#17096: Implement categories for filtered algebras
-------------------------------------+-------------------------------------
       Reporter:  tscrim             |        Owner:  tscrim
           Type:  enhancement        |       Status:  needs_review
       Priority:  major              |    Milestone:  sage-6.4
      Component:  categories         |   Resolution:
       Keywords:  filtered algebras  |    Merged in:
        Authors:  Travis Scrimshaw   |    Reviewers:
Report Upstream:  N/A                |  Work issues:
         Branch:                     |       Commit:
  public/categories/filtered_algebras-17096|  
8a747c073e706950d1b14e77458539e126ff0550
   Dependencies:                     |     Stopgaps:
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Comment (by jhpalmieri):

 Replying to [comment:37 tscrim]:
 > @jhpalmieri
 > I'll make those changes. However we can't get a descending filtration
 unless the grading set can be negated. As for algebras that are both
 filtered and graded, it's the same issue as when an algebra has 2 natural
 gradings (as we use `degree` for both filtration and grading). Although as
 things evolve and the filtration can be generalized from using `degree`,
 this can be rectified. For now, you have to choose the "best" one for
 `degree` (or have it be an optional arg like how I'm doing for Clifford
 algebras).

 I still don't understand this design choice. Why not separate filtrations
 and gradings? A graded object without additional filtration could still be
 considered to be filtered (by having the filtration method default to
 calling `degree`), but this wouldn't have to be the only choice.

 Replying to [comment:60 darij]:

 > Generalizing graded_algebra to modules. This doesn't seem too difficult;
 I am in favor of keeping the name "associated graded *algebra*" even for
 modules, as it seems to have a ring to it that algebraists recognize, but
 maybe some discussion is in order.

 "Have a ring to it". Heh.

 I would object to calling a module an "algebra" if there is no
 multiplicative structure. "Associated graded module" is just fine, or
 "associated graded object" more generally.

--
Ticket URL: <http://trac.sagemath.org/ticket/17096#comment:61>
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