Ultraviolet behaviour of Higgs inflation models

arXiv preprint arXiv:1303.3870, 2013

We have generalized the curvature coupling models of Higgs inflation to study inflation with a scalar field coupling of the form ξΦ a R b M a+2b−4 p . Such higher order scalar and graviton terms can be expected from the renormalization close to Planck scale. We compute the amplitude and spectral index of curvature perturbations generated during inflation and fix the parameters of the model by comparing these with the Planck+WP data. We find that if the scalar self coupling λ is in the range (10 −5 − 0.1), parameter a in the range (2.3 − 3.6) and b in the range (0.68 − 0.22) at the Planck scale, one can have a viable inflation model even for ξ ≃ 1. The tensor to scalar ratio r in this model is small and our model with scalar-curvature couplings is not ruled out by observational limits on r unlike the pure λ 4 Φ 4 theory. By requiring the curvature coupling parameter to be of order unity, we have evaded the problem of unitarity violation in scalar-graviton scatterings which plague the ξΦ 2 R Higgs inflation models. We conclude that the Higgs field may still be a good candidate for being the inflaton in the early universe if one considers higher dimensional curvature coupling.

Journal of Cosmology and Astroparticle Physics, 2008

We consider a quantum corrected inflation scenario driven by a generic GUT or Standard Model type particle model whose scalar field playing the role of an inflaton has a strong non-minimal coupling to gravity. We show that currently widely accepted bounds on the Higgs mass falsify the suggestion of the paper arXiv:0710.3755 (where the role of radiative corrections was underestimated) that the Standard Model Higgs boson can serve as the inflaton. However, if the Higgs mass could be raised to ∼ 230 GeV, then the Standard Model could generate an inflationary scenario with the spectral index of the primordial perturbation spectrum ns ≃ 0.935 (barely matching present observational data) and the very low tensor-to-scalar perturbation ratio r ≃ 0.0006. * To the memory of John Archibald Wheeler.

International Journal of Modern Physics D, 2014

We generalize the scalar-curvature coupling model ξΦ2R of Higgs inflation to ξΦaRb to study inflation. We compute the amplitude and spectral index of curvature perturbations generated during inflation and fix the parameters of the model by comparing these with the Planck + WP data. We find that if the scalar self-coupling λ is in the range 10-5–0.1, parameter a in the range 2.3–3.6 and b in the range 0.77–0.22 at the Planck scale, one can have a viable inflation model even for ξ ≃ 1. The tensor to scalar ratio r in this model is small and our model with scalar-curvature couplings is not ruled out by observational limits on r unlike the pure [Formula: see text] theory. By requiring the curvature coupling parameter to be of order unity, we have evaded the problem of unitarity violation in scalar-graviton scatterings which plague the ξΦ2R Higgs inflation models. We conclude that the Higgs field may still be a good candidate for being the inflaton in the early universe if one considers ...

Physical Review D, 2009

We critically examine the recent claim that the Standard Model Higgs boson H could drive inflation in agreement with observations if |H| 2 has a strong coupling ξ ∼ 10 4 to the Ricci curvature scalar. We first show that the effective theory approach upon which that claim is based ceases to be valid beyond a cutoff scale Λ = m p /ξ, where m p is the reduced Planck mass. We then argue that knowing the Higgs potential profile for the field values relevant for inflation (|H| > m p / √ ξ ≫ Λ) requires knowledge of the ultraviolet completion of the SM beyond Λ. In absence of such microscopic theory, the extrapolation of the pure SM potential beyond Λ is unwarranted and the scenario is akin to other ad-hoc inflaton potentials afflicted with significant fine-tuning. The appealing naturalness of this minimal proposal is therefore lost.

Progress of Theoretical and Experimental Physics, 2014

We consider a possibility that the Higgs field in the Standard Model (SM) serves as an inflaton when its value is around the Planck scale. We assume that the SM is valid up to an ultraviolet cutoff scale , which is slightly below the Planck scale, and that the Higgs potential becomes almost flat above. Contrary to the ordinary Higgs inflation scenario, we do not assume the huge non-minimal coupling, of O(10 4), of the Higgs field to the Ricci scalar. We find that must be less than 5 × 10 17 GeV in order to explain the observed fluctuation of the cosmic microwave background, no matter how we extrapolate the Higgs potential above. The scale 10 17 GeV coincides with the perturbative string scale, which suggests that the SM is directly connected with string theory. For this to be true, the top quark mass is restricted to around 171 GeV, with which can exceed 10 17 GeV. As a concrete example of the potential above , we propose a simple log-type potential. The predictions of this specific model for the e-foldings N * = 50-60 are consistent with the current observation, namely, the scalar spectral index is n s = 0.977-0.983 and the tensor to scalar ratio 0 < r < 0.012-0.010. Other parameters, dn s /d ln k, n t , and their derivatives, are also consistent.

