On Monday AIMS PhD student Patrice Okouma talked to the group about the work he did for his recently submitted PhD thesis on Dark Energy and Cosmic Curvature.
Patrice began by telling us about his work on baryon acoustic oscillations (BAO) and how initial conditions can affect the constraints BAO impose on dark energy. First, he explained how the baryon acoustic oscillations produce a characteristic length scale in the matter power spectrum which can, in turn, be used as a standard ruler with which to measure the expansion of the universe.
BAO is particularly useful because of its potential to better constrain the parameters of dark energy. However, as Patrice explained, these constraints are obtained conditional on a set of assumptions about the initial conditions for cosmological perturbations. In particular, Patrice and his collaborators examined how constraints on dark energy become weaker, if one assumes the possibility of primordial isocurvature fluctuations along with the usual adiabatic ones.
BY using a Fisher analysis, Patrice showed that the uncertainty in our current favored model of dark energy increases by about 50%, while the possibility of a very large (up to 11 sigma) bias in dark energy parameters is also incurred.
Next, Patrice continued by telling us about the work he’s done examining the degeneracy between constraints on curvature and dark energy from the CMB. Modelling dark energy with a time-varying equation of state parameter, Patrice and his collaborators have managed to show that in general dynamical dark energy models, cosmic curvature is still small.