Non-minimal Higgs Inflation Research Articles

Higgs inflation: Constraining the top quark mass and breaking the H0-σ8 correlation

Extending previous results, we explore aspects of the reheating mechanism for non-minimal Higgs inflation in the strong coupling regime. We constrain the radiative corrections for the inflaton's potential by considering the Coleman-Weinberg approximation and use the Renormalization Group Equations for the Higgs field to derive an upper limit on the top quark mass. Using the current Cosmic Microwave Background, Baryon Acoustic Oscillation, and Supernovae data, we obtain mt≤170.44 GeV, confirming the observational compatibility of the model with recent mt estimates reported by the CMS collaboration. We also analyze the breakdown of the well-known correlation involving the Hubble constant H0 and the clustering parameter σ8, which makes the model interesting in light of the cosmological tensions discussed over the last decade.

Probing stochastic gravitational wave background from SU(5) × U(1)χ strings in light of NANOGrav 15-year data

A realistic model of SU(5) × U(1)χ, embedded in SO(10) supersymmetric grand unified theory, is investigated for the emergence of a metastable cosmic string network. This network eventually decays via the Schwinger production of monopole-antimonopole pairs, subsequently generating a stochastic gravitational wave background that is compatible with the NANOGrav 15-year data. In order to avoid the monopole problem in the breaking of both SO(10) and SU(5), a non-minimal Higgs inflation scenario is incorporated. The radiative breaking of the U(1)χ symmetry at a slightly lower scale plays a pivotal role in aligning the string tension parameter with the observable range. The resultant gravitational wave spectrum not only accounts for the signal observed in the most recent pulsar timing array (PTA) experiments but is also accessible to both current and future ground-based and space-based experiments.

Realistic inflation in no-scale U(1) R symmetric flipped SU(5)

We have realized non-minimal Higgs inflation and standard hybrid inflation in the supersymmetric flipped SU(5) model with U(1) R symmetry using the no-scale form of the Kähler potential. In non-minimal Higgs inflation the waterfall Higgs field plays the role of inflaton, and in standard hybrid inflation the gauge singlet field S is employed as an inflaton. The predictions of both models are in good agreement with the Planck 2018 data. For numerical calculations we have fixed the gauge symmetry breaking scale, M, around 2 × 1016 GeV. In both models the inflaton field values are constrained below mP . The tensor to scalar ratio r in non-minimal inflation is of the order of 10-3 and for standard hybrid inflation r is tiny, of order 10-15–10-4. The scalar spectral index in both cases lie within the Planck 1-σ bounds, and the running of the scalar spectral index lies in the range, -dns /d ln k ∼ 6 × 10-4 for non-minimal model and 10-9–10-3 for the standard hybrid model. A realistic scenario of reheating and non-thermal leptogenesis is employed with reheat temperature Tr ∼ 109 GeV for non-minimal model and 106–1010 GeV for standard hybrid model. The R-symmetry plays a vital role in forbidding rapid proton decay, but at the same time it also suppresses terms responsible for generating right handed neutrino masses. A realistic scenario of right handed neutrino masses is obtained by considering effective R symmetry breaking at the nonrenormalizable level with adequate suppression of rapid proton decay.

Nonminimal Higgs inflation within holographic cosmology

We derive a Higgs inflationary model in the context of holographic cosmology, where we consider a universe filled with a Higgs field non-minimally coupled to gravity in a slow-roll regime. The amplitude of density (scalar) perturbations is calculated. In this regard, we show that the background and perturbative parameters characterising the inflationary era are related to the standard one through corrections terms. We found that for the e-fold number $N\sim 58$, the spectral index,$n_{r}$, and the tensor-to-scalar ratio,$r$, values are $0.965$ and $0.021$, respectively, which are in agreement with 2018 Planck observational data. However, as soon as we move from $N\sim 58$, the model is ruled out by the current data.

Non-minimal Higgs inflation in the context of warm scenario in the light of Planck data

We investigate the non-minimally Higgs inflaton (HI) model in the context of warm inflation scenario. Warm little inflaton (WLI) model considers the little Higgs boson as inflaton. The concerns of warm inflation model can be eliminated in WLI model. There is a special case of dissipation parameter in WLI model varGamma =varGamma _0 T. Using this parameter, we study the potential of HI in Einstein frame . Finally we will constrain the parameters of our model using current Planck observational data.

Qualitative dynamics and inflationary attractors in loop cosmology

Qualitative dynamics of three different loop quantizations of spatially flat isotropic and homogeneous models is studied using effective spacetime description of the underlying quantum geometry. These include the standard loop quantum cosmology (LQC), its recently revived modification (referred to as mLQC-I), and another related modification of LQC (mLQC-II) whose dynamics is studied in detail for the first time. Various features of LQC, including quantum bounce and pre-inflationary dynamics, are found to be shared with the mLQC-I and mLQC-II models. We study universal properties of dynamics for chaotic inflation, fractional monodromy inflation, Starobinsky potential, non-minimal Higgs inflation, and an exponential potential. We find various critical points and study their stability, which reveal various qualitative similarities in the post-bounce phase for all these models. The pre-bounce qualitative dynamics of LQC and mLQC-II turns out to be very similar, but is strikingly different from that of mLQC-I. In the dynamical analysis, some of the fixed points turn out to be degenerate for which center manifold theory is used. For all these potentials, non-perturbative quantum gravitational effects always result in a non-singular inflationary scenario with a phase of super-inflation succeeded by the conventional inflation. We show the existence of inflationary attractors, and obtain scaling solutions in the case of the exponential potential. Since all of the models agree with general relativity at late times, our results are also of use in classical theory where qualitative dynamics of some of the potentials has not been studied earlier.

