3 research outputs found
Limits on Primordial Non-Gaussianity from Minkowski Functionals of the WMAP Temperature Anisotropies
We present an analysis of the Minkowski Functionals (MFs) describing the WMAP
three-year temperature maps to place limits on possible levels of primordial
non-Gaussianity. In particular, we apply perturbative formulae for the MFs to
give constraints on the usual non-linear coupling constant fNL. The theoretical
predictions are found to agree with the MFs of simulated CMB maps including the
full effects of radiative transfer. The agreement is also very good even when
the simulation maps include various observational artifacts, including the
pixel window function, beam smearing, inhomogeneous noise and the survey mask.
We find accordingly that these analytical formulae can be applied directly to
observational measurements of fNL without relying on non-Gaussian simulations.
Considering the bin-to-bin covariance of the MFs in WMAP in a chi-square
analysis, we find that the primordial non-Gaussianity parameter is constrained
to lie in the range -70<fNL<91 at 95% C.L. using the Q+V+W co-added maps.Comment: 9 pages, 4 figures, accpeted for publication in MNRA
Curvaton Dynamics and the Non-Linearity Parameters in Curvaton Model
We investigate the curvaton dynamics and the non-linearity parameters in
curvaton model with potential slightly deviating from the quadratic form in
detail. The non-linearity parameter will show up due to the curvaton
self-interaction. We also point out that the leading order of non-quadratic
term in the curvaton potential can be negative, for example in the axion-type
curvaton model. If a large positive is detected, the axion-type
curvaton model will be preferred.Comment: 14 pages, 4 figures; refs adde
Volume Modulus Inflation and the Gravitino Mass Problem
The Hubble constant during the last stages of inflation in a broad class of
models based on the KKLT mechanism should be smaller than the gravitino mass, H
<~ m_{3/2}. We point out that in the models with large volume of
compactification the corresponding constraint typically is even stronger, H <~
m_{3/2}^{3/2}, in Planck units. In order to address this problem, we propose a
class of models with large volume of compactification where inflation may occur
exponentially far away from the present vacuum state. In these models, the
Hubble constant during inflation can be many orders of magnitude greater than
the gravitino mass. We introduce a toy model describing this scenario, and
discuss its strengths and weaknesses.Comment: 24 pages, JHEP style; v2. refs adde