Friday, 02 February, 2018

Multiloop Functional Renormalization Group That Sums Up All Parquet Diagrams

F. B. Kugler and J. von Delft -
Physical Review Letters, 10.1103/PhysRevLett.120.057403 (2018)

We present a multiloop flow equation for the four-point vertex in the functional renormalization group (fRG) framework. The multiloop flow consists of successive one-loop calculations and sums up all parquet diagrams to arbitrary order. This provides substantial improvement of fRG computations for the four-point vertex and, consequently, the self-energy. Using the X-ray-edge singularity as an example, we show that solving the multiloop fRG flow is equivalent to solving the (first-order) parquet equations and illustrate this with numerical results.

journals.aps.org/prl/abstract/10.1103/PhysRevLett.120.057403