The case against scaling defect models of cosmic structure formation

Abstract

We calculate predictions from defect models of structure formation for both the matter and Cosmic Microwave Background (CMB) over all observable scales. Our results point to a serious problem reconciling the observed large-scale galaxy distribution with the COBE normalization, a result which is robust for a wide range of defect parameters. We conclude that standard scaling defect models are in conflict with the data, and show how attempts to resolve the problem by considering non-scaling defects would require radical departures from the standard scaling picture.

Figures (4)

• Figure 1: The (COBE normalized) angular power spectrum of CMB anisotropies for the standard cosmic string model (solid) plotted with the current observational data, the standard CDM curve (dotted). The two dashed curves give the partial contributions from two time windows to either side of $z=100$
• Figure 2: The power spectrum of the dark matter perturbations for the same models and windows shown in Fig. 1, plotted with the data.
• Figure 3: The angular power spectrum of CMB anisotropies for the various non-scaling models discussed in the text. The three most extreme models (which have reasonable values of $b_{100}$) have the highest peaks. Standard CDM is included for reference (dash-dot curve).
• Figure 4: The power spectrum of the dark matter perturbations plotted with the data for the same models as Fig. \ref{['cmb2']}