Tachyon Condensation in Cubic Superstring Field Theory

It has been conjectured by A.Sen that at the stationary point of the tachyon potential for the non-BPS D-brane or brane-anti-D-brane pair, the negative energy density cancels the brane tension. The results of study this conjecture within the frameworks of a cubic superstring field theory (SSFT) will be presented. We compute the tachyon potential at levels (1/2,1) and (2,6). In the first case we obtain that the value of the potential at the minimum is 97.5% of the non BPS D-brane tension. Using a special gauge in the second case we get 105.8 of the tension. We also study the cubic open SSFT expanded around the perturbatively stable vacuum including all scalar fields at levels 0,1/2 and 2. We check that kinetic terms is absent with good accuracy. This gives an evidence for the absence of physical open string states in this vacuum.