Magnetic fields from inflation?

We consider the possibility of generation of the seeds of primordial magnetic field on inflation and show that the effect of the back reaction of this field can be very important. Assuming that back reaction does not spoil inflation we find a rather strong restriction on the amplitude of the primordial seeds which could be generated on inflation. Namely, this amplitude recalculated to the present epoch cannot exceed $10^{-32}G$ in $Mpc$ scales. This field seems to be too small to be amplified to the observable values by galactic dynamo mechanism.Comment: 10 page

Supercurvaton

We discuss observational consequences of the curvaton scenario, which naturally appears in the context of the simplest model of chaotic inflation in supergravity. The non-gaussianity parameter f_NL in this scenario can take values in the observationally interesting range from O(10) to O(100). These values may be different in different parts of the universe. The regions where f_NL is particularly large form a curvaton web resembling a net of thick domain walls, strings, or global monopoles.Comment: 17 pages, 1 figure. Non-perturbative effects related to non-gaussianity in the curvaton scenario are discussed, some references are added. This is the version accepted in JCA

Reheating constraints in inflationary magnetogenesis

Among primordial magnetogenesis models, inflation is a prime candidate to explain the current existence of cosmological magnetic fields. Assuming conformal invariance to be restored after inflation, their energy density decreases as radiation during the decelerating eras of the universe, and in particular during reheating. Without making any assumptions on inflation, on the magnetogenesis mechanism and on how the reheating proceeded, we show that requiring large scale magnetic fields to remain subdominant after inflation gives non-trivial constraints on both the reheating equation of state parameter and the reheating energy scale. In terms of the so-called reheating parameter, we find that ln(Rrad) > -10.1 for large scale magnetic fields of the order 5 x 10^(-15) Gauss today. This bound is then compared to those already derived from Cosmic Microwave Background (CMB) data by assuming a specific inflationary model. Avoiding magnetic field backreaction is always complementary to CMB and can give more stringent limits on reheating for all high energy models of inflation. For instance, a large field matter dominated reheating cannot take place at an energy scale lower than typically 500 GeV if the magnetic field strength today is Bo = 5 x 10^(-15) G, this scale going up to 10^(10) GeV if Bo = 10^(-9) G