Energy quantization for biharmonic maps
  In the present work we establish an energy quantization (or energy identity) result for solutions to scaling invariant variational problems in dimension 4 which includes biharmonic maps (extrinsic and intrinsic). To that aim we first establish an angular energy quantization for solutions to critical linear 4th order elliptic systems with antisymmetric potentials. The method is inspired by the one introduced by the authors previously in arXiv:1109.3599v1 for 2nd order problems. 
P. Laurain, and T. Riviere
math.AP