Density perturbations for a running cosmological constant

Abstract

The dynamics of density and metric perturbations is investigated for the previously developed model where the decay of the vacuum energy into matter (or vice versa) is due to the renormalization group (RG) running of the cosmological constant (CC) term. The evolution of the CC depends on the single parameter ν, which characterizes the running of the CC produced by the quantum effects of matter fields of the unknown high energy theory below the Planck scale. The sign of ν indicates whether bosons or fermions dominate in the running. The spectrum of perturbations is computed assuming an adiabatic regime and an isotropic stress tensor. Moreover, the perturbations of the CC term are generated from the simplest covariant form suggested by the RG model under consideration. The corresponding numerical analysis shows that for ν > 0 there is a depletion of the matter power spectrum at low scales (large wave numbers) as compared to the standard ΛCDM model, whereas for ν < 0 there is an excess of power at low scales. We find that the LSS data rule out the range |ν| > 10 −4 while the values |ν| ≤ 10 −6 look perfectly acceptable. For ν < 0 the excess of power at low scales grows rapidly and the bound is more severe. From the particle physics viewpoint, the values |ν| ≃ 10 −6 correspond to the "desert" in the mass spectrum above the GUT scale M X ∼ 10 16 GeV . Our results are consistent with those obtained in other dynamical models admitting an interaction between dark matter and dark energy. We find that the matter power spectrum analysis is a highly efficient method to discover a possible scale dependence of the vacuum energy.

Effective growth of matter density fluctuations in the running Λ CDM and Λ XCDM models

“…This confirms the results of [25] within the present effective approach. However, as noted earlier, in this model, the variability of Λ is entangled with the non-conservation of matter.…”

“…Our "effective approach" provides a noticeable consistency with the complete calculation of matter and DE perturbations presented for the running ΛCDM model in Ref. [25]. We are, therefore, confident that the same procedure is able to capture the main restrictions that the present data put on the parameter space of the ΛXCDM model.…”

“…A non-vanishing value of ν produces a time evolution of Λ. The explicit solution of the model shows that values |ν| > 10 −4 are most likely excluded [25].…”

Density Perturbations in Decaying Holographic Dark Energy Models

“…The idea of a time-dependent cosmological term has provided different phenomenological implementations [2], being a subject of renewed interest in recent years [3,4,5]. A general feature of all those approaches is the production of a new kind of matter, compatible with the vacuum decay in order to assure the conservation of the total energy-momentum [6].…”

Composite dark energy: Cosmon models with running cosmological term and gravitational coupling

“…The detailed estimate of the effect of the Λ inhomogeneities on these observables requires an analysis far beyond the scope of this paper. To get a hint of the kind of investigation required we refer the reader to the work of [27], which concentrates on a simpler RG model for Λ in which G is constant and there is no cosmon. In this case one finds that the RG running of Λ may have a significant effect on the structure growth, i.e.…”