A-Discriminant Coamoebas in Dimension Three

  The coamoeba of a subvariety V of the torus is the set of arguments 
of points of V.  The closure of a coamoeba is the union of coamoebae 
of its initial schemes, which are indexed by the cones in its tropical 
variety.    We describe the closure of the coamoeba of a reduced  
A-discriminant in dimension three.  Surprisingly, only the initial
schemes coming from elements of the Gale dual of A contribute, which
leads to an inductive construction of an A-discriminat as an overlapping
union of polyhedra.  This is joint work with Mounir Nisse.