A large inflationary tensor-to-scalar ratio r _ { \mathrm { 0.002 } } = 0.20 ^ { +0.07 } _ { -0.05 } is reported by the BICEP2 team based on their B-mode polarization detection , which is outside of the 95 \% confidence level of the Planck best fit model .
We explore several possible ways to reduce the tension between the two by considering a model in which \alpha _ { \mathrm { s } } , n _ { \mathrm { t } } , n _ { \mathrm { s } } and the neutrino parameters N _ { \mathrm { eff } } and \Sigma m _ { \mathrm { \nu } } are set as free parameters .
Using the Markov Chain Monte Carlo ( MCMC ) technique to survey the complete parameter space with and without the BICEP2 data , we find that the resulting constraints on r _ { \mathrm { 0.002 } } are consistent with each other and the apparent tension seems to be relaxed .
Further detailed investigations on those fittings suggest that N _ { \mathrm { eff } } probably plays the most important role in reducing the tension .
We also find that the results obtained from fitting without adopting the consistency relation do not deviate much from the consistency relation .
With available Planck , WMAP , BICEP2 and BAO datasets all together , we obtain r _ { 0.002 } = 0.14 _ { -0.11 } ^ { +0.05 } , n _ { \mathrm { t } } = 0.35 _ { -0.47 } ^ { +0.28 } , n _ { \mathrm { s } } = 0.98 _ { -0.02 } ^ { +0.02 } , and \alpha _ { \mathrm { s } } = -0.0086 _ { -0.0189 } ^ { +0.0148 } ; if the consistency relation is adopted , we get r _ { 0.002 } = 0.22 _ { -0.06 } ^ { +0.05 } .