Primordial black hole production in Critical Higgs Inflation

Jose María Ezquiaga,Juan García-Bellido,Ester Ruiz Morales

doi:10.1016/j.physletb.2017.11.039

Abstract

Primordial Black Holes (PBH) arise naturally from high peaks in the curvature power spectrum of near-inflection-point single-field inflation, and could constitute today the dominant component of the dark matter in the universe. In this letter we explore the possibility that a broad spectrum of PBH is formed in models of Critical Higgs Inflation (CHI), where the near-inflection point is related to the critical value of the RGE running of both the Higgs self-coupling λ(μ) and its non-minimal coupling to gravity ξ(μ). We show that, for a wide range of model parameters, a half-domed-shaped peak in the matter spectrum arises at sufficiently small scales that it passes all the constraints from large scale structure observations. The predicted cosmic microwave background spectrum at large scales is in agreement with Planck 2015 data, and has a relatively large tensor-to-scalar ratio that may soon be detected by B-mode polarization experiments. Moreover, the wide peak in the power spectrum gives an approximately lognormal PBH distribution in the range of masses 0.01–100M⊙, which could explain the LIGO merger events, while passing all present PBH observational constraints. The stochastic background of gravitational waves coming from the unresolved black-hole-binary mergers could also be detected by LISA or PTA. Furthermore, the parameters of the CHI model are consistent, within 2σ, with the measured Higgs parameters at the LHC and their running. Future measurements of the PBH mass spectrum could allow us to obtain complementary information about the Higgs couplings at energies well above the EW scale, and thus constrain new physics beyond the Standard Model.

Highlights

The first direct detection of gravitational waves (GWs) by LIGO has initiated a new era of astronomy [1] and opened the possibility to test the nature of dark matter, specially if its dominant component is primordial black holes (PBH) [2]
In this letter we have explored the possibility that the Standard Model Higgs, with a non-minimal coupling to gravity, may have acted as the inflaton in the early universe, and produced all of the present dark matter from quantum fluctuations that reentered the horizon as huge curvature perturbations and collapsed to form black holes much before primordial nucleosynthesis
Taking into account the renormalization group equations (RGE) running of both the Higgs self-coupling λ and the non-minimal coupling to gravity ξ, we find regions of parameter space allowed by the Standard Model for which the inflaton-Higgs potential acquires a second plateau at smaller scales, around the critical point λ(μ) βλ(μ) = 0

Summary

Introduction

The first direct detection of gravitational waves (GWs) by LIGO has initiated a new era of astronomy [1] and opened the possibility to test the nature of dark matter, specially if its dominant component is primordial black holes (PBH) [2]. The region with denser color represents cases with N ∈ (30, 35), which produce a sufficiently large peak in the power spectrum at small scales to later give rise to PBH through gravitational collapse upon reentry [3] This region tends to give low spectral index, ns < 0.956, and large tensor-to-scalar ratios, r > 0.019, while cases with lower N display a better fit to Planck data but cannot generate significant populations of PBHs. In the right panel of Fig. 2 we show the ratio PR(xmax)/PR(x65) of the amplitude of the fluctuations at its maximum, xmax, over the amplitude at the inflationary plateau, x65, as a function of N.

Production of PBHs and DM

Pl e2N

Conclusions