Decay constants of the charged and neutral pions in magnetic field are considered in the framework of the effective quark-antiquark lagrangian respecting Gell-Mann--Oakes--Renner (GOR) relations at zero field. The σeqB dependence is found in strong fields eqB≫σ for the neutral pion, while the charged pion constant decreases as eqBσ.
@article{arxiv.1503.06616,
title = {Pion decay constants in a strong magnetic field},
author = {Yu. A. Simonov},
journal= {arXiv preprint arXiv:1503.06616},
year = {2016}
}