Compatibility conjecture for the Grossman–Larson coproduct and rooted-tree coproduct

Let H\mathcal H be the Hopf algebra of rooted trees, let HGLH_{GL} be the Grossman–Larson Hopf algebra, and let Δ\Delta and SGLS_{GL} denote the relevant coproduct and antipode, with ΔGL\Delta_{GL} the coproduct transported to HGLH_{GL}. For a linear map m2,4m^{2,4} defined by

m2,4(abcd)=acbd,m^{2,4}(a\otimes b\otimes c\otimes d)=a\otimes c\otimes bd,

Compatibility conjecture. For any rooted tree tt,

(ΔGLidH)Δ(t)=m2,4(ΔΔ)ΔGL(t)(\Delta_{GL}\otimes\operatorname{id}_{\mathcal H})\circ\Delta(t)=m^{2,4}\circ(\Delta\otimes\Delta)\circ\Delta_{GL}(t)

and

ΔSGL(t)=(SGLid)Δ(t).\Delta\circ S_{GL}(t)=(S_{GL}\otimes\operatorname{id})\circ\Delta(t).

These identities would give an analogue of the corresponding compatibility between the Kreimer and Grossman–Larson structures. The source presents them as a question, so their resolution is not established here.

Sources & referencesView supporting material

Primary source

Damien Calaque, Kurusch Ebrahimi-Fard and Dominique Manchon, “Two interacting Hopf algebras of trees”, arXiv:0806.2238 (2011).

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