openQ*D code: a versatile tool for QCD+QED simulations

Abstract

We present the open-source package (. GitLab: https://gitlab.com/rcstar/openQxD . CSIC: https://dx.doi.org/10.20350/digitalCSIC/8591 . https://hdl.handle.net/10261/173334 , 2019), which has been primarily, but not uniquely, designed to perform lattice simulations of QCD+QED and QCD, with and without $$\mathrm {C}^*$$ C ∗ boundary conditions, and O ( a ) improved Wilson fermions. The use of $$\mathrm {C}^*$$ C ∗ boundary conditions in the spatial direction allows for a local and gauge-invariant formulation of QCD+QED in finite volume, and provides a theoretically clean setup to calculate isospin-breaking and radiative corrections to hadronic observables from first principles. The code is based on (Simulation program for lattice QCD ( code). https://cern.ch/luscher/openQCD , 2016) and (Numerical Stochastic Perturbation Theory ( code). https://cern.ch/luscher/NSPT , 2017). In particular it inherits from several core features, e.g. the highly optimized Dirac operator, the locally deflated solver, the frequency splitting for the RHMC, or the 4th order OMF integrator.