Primordial monopoles, proton decay, gravity waves and GUT inflation

TL;DR

This paper explores non-supersymmetric GUT inflation models predicting primordial monopoles with potentially observable fluxes, linking symmetry breaking scales to magnetic monopole properties, proton decay, and gravitational wave signals.

Contribution

It introduces models where intermediate mass monopoles survive inflation, predicts their flux and mass, and connects these with inflationary parameters and proton decay estimates.

Findings

Observable monopole fluxes are possible at $10^{13}$ GeV scale.

Predicted tensor-to-scalar ratio $r \,\gtrsim\, 0.02$ compatible with Planck data.

Proton lifetime estimates are provided for superheavy gauge boson decays.

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 $10^{13}$ GeV for an observable flux level, with the corresponding monopoles an order of magnitude or so heavier. Examples based on $SO(10)$ and $E_6$ 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) $H \sim 7$--$9\times10^{13}$ GeV, with the tensor to scalar ratio $r$ predicted to be $\gtrsim0.02$. Proton lifetime estimates for decays mediated by the superheavy gauge bosons are also provided.