We show that both the Planck and electroweak mass scales can be generated from conformal gravity via the Coleman-Weinberg mechanism of dimensional transmutation. At the first step, the Planck scale is generated via the Coleman-Weinberg mechanism in the sector of conformal gravity, which means that radiative corrections associated with gravitons induce spontaneous symmetry breakdown of a local conformal symmetry. At the second step, the vacuum expectation value of a scalar field is transmitted to the sector of the standard model via a potential involving the conformally invariant part and the contribution from the Coleman-Weinberg mechanism, thereby generating the electroweak scale. The huge hierarchy between the two scales can be explained in terms of a very tiny coupling constant between the scalar and the Higgs field in a consistent way.
We show that the Planck mass scale can be generated from conformal gravity in the Weyl conformal geometry via the Coleman-Weinberg mechanism of dimensional transmutation where quantum corrections stemming from the gravitational field and the Weyl gauge field trigger the symmetry breakdown of a local Weyl symmetry. It is also shown that the vacuum expectation value of a scalar field is transmitted to a sector of the standard model through a potential involving the scale invariant part and the contribution from the Coleman-Weinberg mechanism, thereby generating the electroweak scale.
We argue that there may be no intermediate particle physics energy scale between the Planck mass $M_{Pl}\sim 10^{19}$ GeV and the electroweak scale $M_W \sim 100$ GeV. At the same time, the number of problems of the Standard Model (neutrino masses and oscillations, dark matter, baryon asymmetry of the Universe, strong CP-problem, gauge coupling unification, inflation) could find their solution at $M_{Pl}$ or $M_W$. The crucial experimental predictions of this point of view are outlined.
Using q-theory, we show that the electroweak crossover can generate a remnant vacuum energy density Λ\sim E_{ew}^8 / E_{planck}^4, with effective electroweak energy scale E_{ew} \sim 10^{3} GeV and reduced Planck-energy scale E_{planck} \sim 10^{18} GeV. The obtained expression for the effective cosmological constant Λmay be a crucial input for the suggested solution by Arkani-Hamed et al. of the triple cosmic coincidence puzzle (why the orders of magnitude of the energy densities of vacuum, matter, and radiation are approximately the same in the present Universe).
One of the deepest insights from the general theory of relativity is the relational nature of spacetime. While it is a generally agreed on that the nature of spacetime must be drastically different at the Planck scale, it has been a common practice to assume a full pseudo-Riemannian geometry of spacetime no matter what the physical fields present are, and to apply such geometry to cosmology. In the spirit of preserving the relational description of spacetime, we initiate a discussion on the applicability of general relativity all the way to Planck scale, and propose the possibility that the fu…
We propose a scenario in which the Planck scale is dynamically linked to the electroweak scale induced by top condensation. The standard model field content, without the Higgs, is promoted to a 5D warped background. There is also an additional 5D fermion with the quantum numbers of the right-handed top. Localization of the zero-modes leads, at low energies, to a Nambu-Jona-Lasinio model that also stabilizes the radion field dynamically thus explaining the hierarchy between the Planck scale and v_EW = 174 GeV. The top mass arises dynamically from the electroweak breaking condensate. The other s…
We argue that, as a consequence of the graviton's spin-2, its bremsstrahlung in trans-planckian-energy ($E\gg M_P$) gravitational scattering at small deflection angle can be nicely expressed in terms of helicity-transformation phases and their transfer within the scattering process. The resulting spectrum exhibits deeply sub-planckian characteristic energies of order $M_P^2/E \ll M_P$ (reminiscent of Hawking radiation), a suppressed fragmentation region, and a reduced rapidity plateau, in broad agreement with recent classical estimates.
The issue of electroweak vacuum stability is studied in presence of a scalar field which participates in modifying the minimal chaotic inflation model. It is shown that the threshold effect on the Higgs quartic coupling originating from the Higgs-inflaton sector interaction can essentially make the electroweak vacuum stable upto the Planck scale. On the other hand we observe that the new physics parameters in this combined framework are enough to provide deviation from the minimal chaotic inflation predictions so as to keep it consistent with recent observation by Planck 2015.
We investigate a possibility of the "flatland scenario", in which the electroweak gauge symmetry is radiatively broken via the Coleman-Weinberg mechanism starting from a completely flat Higgs potential at the Planck scale. We show that the flatland scenario is realizable only when an inequality K<1 among the coefficients of the beta-functions is satisfied. We show several models satisfying the condition.
