Quantum field theory of K-mouflage

Abstract

We consider K-mouflage models, which are K-essence theories coupled to matter. We analyze their quantum properties and in particular the quantum corrections to the classical Lagrangian. We setup the renormalization program for these models and show that, contrary to renormalizable field theories where renormalization by infinite counterterms can be performed in one step, K-mouflage theories involve a recursive construction whereby each set of counterterms introduces new divergent quantum contributions which in turn must be subtracted by new counterterms. This tower of counterterms can be in principle constructed step by step by recursion and allows one to calculate the finite renormalized action of the model. In particular, it can be checked that the classical action is not renormalized and that the finite corrections to the renormalized action contain only higher-derivative operators. We concentrate then on the regime where calculability is ensured, i.e., when the corrections to the classical action are negligible. We establish an operational criterion for classicality and show that this is satisfied in cosmological and astrophysical situations for (healthy) K-mouflage models which pass the Solar System tests. These results rely on perturbation theory around a background and are only valid when the background configuration is quantum stable. We analyze the quantum stability of astrophysical and cosmological backgrounds and find that models that pass the Solar System tests are quantum stable. We then consider the possible embedding of the K-mouflage models in an Ultra-Violet completion. We find that the healthy models which pass the Solar System tests all violate the positivity constraint which would follow from the unitarity of the putative UV completion, implying that these healthy K-mouflage theories have no UV completion. We then analyze their behavior at high energy, and we find that the classicality criterion is satisfied in the vicinity of a high-energy collision, implying that the classical K-mouflage theory can be applied in this context. Moreover, the classical description becomes more accurate as the energy increases, in a way compatible with the classicalization concept.

New bounds on dark energy induced fifth forces

“…Combining (17) with the neutrino bounds (12), we obtain from (11) the numerical estimate m ≃m ν ≃ 0.05 eV, hence we get the noticeably short range m −1 ≃ 4 µm, which is compatible with the Eöt-Wash bound (15).…”

“…which includes the contribution of the three neutrinos, see the appendix A of [15] for the one-loop evaluation. The Heaviside factors ensure that the scalaron and the neutrinos no longer contribute to the running at energies below their mass threshold, as they decouple [5].…”

Born–Infeld inspired modifications of gravity

“…It is not hopeless to expect a nice quantum behaviour, at least for some matter fields. For instance, if we start from a massless scalar field in the Born-Infeld frame, in the Einstein frame we would have a K−essence type of theory whose Lagrangian would be of the form K(X), for which the quantum stability of the classical action has already been discussed in detail in [137,85]. A crucial point to notice here is that for the singular free-solutions provided by Born-Infeld theories, NEC violations are not required and, therefore, the usual arguments for the instability and breaking of unitarity of these solutions do not directly apply.…”

Scalar Fields Near Compact Objects: Resummation versus UV Completion

“…Note that as N increases, the screening becomes more efficient, tending to G φ " r 2 {R 2 nl at large N . This screening mechanism is radiatively stable against quantum corrections from light degrees of freedom [68,105], allows for novel cosmologies [106,107] and has also been observed in the strong gravity regime in numerical simulations [108,109].…”