Untitled

2019

Eur. Phys. J. C

We propose a method of projecting the quantum states from a state space of a given geometry into another state space generated by a different geometry, taking care on the correct normalization which is crucial in interpreting the quantum theory. Thanks to this method we can define on any spatially flat FLRW spacetime states in which genuine Minkowskian parameters are measured. We use these Minkowskian states for separating the frequencies in the rest frames of the massive scalar particles defining thus the scalar rest frame vacuum. We show that this vacuum is stable on the de Sitter expanding universe where the energy is conserved. In contrast, on a spatially flat FLRW spacetime with a Milne-type scale factor this vacuum results to be dynamic, corresponding to a time-dependent rest energy interpreted as an effective mass. This dynamic vacuum give rise to a cosmological particle creation which is significant only in the early Milne-type universe considered here. Some interesting features of this new effect are pointed out in a brief analysis.

Section: Discussionmentioning

confidence: 99%

Rest frame vacuum of the Dirac field on spatially flat FLRW spacetimes

2019

Eur. Phys. J. C

“…On the contrary, using a WKB-type method Parker found that this phenomenon does exist in various expanding Robertson-Walker universes [27]. Other authors considered the most realistic conjecture of the QED on such expanding space-times [28] or only on the de Sitter one [29,30]. A general method of investigating QED effects in the first order of perturbations was proposed by Lotze, which calculates the in − out transition probabilities [28] taking into account the 'added-up' decay probability prescribed by Audretsch and Spangehl [31].…”

Section: Introductionmentioning

confidence: 99%

de Sitter QED in Coulomb gauge: First order transition amplitudes

Crucean

2013

Phys. Rev. D

We construct the de Sitter QED in Coulomb gauge assuming that the quantum modes are prepared by a global apparatus which is able to determine a stable and invariant vacuum state, independent on the local coordinates. Then we proceed in traditional manner postulating the appropriate equal-time commutators and anti-commutators of the interacting fields and deriving the perturbation expansion of the scattering operator. In this approach the in − out transitions amplitudes, measured by the same global apparatus, can be calculated exactly by using the reduction formalism and the perturbation procedure as in the flat case but with significant differences due to the de Sitter geometry. A specific feature is that the gravity eliminates the constraints due to the simultaneous momentum-energy conservation giving rise to QED transitions with nonvanishing amplitudes even in the first order of perturbations. Of a special interest could be the first order amplitudes of the electromagnetic particle creation allowed by the expansion of the de Sitter universe. We show that this effect is significant only in the very strong gravity of the early universe.PACS numbers: 04.62.+v 1

“…These manifolds, largely used in the ΛCDM models, are symmetric under translations and, consequently, there are quantum modes expressed in terms of plane waves with similar properties as in special relativity. For this reason these manifolds are useful for studying the behavior of the quantum matter in the presence of classical gravity turning back to the perturbation methods of the quantum field theory where significant results were obtained by many authors [9][10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

“…where ξ σ ( p) and η σ ( p) = iσ 2 ξ * σ are the Pauli spinors of the helicity basis corresponding to the helicities σ = ± 1 2 as given in the Appendix A. The fundamental spinors are solutions of the free Dirac equation whether the modulation functions u ± p (t) and v ± p (t) satisfy the first order differential equations 14) in the chart with the proper time. The solutions of these systems must satisfy the charge-conjugation symmetry [19], 15) and the normalization conditions…”

Section: Introductionmentioning

confidence: 99%

First order QED processes in a spatially flat FLRW space-time with a Milne-type scale factor

Popescu

2020

Chinese Phys. C

The quantum electrodynamics (QED) on a spatially flat (1+3)-dimensional Friedmann-Lemaître-Robertson-Walker (FLRW) spacetime with a Milne-type scale factor is outlined focusing on the amplitudes of the allowed effects in the first order of perturbations. The definition of the transition rates is reconsidered obtaining an appropriate angular behavior of the probability of the pair creation from a photon.PACS: 04.62.+v II. FREE FIELDS ON AN EXPANDIND SPACETIMELet us start defining the spacetime M as the (1 + 3)dimensional spatially flat FLRW manifold having the arXiv:1903.04741v2 [gr-qc]