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7 papers · 2 filters
A Note on the Semi-Classical Approximation in Quantum Gravity
Gilad Lifschytz, Samir D. Mathur, Miguel E. Ortiz
We re-examine the semiclassical approximation to quantum gravity in the canonical formulation, focusing on the definition of a quasiclassical state for the gravitational field. It…
Gravitons and Lightcone Fluctuations
L. H. Ford
Gravitons in a squeezed vacuum state, the natural result of quantum creation in the early universe or by black holes, will introduce metric fluctuations. These metric fluctuations…
Averaged Energy Conditions and Quantum Inequalities
L. H. Ford, Thomas A. Roman
Connections are uncovered between the averaged weak (AWEC) and averaged null (ANEC) energy conditions, and quantum inequality restrictions on negative energy for free massless scal…
Predictions from Quantum Cosmology
Alexander Vilenkin
The world view suggested by quantum cosmology is that inflating universes with all possible values of the fundamental constants are spontaneously created out of nothing. I explore…
Open and Closed Universes, Initial Singularities and Inflation
Arvind Borde
The existence of initial singularities in expanding universes is proved without assuming the timelike convergence condition. The assumptions made in the proof are ones likely to ho…
Approaches to Quantum Cosmology
Alexander Vilenkin
Different proposals for the wave function of the universe are analyzed, with an emphasis on various forms of the tunneling proposal. The issues discussed include the equivalence of…