The Fourier Space Statistics of Seedlike Cosmological Perturbations

We propose a new test for distinguishing observationally cosmological models based on seed-like primordial perturbations (like cosmic strings or textures), from models based on Gaussian fluctuations. We investigate analytically the {\it Fourier space} statistical properties of temperature or density fluctuation patterns generated by seed-like objects and compare these properties with those of Gaussian fluctuations generated during inflation. We show that the proposed statistical test can easily identify temperature fluctuations produced by a superposition of a small number of seeds per horizon scale for {\it any} observational angular resolution and {\it any} seed geometry. However, due to the Central Limit Theorem, the distinction becomes more difficult as the number of seeds in the fluctuation pattern increases.Comment: 12 pages plus 1 Figure (available upon request). Use LaTeX. To appear in M.N.R.A.S., preprint No. CfA-359

Large Scale Structure by Global Monopoles and Cold Dark Matter

A cosmological model in which the primordial perturbations are provided by global monopoles and in which the dark matter is cold has several interesting features. The model is normalized by choosing its single parameter within the bounds obtained from gravitational wave constraints and by demanding coherent velocity f1ows of about 600km/sec on scales of $50 h^{-1} Mpc$. Using this normalization, the model predicts the existence of dominant structures with mass $2\times 10^{16} M_\odot$ on a scale $35 h^{-1}Mpc$ i.e. larger than the horizon at $t_{eq}$. The magnitude of the predicted mass function in the galactic mass range is in good agreement with the observed Schechter function.Comment: 9 pages, 2 Figures (available upon request), use late

Large Scale Cosmological Anomalies and Inhomogeneous Dark Energy

A wide range of large scale observations hint towards possible modifications on the standard cosmological model which is based on a homogeneous and isotropic universe with a small cosmological constant and matter. These observations, also known as "cosmic anomalies" include unexpected Cosmic Microwave Background perturbations on large angular scales, large dipolar peculiar velocity flows of galaxies ("bulk flows"), the measurement of inhomogenous values of the fine structure constant on cosmological scales ("alpha dipole") and other effects. The presence of the observational anomalies could either be a large statistical fluctuation in the context of {\lcdm} or it could indicate a non-trivial departure from the cosmological principle on Hubble scales. Such a departure is very much constrained by cosmological observations for matter. For dark energy however there are no significant observational constraints for Hubble scale inhomogeneities. In this brief review I discuss some of the theoretical models that can naturally lead to inhomogeneous dark energy, their observational constraints and their potential to explain the large scale cosmic anomalies.Comment: 42 pages, 15 figures, Invited Review published in 'Galaxies' at http://www.mdpi.com/2075-4434/2/1/2