2008/06/17 by Martin Bojowald, Rupam Das · 1 citation
Physics and Astronomy · #Black Holes and Theoretical Physics #Noncommutative and Quantum Gravity Theories #Quantum Mechanics and Non-Hermitian Physics #gr-qc
paper · pdf · doi:10.1088/0264-9381/25/19/195006
published as Class.Quant.Grav.25:195006,2008 · 17 pages
arxiv created 2008/06/17 · openalex publication_date 2008/09/11 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/30
Fermions play a special role in homogeneous models of quantum cosmology because the exclusion principle prevents them from forming sizable matter contributions. They can thus describe the matter ingredients only truly microscopically and it is not possible to avoid strong quantum regimes by positing a large matter content. Moreover, possible parity-violating effects are important especially in loop quantum cosmology whose basic object is a difference equation for the wavefunction of the universe defined on a discrete space of triads. The two orientations of a triad are interchanged by a parity transformation, which leaves the difference equation invariant for ordinary matter. Here, we revisit and extend loop quantum cosmology by introducing fermions and the gravitational torsion they imply, which renders the parity issue non-trivial. A treatable locally rotationally symmetric Bianchi model is introduced which clearly shows the role of parity. General wavefunctions cannot be parity-even or odd, and parity-violating effects in matter influence the microscopic big bang transition which replaces the classical singularity in loop quantum cosmology.