The chiral superstring measure constructed in the earlier papers of this series for general gravitino slices χ z ̄ + is examined in detail for slices supported at two points x 1 and x 2, χ z ̄ +=ζ 1δ(z,x 1)+ζ 2δ(z,x 2) , where ζ 1 and ζ 2 are the odd Grassmann valued supermoduli. In this case, the invariance of the measure under infinitesimal changes of gravitino slices established previously is strengthened to its most powerful form: the measure is shown, point-by-point on moduli space, to be locally and globally independent from x α , as well as from the superghost insertion points p a , q α introduced earlier as computational devices. In particular, the measure is completely unambiguous. The limit x α = q α is then well defined. It is of special interest, since it elucidates some subtle issues in the construction of the picture-changing operator Y( z) central to the BRST formalism. The formula for the chiral superstring measure in this limit is derived explicitly.
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