Resumen de New techniques for the analysis of the large scale structure of the Universe
The goal of this thesis is to study the large scale structure of the Universe from a theoretical point of view. In particular, the different chapters of this thesis focus on developing statistic tools to improve the understanding the contents of the Universe. In Chapter 1 a brief introduction of the basics of cosmology and large scale structure of the Universe is presented. This is the starting point for the thesis and provides a vital background material for all the following works developed in the other Chapters. Chapter 2 is concerned to the development of an extension of the Halo Model. We study the possibility of modifying the standard halo model dark matter haloes properties to depend not only on the halo mass but also on the halo environment. Both theoretical and observational studies indicate that properties of dark matter haloes, and specially the way they host galaxies, namely the Halo Occupation Distribution (HOD), depend not only on the mass of the halo host but also on its formation history. This formation history dependence may be related to the halo-surrounding dark matter field. In this work we present a theoretical model that allows to incorporate in a simple way this extra dependence on the environment. In this model the whole population of dark matter haloes is split in two depending on whether the haloes live in high-density environments or in low-density ones. We explore how the dark matter and the galaxy correlation function is affected by this dependence on the environment though the dark matter halo profile or the HOD respectively. In Chapter 3 we explore the possibility of improving the measurement of the growth factor using dark matter tracers. We compare the accuracy in the measurement of the growth factor using a single and two different biased dark matter tracers separately. We make use of realistic bias models, which include non-linear and stochastic parameters, and we calibrate them using dark matter simulations and using haloes of a certain binmass as tracers. We expect that using this method the sample variance could be reduced and the accuracy of the measurements improved as previous works have shown. Chapter 4 is concerned to exploring how possible deviations of General Relativity can be detected using the bispectrum technique. We work with a suit of cosmological simulations of modified gravitational action f (R) models, where cosmic acceleration is induced by a scalar field that acts as a fifth force on all forms of matter. The goal is to see how the bispectrum of the dark matter field on mildly non-linear scales is modified by the extra scalar field. In particular we are interested in see which is the effect on the bispectrum, when different gravity models present the same power spectrum at late times. In Chapter 5 we propose a new simple formula to compute the dark matter bispectrum in the moderate non-linear regime (k < 0.4 h/Mpc) and for redshifts z ? 1.5. Our method is inspired by the approach presented by Scoccimarro and Couchman (2001), but includes a modification of the original formulae and a prescription to better de- scribe the BAO oscillations. Using ?CDM simulations we fit the free parameters of our model. We end up with a simple analytic formula that is able to predict accurately the bispectrum for a ?CDM Universe including the effects of Baryon Acoustic Oscillations. The major conclusions of the works presented in the thesis are summarised and discussed in Chapter 6. Also the possible future projects are discussed.