Variants of kinetically modified non-minimal Higgs inflation in supergravity

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 BICAP2/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 NS < 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.

New type of hill-top inflation

We suggest a new type of hill-top inflation originating from the initial conditions in the form of the microcanonical density matrix for the cosmological model with a large number of quantum fields conformally coupled to gravity. Initial conditions for inflation are set up by cosmological instantons describing underbarrier oscillations in the vicinity of the inflaton potential maximum. These periodic oscillations of the inflaton field and cosmological scale factor are obtained within the approximation of two coupled oscillators subject to the slow roll regime in the Euclidean time. This regime is characterized by rapid oscillations of the scale factor on the background of a slowly varying inflaton, which guarantees smallness of slow roll parameters ϵ and η of the following inflation stage. A hill-like shape of the inflaton potential is shown to be generated by logarithmic loop corrections to the tree-level asymptotically shift-invariant potential in the non-minimal Higgs inflation model and R2-gravity. The solution to the problem of hierarchy between the Planckian scale and the inflation scale is discussed within the concept of conformal higher spin fields, which also suggests the mechanism bringing the model below the gravitational cutoff and, thus, protecting it from large graviton loop corrections.

Kinetically modified nonminimal Higgs inflation in supergravity

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 value. We combine a superpotential, which is uniquely determined by applying a continuous R symmetry, with a class of logarithmic or semi-logarithmic Kahler potentials which exhibit a prominent shift-symmetry with a tiny violation, whose strengths are quantified by c- and c+ respectively. The inflationary observables provide an excellent match to the recent BICEP2/Keck Array and Planck results setting 3.5x10^-3<=r+-=c+/c-<=1/N where N=3 or 2 is the prefactor of the logarithm. Inflation can be attained for subplanckian inflaton values with the corresponding effective theories retaining the perturbative unitarity up to the Planck scale.

Origin of inflation in CFT driven cosmology: $$R^2$$ R 2 -gravity and non-minimally coupled inflaton models

We present a detailed derivation of the recently suggested new type of hill-top inflation [arXiv:1509.07270] originating from the microcanonical density matrix initial conditions in cosmology driven by conformal field theory (CFT). The cosmological instantons of topology $S^1\times S^3$, which set up these initial conditions, have the shape of a garland with multiple periodic oscillations of the scale factor of the spatial $S^3$-section. They describe underbarrier oscillations of the inflaton and scale factor in the vicinity of the inflaton potential maximum, which gives a sufficient amount of inflation required by the known CMB data. We build the approximation of two coupled harmonic oscillators for these garland instantons and show that they can generate inflation consistent with the parameters of the CMB primordial power spectrum in the non-minimal Higgs inflation model and in $R^2$ gravity. In particular, the instanton solutions provide smallness of inflationary slow-roll parameters $\epsilon$ and $\eta<0$ and their relation $\epsilon\sim\eta^2$ characteristic of these two models. We present the mechanism of formation of hill-like inflaton potentials, which is based on logarithmic loop corrections to the asymptotically shift-invariant tree level potentials of these models in the Einstein frame. We also discuss the role of $R^2$-gravity as an indispensable finite renormalization tool in the CFT driven cosmology, which guarantees the non-dynamical (ghost free) nature of its scale factor and special properties of its cosmological garland type instantons. Finally, as a solution to the problem of hierarchy between the Planckian scale and the inflation scale we discuss the concept of a hidden sector of conformal higher spin fields.

Non-minimal Higgs inflation and non-thermal leptogenesis in a supersymmetric Pati-Salam model

We consider a supersymmetric (SUSY) Grand Unified Theory (GUT)based on the gauge group GPS = SU(4)C × SU(2)L × SU(2)R, which incorporates non-minimalchaotic inflation, driven by a quartic potential associated withthe Higgs fields involved in the spontaneous breaking of GPS.The inflationary model relies on renormalizable superpotentialterms and does not lead to overproduction of magnetic monopoles.It is largely independent of the one-loop radiative correctionsand can become consistent with the current observational data onthe inflationary observables, with the symmetry breaking scale ofGPS assuming its SUSY value. Within our model, the strongCP and the μ problems of the minimal SUSY standard model canbe resolved via a Peccei-Quinn symmetry. Moreover baryogenesisoccurs via non-thermal leptogenesis realized by theout-of-equilibrium decay of the right-handed neutrinos, which areproduced by the inflaton's decay. We consider two versions of sucha scenario, assuming that the inflaton decays to the lightest orto the next-to-lightest right-handed neutrino. Both scenaria canbecome compatible with the constraints arising from the baryonasymmetry of the universe, the gravitino limit on the reheatingtemperature and the upper bound on the light neutrino masses,provided that the gravitino is somehow heavy. In the secondscenario, extra restrictions from the SU(4)C GUT symmetryon the heaviest Dirac neutrino mass and the data on theatmospheric neutrino oscillations can be also met.