On ghost structure of vacuum superstring field theory Original Research Article

After discussing the general form of the kinetic operator Q around the tachyon vacuum, we determine the specific form of the pure-ghost kinetic operator Q by requiring the twist invariance of the action. We obtain a novel result that the Grassmann-even piece Qeven of Q must act differently on GSO(+) sector and on GSO(−) sector to preserve the twist invariance, and show that this structure is crucial for gauge invariance of the action. With this choice of Q, we construct a solution in an approximation scheme which is conjectured to correspond to a non-BPS D9-brane. We consider both 0-picture cubic and Berkovitsʹ non-polynomial superstring field theories for the NS sector.