Aspects of Berry phase in QFT

Abstract

When continuous parameters in a QFT are varied adiabatically, quantum states typically undergo mixing---a phenomenon characterized by the Berry phase. We initiate a systematic analysis of the Berry phase in QFT using standard quantum mechanics methods. We show that a non-trivial Berry phase appears in many familiar QFTs. We study a variety of examples including free electromagnetism with a theta angle, and certain supersymmetric QFTs in two and four spacetime dimensions. We also argue that a large class of QFTs with rich Berry properties is provided by CFTs with non-trivial conformal manifolds. Using the operator-state correspondence we demonstrate in this case that the Berry connection is equivalent to the connection on the conformal manifold derived previously in conformal perturbation theory. In the special case of chiral primary states in 2d N=(2,2) and 4d N=2 SCFTs the Berry phase is governed by the tt* equations. We present a technically useful rederivation of these equations using quantum mechanics methods.

50 pages; v2 typos corrected, published version

References in corpus (9)

• Topological Field Theory of Time-Reversal Invariant Insulators
• $t{t}^{\ast }$ equations, localization and exact chiral rings in 4d N=2 SCFTs
• Exact correlation functions in SU(2) N=2 superconformal QCD
• The chiral ring of AdS3/CFT2 and the attractor mechanism
• Operator Mixing in Large $N$ Superconformal Field Theories on ${\mathbb{S}}^4$ and Correlators with Wilson loops
• Large-N correlation functions in $\mathcal{N}=2$ superconformal QCD
• Large $N$ correlation functions in $\mathcal{N}=2$ superconformal quivers
• Berry Phase and Supersymmetry
• Non-Abelian Berry Phase, Instantons and N=(0,4) Supersymmetry

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