Baby Universes and Worldline Field Theories
arXiv:2101.12221 · doi:10.1088/1361-6382/ac37cd
Abstract
The quantum gravity path integral involves a sum over topologies that invites comparisons to worldsheet string theory and to Feynman diagrams of quantum field theory. However, the latter are naturally associated with the non-abelian algebra of quantum fields, while the former has been argued to define an abelian algebra of superselected observables associated with partition-function-like quantities at an asymptotic boundary. We resolve this apparent tension by pointing out a variety of discrete choices that must be made in constructing a Hilbert space from such path integrals, and arguing that the natural choices for quantum gravity differ from those used to construct QFTs. We focus on one-dimensional models of quantum gravity in order to make direct comparisons with worldline QFT.
37 pages, 3 figures. v2: fixed typos, added reference. v3: additional comments, references updated. v4: further improvements, added references
References in corpus (15)
- Transcending the ensemble: baby universes, spacetime wormholes, and the order and disorder of black hole information
- JT gravity as a matrix integral
- Random Statistics of OPE Coefficients and Euclidean Wormholes
- Gravity/Ensemble Duality
- Eigenstate Thermalization and Disorder Averaging in Gravity
- Feynman Propagator for a Free Scalar Field on a Causal Set
- More quantum noise from wormholes
- Wormhole calculus, replicas, and entropies
- Bulk reconstruction and the Hartle-Hawking wavefunction
- Density matrices in quantum gravity
- Spin structures and baby universes
- Nonlocal gravity with worldline inversion symmetry
- Toward a 3d Ising model with a weakly-coupled string theory dual
- String Perturbation Theory on the Schwinger-Keldysh Time Contour
- Holographic baby universes: an observable story
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- A proof of loop equations in 2d topological gravity
- Quantum Computing for Inflationary, Dark Energy and Dark Matter Cosmology