Primordial monopoles, proton decay, gravity waves and GUT inflation

Abstract

We consider non-supersymmetric GUT inflation models in which intermediate mass monopoles may survive inflation because of the restricted number of e-foldings experienced by the accompanying symmetry breaking. Thus, an observable flux of primordial magnetic monopoles, comparable to or a few orders below the Parker limit may be present in the galaxy. The mass scale associated with the intermediate symmetry breaking is 1013 GeV for an observable flux level, with the corresponding monopoles an order of magnitude or so heavier. Examples based on SO(10) and E6 yield such intermediate mass monopoles carrying respectively two and three units of Dirac magnetic charge. For GUT inflation driven by a gauge singlet scalar field with a Coleman–Weinberg or Higgs potential, compatibility with the Planck measurement of the scalar spectral index yields a Hubble constant (during horizon exit of cosmological scales) H∼7–9×1013 GeV, with the tensor to scalar ratio r predicted to be ≳0.02. Proton lifetime estimates for decays mediated by the superheavy gauge bosons are also provided.