#18632: Allow cyclic quivers in quiver representation
-------------------------------------+-------------------------------------
       Reporter:  SimonKing          |        Owner:
           Type:  enhancement        |       Status:  new
       Priority:  major              |    Milestone:  sage-6.8
      Component:  algebra            |   Resolution:
       Keywords:  quiver             |    Merged in:
  representation, days65, days64.5   |    Reviewers:
        Authors:                     |  Work issues:
Report Upstream:  N/A                |       Commit:
         Branch:                     |  3ff899a738ee86c9156d428a5dfa4819c42b07ba
  public/18632_cyclic_quiver_representations|     Stopgaps:
   Dependencies:  #17435             |
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Comment (by SimonKing):

 It is already possible to define a representation of a cyclic quiver by
 assigning finite-dimensional vector spaces to each vertex and assigning
 matrices (defining a transformation) to each arrow.

 What is currently not possible is to provide the right-module that is
 given, say, by all paths that start at vertex `v` (the result is a
 projective indecomposable module). Reason is that the current code would
 first try to create vector space basis of the to-be-created module
 (=representation) by forming the '''list''' of all paths starting at `v`.
 Of course, that list may be infinite in the case of a cyclic quiver, thus,
 the code is doomed.

 My guess is (by looking at the current code) that what we really need is a
 container that represents a vector space basis for the module, so that we
 can
  - use the basis as a cache key (quiver representations use a
 `UniqueFactory`)
  - test whether a path of the quiver belongs to the basis
  - iterate over the basis elements

 The previous commit provides these three features for families of paths
 that are closed under multiplication from the right, and a similar thing
 would be needed for left-closed path families as well.

--
Ticket URL: <http://trac.sagemath.org/ticket/18632#comment:6>
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