Journal of Cosmology and Astroparticle Physics, 2009

We consider the renormalization group improvement in the theory of the Standard Model Higgs boson playing the role of an inflaton with a strong non-minimal coupling to gravity. It suggests the range of the Higgs mass 135.6 GeV M H 184.5 GeV compatible with the current CMB data (the lower WMAP bound on n s ), which is close to the widely accepted range dictated by the electroweak vacuum stability and perturbation theory bounds. We find the phenomenon of asymptotic freedom induced by this non-minimal curvature coupling, which brings the theory to the weak coupling domain everywhere except at the lower and upper boundary of this range. The renormalization group running of the basic quantity A I -the anomalous scaling in the non-minimally coupled Standard Model, which analytically determines all characteristics of the CMB spectrum -brings A I to small negative values at the inflation scale. This property is crucial for the above results and may also underlie the formation of initial conditions for the inflationary dynamics in quantum cosmology.

Journal of Cosmology and Astroparticle Physics, 2019

We study the consequences of (beyond) positivity of scattering amplitudes in the effective field theory description of the Higgs-Dilaton inflationary model. By requiring the EFT to be compatible with a unitary, causal, local and Lorentz invariant UV completion, we derive constraints on the Wilson coefficients of the first higher order derivative operators. We show that the values allowed by the constraints are consistent with the phenomenological applications of the Higgs-Dilaton model.

Physical Review D, 2017

We consider the prescription dependence of the Higgs effective potential under the presence of general nonminimal couplings. We evaluate the fermion loop correction to the effective action in a simplified Higgs-Yukawa model whose path integral measure takes simple form either in the Jordan or Einstein frame. The resultant effective action becomes identical in both cases when we properly take into account the quartically divergent term coming from the change of measure. Working in the counterterm formalism, we clarify that the difference between the prescriptions I and II comes from the counter term to cancel the logarithmic divergence. This difference can be absorbed into the choice of treelevel potential from the infinitely many possibilities, including all the higher-dimensional terms. We also present another mechanism to obtain a flat potential by freezing the running of the effective quartic coupling for large field values, using the nonminimal coupling in the gauge kinetic function.

arXiv (Cornell University), 2020

We study a two-field quintessential Higgs inflation model in which a quintessence field with an exponential potential e −βφ/M P is coupled to the Higgs field from the beginning of inflation. The Higgs field itself is also non-minimally coupled to gravity. The inflationary predictions of this model for n s and r are in good agreement with Planck 2018 data. We calculate the observables n s and r against the free parameter β. Comparing these parameters with the observed n s and r in Planck 2018 paper, we find β 8 × 10 −3 that strongly disfavors the Swampland conjecture. I. INTRODUCTION Cosmologists consider two accelerating eras of cosmic expansion history. The first is an inflationary era where a scalar field, called inflaton, with negative pressure and a slowroll evolution, is responsible for accelerating expansion in the early universe [1]. Based on the latest Planck papers [2, 3], single field potentials with plateau-like shapes are the most favored inflationary models by Planck temperature, polarization, and lensing data combined with the BICEP2/Keck Array BK15 data. In between the single field inflationary models, the Higgs model [4, 5] has the best consistency with the Planck 2018 data. It belongs to a general class of inflationary models where a scalar field has a non-minimal coupling to gravity [6].

Journal of Cosmology and Astroparticle Physics, 2016

We consider models of chaotic inflation driven by the real parts of a conjugate pair of Higgs superfields involved in the spontaneous breaking of a grand unification symmetry at a scale assuming its Supersymmetric (SUSY) value. Employing Kähler potentials with a prominent shift-symmetric part proportional to c − and a tiny violation, proportional to c + , included in a logarithm we show that the inflationary observables provide an excellent match to the recent Planck and BICEP2/Keck Array results setting, e.g., 6.4•10 −3 r ± = c + /c − 1/N where N = 2 or 3 is the prefactor of the logarithm. Deviations of these prefactors from their integer values above are also explored and a region where hilltop inflation occurs is localized. Moreover, we analyze two distinct possible stabilization mechanisms for the non-inflaton accompanying superfield, one tied to higher order terms and one with just quadratic terms within the argument of a logarithm with positive prefactor N S < 6. In all cases, inflation can be attained for subplanckian inflaton values with the corresponding effective theories retaining the perturbative unitarity up to the Planck scale.