  We look at the foundations of electromagnetism in this 1st LeCosPA Symposium.
For doing this, after some review (constraints on photon mass etc.), we use two
approaches. The first one is to formulate a Parametrized Post-Maxwellian (PPM)
framework to include QED corrections and a pseudoscalar photon interaction. PPM
framework includes lowest corrections to unified electromagnetism-gravity
theories based on connection approach. It may also overlap with corrections
implemented from generalized uncertainty principle (GUP) when
electromagnetism-gravity coupling is considered. We discuss various vacuum
birefringence experiments - ongoing and proposed - to measure these parameters.
The second approach - the chi-g framework is to look at electromagnetism in
gravity and various experiments and observations to determine its empirical
foundation. The SME (Standard Model Extension) and SMS (Standard Model
Supplement) overlap with the chi-g framework in their photon sector. We found
that the foundation is solid with the only exception of a potentially possible
pseudoscalar-photon interaction. We discussed its experimental constraints and
look forward to more future experiments.
