2003/12/08 by D. H. Coule, Coule, D. H. · 7 citations
Mathematics · Physics and Astronomy · #Arrow of time #Big Bounce #Black Holes and Theoretical Physics #Classical mechanics #Cosmology #Cosmology and Gravitation Theories #Dark energy #De Sitter universe #Epistemology #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #Initial singularity #Loop quantum cosmology #Mathematics #Naturalness #Noncommutative and Quantum Gravity Theories #Nothing #Philosophy #Physics #Quantum #Quantum cosmology #Quantum gravity #Quantum mechanics #Scalar (mathematics) #Singularity #Theoretical physics #Unitarity #Universe #Wave function #gr-qc
paper · pdf · doi:10.48550/arxiv.gr-qc/0312045
published in arXiv (Cornell University) (Cornell University) · 21 pages, dispute with astro-ph/0311015 addressed
openalex publication_date 2003/12/08 · arxiv created 2004/02/06 · arxiv updated 2016/08/31 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/08
We compare the recent loop quantum cosmology approach of Bojowald and co-workers with earlier quantum cosmological schemes. Because the weak-energy condition can now be violated at short distances, and not necessarily with a high energy density, a number of possible instabilities are suggested: flat space unstable to expansion or baby universe production. Or else a Machian type principle is required to prevent such behaviour. Allowing a bounce to prevent an approaching singularity seems incompatible with other standard notions concerning the arrow of time and unitarity. Preventing rapid oscillations in the wavefunction appears in conflict with more general scalar-tensor gravity. Other approaches such as ``creation from nothing'' or from some quiescent state, static or time machine, are also assessed on grounds of naturalness and fine tuning.