  We construct a gauge-invariant action for covariant type II string field
theory in the NS-NS sector. Our construction is based on the large Hilbert
space description and Zwiebach's string products are used. First, we rewrite
the action for bosonic string field theory into a new form where a state in the
kernel of the generator of the gauge transformation appears explicitly. Then we
use the same strategy and write down our type II action, where a projector onto
the small Hilbert space plays an important role. We present lower-order terms
up to quartic order and show that three-point amplitudes are reproduced
correctly.

High Energy Physics - Theory