83 research outputs found
The Lyman α forest as a tool for disentangling non-Gaussianities
© 2014 IOP Publishing Ltd and Sissa Medialab srl . Detection of primordial non-Gaussianity will give us an unprecedented detail of the physics of inflation. As observational probes are now exploring new expanses of the inflationary landscape, it is crucial to distinguish and disentangle effects of various non-Gaussianities beyond f NL . In this work, we calculate the effects of non-Gaussianities parametrized by f NL and the cubic-order g NL , on the Lyman α-forest flux measurements. We give the expressions of the bias due to f NL and g NL , which can be deduced from accurate measurements of the transmitted flux. We show how these two effects can be cleanly disentangled via a flux transformation, which also keeps the error in check
On the abundance of extreme voids
Cosmic voids have been shown to be an effective probe of cosmology, complementary to galaxy clusters. In this work, we present a simple theoretical framework for predicting of the size of the largest voids expected within a given redshift and volume. Our model is based on the exact extreme-value statistics which has previously been successfully applied to massive galaxy clusters. We implement our formalism using the void-abundance models and compare the extreme-void predictions to simulations and observations. We find that the simplest void models can only explain the extreme-void abundance with ad hoc parameter adjustments. We argue that the prediction extreme-void distribution should be used as an additional test on theories of void abundance
The Lyman-alpha Forest as a tool for disentangling non-Gaussianities
Detection of primordial non-Gaussianity will give us an unprecedented detail
of the physics of inflation. As observational probes are now exploring new
expanses of the inflationary landscape, it is crucial to distinguish and
disentangle effects of various non-Gaussianities beyond f_NL. In this work, we
calculate the effects of non-Gaussianities parametrized by f_NL and the
cubic-order g_NL, on the Lyman-alpha-forest flux measurements. We give the
expressions of the bias due to f_NL and g_NL, which can be deduced from
accurate measurements of the transmitted flux. We show how these two effects
can be cleanly disentangled via a flux transformation, which also keeps the
error in check.Comment: 12 pages, 5 figures. Accepted for publication in JCA
Inflation model building with an accurate measure of e-folding
It has become standard practice to take the logarithmic growth of the scale factor as a measure of the amount of inflation, despite the well-known fact that this is only an approximation for the true amount of inflation required to solve the horizon and flatness problems. The aim of this work is to show how this approximation can be completely avoided using an alternative framework for inflation model building. We show that using the inverse Hubble radius, H=aH , as the key dynamical parameter, the correct number of e-folding arises naturally as a measure of inflation. As an application, we present an interesting model in which the entire inflationary dynamics can be solved analytically and exactly, and, in special cases, reduces to the familiar class of power-law models
Constraining isocurvature perturbations with the 21 cm emission from minihaloes
We investigate the effects of isocurvature perturbations on the 21 cm radiation from minihaloes (MHs) at high redshifts and examine constraints on the isocurvature amplitude and power spectrum using the next generation of radio telescopes such as the Square Kilometre Array. We find that there is a realistic prospect of observing the isocurvature imprints in the 21 cm emission from MHs, but only if the isocurvature spectral index is close to 3 (i.e. the spectrum is blue). When the isocurvature fraction increases beyond ∼10 per cent of the adiabatic component, we observe an unexpected decline in the 21 cm fluctuations from small-mass MHs, which can be explained by the incorporation small MHs into larger haloes. We perform a detailed Fisher-matrix analysis and conclude that the combination of future cosmic microwave background and 21 cm experiments (such as CMBPol and the Fast Fourier Transform Telescope) is ideal in constraining the isocurvature parameters, but will stop short of distinguishing between cold dark matter and baryon types of isocurvature perturbations, unless the isocurvature fraction is large and the spectrum is blue
On the abundance of extreme voids II : a survey of void mass functions
The abundance of cosmic voids can be described by an analogue of halo mass functions for galaxy clusters. In this work, we explore a number of void mass functions: from those based on excursion-set theory to new mass functions obtained by modifying halo mass functions. We show how different void mass functions vary in their predictions for the largest void expected in an observational volume, and compare those predictions to observational data. Our extreme-value formalism is shown to be a new practical tool for testing void theories against simulation and observation
Primordial Gravitational Waves and Reheating in a New Class of Plateau-Like Inflationary Potentials
We study a new class of inflation model parametrized by the Hubble radius, such that aH∝exp(−αφ)n. These potentials are plateau-like, and reduce to the power-law potentials in the simplest case n=2. We investigate the range of model parameters that is consistent with current observational constraints on the scalar spectral index and the tensor-to-scalar ratio. The amplitude of primordial gravitational waves in these models is shown to be accessible by future laser interferometers such as DECIGO. We also demonstrate how these observables are affected by the temperature and equation of state during reheating. We find that a large subset of this model can support instantaneous reheating, as well as very low reheating temperatures of order a few MeV, giving rise to interesting consequences for dark-matter production
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