Cosmic Strings, Inflation, and Gravity Waves
  We investigate the impact of Coleman-Weinberg inflation on the stochastic
gravity wave background spectrum emitted by intermediate scale cosmic strings.
The string network is partially inflated and re-enters the horizon at later
times after the end of inflation, such that the short string loops are not
produced. This leads to a significant modification of the gravity wave spectrum
that we explore in detail. We find that Coleman-Weinberg inflation can help to
satisfy the Parkes Pulsar Timing Array (PPTA) bound for dimensionless string
tension values in the range $G\mu > 1.1\times 10^{-10}$. We also identify the
modified gravity wave spectra which, in the case of inflation, are compatible
with the North American Nanohertz Observatory for Gravitational Waves
(NANOGrav) data. We then discuss the formation of monopoles and strings at the
same breaking scale and the compatibility of the Monopole, Astrophysics and
Cosmic Ray Observatory (MACRO) bound with the PPTA bound, and also with the
NANOGrav data. Finally, an example of a realistic non-supersymmetric $E_6$
model incorporating successful Coleman-Weinberg inflation is presented in which
monopoles and strings both survive inflation and are present at an observable
level.
