Gauge Is More Than Mathematical Redundancy
arXiv:2009.10362 · doi:10.1007/978-3-030-51197-5_4
Abstract
Physical systems may couple to other systems through variables that are not gauge invariant. When we split a gauge system into two subsystems, the gauge-invariant variables of the two subsystems have less information than the gauge invariant variables of the original system; the missing information regards degrees of freedom that express relations between the subsystems. All this shows that gauge invariance is a formalization of the relational nature of physical degrees of freedom. The recent developments on boundary variables and boundary charges are clarified by this observation.
3 pages. To appear in the proceedings of the conference "One Hundred Years of Gauge Theory, Bad Honnef 2018", S. De Bianchi and C. Kiefer eds