Conveners
The classical limit of the Magnus expansion
- Graham Brown
Description
The Magnus expansion has recently emerged as an alternative to the conventional Dyson expansion in QFT. In the Magnus expansion, we perturbatively expand the logarithm of the S-matrix. The matrix elements of this logarithm are Magnus amplitudes, which have many pleasing properties, including a well-behaved classical limit. In this talk, we will study the classical limit of certain Magnus amplitudes and show explicitly that they are free of classically singular terms. Our analysis will rely on an algebra of permutations, which we will also use to derive new closed-form expressions for Murua coefficients at any loop order. Based on: arXiv:2609.40291.