Hadronic light-by-light contribution to aμ: extended Nambu-Jona-Lasinio, chiral quark models and chiral Lagrangians

This talk discusses our old work on the hadronic light-by-light contribution to the muon anomalous magnetic moment and some more recent contributions. I discuss the various contributions starting with pseudoscalar meson exchange, the quark- and pion-loop, as well as scalar and a₁-exchange. For the π⁰-exchange I point out a possible large enhancement when only connected contributions are included. For the quark-loop I include some comments about the more recent estimates of this contribution. The pion-loop is discussed in more detail, in particular I discuss our unpublished work on including effects from a₁ and the polarizability.