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Register a new userA Cosmological Signature of the SM Higgs Instability: Gravitational Waves
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A fundamental property of the Standard Model is that the Higgs potential becomes unstable at large values of the Higgs field. For the current central values of the Higgs and top masses, the instability scale is about $10^{11}$ GeV and therefore not accessible by colliders. We show that a possible signature of the Standard Model Higgs instability is the production of gravitational waves sourced by Higgs fluctuations generated during inflation. We fully characterise the two-point correlator of such gravitational waves by computing its amplitude, the frequency at peak, the spectral index, as well as their three-point correlators for various polarisations. We show that, depending on the Higgs and top masses, either LISA or the Einstein Telescope and Advanced-Ligo, could detect such stochastic background of gravitational waves. In this sense, collider and gravitational wave physics can provide fundamental and complementary informations. Furthermore, the consistency relation among the three- and the two-point correlators could provide an efficient tool to ascribe the detected gravitational waves to the Standard Model itself. Since the mechanism described in this paper might also be responsible for the generation of dark matter under the form of primordial black holes, this latter hypothesis may find its confirmation through the detection of gravitational waves.
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In this work we discuss two different phases of a complex singlet extension of the Standard Model (SM) together with an extension that also includes new fermion fields. All models allow for a strong first-order electroweak phase transition and the detection of primordial gravitational waves (GWs) in planned experiments such as LISA is shown to be possible in one of the phases of the singlet extension and also in the model with extra fermions. In the singlet extension with no additional fermions, the detection of GWs strongly depends on the phase of the Higgs potential at zero temperature. We study for the first time the impact of the precision in the determination of the SM parameters on the strength of the GWs spectrum. It turns out that the variation of the SM parameters such as the Higgs mass and top quark Yukawa coupling in their allowed experimental ranges has a notable impact on GWs detectability prospects.
We propose that the Standard Model (SM) Higgs is responsible for generating the cosmological perturbations of the universe by acting as an isocurvature mode during a de Sitter inflationary stage. In view of the recent ATLAS and CMS results for the Higgs mass, this can happen if the Hubble rate during inflation is in the range $(10^{10}- 10^{14})$ GeV (depending on the SM parameters). Implications for the detection of primordial tensor perturbations through the $B$-mode of CMB polarization via the PLANCK satellite are discussed. For example, if the Higgs mass value is confirmed to be $m_h=125.5$ GeV and $m_t, alpha_s$ are at their central values, our mechanism predicts tensor perturbations too small to be detected in the near future. On the other hand, if tensor perturbations will be detected by PLANCK through the $B$-mode of CMB, then there is a definite relation between the Higgs and top masses, making the mechanism predictive and falsifiable.
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