Critical Higgs Inflation and Second Order Gravitational Wave Signatures. (arXiv:1905.13581v1 [hep-ph])
<a href="http://arxiv.org/find/hep-ph/1/au:+Drees_M/0/1/0/all/0/1">Manuel Drees</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Xu_Y/0/1/0/all/0/1">Yong Xu</a>
The self coupling $lambda$ of the Higgs boson in the Standard Model may show
critical behavior, i.e. the Higgs potential may have a point at an energy scale
$sim 10^{17-18}$ GeV where both the first and second derivatives (almost)
vanish. Since $lambda$ is very small in this region, the Higgs boson can serve
as inflaton even if its nonminimal coupling to the curvature scalar is only
${cal O}(10)$, thereby alleviating concerns about the perturbative unitarity
of the theory. We find that just before the Higgs as inflaton enters the flat
region of the potential the usual slow–roll conditions are violated. This
leads to “overshooting” behavior, which in turn strongly enhances scalar
curvature perturbations because of the excitation of entropic (non–adiabatic)
perturbations. For appropriate choice of the free parameters these large
density perturbations occur at length scales relevant for the formation of
primordial black holes. Even if these perturbations are not quite large enough
to trigger copious black hole formation, they source second order tensor
perturbations, i.e. primordial gravitational waves; the corresponding energy
density can be detected by the proposed space-based gravitational wave
detectors DECIGO and BBO.
The self coupling $lambda$ of the Higgs boson in the Standard Model may show
critical behavior, i.e. the Higgs potential may have a point at an energy scale
$sim 10^{17-18}$ GeV where both the first and second derivatives (almost)
vanish. Since $lambda$ is very small in this region, the Higgs boson can serve
as inflaton even if its nonminimal coupling to the curvature scalar is only
${cal O}(10)$, thereby alleviating concerns about the perturbative unitarity
of the theory. We find that just before the Higgs as inflaton enters the flat
region of the potential the usual slow–roll conditions are violated. This
leads to “overshooting” behavior, which in turn strongly enhances scalar
curvature perturbations because of the excitation of entropic (non–adiabatic)
perturbations. For appropriate choice of the free parameters these large
density perturbations occur at length scales relevant for the formation of
primordial black holes. Even if these perturbations are not quite large enough
to trigger copious black hole formation, they source second order tensor
perturbations, i.e. primordial gravitational waves; the corresponding energy
density can be detected by the proposed space-based gravitational wave
detectors DECIGO and BBO.
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