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Algebraic Observational Cosmology
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Algebraic Observational Cosmology
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What can be measured by an observer in our universe? We address this question by constructing an algebra of gravitationally-dressed observables accessible to a comoving observer in FLRW spacetimes that are asymptotically de Sitter in the past, describing an inflationary epoch. An essential quantized degree of freedom is the zero-mode of the inflaton, which leads to fluctuations in the effective cosmological constant during inflation and prevents the existence of a maximum entropy state in the semiclassical limit. Due to the inaccessibility of measurements beyond our cosmological horizon, we demonstrate that all states are mixed with well-defined von Neumann entropy (up to a state-independent constant). For semiclassical states, the von Neumann entropy corresponds to the generalized entropy of the observer's causal diamond, a fine-grained quantity that is sensitive to the initial conditions of the universe.
Forward citations
Cited by 10 Pith papers
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Uniqueness of null-local modular flow
For the free massless scalar in a Minkowski causal diamond, the vacuum is the unique state or weight in the vacuum sector whose modular flow is local on the null boundary.
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A de Sitter Anti-Scrambling Algebra
In a toy model of de Sitter quantum gravity, shockwave time advances break the KMS condition and prevent the Hartle-Hawking state from being a trace on the observer's crossed-product algebra.
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Observers, local measurements, and topology
Measurement correlations along an observer's worldline define a simplicial complex whose homology is proposed to be the topology of the accessible quantum-gravitational spacetime.
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Subregion observer rules from generalized entanglement wedges
Two sets of holographic tensor network rules from independent papers are shown to be equivalent, connecting observer inclusion with generalized entanglement wedge proposals.
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An observer's quantization of 3d de Sitter
Proposes an SL(2,Z) sum of Kerr-lens geometries in 3d dS gravity whose spectral density is computed via crosscap amplitudes in CLS ⊗ CLS, matching semi-classical predictions and reducing in a simple case to GΣ ⊗ GΣ on...
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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 des...
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On Perturbatively Dressed Observables
Perturbative dressing of local operators in QED and GR induces kinematic singularities and is mathematically equivalent to dynamical temporal gauge fixing.
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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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Limits on the Statistical Description of Charged de Sitter Black Holes
Adopting the Bousso-Hawking observer normalization for RNdS black holes produces finite heat capacity near the Nariai limit while confirming vanishing capacity in cold and ultracold limits, limiting statistical descriptions.
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Implication of dressed form of relational observable on von Neumann algebra
Dressed relational observables imply quasi-de Sitter space corresponds to Type II_∞ von Neumann algebra with diverging trace in the gravity decoupling limit, unlike the finite-trace Type II_1 algebra for de Sitter space.
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