Gravitational null rays are quantized in a diffeomorphism-covariant way using the gravitational dressing time as quantum reference frame, producing a Virasoro crossed-product algebra of gauge-invariant observables.
Crossed product algebras and generalized entropy for subregions
6 Pith papers cite this work. Polarity classification is still indexing.
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abstract
An early result of algebraic quantum field theory is that the algebra of any subregion in a QFT is a von Neumann factor of type III$_1$, in which entropy cannot be well-defined because such algebras do not admit a trace or density states. However, associated to the algebra is a modular group of automorphisms characterizing the local dynamics of degrees of freedom in the region, and the crossed product of the algebra with its modular group yields a type II$_\infty$ factor, in which traces and hence von Neumann entropy can be well-defined. In this work, we generalize recent constructions of the crossed product algebra for the TFD to, in principle, arbitrary spacetime regions in arbitrary QFTs, paving the way to the study of entanglement entropy without UV divergences. In contrast to previous works, we emphasize that this construction is independent of gravity. In this sense, the crossed product construction represents a refinement of Haag's assignment of nets of observable algebras to spacetime regions by providing a natural construction of a type II factor. We present several concrete examples: a QFT in Rindler space, a CFT in an open ball of Minkowski space, and arbitrary boundary subregions in AdS/CFT. In the holographic setting, we provide a novel argument for why the bulk dual must be the entanglement wedge, and discuss the distinction arising from boundary modular flow between causal and entanglement wedges for excited states and disjoint regions.
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An operator-algebraic quantization of the characteristic initial-value problem yields a candidate on-shell algebra for a gravitational subregion bounded by two null hypersurfaces.
A semiclassical construction of fiducial observers in JT gravity, fixed by conformal isometry flow, is extended to the quantum regime to compute wormhole contributions yielding finite thermal entropy and a quantum description of the stretched horizon.
Semiclassical crossed product constructions extend the algebraic reconstruction theorem to type III algebras and yield an algebraic Ryu-Takayanagi formula for holographic duality.
A mutually-commuting von Neumann algebra model is constructed for arbitrary quantum networks, yielding Bell-type inequalities whose violation depends on specific algebraic structural conditions of the observables.
Mutually-commuting von Neumann algebra models for entanglement swapping networks yield bounds on Bell-type inequalities whose maximal violations partially classify the underlying algebra types.
citing papers explorer
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Gravitational null rays: Covariant Quantization and the Dressing Time
Gravitational null rays are quantized in a diffeomorphism-covariant way using the gravitational dressing time as quantum reference frame, producing a Virasoro crossed-product algebra of gauge-invariant observables.
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Quantization of Gravity on Null Hypersurfaces
An operator-algebraic quantization of the characteristic initial-value problem yields a candidate on-shell algebra for a gravitational subregion bounded by two null hypersurfaces.
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Fiducial observers and the thermal atmosphere in the black hole quantum throat
A semiclassical construction of fiducial observers in JT gravity, fixed by conformal isometry flow, is extended to the quantum regime to compute wormhole contributions yielding finite thermal entropy and a quantum description of the stretched horizon.
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Semiclassical algebraic reconstruction for type III algebras
Semiclassical crossed product constructions extend the algebraic reconstruction theorem to type III algebras and yield an algebraic Ryu-Takayanagi formula for holographic duality.
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Mutually-commuting von Neumann algebra models of quantum networks and violation of Bell-type inequalities
A mutually-commuting von Neumann algebra model is constructed for arbitrary quantum networks, yielding Bell-type inequalities whose violation depends on specific algebraic structural conditions of the observables.
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Violation of Bell-type Inequalities on Mutually-commuting von Neumann Algebra Models of Entanglement Swapping Networks
Mutually-commuting von Neumann algebra models for entanglement swapping networks yield bounds on Bell-type inequalities whose maximal violations partially classify the underlying algebra types.