Constraint on the primordial vector mode and its magnetic field generation from seven-year Wilkinson Microwave Anisotropy Probe Observations

الأصل · EN

A primordial vector mode and its associated magnetic field generation are investigated. Firstly, we put an observational constraint on the amount of the primordial vector mode from the seven-year WMAP data. The constraint is found as rᵥ -r/40+0.012, where rᵥ and r are the amounts of vector and tensor perturbation amplitudes with respect to the scalar one, respectively. Secondly, we calculate the spectrum of magnetic fields inevitably created from the primordial vector mode, given the constraint on rᵥ. It is found that the maximum amount of magnetic fields generated from the vector mode is given by B 10⁻²² G (rᵥ/0.012)¹/² (k/0.002)⁽ⁿᵛ⁺¹⁾/² with nᵥ being a spectral index of the vector mode. We find a non-trivial cancellation of the magnetic field generation in the radiation dominated era, which creates a characteristic cut off in the magnetic field spectrum around k≈ 1.0 Mpc⁻¹.