Graph Multiplihedra -- a tentative beginning.

A new algorithm for convex hulls of graph associahedra. 

An algorithm for convex hulls of graph multilihedra.


 Some 3-d examples of graph multiplihedra.  


 The 4-d multicyclohedron.


 Graph composihedra and opposihedra/cubohedra: quotients of the multiplihedra.


 Realizing quotients of the multiplihedra.
 

 The full poset structure of painted tubes.  


 Appendix: vertices of the multicyclohedron.


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Here are some notes about graph multiplihedra. The two key sources are S. Devadoss's 	
	two papers    on graph associahedra, and S.Forcey's 
	paper    on multiplihedra. In fact, the following notes assume that you have first read and enjoyed the excellent short paper by Devadoss 
	here.      
 













Note that the tubing above is missing its outermost colored tube. Exercise: what color must that outer tube be?


















 






Here is a Schlegel diagram for the graph multiplihedra of the cycle of four vertices. The polytope has 104 vertices and  28 facets. Is it simple?



In the following notes the naming is not yet final. It turns out that Satyan Devadoss and his students
actually discovered what are called here the graph opposihedra some time ago; in their work on configuration spaces.
They called these polytopes cubohedra, since they are truncations of cubes.


















Note that the cubohedra/opposihedra for the usual associahedra K(n) is K(n+1). 
Is the final target always an n-dimensional cube, for n the number of graph nodes? 
This question might be equivalent to the question of the veracity of 
the following equation: v(OK(G))-v(J(G))+v(CK(G))=2^n, where v(X) gives the number of vertices.
 


The following notes are about realizing the above quotient polytopes as convex hulls. 




Above we see a square for q in (0,1), allowing s and t to range over [0,1]. (s stands for
source and t for target. Note that s=0 corresponds to an associative source and t = 0 to an associative target.
Two pages below we see the full picture, also allowing q to range over [0,1]. New polytopes are introduced! But 
first here is the calculation of points for all three parameters  exactly one half.








Here is the drawing of actual points calculated for q=1, and various values of s and t. 
All the five important polytopes appear: associahedron, cubohedron (here K(n+1)), composihedron, multiplihedron,
and cube. There are also four new polytopes, which are the top and bottom halves of the cube 
and the multiplihedron 
when the associahedron is seen as a cross section of the cube (respectively the multiplihedron). 
Does this also happen for higher dimensions? 








Also note that the only rule is as follows:
 If a tube x contains any red at all then x itself must be red.  












Here are the vertices of the above "multicyclohedron" to be entered into the 
	
		web demo of polymake    in order to see a rotatable version.
	

	POINTS

	1 1 7 1 4

	1 1 4 1 7

	1 7 1 4 1

	1 4 1 7 1

	1 3 7 1 2

	1 7 1 2 3 

	1 1 2 3 7

	1 2 3 7 1

	1 3 2 1 7

	1 2 1 7 3

	1 1 7 3 2

	1 7 3 2 1

	1 7 3 1 2

	1 3 1 2 7

	1 1 2 7 3

	1 2 7 3 1

	1 7 2 1 3

	1 2 1 3 7

	1 1 3 7 2

	1 3 7 2 1

	1 1/2 7 1 4

	1 1/2 4 1 7

	1 7 1/2 4 1

	1 4 1/2 7 1

	1 3 7 1/2 2

	1 7 1/2 2 3 

	1 1/2 2 3 7

	1 2 3 7 1/2

	1 3 2 1/2 7

	1 2 1/2 7 3

	1 1/2 7 3 2

	1 7 3 2 1/2

	1 7 3 1/2 2

	1 3 1/2 2 7

	1 1/2 2 7 3

	1 2 7 3 1/2

	1 7 2 1/2 3

	1 2 1/2 3 7

	1 1/2 3 7 2

	1 3 7 2 1/2

	1 1 7 1/2 4

	1 1 4 1/2 7

	1 7 1 4 1/2

	1 4 1 7 1/2

	1 3 7 1/2 2/2

	1 7 1/2 2/2 3 

	1 1/2 2/2 3 7

	1 2/2 3 7 1/2

	1 3 2/2 1/2 7

	1 2/2 1/2 7 3

	1 1/2 7 3 2/2

	1 7 3 2/2 1/2

	1 7 3 1/2 2/2

	1 3 1/2 2/2 7

	1 1/2 2/2 7 3

	1 2/2 7 3 1/2

	1 7 2/2 1/2 3

	1 2/2 1/2 3 7

	1 1/2 3 7 2/2

	1 3 7 2/2 1/2

	1 1/2 7 1/2 4

	1 1/2 4 1/2 7

	1 7 1/2 4 1/2

	1 4 1/2 7 1/2

	1 3/2 7 1/2 2/2

	1 7 1/2 2/2 3/2 

	1 1/2 2/2 3/2 7

	1 2/2 3/2 7 1/2

	1 3/2 2/2 1/2 7

	1 2/2 1/2 7 3/2

	1 1/2 7 3/2 2/2

	1 7 3/2 2/2 1/2

	1 7 3/2 1/2 2/2

	1 3/2 1/2 2/2 7

	1 1/2 2/2 7 3/2

	1 2/2 7 3/2 1/2

	1 7 2/2 1/2 3/2

	1 2/2 1/2 3/2 7

	1 1/2 3/2 7 2/2

	1 3/2 7 2/2 1/2

	1 1/2 7 1/2 4/2

	1 1/2 4/2 1/2 7

	1 7 1/2 4/2 1/2

	1 4/2 1/2 7 1/2

	1 3/2 7/2 1/2 2/2

	1 7/2 1/2 2/2 3/2 

	1 1/2 2/2 3/2 7/2

	1 2/2 3/2 7/2 1/2

	1 3/2 2/2 1/2 7/2

	1 2/2 1/2 7/2 3/2

	1 1/2 7/2 3/2 2/2

	1 7/2 3/2 2/2 1/2

	1 7/2 3/2 1/2 2/2

	1 3/2 1/2 2/2 7/2

	1 1/2 2/2 7/2 3/2

	1 2/2 7/2 3/2 1/2

	1 7/2 2/2 1/2 3/2

	1 2/2 1/2 3/2 7/2

	1 1/2 3/2 7/2 2/2

	1 3/2 7/2 2/2 1/2

	1 1/2 7/2 1/2 4/2

	1 1/2 4/2 1/2 7/2

	1 7/2 1/2 4/2 1/2

	1 4/2 1/2 7/2 1/2

	

	
 

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