The landscape of polymer quantum cosmology
arXiv:2203.07044 · doi:10.1103/PhysRevD.107.086007
Abstract
We show that the quantization ambiguities of loop quantum cosmology, when considered in wider generality, can be used to produce discretionary dynamical behavior. There is an infinite dimensional space of ambiguities which parallels the infinite list of higher curvature corrections in perturbative quantum gravity. There is however an ensemble of qualitative consequences which are generic in the sense that they are independent of these ambiguities. Among these, one has well defined fundamental dynamics across the big bang, and the existence of extra microscopic quantum degrees of freedom that might be relevant in discussions about unitarity in quantum gravity. We show that (in addition to the well known bouncing solutions of the effective equations) there are other generic type of solutions for sufficiently soft initial conditions in the matter sector (tunneling solutions) where the scale factor goes through zero and the spacetime orientation is inverted. We also show that generically, a contracting semiclassical universe branches off at the big bang into a quantum superposition of universes with different quantum numbers. Despite their lack of quantitative predictive power these models offer a fertile playground for the discussion of qualitative and conceptual issues in quantum gravity.
References in corpus (40)
- Loop Quantum Cosmology: A Status Report
- Quantum Nature of the Big Bang: Improved dynamics
- Quantum Spin Dynamics (QSD)
- Barbero's Hamiltonian derived from a generalized Hilbert-Palatini action
- Robustness of key features of loop quantum cosmology
- QSD V : Quantum Gravity as the Natural Regulator of Matter Quantum Field Theories
- Real and complex connections for canonical gravity
- Corrections to the Friedmann Equations from LQG for a Universe with a Free Scalar Field
- On the Trace-Free Einstein Equations as a Viable Alternative to General Relativity
- Quantum Gravity, Torsion, Parity Violation and all that
- Physical effects of the Immirzi parameter
- White Holes as Remnants: A Surprising Scenario for the End of a Black Hole
- Improved and Perfect Actions in Discrete Gravity
- Fermions in Ashtekar-Barbero Connections Formalism for Arbitrary Values of the Immirzi Parameter
- On the Hamiltonian Constraint of Loop Quantum Cosmology
- Cosmological Effective Hamiltonian from full Loop Quantum Gravity Dynamics
- Quantum Cosmology from Group Field Theory Condensates: a Review
- Emergent Friedmann dynamics with a quantum bounce from quantum gravity condensates
- Towards Cosmological Dynamics from Loop Quantum Gravity
- Covariance in models of loop quantum gravity: Spherical symmetry
- On the regularization ambiguities in loop quantum gravity
- Coarse graining methods for spin net and spin foam models
- Why are the effective equations of loop quantum cosmology so accurate?
- Quantum-Reduced Loop Gravity: Cosmology
- Quantization ambiguities and bounds on geometric scalars in anisotropic loop quantum cosmology
- Some implications of signature-change in cosmological models of loop quantum gravity
- Small black/white hole stability and dark matter
- 4d Lorentzian Holst action with topological terms
- Unimodular loop quantum gravity and the problems of time
- Evaporating black-to-white hole
- Lattice loop quantum cosmology: scalar perturbations
- New Hamiltonians for loop quantum cosmology with arbitrary spin representations
- Quantum dynamics of the black hole interior in LQC
- Towards an Anomaly-Free Quantum Dynamics for a Weak Coupling Limit of Euclidean Gravity: Diffeomorphism Covariance
- Gravitational dynamics: A novel shift in the Hamiltonian paradigm
- The constraint algebra in Smolins' limit of 4d Euclidean Gravity
- Operator Spin Foams: holonomy formulation and coarse graining
- Black to white transition of a charged black hole
- Unimodular Loop Quantum Cosmology
- Cosmological implications of generalized holonomy corrections
Cited by in corpus (5)
- Impact of generalized holonomy corrections on the cosmological primordial power spectra
- The role of spatial curvature in constraining the Universe anisotropies across a Big Bounce
- Generic features of a polymer quantum black hole
- Classical and quantum trace-free Einstein cosmology
- Polymer quantum mechanics on compact configuration spaces