Perturbative Renormalisation for Not-Quite-Connected Bialgebras

© 2015, Springer Science+Business Media Dordrecht. We observe that the Connes–Kreimer Hopf-algebraic approach to perturbative renormalisation works not just for Hopf algebras but more generally for filtered bialgebras B with the property that B0 is spanned by group-like elements (e.g. pointed bialgebras with the coradical filtration). Such bialgebras occur naturally both in quantum field theory, where they have some attractive features, and elsewhere in combinatorics, where they cover a comprehensive class of incidence bialgebras. In particular, the setting allows us to interpret Möbius inversion as an instance of renormalisation.