On finite Morse index solutions to the quadharmonic Lane-Emden equation
  In this paper, we compute the Joseph-Lundgren exponent for the quadharmonic Lane-Emden equation, derive a monotonicity formula and classify the finite Morse index solution to the following quadharmonic Lane-Emden equation: \noindent \begin{equation}\nonumber \Delta^4 u=|u|^{p-1}u\;\;\;\;\hbox{in}\;\;\;\;\; \R^n. \end{equation} As a byproduct, we also get a monotonicity formula for the quadharmonic maps $ \Delta^4 u=0$. 
Senping Luo, Juncheng Wei, and Wenming Zou
math.AP