This paper deals with the ontology of the vector potential. When the state of the system has the full gauge symmetry of the Hamiltonian, the electromagnetic vector potential may be interpreted as a convenient tool of a mathematical formulation, with no ontological meaning.
I argue that this interpretation is in difficulty because the vector potential becomes proportional to the supercurrent in the superfluid phases, which are spontaneously broken gauge symmetry phases, where particle number is not conserved.
I suggest that when gauge symmetry is spontaneously broken, the vector potential becomes an emergent material object of nature.
Read more at http://arxiv.org/pdf/1401.8146v1.pdf