Physical naturalness and dynamical breaking of classical scale invariance

Abstract

We propose a model of a confining dark sector, dark technicolor, that communicates with the Standard Model through the Higgs portal. In this model electroweak symmetry breaking and dark matter share a common origin, and the electroweak scale is generated dynamically. Our motivation to suggest this model is the absense of evidence for new physics from recent LHC data. Although the conclusion is far from certain at this point, this lack of evidence may suggest that no mechanism exists at the electroweak scale to stabilise the Higgs mass against radiative corrections from UV physics. The usual reaction to this puzzling situation is to conclude that the stabilising new physics is either hidden from us by accident, or that it appears at energies that are currently inaccessible, such that nature is indeed fine-tuned. In order to re-examine the arguments that have lead to this dichotomy, we review the concept of naturalness in effective field theories, discussing in particular the role of quadratic divergences in relation to different energy scales. This leads us to suggest classical scale invariance as a guidline for model building, implying that explicit mass scales are absent in the underlying theory. arXiv:1304.7006v2 [hep-ph]

Dynamically induced Planck scale and inflation

“…3 In our framework this requirement implies 6) where t = lnμ,μ is the renormalisation scale and β λ S is the β function of λ S . As usual, we resum log-enhanced quantum corrections by identifying the renormalisation scaleμ with the inflaton field value s. Moreover, in order to ensure that λ S (v s ) = 0 is not just a stationary point but a minimum, we need to impose the requirement…”

“…The range of λ Sσ (v s ) in the right panel of figure 2 is determined by the normalisation of the spectrum P R = V E (s * )/24π 2M 4 Pl (s * 13 GeV that are in the physical range, verifying our model independent results in the previous subsection. 6 The large values of the couplings are needed to get a significant deviation from quadratic inflation.…”

“…The 5 Notice that a large ξ-coupling does not necessarily spoil perturbative unitarity if the VEV of the corresponding scalar field is large [68,86]. 6 We choose yσ(vs) = 0 for simplicity. If yσ = 0, the predictions for inflation do not change, since its negative influence on the running of λSσ must be countered by a larger value of λσ in order to get the correct value for PR.…”

“…On the contrary, heavy new particles coupled to the Higgs boson would lead to large physical corrections to the Higgs mass: the associated fine-tuning could be probed by experiments [5][6][7]. Thereby, one is led to redefine natural models as those where new physics heavier than the weak scale is weakly coupled to the Higgs.…”

Dynamical generation of the weak and Dark Matter scales from strong interactions

“…In this context, dynamical generation of the weak scale via dimensional transmutation has been realised with weakly-coupled dynamics, in models where an extra scalar S has interactions that drive its quartic λ S |S| 4 negative around or above the weak scale: S acquires a vev at this scale, and its interaction λ HS |H| 2 |S| 2 effectively becomes a Higgs mass term, m 2 = λ HS S 2 . A related possibility is that the scalar S is interacting with techni-quarks [29,30] or charged under a techni-color gauge group ( [31,32]; see also [52], in the past other authors considered a similar idea, but without an elementary Higgs [53,54]) and again S acquires a vev or forms a condensate. In all these models S can be pushed arbitrarily above the weak scale by making λ HS arbitrarily small, leaving no observable signals.…”