  • create from label

• (craig) Implement f.number() for f a newform.

• (craig) Compute the Hecke algebra image in End(A) and find a good clean way to represent for Hecke stable. New object that is a subring of End(A). Have methods like R.index_in(S).

• (craig) abelian varieties should cache their ambient modular abelian variety
• (craig) Compute End(A):

  • for simple Af

  • in general.
  • disc of it.
• (craig) Degeneracy maps
• (william/craig) Morphisms:
  • Kernels
  • Cokernels
• (william/craig) Isogenies:
  • Complementary -- invert matrix, clear denom.
  • Dual
• (william) Intersection pairing
• (?) Poincare Reducibility:
  • projection
  • quotients by abelian subvariety
• (craig/william) Minimal isogeny degree for A, B simple.
• (craig/william) Create a small mock database

Todo on Monday, March 17

• Write doctests, etc., for everything above.
• Optimize everything

Todo on Tuesday, March 18

• Write paper

Todo on Wednesday, March 19

• Write paper