This talk introduces new tests of fundamental physics by means of the
analysis of disturbances on the electromagnetic signals' propagation. We
relate scalar coupling models in the electromagnetic sector to the
"system-free" formulation of Maxwell’s equations. At the macroscopic
scale, the disturbances on the electromagnetic waves are equivalent to
that which occur during the propagation in an inhomogeneous medium. This
talk introduces an original theoretical approach and shows the relevance
of the method by a first quantification of the expected perturbations
induced by a specific case of transient dark matter signature, the
domain walls. As an application, we focus on the measurable phase shift
in the GNSS signals' carrier.
