Speaker
Description
We present continuum extrapolated results of the QCD contribution to the axion-photon coupling extracted from Lattice QCD simulations. Our simulations employ 2+1 flavors of improved staggered fermions for physical quark masses with electromagnetic background fields with nonzero $\vec{E}\cdot\vec{B}$. These electromagnetic fields induce a non-zero expectation value of the topological charge and the axion-photon coupling is extracted as the linear coefficient of this dependence. The continuum extrapolation is affected by discretization artifacts of staggered fermions, which prevent the emergence of true topological zero modes in the Dirac spectrum. To overcome this issue, the fermion determinant is reweighted for which an estimation technique based on the Lanczos quadrature is employed.
