  We study the BSFT actions by using an analytic continuation in momentum
space. We compute various two- and three- point functions for some low-lying
excitations including massive states on BPS/non-BPS D-branes. The off-shell
two-point functions for the tachyon, the gauge field and the massive fields are
found to reproduce the well-known string mass-shell conditions. We compare our
action with the tachyon actions previously obtained by the derivative expansion
(or the linear tachyon profiles), and find complete agreement. Furthermore, we
reproduce the correct on-shell value of the tachyon-tachyon-gauge three-point
function on brane-anti-brane systems. Though inclusion of the massive modes has
been thought difficult because of the non-renormalizability in string sigma
models, we overcome this by adopting general off-shell momenta and the analytic
continuation.
