2014/02/28 by Stephon Alexander, Cosimo Bambi, Antonino Marcianò +2
Physics and Astronomy · #Black Holes and Theoretical Physics #Classical mechanics #Cosmology #Cosmology and Gravitation Theories #De Sitter universe #Fermion #General relativity #Geometry #Initial singularity #Invariant (physics) #Mathematical physics #Noncommutative and Quantum Gravity Theories #Physics #Quantum mechanics #Scale invariance #Singularity #Theoretical physics #Universe #astro-ph.CO #gr-qc #hep-th
paper · pdf · doi:10.1103/physrevd.90.123510
published as Phys. Rev. D 90, 123510 (2014) · 8 pages, 1 figure. v2: refereed version
arxiv created 2014/11/13 · openalex publication_date 2014/12/05 · arxiv updated 2014/12/10 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We develop a nonsingular bouncing cosmology using a nontrivial coupling of general relativity to fermionic fields. The usual big bang singularity is avoided thanks to a negative energy density contribution from the fermions. Our theory is ghost free since the fermionic operator that generates the bounce is equivalent to torsion, which has no kinetic terms. The physical system consists of standard general relativity plus a topological sector for gravity and fermionic matter described by Dirac fields with a nonminimal coupling. We show that a scale-invariant power spectrum generated in the contracting phase can be recovered by suitable choices of fermion number density and bare mass, thus providing a possible alternative to the inflationary scenario.