The Λ -dominated universe solution is of particular interest because the second derivative with respect to time is positive, non-zero; in other words implying an accelerating expansion of the universe, making ρ Λ a candidate for dark energy : a ( t ) = a i exp ⁡ ⁡ ( ( t − − t i ) H 0 Ω Ω 0 , Λ Λ ) d 2 a ( t ) d t 2 = a i H 0 2 Ω Ω 0 , Λ Λ exp ⁡ ⁡ ( ( t − − t i ) H 0 Ω Ω 0 , Λ Λ )