Conveners
Cosmic microwave background and Large Scale Structure
- Jan Hamann
Cosmic microwave background and Large Scale Structure
- Luke Barnes
Cosmic microwave background and Large Scale Structure
- David Parkinson (University of Queensland)
Cosmic microwave background and Large Scale Structure
- David Wiltshire (University of Canterbury)
Measurements of the polarisation of the cosmic microwave background (CMB) are rapidly becoming an important tool to test the standard model of cosmology. In particular, searches for the faint CMB B-mode signals offer the prospect of detecting inflationary gravitational waves on large angular scales and mapping out the large scale distribution of matter in the Universe through CMB lensing on...
Galaxy clusters are the largest gravitationally bound objects in the Universe and provide crucial insight to the standard model of cosmology. The abundance of these as a function of mass and redshift is highly sensitive to the cosmological parameters such as amplitude of matter fluctuations and dark energy equation of state parameter.
While galaxy clusters yield tremendously powerful tests...
We investigate constraints on cosmic reionization extracted from the Planck cosmic microwave background (CMB) data. We combine the Planck CMB anisotropy data in temperature with the low-multipole polarization data to fit ΛCDM models with various parameterizations of the reionization history. We obtain a Thomson optical depth τ = 0.058 ± 0.012 for the commonly adopted instantaneous reionization...
Cosmic Microwave Background (CMB) has been well known as a proof of the hot
big bang model. In recent years, thanks to the precise observations by WMAP
and PLANCK satellites, we come to see the detailed structure of CMB
temperature (or polarization) fluctuations. In this work, we forces on the
irregular oscillations of their angular power spectra around multipole
$\ell\sim120$. These...
Recently a number of alternative dark matter models have been introduced as a means of explaining the physics of small-scale structure formation. These include, warm dark matter and dark matter with late kinetic decoupling both of which differ substantially from the canonical cold dark matter formalism. One interesting way of constraining the phenomenology in these models is to look at the...
The standard model for the evolution of the universe is the Lambda cold dark matter (Λ-CDM) model. Its widespread acceptance is due to its simplicity and agreement with a whole host of different astronomical observations. However much is still unknown about the Dark Sector. While Λ-CDM successfully predicts the large scale properties of the universe, there are some discrepancies on the smaller...
Using state of the art numerical simulations, I have unravelled observational signatures of several alternative cosmological models in the large-scale structure of the cosmic web. The key observational probe under study is evolution of cosmological voids, to provide us with clues to the underlying cosmology of the Universe. While the ultimate goal will be to include galaxy formation recipes to...
We compare the topological properties of the dark matter distribution in a number of cosmological models using hydrodynamical simulations and the cosmological genus statistic. Genus curves are computed from z=11 to z=0 for Lambda-CDM, Quintessence and Warm Dark Matter models, over a scale range of 1 to 20 h^-1 Mpc. The curves are analysed in terms of their Hermite spectra to describe the power...
The angular power spectra of the CMB temperature anisotropies reconstructed from Planck data seem to present ‘too much’ gravitational lensing distortion. This is quantified by the control parameter $A_L$ that should be compatible with unity for a standard cosmology. With the class Boltzmann solver and the profile likelihood method, we measure for this parameter a 2.6σ shift from 1 using the...
Cosmological constraints on the scalar-tensor theory of gravity by analyzing the angular power spectrum data of the cosmic microwave background (CMB) obtained from the Planck 2015 results are presented. We consider the harmonic attractor model, in which the scalar field has a harmonic potential with curvature ($\beta$) in the Einstein frame and the theory relaxes toward the Einstein gravity...
The observed galaxy clustering in redshift space, in nature, appears to be anisotropic due to the redshift-space distortion effects. This anisotropic clustering offers an interesting opportunity to probe gravity on cosmological scales. While the redshift-space distortion of galaxy clustering have been quantified and characterized by the two-point statistics, higher-order statistics such as...
In the framework of the spherical collapse model, we study the non-linear growth of cosmic structures in the minimally and non-minimally coupled quintessence cosmologies. In non-minimally coupled quintessence models there is a non-minimally coupling between the scalar field and the Ricci scalar. We first investigate the background Hubble expansion in these models and then follow the models in...
In the context of the standard cosmological perturbation theory, non-linear couplings of first-order scalar perturbations create second-order vector perturbations, which generate magnetic fields through the Harrison mechanism.
We find that the magnetic fields from the purely second-order vector perturbations partially cancel out the magnetic fields from one of the product-terms of the...
The Einstein Equivalence Principle (EEP) is one of the fundamental principles in General Relativity. One of the consequences of the EEP in the cosmological context is the energy independency of the cosmological redshift effect. Here we propose a new test of the energy independency of the redshift effect by the measurement of the spectral distortions of the Cosmic Microwave Background (CMB). In...
In general relativity inhomogeneities generically produce differential cosmic expansion which is not equivalent to a homogeneous isotropic cosmology plus local boosts, as assumed in the current standard model. We present the first ray tracing simulations of local structure that exhibit this, using exact solutions of Einstein's equations constrained by both actual large galaxy surveys (the...
Massive galaxy clusters, being at the high mass end of the mass function are becoming a common tool in cosmology. Their
abundance is a strong indicator of non-linear structure formation and it depends on the value of important cosmological
parameters, such as the matter density parameter $\Omega_{\rm m}$, the mater power spectrum normalization $\sigma_8$
and the dark energy equation of...
The standard $\Lambda$CDM model with WIMP dark matter describes the large scale features of the universe
quite well with some potential unsolved astrophysical problems in the small scale. In this study, we propose
a different type of CDM which forms much after the BBN and before the epoch of matter radiation
equality. We consider two such dark matter models. The Late Forming Dark Matter...
