DISTINGUISHING CAUSAL SEEDS FROM INFLATION

Causal seed models, such as cosmological defects, generically predict a distinctly different structure to the CMB power spectrum than inflat ion, due to the behavior of the perturbations outside the horizon. We provide a general analysis of their causal generation from isocurvatur e initial conditions by analyzing the role of stress perturbations and conservation laws in the causal evolution. Causal stress perturbation s tend to generate an isocurvature pattern of peak heights in the CMB spectrum and shift the first compression, i.e., main peak, to smaller angular scales than those in the inflationary case, unless the pressur e and anisotropic stress fluctuations balance in such a way as to reve rse the sense of gravitational interactions while also maintaining con stant gravitational potentials. Aside from this case, these causal see d models can be cleanly distinguished from inflation by CMB experiment s currently underway.