GL(1) Charged States in Twistor String Theory
  We discuss the appearance of the GL(1) charged physical operators in the twistor string theory. These operators are shown to be BRST-invariant and non-trivial, and some of their correlators and conformal beta-functions are computed. Remarkably, the non-conservation of the GL(1)-charge in interactions involving these operators is related to the anomalous term in the Kac-Moody current algebra. While these operators play no role in the maximum helicity violating (MHV) amplitudes of Yang-Mills theory, they are shown to contribute non-trivially to non-MHV correlators in the worldsheet instanton backgrounds. We argue that these operators describe the non-perturbative dynamics of solitons in conformal supergravity. However, the exact form of such solitonic solutions is yet to be determined. 
Dimitri Polyakov