SciPost Phys. 6, 042 (2019) ·
published 5 April 2019

· pdf
We show how the traversable wormhole induced by a doubletrace deformation of
the thermofield double state can be understood as a modular inclusion of the
algebras of exterior operators. The effect of this deformation is the creation
of a new region of spacetime deep in the bulk, corresponding to a nontrivial
center between the left and right algebras. This setup provides a precise
framework for investigating how black hole interiors are encoded in the CFT. In
particular, we use modular theory to demonstrate that state dependence is an
inevitable feature of any attempt to represent operators behind the horizon.
Building on this geometrical structure, we propose that modular inclusions may
provide a more precise means of investigating the nascent relationship between
entanglement and geometry in the context of the emergent spacetime paradigm.
Shira Chapman, Jens Eisert, Lucas Hackl, Michal P. Heller, Ro Jefferson, Hugo Marrochio, Robert C. Myers
SciPost Phys. 6, 034 (2019) ·
published 15 March 2019

· pdf
Motivated by holographic complexity proposals as novel probes of black hole
spacetimes, we explore circuit complexity for thermofield double (TFD) states
in free scalar quantum field theories using the Nielsen approach. For TFD
states at t = 0, we show that the complexity of formation is proportional to
the thermodynamic entropy, in qualitative agreement with holographic complexity
proposals. For TFD states at t > 0, we demonstrate that the complexity evolves
in time and saturates after a time of the order of the inverse temperature. The
latter feature, which is in contrast with the results of holographic proposals,
is due to the Gaussian nature of the TFD state of the free bosonic QFT. A novel
technical aspect of our work is framing complexity calculations in the language
of covariance matrices and the associated symplectic transformations, which
provide a natural language for dealing with Gaussian states. Furthermore, for
free QFTs in 1+1 dimension, we compare the dynamics of circuit complexity with
the time dependence of the entanglement entropy for simple bipartitions of
TFDs. We relate our results for the entanglement entropy to previous studies on
nonequilibrium entanglement evolution following quenches. We also present a
new analytic derivation of a logarithmic contribution due to the zero momentum
mode in the limit of vanishing mass for a subsystem containing a single degree
of freedom on each side of the TFD and argue why a similar logarithmic growth
should be present for larger subsystems.