#12930: Poset of Alternating sign matrices
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   Reporter:  aschilling     |             Owner:  sage-combinat                
    
       Type:  enhancement    |            Status:  new                          
    
   Priority:  major          |         Milestone:  sage-5.1                     
    
  Component:  combinatorics  |          Keywords:  alternating sign matrices, 
posets
Work issues:                 |   Report Upstream:  N/A                          
    
  Reviewers:                 |           Authors:                               
    
  Merged in:                 |      Dependencies:                               
    
   Stopgaps:                 |  
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 Implementation of the poset of alternating sign matrices

 This is best done by implementing a bijection to monotone triangles (or
 contre tableaux). This was already done in MuPAD

 http://mupad-combinat.svn.sourceforge.net/viewvc/mupad-combinat/trunk
 /MuPAD-Combinat/lib/COMBINAT/alternatingSignMatrices.mu?view=log

 One way of the bijection is already implemented::

 {{{
   sage: import sage.combinat.alternating_sign_matrix as asm
         sage: asm.from_contre_tableau([[1, 2, 3], [1, 2], [1]])
         [0 0 1]
         [0 1 0]
         [1 0 0]
         sage: asm.from_contre_tableau([[1, 2, 3], [2, 3], [3]])
         [1 0 0]
         [0 1 0]
         [0 0 1]
 }}}

 It remains to implement the reverse bijection, and the ASM lattice from
 the ContreTableaux lattice.

-- 
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12930>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica, 
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