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Register a new userQuantum gravity corrections to the standard model Higgs in Einstein and $R^2$ gravity
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We evaluate quantum gravity corrections to the standard model Higgs potential $V(phi)$ a la Coleman-Weinberg and examine the stability question of $V(phi)$ at scales of Planck mass $M_{rm Pl}$. We compute the gravity one-loop corrections by using the momentum cut-off in Einstein gravity. The gravity corrections affect the potential in a significant manner for the value of $Lambda= (1 - 3)M_{rm Pl}.$ In view of reducing the UV cut-off dependence we also make a similar study in the $R^2$ gravity.
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We study one-loop quantum gravity corrections to the standard model Higgs potential $V(phi)$ $grave{rm a}$ la Coleman-Weinberg and examine the stability question of $V(phi)$ in the energy region of Planck mass scale, $musimeq M_{rm Pl}$ ($M_{rm Pl}=1.22times10^{19}{rm GeV}$). We calculate the gravity one-loop corrections to $V(phi)$ in Einstein gravity by using the momentum cut-off $Lambda$. We have found that even small gravity corrections compete with the standard model term of $V(phi)$ and affect the stability argument of the latter part alone. This is because the latter part is nearly zero in the energy region of $M_{rm Pl}$.
We study inflation driven by the Higgs field in the Einstein-Cartan formulation of gravity. In this theory, the presence of the Holst and Nieh-Yan terms with the Higgs field non-minimally coupled to them leads to three additional coupling constants. For a broad range of parameters, we find that inflation is both possible and consistent with observations. In most cases, the spectral index is given by $n_s=1-2/N_star$ (with $N_star$ the number of e-foldings) whereas the tensor-to-scalar ratio $r$ can vary between about $10^{-10}$ and $1$. Thus, there are scenarios of Higgs inflation in the Einstein-Cartan framework for which the detection of gravitational waves from inflation is possible in the near future. In certain limits, the known models of Higgs inflation in the metric and Palatini formulations of gravity are reproduced. Finally, we discuss the robustness of inflationary dynamics against quantum corrections due to the scalar and fermion fields.
This article describes a single species of non-interacting massless dust on $mathbb{R}^{0|18}$, whose behaviour in the low-energy limit is equivalent to an interacting family of massive particles resembling the Standard Model plus WIMPs on a curved 3+1D space--time manifold (though with some liberties taken with gravity). The coupling between mass and curvature is not strictly equivalent to general relativity, but reproduces the usual metrics for large uncharged spherically symmetric sources at reasonable distances from the event horizon. Tunable parameters may be chosen so that electroweak particle masses and force couplings calculated to tree level lie within a few percent of their Standard Model values. This model is consequently of interest as a novel approximation to the Standard Model and gravitation. Extensive new physics, including a tripartite coloured preon substructure for fermions, is predicted at energies beyond the strong nuclear scale.
Thermal leptogenesis, in the framework of the standard model with three additional heavy Majorana neutrinos, provides an attractive scenario to explain the observed baryon asymmetry in the universe. It is based on the out-of-equilibrium decay of Majorana neutrinos in a thermal bath of standard model particles, which in a fully quantum field theoretical formalism is obtained by solving Kadanoff-Baym equations. So far, the leading two-loop contributions from leptons and Higgs particles are included, but not yet gauge corrections. These enter at three-loop level but, in certain kinematical regimes, require a resummation to infinite loop order for a result to leading order in the gauge coupling. In this work, we apply such a resummation to the calculation of the lepton number density. The full result for the simplest vanilla leptogenesis scenario is by $mathcal{O}(1)$ increased compared to that of quantum Boltzmann equations, and for the first time permits an estimate of all theoretical uncertainties. This step completes the quantum theory of leptogenesis and forms the basis for quantitative evaluations, as well as extensions to other scenarios.
Concerning the gravitational corrections to the running of gauge couplings two different results were reported. Some authors claim that gravitational correction at the one-loop level indicates an interesting effect of universal gravitational decreasing of gauge couplings, that is, gravitational correction works universally in the direction of asymptotic freedom no matter how the gauge coupling behaves without gravity, while others reject the presence of gravitational correction at the one-loop level at all. Being these calculations done in the framework of an effective field theory approach to general relativity, we wanted to draw attention to a recently discovered profound quantum-gravitational effect of space-time dimension running that inevitably affects the running of gauge couplings. The running of space-time dimension indicating gradual reduction of dimension as one gets into smaller scales acts on the coupling constants in the direction of asymptotic freedom and therefore in any case manifests the plausibility of this quantum-gravitational effect. Curiously enough, the results are also in perfect quantitative agreement with those of Robinson and Wilczek.
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