A test of the nature of cosmic acceleration using galaxy redshift distortions

Understand

Observations of distant supernovae indicate that the Universe is now in a phase of accelerated expansion the physical cause of which is a mystery.

• Formally, this requires the inclusion of a term acting as a negative pressure in the equations of cosmic expansion, accounting for about 75 per cent of the total energy density in the Universe.
• The simplest option for this "dark energy" corresponds to a cosmological constant, perhaps related to the quantum vacuum energy.
• Physically viable alternatives invoke either the presence of a scalar field with an evolving equation of state, or extensions of general relativity involving higher-order curvature terms or extra dimensions.