A Nearly Gaussian Hubble-patch in a non-Gaussian Universe

Local-type primordial non-Gaussianity couples
statistics of the curvature perturbation \zeta on vastly different physical
scales. Because of this coupling, statistics (i.e. the polyspectra) of \zeta in
our Hubble volume may not be representative of those in the larger universe -- that
is, they may be biased. The bias depends on the local background value of
\zeta, which includes contributions from all modes with wavelength k ~ and is therefore enhanced if the entire post-inflationary patch is large
compared with our Hubble volume. I will discuss the bias to
locally-measured statistics for general local-type non-Gaussianity. I will
discuss three examples in detail: (i) the usual fNL, gNL model, (ii) a strongly
non-Gaussian model with \zeta ~ \zeta_G^p, and (iii) two-field non-Gaussian
initial conditions. In each scenario one may generate statistics in a
Hubble-size patch that are weakly Gaussian and consistent with observations
despite the fact that the statistics in the larger, post-inflationary patch
look very different. Finally, I will present a worked example of how the
variation in local statistics arises in the curvaton scenario.

Event Type: 
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Event Date: 
Mardi, Octobre 8, 2013 - 11:00 to 12:30
Space Room
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