#17989: Double Affine Hecke Algebra
-------------------------------------+-------------------------------------
       Reporter:  nthiery            |        Owner:
           Type:  enhancement        |       Status:  new
       Priority:  major              |    Milestone:  sage-6.6
      Component:  combinatorics      |   Resolution:
       Keywords:  daha, days64       |    Merged in:
        Authors:  Mark Shimozono     |    Reviewers:  Dan Bump, ...
Report Upstream:  N/A                |  Work issues:
         Branch:                     |       Commit:
  u/mshimo/combinat/double_affine_hecke_algebra|  
da9705f7d218478f6d5e24adce0872b4196198ba
   Dependencies:                     |     Stopgaps:
-------------------------------------+-------------------------------------

Comment (by nthiery):

 Some notes from the discussion at SD64:

 * Generic features to be extracted from #15375

 - Exp functor:

   Currently in sage/groups/exp.py ; could be sage/monoids/exp.py

       class Exp(...)
          def log(self):
              return self._log

       sage: Exp(my_additive_group)
       sage: Exp(additive_group_morphism)

       sage: my_additive_group.exp()  # return the associated
 multiplicative group

   Possibly make it a functorial construction (can be postponed to later):

       Create sage.categories.additive_group_exp along the lines of
       sage.categories.cartesian_product

       class AdditiveMagmas:
           class Exp:
               class ParentMethods:
                    @abstract_method
                    def log(self):
                        ...
               class ElementMethods:
                    def _mul_(self, other):
                        return self.parent()(self.value+other.value)

           class Unital:
               class Exp:
                   class ParentMethods:
                        def one():
                            return self(self.log().zero())
       ....

 - Semidirect product of groups:
   Put Mark's implementation in
 sage.groups.semidirect_product.SemiDirectProduct

   Have Groups.ParentMethods.semidirect_product call it (currently it
   says NotImplemented)

   Bonus: if PermutationGroup.semidirect_product is called with the
   second group not being a permutation group, call the generic
   implementation. Same for finitely presented groups.


 * Generic features to be extracted from #17989 (Daha)

 - Improvements to tensor products

 - Tensor product of morphisms (see ticket by Nicolas Borie?)

 - Tensor products without flattening? For tensor product of algebras

   What happens in Sage if you one does a tensor product of algebras
   that are themselves tensor products? *boom*

   To be further discussed; probably tensor_product should take a flag
 flatten=True

 - Smash product

--
Ticket URL: <http://trac.sagemath.org/ticket/17989#comment:2>
Sage <http://www.sagemath.org>
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