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The rotation of polarization by gravitational waves
Valerio Faraoni
There are conflicting statements in the literature about the gravitational Faraday rotation of the plane of polarization of polarized electromagnetic radiation travelling through a…
Matter instability in modified gravity
Valerio Faraoni
The Dolgov-Kawasaki instability discovered in the matter sector of the modified gravity scenario incorporating a 1/R correction to Einstein gravity is studied in general f(R) theor…
On the total energy of open Friedmann-Robertson-Walker universes
V. Faraoni, F. I. Cooperstock
The idea that the universe has zero total energy when one includes the contribution from the gravitational field is reconsidered. A Hamiltonian is proposed as an energy for the exa…
Einstein frame or Jordan frame ?
Valerio Faraoni, Edgard Gunzig
Scalar-tensor theories of gravity can be formulated in the Jordan or in the Einstein frame, which are conformally related. The issue of which conformal frame is physical is a conte…
Tales of tails in cosmology
Valerio Faraoni, Edgard Gunzig
Late time mild inflation (LTMI) proposes to solve the age of the universe problem and the discrepancy between locally and globally measured values of the Hubble parameter. However,…
The influence of the cosmological expansion on local systems
F. I. Cooperstock, V. Faraoni, D. N. Vollick
Following renewed interest, the problem of whether the cosmological expansion affects the dynamics of local systems is reconsidered. The cosmological correction to the equations of…
Lensing by gravitational waves in scalar-tensor gravity: Einstein frame analysis
Valerio Faraoni, Edgard Gunzig
The amplification of a light beam due to intervening gravitational waves is studied. The previous Jordan frame result according to which the amplification is many orders of magnitu…
Multiple imaging by gravitational waves
Valerio Faraoni
Gravitational waves act like lenses for the light propagating through them. This phenomenon is described using the vector formalism employed for ordinary gravitational lenses, whic…
The creation of multiple images by a gravitational wave
Valerio Faraoni
We describe gravitational lensing by a gravitational wave, in the regime in which multiple images of a light source are created. We adapt the vector formalism employed for ordinary…
Light amplification by gravitational waves in scalar-tensor theories of gravity
Valerio Faraoni
It is shown that the amplification of a light beam by gravitational waves in scalar-tensor theories of gravity is a first order effect in the wave amplitudes. In general relativity…
Non-minimal coupling of the scalar field and inflation
Valerio Faraoni
We study the prescriptions for the coupling constant of a scalar field to the Ricci curvature of spacetime in specific gravity and scalar field theories. The results are applied to…
COBE CONSTRAINTS ON KALUZA-KLEIN COSMOLOGIES
V. Faraoni, F. I. Cooperstock, J. M. Overduin
A class of Kaluza-Klein cosmologies recently proposed is compared with observations of the cosmic microwave background. Some models are ruled out, while others turn out to be viabl…
A Singularity-Free Cosmological Model with a Conformally Coupled Scalar Field
S. S. Bayin, F. I. Cooperstock, V. Faraoni
We explore the possibility of describing our universe with a singularity--free, closed, spatially homogeneous and isotropic cosmological model, using only general relativity and a…
Laser Interferometric Detectors of Gravitational Waves
F. I. Cooperstock, V. Faraoni
A laser interferometric detector of gravitational waves is studied and a complete solution (to first order in the metric perturbation) of the coupled Einstein-Maxwell equations wit…
On the rotation of polarization by a gravitational lens
Valerio Faraoni
It is proved that the field of a gravitational lens induces no rotation in the polarization vector of electromagnetic radiation, in agreement with the previous literature, but with…
On the Tail Problem in Cosmology
Valerio Faraoni, Sebastiano Sonego
The tail problem for the propagation of a scalar field is considered in a cosmological background, taking a Robertson-Walker spacetime as a specific example. The explicit radial de…
Nonstationary Gravitational Lenses and the Fermat Principle
Valerio Faraoni
We apply Perlick's (1990a) rigorous formulation of the Fermat principle in arbitrary spacetimes to prove the correctness of the description of gravitational lensing by gravitationa…