Effects of long cosmic strings on the anisotropies of the cosmic background radiation

We have examined the effects of infinitely long cosmic strings on the anisotropies of the 2.7 K cosmic microwave background (CMB) radiation using a simplified model. It is assumed that N long cosmic strings are moving fast in each horizon volume during the e-folding times of the expansion of the universe. From the simulated anisotropies of the CMB over the whole sky, we have calculated the rms sky variation with a 10 deg FWHM Gaussian smoothing, the quadrupole moment, and the chi-squared test for the correlation functions. The comparison of the simulation with the COBE DMR results constrains the parameters. The effective power spectrum index is n = 1.1 +/- 0.5. Since the COBE results are well reproduced by our simulation, there remains a possibility that the CMB anisotropies detected by COBE are mainly due to cosmic strings. The characteristic feature for the cosmic string model is the discontinuities in the amplitude of CMB anisotropy. We discuss this as well as the constraint from smaller angles.