Slicing cones in various ways with a plane generates conic sections identified geometrically as hyperbolas, parabolas, or ellipses and algebraically, when suitably rotated, as certain rescaled quadratic polynomials, or forms, in two variables.

The refined face partition polynomials of the permutohedra (OEIS A049019) and associahedra (or Stasheff polytopes, A133437) and partition polynomials for noncrossing partitions (A134264) can all be algebraically related by re-scaling the associated monomials per the calculus of compositional and multiplicative inversion of power series, so this represents the algebraic analogue of the rescaling of the quadratic equations for conics.

Which geometric structures, such as possibly the noncrossing hypertrees of McCammond, brick polytopes, or simply polygons, when "sliced" in different ways, provide  representations of permutohedra, associahedra, and noncrossing partitions?

Ancillary question: Is there a geometric complex (possibly the Whitehouse simplicial complex, related to phylogenetic trees, or the trees themselves) that can be associated to Lagrange (compositional) inversion of exponential generating functions (i.e., formal Taylor, or divided powers, series) and can be incorporated in this geometric scheme if one exists?


2-truncated cubes provide the "slicings" to generate the associahedra or permutahedra.

See "Upper and lower bound theorems for graph-associahedra" by Buchstaber and Volodin, "Cubical realizations of flag nestohedra and Gal's conjecture" by Volodin, and "Geometric realization of $\gamma$-vectors of 2-truncated cubes" by Volodin.

  • $\begingroup$ And "The diagonal of the associahedra" by Naruki Masuda, Hugh Thomas, Andy Tonks, Bruno Vallette arxiv.org/abs/1902.08059 $\endgroup$ – Tom Copeland Sep 7 '19 at 13:41
  • $\begingroup$ See also "Diagonals on the Permutahedra, Multiplihedra and Associahedra" by Samson Saneblidze, Ronald Umble arxiv.org/abs/math/0209109 $\endgroup$ – Tom Copeland Sep 7 '19 at 17:03
  • $\begingroup$ "Direct families of polytopes with nontrivial Massey products" by Victor Buchstaber and Ivan Limonchenko arxiv.org/abs/1811.02221 $\endgroup$ – Tom Copeland Mar 21 '20 at 18:08
  • $\begingroup$ See also p. 16 of "Toric Topology of Stasheff Polytopes" by Buchstaber $\endgroup$ – Tom Copeland Sep 30 '20 at 20:44
  • $\begingroup$ See Fig. 1.4 on p. 18 of "From permutahedra to associahedra, a walk through geometric and algebraic combinatorics" by Vincent Pilaud lix.polytechnique.fr/~pilaud/documents/reports/… $\endgroup$ – Tom Copeland Oct 25 '20 at 20:24

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.