Agravity

Abstract

Abstract:We explore the possibility that the fundamental theory of nature does not contain any scale. This implies a renormalizable quantum gravity theory where the graviton kinetic term has 4 derivatives, and can be reinterpreted as gravity minus an anti-graviton. We compute the super-Planckian RGE of adimensional gravity coupled to a generic matter sector. The Planck scale and a flat space can arise dynamically at quantum level provided that a quartic scalar coupling and its β function vanish at the Planck scale. This is how the Higgs boson behaves for M h ≈ 125 GeV and M t ≈ 171 GeV. Within agravity, inflation is a generic phenomenon: the slow-roll parameters are given by the β-functions of the theory, and are small if couplings are perturbative. The predictions n s ≈ 0.967 and r ≈ 0.13 arise if the inflaton is identified with the Higgs of gravity. Furthermore, quadratically divergent corrections to the Higgs mass vanish: a small weak scale is natural and can be generated by agravity quantum corrections.

Induced gravity II: grand unification

“…In addition to renormalizability and AF for all couplings, we, as do the authors of ref. [6], restrict our attention to such extensions that are classically scale invariant. This bequeathes certain naturalness properties to the theory that are essential to avoid issues of fine-tuning, even in the presence of the breaking of scale invariance by the conformal anomaly [7,8].…”

“…In fact, because of AF, the classical form of the renormalized action is an increasingly good approximation the larger the scale µ so these constraints are reliable for µ sufficiently large. 6 As the scale µ decreases, one must determine from the renormalization-group-improved effective action how far down in the infrared (IR) direction these inequalities will continue to remain necessary, assuming that it remains within the realm of a perturbative calculation.…”

“…For reasons explained in ref. [4], we adopt the beta-functions of Salvio and Strumia [6], which differ for matter couplings from earlier results [16]. For the SO(N ) case with a single adjoint scalar field, the remaining beta-functions are 9…”

“…may be used to calculate beta-functions [6] and correlation functions at very short distances. There is nothing obviously problematic with this scalar-tensor theory so long as one realizes that it is limited in scope.…”

Gauges and functional measures in quantum gravity II: higher-derivative gravity

“…So far, none of these arguments has convinced the community at large, so the issue of the ghosts remains open for the time being. However, the hope that a way out may exist has generated new interest in these theories in recent times, also among particle physicists [20][21][22]. It seems therefore appropriate to keep investigating the quantum properties of these theories.…”