Quantum gravity, information theory and the CMB

Abstract

We review connections between the metric of spacetime and the quantum fluctuations of fields. In particular, we discuss the finding that the spacetime metric can be expressed entirely in terms of the 2-point correlators of the fluctuations of quantum fields. We also discuss the open question whether the knowledge of only the spectra of the quantum fluctuations of fields suffices to determine the spacetime metric. This question is of interest because spectra are geometric invariants and their quantization would, therefore, have the benefit of not requiring the modding out of the diffeomorphism group. Further, we discuss the fact that spacetime at the Planck scale need not necessarily be either discrete or continuous. Instead, results from information theory show that spacetime may be simultaneously discrete and continuous in the same way that information can. Finally, we review the finding that a covariant natural ultraviolet cutoff at the Planck scale implies a signature in the cosmic microwave background (CMB) that may become observable.

Based on an invited presentation at the Lemaitre Workshop (9-12 May 2017, Vatican Observatory)

References in corpus (8)

• GUP parameter from quantum corrections to the Newtonian potential
• The causal set approach to quantum gravity
• Minimum Length Cutoff in Inflation and Uniqueness of the Action
• Spacetime could be simultaneously continuous and discrete in the same way that information can
• On Information Theory, Spectral Geometry and Quantum Gravity
• Exact solution of inflationary model with minimum length
• Shape from sound: toward new tools for quantum gravity
• Natural Covariant Planck Scale Cutoffs and the Cosmic Microwave Background Spectrum

Cited by in corpus (13)

• Quantum Temporal Superposition: the case of QFT
• Hubble tension bounds the GUP and EUP parameters
• Hubble tension as a guide for refining the early Universe: Cosmologies with explicit local Lorentz and diffeomorphism violation
• Replacing the Notion of Spacetime Distance by the Notion of Correlation
• Bounding generalized relative entropies: Nonasymptotic quantum speed limits
• The geometry of spacetime from quantum measurements
• Testing Generalised Uncertainty Principles through Quantum Noise
• Spacetime curvature from ultra rapid measurements of quantum fields
• Higher-order generalized uncertainty principle applied to gravitational baryogenesis
• Lorentzian Spectral Geometry with Causal Sets
• Locally detecting UV cutoffs on a sphere with particle detectors
• Lorentz-covariant sampling theory for fields
• Impact of particle production during inflation on the CMB detection