Advances in Astronomy
The prevailing constant Lambda -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 Lambda 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 super(-52) m super(2) ). Moreover, the dark energy density represented by Lambda is presumed to have remained unchanged as the universe expanded by 26 orders of magnitude. Attempts to overcome this deficiency often invoke a variable Lambda -G model. Cosmic constraints from action principles require that either both G and Lambda remain time-invariant or both vary in time. Here, we propose a variable Lambda -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%. Lambda decreases ( Lambda ~ super( tau -2) , where tau is the normalized cosmic time) and G increases (G~ super( tau n) ) with cosmic time. The model results depend only on the chosen value of Lambda at present and in the far future and not directly on G.
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Kantha, Lakshmi, "A Time-Dependent Lambda and G Cosmological Model Consistent with Cosmological Constraints" (2016). Aerospace Engineering Sciences Faculty Contributions. 10.