Einstein field equations [1]:
Rµν - (1/2)gµνR + Λgµν = Tµν ...... (EQ.1)
where Λ is the cosmological constant, gµν is the spacetime metric, and Rµν is the Ricci tensor. EQ.1 expresses the relationship between the amount of energy-momentum (mass) and the curvature of spacetime in a region (or point) of spacetime.
The basic Friedmann equation that dominates the expansion of the universe [2]:
(a')2+K=8πGρa(t)2/3 ...... (EQ.2)
where a(t) is the Robertson-Walker scale factor, and it determines how large-scale distances in space change with time in Friedmann-Lemaître -Robertson-Walker metric:
ds2=gµνdxµdxν=dt2-a2(t)dX2 ....... EQ.3
And it is a solution of Einstein field equations. Two Space-Time properties are expressed here: curvature and expansion over time.
What causes Space-Time Curvature is local energy. What drives spacetime expansion is dark energy. ”Physics welcomes the idea that space contains energy whose gravitational effect approximates that of Einstein's cosmological constant,Λ; today the concept is termed dark energy or quintessence." [3] Dark energy is not the usual matter and radiation[2].
Our questions are:
1) Space-time is interconnected, confined by the speed of light c =Δx /Δt; the factor a(t) that determines space-time is of a kinetic nature; what makes it relevant only to time (it affects all of space in the same way as time passes) [4] and not to space?
2) Can the Einstein field equations essentially be written as two separate equations, the bending effect equation and the expansion effect equation?
3) How does Space-Time know to distinguish between energy and dark energy if Space-Time Curvature and Expansion are both different properties?
4) Can local Space-Time Curvature geometrically affect expansion if it appears to be strongly curved?
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Notes
* “How the view of space-time is unified (3)-If GR's space-time is not curved, what should it be? ”https://www.researchgate.net/post/NO17How_the_view_of_space-time_is_unified_3-If_GRs_space-time_is_not_curved_what_should_it_be
** How the View of Space-Time is Unified (4) - Is Space-Time Expansion a Space-Time Creation?
https://www.researchgate.net/post/NO18How_the_View_of_Space-Time_is_Unified_4-Is_Space-Time_Expansion_a_Space-Time_Creation
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Refererncs
[1] Grøn, Ø., & Hervik, S. (2007). Einstein's Field Equations. In Einstein's General Theory of Relativity: With Modern Applications in Cosmology (pp. 179-194). Springer New York. https://doi.org/10.1007/978-0-387-69200-5_8
[2] Weinberg, S. (2008). COSMOLOGY (Chinese ed.). Oxford University Press.
[3] Peebles, P. J. E., & Ratra, B. (2003). The cosmological constant and dark energy. Reviews of Modern Physics, 75(2), 559.
[4] https://profoundphysics.com/the-friedmann-equations-explained-a-complete-guide/