Berry phase and quantum structural realism

Two main claims are made in this lecture: First, the Berry phase is a geometric quantum holonomy that is directly rooted in the very structure of quantum theory itself. Common wisdom tells us that the state space of quantum theory is a projective Hilbert space. This structure is however insufficient to account for the Berry phase, the full quantum structure must rather be considered as a U(1) principal bundle over the projective Hilbert space. Second, this quantum bundle structure should ontologically be seen as a real and causally efficacious trace of nature, the quantum phase therefore directly supports ontic structural realism.