Exploring parameter constraints on quintessential dark energy: The pseudo-Nambu-Goldstone-boson model

We analyze the constraining power of future dark energy experiments for pseudo-Nambu-Goldstone-boson (PNGB) quintessence. Following the Dark Energy Task Force (DETF) methodology, we forecast data for three experimental stages: Stage 2 represents in-progress projects relevant to dark energy; Stage 3 refers to medium-sized experiments; Stage 4 comprises larger projects. We determine the posterior probability distribution for the parameters of the PNGB model using Markov Chain Monte Carlo analysis. Utilizing data generated on a ΛCDM cosmology, we find that the relative power of the different data stages on PNGB quintessence is roughly comparable to the DETF results for the w₀-wₐ parametrization of dark energy. We also generate data based on a PNGB cosmological model that is consistent with a ΛCDM fiducial model at Stage 2. We find that Stage 4 data based on this PNGB fiducial model will rule out a cosmological constant by at least 3σ.