Curved Extended Superspace from Yang-Mills Theory a la Strings

The massless superfield content of four-dimensional compactifications of closed superstrings with extended (N=2, 3, or 4) supersymmetry is derived by multiplying two (N=0, 1, or 2) Yang-Mills multiplets. In some cases these superfields are known, and the low-energy actions are determined from the fact that the compensator (dilaton) supermultiplets occur quadratically classically. In the other cases these superfields suggest new formulations of extended superspace theories.