CMB anisotropies generated by cosmic string loops
  We investigate the contribution of cosmic string loops to the Cosmic
Microwave Background (CMB) anisotropies. This is done by extending the
Unconnected Segment Model (USM) to include the contribution of the cosmic
string loops created throughout the cosmological evolution of a cosmic string
network to the stress-energy tensor. We then implement this extended USM in the
publicly available CMBACT code and obtain the linear CDM power spectrum and the
CMB angular power spectra generated by cosmic string loops. We find that the
shape of the angular power spectra generated by loops is, in general, similar
to that of long strings. However, there is generally an enhancement of the
anisotropies on small angular scales. Vector modes produced by loops dominate
over those produced by long strings for large multipole moments $\ell$. The
contribution of loops to the CMB anisotropies generated by cosmic string
networks may reach a level of $10\%$ for large loops but decreases as the size
of loops decreases. This contribution may then be significant and, thus, this
extension provides a more accurate prediction of the CMB anisotropies generated
by cosmic string networks.
