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 sigma(10- degrees) with a 10-degrees FWHM Gaussian smoothing, the quadrupole mom ent, and the chi2 test for the correlation functions. The comparison o f the simulation with the COBE DMR results constrains the parameters t o be in the range 0.9 < N1/2(Gmubetagamma/10(-6)) < 4.1 with N < 6. Th e effective power spectrum index is n = 1.1 +/- 0.5. Since the COBE re sults are well reproduced by our simulation, there remains a possibili ty that the CMB anisotropies detected by COBE are mainly due to cosmic strings. The characteristic feature for the cosmic string model is th e discontinuities in the amplitude of CMB anisotropy. We discuss this as well as the constraint from smaller angles.