25,782 research outputs found
Does the WTO Agreement on Agriculture Endanger Food Security in Sub-Saharan Africa?
food security, WTO Agreement on Agriculture, Sub-Saharan Africa, special and differential treatment
Canonical characters on quasi-symmetric functions and bivariate Catalan numbers
Every character on a graded connected Hopf algebra decomposes uniquely as a
product of an even character and an odd character (Aguiar, Bergeron, and
Sottile, math.CO/0310016).
We obtain explicit formulas for the even and odd parts of the universal
character on the Hopf algebra of quasi-symmetric functions. They can be
described in terms of Legendre's beta function evaluated at half-integers, or
in terms of bivariate Catalan numbers:
Properties of characters and of quasi-symmetric functions are then used to
derive several interesting identities among bivariate Catalan numbers and in
particular among Catalan numbers and central binomial coefficients
Multigraded combinatorial Hopf algebras and refinements of odd and even subalgebras
We develop a theory of multigraded (i.e., -graded) combinatorial Hopf
algebras modeled on the theory of graded combinatorial Hopf algebras developed
by Aguiar, Bergeron, and Sottile [Compos. Math. 142 (2006), 1--30]. In
particular we introduce the notion of canonical -odd and -even
subalgebras associated with any multigraded combinatorial Hopf algebra,
extending simultaneously the work of Aguiar et al. and Ehrenborg. Among our
results are specific categorical results for higher level quasisymmetric
functions, several basis change formulas, and a generalization of the
descents-to-peaks map.Comment: 49 pages. To appear in the Journal of Algebraic Combinatoric
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