Scale invariance may be a classical symmetry which is broken radiatively. This provides a simple way to stabilise the scale of electroweak symmetry breaking against radiative corrections. But for such a theory to be fully realistic, it must actually incorporate a hierarchy of scales, including the Planck and the neutrino mass scales in addition to the electroweak scale. The dark matter sector and the physics responsible for baryogenesis may or may not require new scales, depending on the scenario. We develop a generic way of using hidden sectors to construct a technically-natural hierarchy of …
A novel cosmological scenario, capable to generate the observed baryon number at the electroweak scale for very small CP violating angles, is presented. The proposed mechanism can be applied in conventional FRW cosmology, but becomes extremely efficient due to accretion in the context of early cosmic expansion with high energy modifications. Assuming that our universe is a Randall-Sundrum brane, baryon asymmetry can easily be produced by Hawking radiation of very small primordial black holes. The Hawking radiation reheats a spherical region around every black hole to a high temperature and the…
The LHC and other experiments show so far no sign of new physics and long-held beliefs about naturalness should be critically reexamined. We discuss therefore in this paper a model with a combined breaking of conformal and electroweak symmetry by a strongly coupled hidden sector. Even though the conformal symmetry is anomalous, this may still provide an explanation of the smallness of electroweak scale compared to the Planck scale. Specifically we start from a classically conformal model, in which a strongly coupled hidden sector undergoes spontaneous chiral symmetry breaking. A coupling via a…
We consider a minimal classically scale-invariant extension of the Standard Model. In this theory, the Higgs mechanism is triggered and the electroweak symmetry breaking is generated radiatively by the Coleman-Weinberg sector which is coupled to the SM Higgs. We extend the Higgs portal interactions of the theory to include an additional singlet which is also non-minimally coupled to gravity. This generates a single-field slow-roll inflation mechanism in the effective field theory formulation which is robust up to Planck scales. Our approach does not require integrating in any additional new ph…
We construct a model consisting of many D3-branes with only positive tension in a five-dimensional anti-de Sitter space-time geometry. It is shown that this type of model naturally realizes not only exponential mass hierarchy between the Planck scale and the electroweak scale but also trapping of the graviton on the D3-branes. It is pointed out that our model may have a flexibility to explain the existence of more than one disparate mass scales, such as the electroweak scale and the GUT scale, on the same D3-brane.
We revisit a single field inflationary model based on Coleman-Weinberg potentials. We show that in small field Coleman-Weinberg inflation, the observed amplitude of perturbations needs an extremely small quartic coupling of the inflaton, which might be a signature of radiative origin. However, the spectral index obtained in a standard cosmological scenario turns out to be outside the 2 sigma region of the Planck data. When a non-standard cosmological framework is invoked, such as brane-world cosmology in the Randall-Sundrum model, the spectral index can be made consistent with Planck data with…
We propose UV complete (Partially) Composite Higgs models with compositeness scale up to the Planck scale assisted by a novel mechanism. This mechanism is based on softly breaking a global $ \mathbb{Z}_2 $ symmetry by technically natural small vacuum misalignment, dynamically triggering the electroweak symmetry breaking and Standard Model fermion mass generation. This mechanism can be present in various models based on vacuum misalignment. For concreteness, we demonstrate it in a minimal partially composite two-Higgs scheme, where the Higgs is a mixture of a composite and an elementary state, …
If the mass of the Higgs boson is put to zero, the classical Lagrangian of the Standard Model (SM) becomes conformally invariant (CI). Taking into account quantum non-perturbative QCD effects violating CI leads to electroweak symmetry breaking with the scale $v \sim Λ_{\rm QCD}\sim 100$ MeV which is three orders of magnitude less than it is observed experimentally. Depending on the mass of the top quark, the radiative corrections may lead to another minimum of the effective potential for the Higgs field with $v \gtrsim M_P$, where $M_P$ is the Planck mass, at least $16$ orders of magnitude mor…
Combining the quantum scale invariance with the absence of new degrees of freedom above the electroweak scale leads to stability of the latter against perturbative quantum corrections. Nevertheless, the hierarchy between the weak and the Planck scales remains unexplained. We argue that this hierarchy can be generated by a non-perturbative effect relating the low energy and the Planck-scale physics. The effect is manifested in the existence of an instanton configuration contributing to the vacuum expectation value of the Higgs field. We analyze such configurations in several toy models and in a…
