Analyticity and sum rules for photon GPDs
  The photon is explored as an object to test the applications of QCD to the perturbatively calculable collinear parton distributions. We investigate analytic properties of DVCS amplitudes and related sum rules of generalized parton distributions of the photon using as an input their earlier calculations in the leading order. The relation of these GPDs to the quintessential functions in the framework of the dual parametrization approach is also found. 
I. R. Gabdrakhmanov, O. V. Teryaev
hep-ph hep-th