Is cosmological expansion caused by dark energy?

People hear about dark energy, conceptualize it as a kind of universal repulsion of space itself, and then tend to say that cosmological expansion must be caused by dark energy. Is this correct?

• – user4552 Apr 26 '18 at 21:15
• – AccidentalFourierTransform Apr 26 '18 at 21:24

The cosmological expansion of the universe from the initial big bang is mathematically modelled by the Freedman-Lemaitre-Robertson-Walker equations, which are a solution to the Einstein's field equations (which represents a mathematical description of the gravity, and predicted the space-time curvature). There is not dark energy in that models, which are a correct description of the expansion of the universe until a "more recent epoch" ($z \sim 0.5$). Later in the history of the universe an acceleration was inferred from a detailed study of the light curves of type Ia supernovae.