L. Campanelli

Testing the Isotropy of the Universe with Type Ia Supernovae

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 state. We find that the amount of deviation from isotropy of the equation of state of dark energy, the skewness �, and the present level of anisotropy of the large-scale geometry of the Universe, the actual shear �0, are constrained in the ranges −0.16 . � . 0.12 and −0.012 . �0 . 0.012 (1� C.L.) by Union2 data. Supernova data are then compatible with a standard isotropic universe (� = �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.

Inflation-produced magnetic fields in nonlinear electrodynamics

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 Lagrangian, our results do not exclude the possibility that these fields could be astrophysically interesting.

Helical Magnetic Fields from Inflation

We analyze the generation of seed magnetic fields during de Sitter inflation considering a noninvariant conformal term in the electromagnetic Lagrangian of the form , where I(ϕ) is a pseudoscalar function of a nontrivial background field ϕ. In particular, we consider a toy model that could be realized owing to the coupling between the photon and either a (tachyonic) massive pseudoscalar field or a massless pseudoscalar field nonminimally coupled to gravity, where I follows a simple power law behavior I(k,η) = g/(-kη)β during inflation, while it is negligibly small subsequently. Here, g is a positive dimensionless constant, k the wave number, η the conformal time, and β a real positive number. We find that only when β = 1 and 0.1 ≲ g ≲ 2 can astrophysically interesting fields be produced as excitation of the vacuum, and that they are maximally helical.

Inflation-Produced Magnetic Fields in R^n F^2 and I F^2 models

We reanalyze the production of seed magnetic fields during inflation in

Evolution of inflation-generated magnetic field through phase transitions

(R/{m}^{2}{)}^{n}{F}_{\ensuremath{\mu}\ensuremath{\nu}}{F}^{\ensuremath{\mu}\ensuremath{\nu}}

Lorentz symmetry violation and galactic magnetism

and

Spinning supersymmetric Q balls

I{F}_{\ensuremath{\mu}\ensuremath{\nu}}{F}^{\ensuremath{\mu}\ensuremath{\nu}}

COSMIC PARALLAX IN ELLIPSOIDAL UNIVERSE

models, where

Evolution of primordial magnetic fields in mean-field approximation

n

DYNAMICS OF FERROMAGNETIC WALLS: GRAVITATIONAL PROPERTIES

is a positive integer,