Loïc Foissy

  1. Left ideals in an enveloping algebra, prelie products and applications to simple complex Lie algebras.

    Authors: Loïc Foissy
    Subjects: Rings and Algebras
    Abstract

    We characterize prelie algebras in words of left ideals of the enveloping
    algebras and in words of modules, and use this result to prove that a simple
    complex finite-dimensional Lie algebra is not prelie, with the possible
    exception of f4.

  2. Systems of Dyson-Schwinger equations.

    Authors: Loïc Foissy
    Subjects: Rings and Algebras
    Abstract

    We consider systems of combinatorial Dyson-Schwinger equations (briefly,
    SDSE) X_1=B^+_1(F_1(X_1,...,X_N))...X_N=B^+_N(F_N(X_1,...,X_N)) in the
    Connes-Kreimer Hopf algebra H_I of rooted trees decorated by I={1,...,N},where
    B^+_i is the operator of grafting on a root decorated by i, and F_1...,F_N are
    non-constant formal series.The unique solution X=(X_1,...,X_N) of this equation
    generates a graded subalgebra H_S of H_I. We characterize here all the families
    of formal series (F_1,...,F_N) such that H_S is a Hopf subalgebra.

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