Image Details
Caption: Figure 13.
Preference of the SPT+ WMAP 7 data for negative running remains as additional parameters are freed. The marginalized one-dimensional posteriors for dn s / dln k from the CMB in the ΛCDM+ dn s / dln k model is shown by the black solid line. The preference for negative running is reduced when Y p is allowed to vary (blue dashed line), although this depends on extremely high helium abundances. If an upper limit based on solar abundances is set on Y p , the preference for negative running is mostly restored (blue dot-dashed line). Allowing N eff to vary (orange solid line) increases the preference for negative running.
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