Measuring Unified Dark Matter with 3D Cosmic Shear
  We present parameter estimation forecasts for future 3D cosmic shear surveys
for a class of Unified Dark Matter (UDM) models, where a single scalar field
mimics both Dark Matter (DM) and Dark Energy (DE). These models have the
advantage that they can describe the dynamics of the Universe with a single
matter component providing an explanation for structure formation and cosmic
acceleration. A crucial feature of the class of UDM models we use in this work
is characterised by a parameter, c_inf (in units of the speed of light c=1),
that is the value of the sound speed at late times, and on which structure
formation depends. We demonstrate that the properties of the DM-like behaviour
of the scalar field can be estimated with very high precision with large-scale,
fully 3D weak lensing surveys. We found that 3D weak lensing significantly
constrains c_inf, and we find minimal errors 0.00003, for the fiducial value
c_inf=0.001, and 0.000026, for c_inf=0.012. Moreover, we compute the Bayesian
evidence for UDM models over the LCDM model as a function of c_inf. For this
purpose, we can consider the LCDM model as a UDM model with c_inf=0. We find
that the expected evidence clearly shows that the survey data would
unquestionably favour UDM models over the LCDM model, for the values
c_inf>0.001.
