Open superstring theory and superalgebra of the brane-antibrane system

Open superstring theory is formulated in terms of a nondegenerate supertran slation algebra. A supercharge for a tachyonic superstring can also be defi ned classically by taking into account the leakage of the supercurrent whic h is compensated by fermionic and bosonic auxiliary fields. The anticommuta tor of two supercharges of the tachyonic superstring does not contain the z ero eigenvalue and so this string is not a BPS state. Brane-antibrane annih ilation scenarios are described by these superalgebras defined on the sum o f world-volumes of a D-brane, an anti-D-brane and a tachyonic superstring. (C) 2001 Elsevier Science B.V. All rights reserved.