Hyperinflation generalised: from its attractor mechanism to its tension with the `swampland conjectures’. (arXiv:1901.08603v1 [hep-th])

Hyperinflation generalised: from its attractor mechanism to its tension with the `swampland conjectures’. (arXiv:1901.08603v1 [hep-th])
<a href="http://arxiv.org/find/hep-th/1/au:+Bjorkmo_T/0/1/0/all/0/1">Theodor Bjorkmo</a>, <a href="http://arxiv.org/find/hep-th/1/au:+Marsh_M/0/1/0/all/0/1">M. C. David Marsh</a>

In negatively curved field spaces, inflation can be realised even in steep
potentials. Hyperinflation invokes the `centrifugal force’ of a field orbiting
the hyperbolic plane to sustain inflation. We generalise hyperinflation by
showing that it can be realised in models with any number of fields
($N_fgeq2$), and in broad classes of potentials that, in particular, don’t
need to be rotationally symmetric. For example, hyperinflation can follow a
period of radial slow-roll inflation that undergoes geometric destabilisation,
yet this inflationary phase is not identical to the recently proposed scenario
of `side-tracked inflation’. We furthermore provide a detailed proof of the
attractor mechanism of (the original and generalised) hyperinflation, and
provide a novel set of characteristic, explicit models. We close by discussing
the compatibility of hyperinflation with observations and the recently much
discussed `swampland conjectures’. Observationally viable models can be
realised that satisfy either the `de Sitter conjecture’ ($V’/Vgtrsim 1$) or
the `distance conjecture’ ($Delta phi lesssim 1$), but satisfying both
simultaneously brings hyperinflation in some tension with successful reheating
after inflation. However, hyperinflation can get much closer to satisfying all
of these criteria than standard slow-roll inflation. Furthermore, while the
original model is in stark tension with the weak gravity conjecture,
generalisations can circumvent this issue.

In negatively curved field spaces, inflation can be realised even in steep
potentials. Hyperinflation invokes the `centrifugal force’ of a field orbiting
the hyperbolic plane to sustain inflation. We generalise hyperinflation by
showing that it can be realised in models with any number of fields
($N_fgeq2$), and in broad classes of potentials that, in particular, don’t
need to be rotationally symmetric. For example, hyperinflation can follow a
period of radial slow-roll inflation that undergoes geometric destabilisation,
yet this inflationary phase is not identical to the recently proposed scenario
of `side-tracked inflation’. We furthermore provide a detailed proof of the
attractor mechanism of (the original and generalised) hyperinflation, and
provide a novel set of characteristic, explicit models. We close by discussing
the compatibility of hyperinflation with observations and the recently much
discussed `swampland conjectures’. Observationally viable models can be
realised that satisfy either the `de Sitter conjecture’ ($V’/Vgtrsim 1$) or
the `distance conjecture’ ($Delta phi lesssim 1$), but satisfying both
simultaneously brings hyperinflation in some tension with successful reheating
after inflation. However, hyperinflation can get much closer to satisfying all
of these criteria than standard slow-roll inflation. Furthermore, while the
original model is in stark tension with the weak gravity conjecture,
generalisations can circumvent this issue.

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