2 research outputs found
About Jordan and Einstein frames: a study in inflationary magnetogenesis
There has been considerable interest in the community to understand if the
Einstein and Jordan frames are either physically equivalent to each other or if
there exists a preference frame where interpretations of physical observables
should be done. In this paper, we want to broaden the discussion about this
equivalence by making a detailed side-by-side comparison of the physical
quantities in both frames in the context of cosmic magnetogenesis. We have
computed the evolution of the vector potential in each frame along with some
observables such as the spectral index, and the magnetic field amplitude. We
found that contrary to the Einstein frame, the electric and magnetic energy
densities in Jordan Frame do not depend on any parameter associated with the
scalar field. Furthermore, in the Einstein frame and assuming scale-invariant
for the magnetic field, most of the total energy density contribution comes
from the electric and magnetic densities. Finally, we show the ratio between
magnetic field signals in both frames printed in the CMB. We expect that the
results presented contribute to the ongoing discussion on the relation between
these two frames.Comment: 23 pages, 15 figures. New references added. Typos are correcte
Evolution of magnetic fields through cosmological perturbation theory
The origin of galactic and extra-galactic magnetic fields is an unsolved
problem in modern cosmology. A possible scenario comes from the idea of these
fields emerged from a small field, a seed, which was produced in the early
universe (phase transitions, inflation, ...) and it evolves in time.
Cosmological perturbation theory offers a natural way to study the evolution of
primordial magnetic fields. The dynamics for this field in the cosmological
context is described by a cosmic dynamo like equation, through the dynamo term.
In this paper we get the perturbed Maxwell's equations and compute the energy
momentum tensor to second order in perturbation theory in terms of gauge
invariant quantities. Two possible scenarios are discussed, first we consider a
FLRW background without magnetic field and we study the perturbation theory
introducing the magnetic field as a perturbation. The second scenario, we
consider a magnetized FLRW and build up the perturbation theory from this
background. We compare the cosmological dynamo like equation in both scenarios