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Species substitution,
graph suspension, and graded Hopf algebras of painted tree
polytopes
Lisa Berry, Stefan Forcey, Maria Ronco and Patrick Showers |
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Algebraic & Geometric Topology 19 (2019) 1019–1078
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Abstract |
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Combinatorial Hopf algebras of trees exemplify the connections between operads and bialgebras. Painted trees were introduced recently as examples of how graded Hopf operads can bequeath Hopf structures upon compositions of coalgebras. We put these trees in context by exhibiting them as the minimal elements of face posets of certain convex polytopes. The full face posets themselves often possess the structure of graded Hopf algebras (with one-sided unit). We can enumerate faces using the fact that they are structure types of substitutions of combinatorial species. Species considered here include ordered and unordered binary trees and ordered lists (labeled corollas). Some of the polytopes that constitute our main results are well known in other contexts. First we see the classical permutohedra, and then certain generalized permutohedra: specifically the graph associahedra of suspensions of certain simple graphs. As an aside we show that the stellohedra also appear as liftings of generalized permutohedra: graph composihedra for complete graphs. Thus our results give examples of Hopf algebras of tubings and marked tubings of graphs. We also show an alternative associative algebra structure on the graph tubings of star graphs. |
Keywords
associahedron, multiplihedron, composihedron, binary tree,
cofree coalgebra, Hopf algebra, operad, species
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Mathematical Subject Classification 2010
Primary: 18D50, 52B11, 57T05
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References |
Publication
Received: 24 April 2018
Revised: 8 July 2018
Accepted: 22 August 2018
Published: 12 March 2019
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Authors |
| Lisa Berry | |
| Bio-Med Science Academy Rootstown, OH United States |
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| Stefan Forcey | |
| Department of Mathematics The University of Akron Akron, OH United States |
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| http://www.math.uakron.edu/~sf34/ | |
| Maria Ronco | |
| Department of Physics and
Mathematics The University of Talca Talca Chile |
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| Patrick Showers | |
| Department of Mathematics The University of Akron Akron, OH United States |
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