  A period of inflation in the early universe produces a nearly scale-invariant
spectrum of gravitational waves over a huge range in wavelength. If the
amplitude of this gravitational wave background is large enough to be
detectable with microwave background polarization measurements, it will also be
detectable directly with a space-based laser interferometer. Using a Monte
Carlo sampling of inflation models, we demonstrate that the combination of
these two measurements will strongly constrain the expansion history during
inflation and the physical mechanism driving it.
