English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We analyze the dynamical implications of an exponential Lagrangian densityfor the gravitational field, as referred to an isotropic FRW Universe. Then, wediscuss the features of the generalized deSitter phase, predicted by the newFriedmann equation. The existence of a consistent deSitter solution arises onlyif the ratio between the vacuum-energy density and that associated with thefundamental length of the theory acquires a tantalizing negative character.This choice allows us to explain the present universe dark energy as a relic ofthe vacuum-energy cancellation due to the cosmological constant intrinsicallycontained in our scheme. The corresponding scalar-tensor description of themodel is addressed too, and the behavior of the scalar field is analyzed forboth negative and positive values of the cosmological term. In the first case,the Friedmann equation is studied both in vacuum and in presence of externalmatter, while, in the second case, the quantum regime is approached in theframework of ''repulsive'' properties of the gravitational interaction, asdescribed in recent issues in Loop Quantum Cosmology. In particular, in thevacuum case, we find a pure non-Einsteinian effect, according to which anegative cosmological constant provides an accelerating deSitter dynamics, inthe region where the series expansion of the exponential term does not hold.

Dark Energy as a Relic of the Vacuum-Energy Cancellation?