2 research outputs found
Seed perturbations for primordial magnetic fields from MSSM flat directions
We demonstrate that the MSSM flat directions can naturally account for the
seed magnetic fields in the early Universe. The non-zero vacuum expectation
value of an MSSM flat direction condensate provides masses to the gauge fields
and thereby breaks conformal invariance. During inflation the condensate
receives spatial perturbations and gauge currents are
generated together with (hyper)magnetic fields. When these long wavelength
vector perturbations reenter our horizon they give rise to magnetic
fields with an amplitude of Gauss, as required by the dynamo
mechanism.Comment: 4 pages, RevTeX
Non-Gaussianity from Instant and Tachyonic Preheating
We study non-Gaussianity in two distinct models of preheating: instant and
tachyonic. In instant preheating non-Gaussianity is sourced by the local terms
generated through the coupled perturbations of the two scalar fields. We find
that the non-Gaussianity parameter is given by ,
where is a coupling constant, so that instant preheating is unlikely to be
constrained by WMAP or Planck. In the case of tachyonic preheating
non-Gaussianity arises solely from the instability of the tachyon matter and is
found to be large. We find that for single field inflation the present WMAP
data implies a bound on the scale of tachyonic
instability. We argue that the tachyonic preheating limits are useful also for
string-motivated inflationary models.Comment: 12 pages, 1 figure, additional discussion, improved constraint on the
scale of tachyonic preheatin