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abstract
We study the static patch of de Sitter space in the presence of a timelike boundary. We impose that the conformal class of the induced metric and the trace of the extrinsic curvature, $K$, are fixed at the boundary. We present the thermodynamic structure of de Sitter space subject to these boundary conditions, for static and spherically symmetric configurations to leading order in the semiclassical approximation. In three spacetime dimensions, and taking $K$ constant on a toroidal Euclidean boundary, we find that the spacetime is thermally stable for all $K$. In four spacetime dimensions, the thermal stability depends on the value of $K$. It is established that for sufficiently large $K$, the de Sitter static patch subject to conformal boundary conditions is thermally stable. This contrasts the Dirichlet problem for which the region encompassing the cosmological horizon has negative specific heat. We present an analysis of the linearised Einstein equations subject to conformal boundary conditions. In the worldline limit of the timelike boundary, the underlying modes are linked to the quasinormal modes of the static patch. In the limit where the timelike boundary approaches the cosmological event horizon, the linearised modes are interpreted in terms of the shear and sound modes of a fluid dynamical system. Additionally, we find modes with a frequency of positive imaginary part. Measured in a local inertial reference frame, and taking the stretched cosmological horizon limit, these modes grow at most polynomially.
Forward citations
Cited by 9 Pith papers
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Dirichlet walls and the end of time
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JT gravity on the worldline
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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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Ill-posedness of the Cauchy problem for linearized gravity in a cavity with conformal boundary conditions
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Holographic entanglement entropy with conformal boundary conditions
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Quantum Liouville Cosmology
Timelike Liouville disk path integrals in fixed K-representation produce Hartle-Hawking-like states, a conjecture for all-loop wavefunctions, and a K-independent inner product for 2D quantum cosmology.
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Fluid Boundary Conditions from AdS/BCFT
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Quantum stress-energy at timelike boundaries: testing a new beyond-$\Lambda$CDM parameter with cosmological data
Timelike boundaries sourcing negative, 1/a-scaling vacuum energy fit CMB+BAO data slightly better than LCDM and relax the neutrino-mass constraint, though the preference is only about 2 sigma.
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Cosmological horizon thermodynamics in Gauss-Bonnet quasi-dilaton Massive Gravity
Gauss-Bonnet quasi-dilaton massive gravity is claimed to obey horizon thermodynamics and the holographic entropy bound, provided the Gauss-Bonnet coupling is non-negative.
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