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Lagrange's Theorem for Hopf Monoids in Species

Published online by Cambridge University Press:  20 November 2018

Marcelo Aguiar
Affiliation:
Department of Mathematics, Texas A&M University, College Station, TX, 77843, USA, e-mail: [email protected]
Aaron Lauve
Affiliation:
Department of Mathematics and Statistics, Loyola University Chicago, Chicago, IL, 60660, USA, e-mail: [email protected]
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Abstract

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Following Radford's proof of Lagrange's theorem for pointed Hopf algebras, we prove Lagrange‘s theorem for Hopf monoids in the category of connected species. As a corollary, we obtain necessary conditions for a given subspecies $\mathbf{k}$ of a Hopf monoid $\mathbf{h}$ to be a Hopf submonoid: the quotient of any one of the generating series of $\mathbf{h}$ by the corresponding generating series of $\mathbf{k}$ must have nonnegative coefficients. Other corollaries include a necessary condition for a sequence of nonnegative integers to be the dimension sequence of a Hopf monoid in the form of certain polynomial inequalities and of a set-theoretic Hopf monoid in the form of certain linear inequalities. The latter express that the binomial transform of the sequence must be nonnegative.

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 2013

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