Phantom-like dark energy from quantum gravity

Abstract

We analyse the emergent cosmological dynamics corresponding to the mean field hydrodynamics of quantum gravity condensates, in the tensorial group field theory formalism. We focus in particular on the cosmological effects of fundamental interactions, and on the contributions from different quantum geometric modes. The general consequence of such interactions is to produce an accelerated expansion of the universe, which can happen both at early times, after the quantum bounce predicted by the model, and at late times. Our main result is that, while this fails to give a compelling inflationary scenario in the early universe, it produces naturally a phantom-like dark energy dynamics at late times, compatible with cosmological observations. By recasting the emergent cosmological dynamics in terms of an effective equation of state, we show that it can generically cross the phantom divide, purely out of quantum gravity effects without the need of any additional phantom matter. Furthermore, we show that the dynamics avoids any Big Rip singularity, approaching instead a de Sitter universe asymptotically.

Effective dynamics of scalar cosmological perturbations from quantum gravity

“…Second, a bouncing regime, characterized by a possible (depending on the impact of quantum fluctuations and on initial conditions) averaged resolution of the cosmological singularity into a quantum bounce. Moreover, phenomenological studies on the GFT interactions connected them to geometric inflation [66] and phantom dark energy [67]. These results have also been obtained recently using an extended Barrett-Crane (BC) model, which suggests that the emergent behavior of these theories may in fact be universal (at least at this level of approximation and for the few observables that have been considered so far) [68].…”

“…Clearly, this can only be a transient regime, and one expects that, eventually, interactions do become important (see e.g. [62,67,83], for some works which study the phenomenological implications of the inclusion of interactions).…”

Quantum gravity phenomenology at the dawn of the multi-messenger era -- A review

“…The fundamental GFT interactions can generate an effective inflationary phase in the early universe (without an inflaton), a cyclic dynamics, and, in some generality, a phantom dark energy-like accelerated expansion at late times (without any phantom field) with asymptotic de Sitter phase [190,[198][199][200]. GFT condensate cosmology has been extended to include anisotropies [190,201], and inhomogeneities [202][203][204], with very promising results, but not going yet beyond consistency with basic observational constraints: dynamical suppression of anisotropies at late times, and an approximately scale invariant power spectrum of inhomogeneities in the early universe, with good classical evolution.…”

Frontiers of Quantum Gravity: shared challenges, converging directions

“…Again, quantum gravity approaches can provide a fundamental framework in which effective field theory models of a dynamical dark energy can be embedded [], but also provide alternative mechanisms producing an effective dark energy-driven acceleration as a manifestation of underlying quantum gravity interactions [151].…”