Imprints of Primordial Non-Gaussianity on Large Scale Structure in the Universe
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Date
2016
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University of the Western Cape
Abstract
Large scale structure in the universe is one of the most important probing tools for
cosmological modelling. Assuming the hot big bang model of the universe, the expansion
history has undergone two phases of acceleration. The primordial phase which
had been considered to be responsible for seeding the structure formation and the late
phase driven by the mysterious component of the cosmos, Dark Energy. Early inhomogeneity
in the structure formation could though leave a signature on the late time
universe. We assume the cosmos to have non-Gaussian initial conditions. Gravitational
instability is thought to be responsible for late structure evolution. On local scales,
non-linear e ects dissipate primordial signal of non-Gaussianity, however on very large
scales, the signal is well preserved. Initial non-Gaussianity introduce a scale dependent
signature on the galaxy power spectrum on very large scales. This could be very useful
to constrain non-Gaussianity parameter via upcoming large scale structure surveys. In
this thesis, we show that on very large scales, interacting dark energy perturbations induce
a scale-dependent e ect on the galaxy power spectrum on large scales. This could
degenerate with primordial non-Gaussianity signal, though a disentanglement between
the two signatures are necessary for observational constraints. On small scales, N-body
simulations for standard cosmological models are used to investigate the signature of
primordial non-Gaussianity on halo mass function. It has a signi cant e ect on very
large halos however it is negligible for small mass halos. Interacting Dark Energy is
assumed to have a similar e ect on small scales. We prepare the basis for future work
that will combine simulations for Interacting Dark Energy models with non-Gaussian
initial conditions.
Description
Philosophiae Doctor - PhD