2008/07/31 by J. Ambjørn, J. Ambjorn, A. Goerlich +3 · 1 citation
Physics and Astronomy · #Black Holes and Theoretical Physics #Classical mechanics #Cosmology and Gravitation Theories #De Sitter universe #Effective action #Gravitation #Noncommutative and Quantum Gravity Theories #Path integral formulation #Physics #Planck #Planck length #Planck scale #Quantum #Quantum cosmology #Quantum fluctuation #Quantum gravity #Quantum mechanics #Regularization (linguistics) #Theoretical physics #Universe #astro-ph #gr-qc #hep-th
paper · pdf · doi:10.1103/physrevd.78.063544
published as Phys.Rev.D78:063544,2008 · Article unchanged. Line added in acknowledgment
openalex publication_date 2008/09/26 · arxiv created 2009/01/08 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The dynamical generation of a four-dimensional classical universe from nothing but fundamental quantum excitations at the Planck scale is a long-standing challenge to theoretical physicists. A candidate theory of quantum gravity which achieves this goal without invoking exotic ingredients or excessive fine-tuning is based on the nonperturbative and background-independent technique of causal dynamical triangulations. We demonstrate in detail how in this approach a macroscopic de Sitter universe, accompanied by small quantum fluctuations, emerges from the full gravitational path integral, and how the effective action determining its dynamics can be reconstructed uniquely from Monte Carlo data. We also provide evidence that it may be possible to penetrate to the sub-Planckian regime, where the Planck length is large compared to the lattice spacing of the underlying regularization of geometry.