Abstract :
It was earlier shown that an SO(9,1) θα spinor variable can be constructed from RNS matter and ghost fields. θα has a bosonic world-sheet super-partner λα which plays the role of a twistor variable, satisfying λГμλ = ∂xμ + iθΦμ∂Θ. For Type IIA superstrings, the left-moving [θLα, λLα] and right-moving [θRα, λRα] can be combined into 32-component SO (10,1) spinors [θA, λA]. This suggests that λAГAB11λB = 2λLαλRα can be interpreted as momentum in the eleventh direction. Evidence for this interpretation comes from the zero-momentum vertex operators of the Type IIA superstring and from consideration of D0-branes. As in the work of Bars, one finds an SO(10,2) structure for the Type IIA superstring and an SO(9, 1) × SO(2, 1) structure for the Type IIB superstring.
