A Time-Dependent Λ and G Cosmological Model Consistent with Cosmological Constraints

الملخص EN

The prevailing constant Λ-G cosmological model agrees with observational evidence including the observed red shift, Big Bang Nucleosynthesis (BBN), and the current rate of acceleration.

It assumes that matter contributes 27% to the current density of the universe, with the rest (73%) coming from dark energy represented by the Einstein cosmological parameter Λ in the governing Friedmann-Robertson-Walker equations, derived from Einstein’s equations of general relativity.

However, the principal problem is the extremely small value of the cosmological parameter (~10−52 m2).

Moreover, the dark energy density represented by Λ is presumed to have remained unchanged as the universe expanded by 26 orders of magnitude.

Attempts to overcome this deficiency often invoke a variable Λ-G model.

Cosmic constraints from action principles require that either both G and Λ remain time-invariant or both vary in time.

Here, we propose a variable Λ-G cosmological model consistent with the latest red shift data, the current acceleration rate, and BBN, provided the split between matter and dark energy is 18% and 82%.

Λ decreases (Λ~τ-2, where τ is the normalized cosmic time) and G increases (G~τn) with cosmic time.

The model results depend only on the chosen value of Λ at present and in the far future and not directly on G.