Manifestly gauge-invariant cosmological perturbation theory from full loop quantum gravity
Han M, Li H, Liu H (2020)
Publication Type: Journal article
Publication year: 2020
Journal
Book Volume: 102
Journal Issue: 12
DOI: 10.1103/PhysRevD.102.124002
Abstract
We apply the full theory of Loop Quantum Gravity (LQG) to cosmology and present a top-down derivation of gauge-invariant cosmological perturbation theory from quantum gravity. The derivation employs the reduced phase space formulation of LQG and the new discrete path integral formulation defined in M. Han and H. Liu, Phys. Rev. D 101, 046003 (2020). We demonstrate that in the semiclassical approximation and continuum limit, the result coincides with the existing formulation of gauge-invariant cosmological perturbation theory in, e.g., K. Giesel et al., Classical Quantum Gravity 27, 055006 (2010). Time evolution of cosmological perturbations is computed numerically from the new cosmological perturbation theory of LQG, and various power spectrums are studied for scalar mode and tensor mode perturbations. Comparing these power spectrums with predictions from the classical theory demonstrate corrections in the ultralong wavelength regime. These corrections are results from the lattice discretization in LQG. In addition, tensor mode perturbations at late time demonstrate the emergence of spin-2 gravitons as low energy excitations from LQG. The graviton has a modified dispersion relation and reduces to the standard graviton in the long wavelength limit.
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APA:
Han, M., Li, H., & Liu, H. (2020). Manifestly gauge-invariant cosmological perturbation theory from full loop quantum gravity. Physical Review D, 102(12). https://dx.doi.org/10.1103/PhysRevD.102.124002
MLA:
Han, Muxin, Haida Li, and Hongguang Liu. "Manifestly gauge-invariant cosmological perturbation theory from full loop quantum gravity." Physical Review D 102.12 (2020).
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