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 consider the possibility that the total dark energy (DE) of the Universeis made out of two dynamical components of different nature: a variablecosmological term, Lambda, and a dynamical ``cosmon'', X, possibly interactingwith Lambda but not with matter -- which remains conserved. We call thisscenario the LXCDM model. One possibility for X would be a scalar field, but itis not the only one. The overall equation of state (EOS) of the LXCDM model caneffectively appear as quintessence or phantom energy depending on the mixtureof the two components. Both the dynamics of Lambda and of X could be linked tohigh energy effects near the Planck scale. In the case of Lambda it may berelated to the running of this parameter under quantum effects, whereas X mightbe identified with some fundamental field (say, a dilaton) left over as alow-energy ``relic'' by e.g. string theory. We find that the dynamics of theLXCDM model can trigger a future stopping of the Universe expansion and cankeep the ratio rho_D/rho_m (DE density to matter-radiation density) bounded andof order 1. Therefore, the model could explain the so-called ``cosmologicalcoincidence problem''. This is in part related to the possibility that thepresent value of the cosmological term can be Lambda<0 in this framework (thecurrent total DE density nevertheless being positive). However, a cosmic haltcould occur even if Lambda>0 because of the peculiar behavior of X as ``PhantomMatter''. We describe various cosmological scenarios made possible by thecomposite and dynamical nature of LXCDM, and discuss in detail their impact onthe cosmological coincidence problem.Comment: LaTeX, 53 pages, 15 figures. Comments and references added. Version  accepted in JCA

ΛXCDM: a cosmon model solution to the cosmological coincidence problem?