The detection of a time variation of the angle between two distant sources would reveal an anisotropic expansion of the Universe. We study this effect of cosmic parallax within the ellipsoidal universe model, namely a particular homogeneous anisotrop
ic cosmological model of Bianchi type I, whose attractive feature is the potentiality to account for the observed lack of power of the large-scale cosmic microwave background anisotropy. The preferred direction in the sky, singled out by the axis of symmetry inherent to planar symmetry of ellipsoidal universe, could in principle be constrained by future cosmic parallax data. However, that will be a real possibility if and when the experimental accuracy will be enhanced at least by two orders of magnitude.
We analyze the magnitude-redshift data of type Ia supernovae included in the Union and Union2 compilations in the framework of an anisotropic Bianchi type I cosmological model and in the presence of a dark energy fluid with anisotropic equation of st
ate. We find that the amount of deviation from isotropy of the equation of state of dark energy, the skewness delta, and the present level of anisotropy of the large-scale geometry of the Universe, the actual shear Sigma_0, are constrained in the ranges -0.16 < delta < 0.12 and -0.012 < Sigma_0 < 0.012 (1sigma C.L.) by Union2 data. Supernova data are then compatible with a standard isotropic universe (delta = Sigma_0 = 0), but a large level of anisotropy, both in the geometry of the Universe and in the equation of state of dark energy, is allowed.
We analyze the generation of primordial magnetic fields during de Sitter inflation in a Lorentz-violating theory of Electrodynamics containing a Chern-Simons term which couples the photon to an external four-vector. We find that, for appropriate magn
itude of the four-vector, the generated field is maximally helical and, through an inverse cascade caused by turbulence of primeval plasma, reaches at the time of protogalactic collapse an intensity and correlation length such as to directly explain galactic magnetism.
We re-analyze the production of seed magnetic fields during Inflation in (R/m^2)^n F_{mu u}F^{mu u} and I F_{mu u}F^{mu u} models, where n is a positive integer, R the Ricci scalar, m a mass parameter, and I propto eta^alpha a power-law function
of the conformal time eta, with alpha a positive real number. If m is the electron mass, the produced fields are uninterestingly small for all n. Taking m as a free parameter we find that, for n geq 2, the produced magnetic fields can be sufficiently strong in order to seed dynamo mechanism and then to explain galactic magnetism. For alpha gtrsim 2, there is always a window in the parameters defining Inflation such that the generated magnetic fields are astrophysically interesting. Moreover, if Inflation is (almost) de Sitter and the produced fields almost scale-invariant (alpha simeq 4), their intensity can be strong enough to directly explain the presence of microgauss galactic magnetic fields.
We study the generation of primeval magnetic fields during inflation era in nonlinear theories of electrodynamics. Although the intensity of the produced fields strongly depends on characteristics of inflation and on the form of electromagnetic Lagra
ngian, our results do not exclude the possibility that these fields could be astrophysically interesting.
