Horizon edge mode spectra in de Sitter and Nariai spacetimes exhibit universal shift symmetries that produce novel symmetry breaking in one-loop partition functions.
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A clock is just a way to tell the time: gravitational algebras in cosmological spacetimes
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abstract
We study the algebra of observables in semiclassical quantum gravity for cosmological backgrounds, focusing on two key examples: slow-roll inflation and evaporating Schwarzschild-de Sitter black holes. In both cases, we demonstrate the existence of a nontrivial algebra of diffeomorphism-invariant observables \emph{without} the introduction of an external clock system or the presence of any asymptotic gravitational charges. Instead, the rolling inflaton field and the evaporating black hole act as physical clocks that allow a definition of gauge-invariant observables at $G = 0$. The resulting algebras are both Type II$_\infty$ factors, but neither is manifestly a crossed product algebra. We establish a connection between the Type II entropy of these algebras and generalized entropies for appropriate states. Our work extends previous results on Type II gravitational algebras and highlights the crucial role of out-of-equilibrium dynamics for defining gauge-invariant observables in semiclassical canonically quantised gravity. We also briefly discuss the construction of gauge-invariant algebras for compact wedges bounded by extremal surfaces in generic spacetimes (i.e. in the absence of any Killing symmetry). In contrast to the inflaton and black hole cases, this algebra does end up being a simple crossed product. No clock or asymptotic charges are required because of the absence of any symmetry in the classical background.
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For charged de Sitter black holes, choosing the Bousso-Hawking observer normalization keeps the heat capacity finite in the Nariai limit, removing the expected log-T breakdown except in the cold and ultracold limits.
In 2D centaur geometries the entropy difference of a modular-conjugate Hawking-pair probe traces an inverse mini-Page curve that bottoms at τ≈β/8, marking when information begins to leave the cosmological horizon.
Two sets of holographic tensor network rules from independent papers are shown to be equivalent, connecting observer inclusion with generalized entanglement wedge proposals.
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 the observer worldline.
Constructs a phase space for gravitational degrees of freedom on null ray segments with commuting localized observables via edge modes and dressing time, then introduces an effective classical theory with Virasoro deformations to capture diffeomorphism anomalies and distinguish gauge, physical, and
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.
Perturbative dressing of local operators in QED and GR induces kinematic singularities and is mathematically equivalent to dynamical temporal gauge fixing.
Nucleated black holes in de Sitter space evaporate via standard Hawking radiation back to the empty vacuum, rendering nucleation a temporary fluctuation.
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.
The paper organizes important open questions in quantum gravity and quantum information into four themes without presenting new results or derivations.
citing papers explorer
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Horizon Edge Partition Functions in $\Lambda>0$ Quantum Gravity
Horizon edge mode spectra in de Sitter and Nariai spacetimes exhibit universal shift symmetries that produce novel symmetry breaking in one-loop partition functions.
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Limits on the Statistical Description of Charged de Sitter Black Holes
For charged de Sitter black holes, choosing the Bousso-Hawking observer normalization keeps the heat capacity finite in the Nariai limit, removing the expected log-T breakdown except in the cold and ultracold limits.
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The mini-Page Curve in Cosmology
In 2D centaur geometries the entropy difference of a modular-conjugate Hawking-pair probe traces an inverse mini-Page curve that bottoms at τ≈β/8, marking when information begins to leave the cosmological horizon.
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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 the observer worldline.
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Localization and anomalous reference frames in gravity
Constructs a phase space for gravitational degrees of freedom on null ray segments with commuting localized observables via edge modes and dressing time, then introduces an effective classical theory with Virasoro deformations to capture diffeomorphism anomalies and distinguish gauge, physical, and
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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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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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The Fate of Nucleated Black Holes in de Sitter Quantum Gravity
Nucleated black holes in de Sitter space evaporate via standard Hawking radiation back to the empty vacuum, rendering nucleation a temporary fluctuation.
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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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Rethinking quantum information in gravity and fields
The paper organizes important open questions in quantum gravity and quantum information into four themes without presenting new results or derivations.