Emergent Lorentz symmetry and the Unruh effect in a Lorentzian fermionic tensor network

• Published in: Physical review. D 2019-04, Vol.99 (8), p.1, Article 086007
• Main Authors: Yang, Zhi, Bhattacharyya, Arpan, Cheng, Long, Hung, Ling-Yan, Ning, Sirui
• Format: Article
• Language: English
• Subjects: Bosons; Commutators; Fermions; Field theory; Mathematical analysis; Networks; Quantum field theory; Quantum theory; Switching theory; Tensors
• ISSN: 2470-0010; 2470-0029
• DOI: 10.1103/PhysRevD.99.086007

In this paper we attempt to understand Lorentzian tensor networks, as a preparation for constructing tensor networks that can describe more exotic backgrounds such as black holes. To define notions of reference frames and switching of reference frames on a tensor network, we will borrow ideas from the algebraic quantum field theory literature. With these definitions, we construct simple examples of Lorentzian tensor networks, based on Gaussian models of fermions, and solve the spectrum for a choice of "inertial frame." In particular, the tensor network can be viewed as a periodically driven Floquet system that bypasses the "doubling problem" and gives rise to fermions with exactly linear dispersion relations. We will find that a boost operator connecting different inertial frames and notions of "Rindler observers" can be defined and that important physics in Lorentz invariant quantum field theory, such as the Unruh effect, can be captured by such a skeleton of spacetime. We find interesting subtleties when the same approach is directly applied to bosons-the operator algebra contains commutators that take the wrong sign-resembling bosons behind horizons.