Spacetime symmetries and conformal data in the continuous multi-scale entanglement renormalization ansatz

Abstract

The generalization of the multi-scale entanglement renormalization ansatz (MERA) to continuous systems, or cMERA [Haegeman et al., Phys. Rev. Lett, 110, 100402 (2013)], is expected to become a powerful variational ansatz for the ground state of strongly interacting quantum field theories. In this paper we investigate, in the simpler context of Gaussian cMERA for free theories, the extent to which the cMERA state $|Ψ^Λ\rangle$ with finite UV cut-off $Λ$ can capture the spacetime symmetries of the ground state $|Ψ\rangle$. For a free boson conformal field theory (CFT) in 1+1 dimensions as a concrete example, we build a quasi-local unitary transformation $V$ that maps $|Ψ\rangle$ into $|Ψ^Λ\rangle$ and show two main results. (i) Any spacetime symmetry of the ground state $|Ψ\rangle$ is also mapped by $V$ into a spacetime symmetry of the cMERA $|Ψ^Λ\rangle$. However, while in the CFT the stress-energy tensor $T_{μν}(x)$ (in terms of which all the spacetime symmetry generators are expressed) is local, the corresponding cMERA stress-energy tensor $T_{μν}^Λ(x) = V T_{μν}(x) V^{\dagger}$ is quasi-local. (ii) From the cMERA, we can extract quasi-local scaling operators $O^Λ_α(x)$ characterized by the exact same scaling dimensions $Δ_α$, conformal spins $s_α$, operator product expansion coefficients $C_{αβγ}$, and central charge $c$ as the original CFT. Finally, we argue that these results should also apply to interacting theories.