BosonFlow: A C++ codebase for dynamic fRG and single-boson exchange in correlated fermion systems

TL;DR

BosonFlow is a comprehensive C++ codebase implementing advanced fRG and parquet methods for studying correlated fermion systems, enabling detailed dynamic vertex and self-energy calculations.

Contribution

It introduces a unified, flexible C++ implementation of fRG and parquet equations with multiple flow schemes and extensions for correlated electron models.

Findings

Provides full dynamic vertex and self-energy computations.

Supports multiple self-energy flow equations and cutoff schemes.

Serves as a reference and foundation for future many-body method development.

Abstract

We present a unified C++ implementation of the functional renormalization group and the parquet equations within the single-boson exchange formalism for several paradigmatic tight-binding and impurity models at equilibrium. The implementation computes the full dynamic vertex and self-energies, with momentum dependence treated using a truncated unity framework. We implement multiple self-energy flow equations, cutoff schemes, and extensions ranging from the dynamical functional renormalization group to multiloop flow equations that incorporate cutoffs in both the propagator and the interaction. The codebase serves as a reference for recent developments in the fRG and parquet methods for correlated electron systems and provides a flexible foundation for developing new many-body approaches and extensions.