Dark Energy in Light of the Cosmic Horizon

Understand

Based on dramatic observations of the CMB with WMAP and of Type Ia supernovae with the Hubble Space Telescope and ground-based facilities, it is now generally believed that the Universe's expansion is accelerating.

• Within the context of standard cosmology, the Universe must therefore contain a third `dark' component of energy, beyond matter and radiation.
• However, the current data are still deemed insufficient to distinguish between an evolving dark energy component and the simplest model of a time-independent cosmological constant.
• In this paper, we examine the role played by our cosmic horizon R0 in our interrogation of the data, and reach the rather firm conclusion that the existence of a cosmological constant is untenable.