Gauge Invariant Overlaps for Classical Solutions in Open String Field   Theory
  We calculate gauge invariant observables for Schnabl's solution with analytic method and with the level truncation approximation. We also compute them for the numerical solution initially obtained by Sen and Zwiebach in the level truncation approximation to compare with the one for Schnabl's solution. The results are consistent with the expectation that they may be gauge equivalent. We briefly discuss the gauge invariant observables and the action for a marginal solution with a nonsingular current. 
Teruhiko Kawano, Isao Kishimoto, Tomohiko Takahashi