Forecast Constraints on Inflation from Combined CMB and Gravitational
  Wave Direct Detection Experiments
  We study how direct detection of the inflationary gravitational wave
background constrains inflationary parameters and complements CMB polarization
measurements. The error ellipsoids calculated using the Fisher information
matrix approach with Planck and the direct detection experiment, BBO (Big Bang
Observer), show different directions of parameter degeneracy, and the
degeneracy is broken when they are combined. For a slow-roll parameterization,
we show that BBO could significantly improve the constraints on the
tensor-to-scalar ratio compared with Planck alone. We also look at a quadratic
and a natural inflation model. In both cases, if the temperature of reheating
is also treated as a free parameter, then the addition of BBO can significantly
improve the error bars. In the case of natural inflation, we find that the
addition of BBO could even partially improve the error bars of a cosmic
variance-limited CMB experiment.
