#12630: Add representations of quivers and quiver algebras to sage
------------------------------------------------------------------------------+
       Reporter:  JStarx                                                      | 
        Owner:  AlexGhitza                                            
           Type:  enhancement                                                 | 
       Status:  needs_work                                            
       Priority:  major                                                       | 
    Milestone:  sage-5.11                                             
      Component:  algebra                                                     | 
   Resolution:                                                        
       Keywords:  algebra, quiver, module, days49                             | 
  Work issues:  Use existing infrastructure for Homspase and Morphism.
Report Upstream:  N/A                                                         | 
    Reviewers:                                                        
        Authors:  Jim Stark, Simon King, Mathieu Guay-Paquet, Aladin Virmaux  | 
    Merged in:                                                        
   Dependencies:  #12412, #12413                                              | 
     Stopgaps:                                                        
------------------------------------------------------------------------------+

Old description:

> This will add classes dealing with quivers, quiver algebras,
> representations of quivers, elements of these representations,
> homomorphisms between these representations, and spaces of homomorphisms
> between these representations.
>
> There's a lot here that is really easily computable.  We can compute
> socles, quotients, radicals, duals, and more for any finite dimensional
> representation.  We can compute projective covers of modules so
> Auslander-Rieten translations have been implemented and there's certainly
> potential for future enhancements dealing with homology and cohomology.
> There's only so much I can say here but everything is fully documented
> and should be self explanatory.
>
> Two shortcomings are that quivers need to be acyclic (to keep things
> finite dimensional) and this code does not handle quivers with relations.
> As far as quivers with relations go there are comments in the code
> detailing what should be done to implement that.  It's well within the
> reach of Sage, I just don't have the time to do it at the moment.
>
> __Apply__
>
> The second patch is supposed to split the code into chewable bits (so
> that maintenance and cythonization will become easier), introduces a
> parent structure for the paths of a quiver (namely: a free small
> category), makes paths inherit from Element (but ''not'' from
> `UniqueRepresentation`!) and fixes some tests. But there is more to do.
>
> * [attachment:trac_12630_quivers_v2.patch]
> * [attachment:trac12630_refactor_code.patch]

New description:

 This will add classes dealing with quivers, quiver algebras,
 representations of quivers, elements of these representations,
 homomorphisms between these representations, and spaces of homomorphisms
 between these representations.

 There's a lot here that is really easily computable.  We can compute
 socles, quotients, radicals, duals, and more for any finite dimensional
 representation.  We can compute projective covers of modules so Auslander-
 Rieten translations have been implemented and there's certainly potential
 for future enhancements dealing with homology and cohomology.  There's
 only so much I can say here but everything is fully documented and should
 be self explanatory.

 Two shortcomings are that quivers need to be acyclic (to keep things
 finite dimensional) and this code does not handle quivers with relations.
 As far as quivers with relations go there are comments in the code
 detailing what should be done to implement that.  It's well within the
 reach of Sage, I just don't have the time to do it at the moment.

 __Apply__

 The second patch is supposed to split the code into chewable bits (so that
 maintenance and cythonization will become easier), introduces a parent
 structure for the paths of a quiver (namely: a free small category), makes
 paths inherit from Element (but ''not'' from `UniqueRepresentation`!) and
 fixes some tests. But there is more to do.

 * [attachment:trac_12630_quivers_v2.patch]
 * [attachment:trac12630_refactor_code.2.patch]

--

Comment (by SimonKing):

 Please post the little patch---for reviewing.

 Moreover, on Trac, one can only replace patches (with the same name) that
 one has posted oneself. Hence, the name of the patch-to-be-applied has
 changed. So, we now have

  Apply trac_12630_quivers_v2.patch 12630_refactor_code.2.patch

-- 
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12630#comment:77>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica, 
and MATLAB

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