Nonminimal hints for asymptotic safety

Abstract

In the asymptotic-safety scenario for gravity, nonzero interactions are present in the ultraviolet. This property should also percolate into the matter sector. Symmetry- based arguments suggest that nonminimal derivative interactions of scalars with curvature tensors should therefore be present in the ultraviolet regime. We perform a nonminimal test of the viability of the asymptotic-safety scenario by working in a truncation of the Renormalization Group flow, where we discover the existence of an interacting fixed point for a corresponding nonminimal coupling. The back-coupling of such nonminimal interactions could in turn destroy the asymptotically safe fixed point in the gravity sector. As a key finding, we observe nontrivial indications of stability of the fixed-point properties under the impact of nonminimal derivative interactions, further strengthening the case for asymptotic safety in gravity-matter systems.Comment: 13 pages, 8 figures, 1 tabl

A link that matters: towards phenomenological tests of unimodular asymptotic safety

“…As gravity is "blind" to internal symmetries, For the Higgs self-coupling, the situation is slightly different: A screening quantum-gravity contribution actually results in a prediction of the Higgs mass close to the experimental value [52]. This is a consequence of the fact that a Higgs mass of about 125 GeV is connected to a near-vanishing Higgs quartic coupling 7 , which in turn follows from a screening quantum-gravity contribution, as found in [36,53,77,82,83,87,175]. On the other hand, an antiscreening contribution would result in the Higgs self-coupling being a free parameter of the theory, such that the model would also be UV complete, albeit less predictive.…”

“…In standard gravity, the gravitational contribution to the beta functional of the scalar potential is towards irrelevance at the free fixed point, V * = 0 [52,77,82,83,87,175]. This implies that (with the possible exception of the mass term, which may remain relevant), all terms in the potential are driven to zero under the impact of quantum-gravity fluctuations 10 , i.e., quantum-gravity fluctuations tend to flatten scalar potentials.…”

“…Therefore the fixed point at λ i 1 ...in = 0, which is guaranteed to exist in the absence of explicit shift-symmetry-breaking contributions, is infrared attractive for η φ | grav > 0. Under the assumption that this fixed-point structure is realized in the corresponding more involved systems despite the presence of additional fields, this could have potential phenomenological consequences, such as a prediction of the Higgs mass in the vicinity of the observed value [52,87,181], the decoupling of the Higgs portal to uncharged scalar dark matter [82], and in general the vanishing of all quartic scalar couplings which could rule out certain breaking chains in grand unified theories [182].…”

“…Yet, there is another crucial requirement that a viable model has to satisfy, namely the consistency with observational constraints. Here, it appears to be possible to make progress that could allow to rule out such a model based on phenomenological consistency in the matter sector, e.g., [52][53][54][55][56][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89].…”

Asymptotic safety, string theory and the weak gravity conjecture

“…In such a setting, the physics in the deep IR is essentially determined by the ASSM. This might include the intriguing consequence that the Higgs mass [1,74,75], the top quark mass [2], the bottom quark mass [5] and the Abelian gauge coupling [3,76] could emerge as predictions of string theory. This follows since functional RG studies indicate that the respective couplings come out as irrelevant couplings with finite asymptotically safe fixed-point values.…”