201 citations · 2.4k across the 113 of their papers we have counts for
14 papers · 1 filter
What is the Magnus Expansion?
Kurusch Ebrahimi-Fard, Igor Mencattini, Alexandre Quesney
The Magnus expansion, introduced by Wilhelm Magnus in 1954, is an infinite Lie series employed to express solutions for first-order homogeneous linear differential equations involv…
Effective Action in Free Probability
Kurusch Ebrahimi-Fard, Frederic Patras
Recent works have explored relations between classical and quantum statistical physics on the one hand and Voiculescu's theory of free probability on the other. Motivated by these…
Post-Lie Algebras, Factorization Theorems and Isospectral-Flows
Kurusch Ebrahimi-Fard, Igor Mencattini
In these notes we review and further explore the Lie enveloping algebra of a post-Lie algebra. From a Hopf algebra point of view, one of the central results, which will be recalled…
The combinatorics of Green's functions in planar field theories
Kurusch Ebrahimi-Fard, Frederic Patras
The aim of this work is to outline in some detail the use of combinatorial algebra in planar quantum field theory. Particular emphasis is given to the relations between the differe…
Time-ordering and a generalized Magnus expansion
Michel Bauer, Raphael Chetrite, Kurusch Ebrahimi-Fard +1
Both the classical time-ordering and the Magnus expansion are well-known in the context of linear initial value problems. Motivated by the noncommutativity between time-ordering an…
Exponential Renormalization II: Bogoliubov's R-operation and momentum subtraction schemes
Kurusch Ebrahimi-Fard, Frederic Patras
This article aims at advancing the recently introduced exponential method for renormalisation in perturbative quantum field theory. It is shown that this new procedure provides a m…