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This whole equation, as you'll note, provides the basic rate of expansion. It's true that the $\frac{8\pi G\rho}{3}$ term decelerates expansion, however this is mostly because both $\rho$ and $\frac{1}{a^2}$ fall off as $a$ increases. Even with $\lambda$ positive and small, it remains constant, which means that as $\rho$ and $\frac{1}{a^2}$ drop to zero, the ...


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To start with, the cosmological constant, vacuum energy, and dark energy are mostly used interchangeably in cosmology. This is because the cosmological constant is observationally indistinguishable from vacuum energy by the Einstein field equations. The term "dark energy" was, as far as I am aware, introduced when the expansion of the universe was observed ...



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