Inverse boundary value problems for the perturbed polyharmonic operator
  We show that a first order perturbation $A(x)\cdot D+q(x)$ of the polyharmonic operator $(-\Delta)^m$, $m\ge 2$, can be determined uniquely from the set of the Cauchy data for the perturbed polyharmonic operator on a bounded domain in $R^n$, $n\ge 3$. Notice that the corresponding result does not hold in general when $m=1$. 
Katsiaryna Krupchyk, Matti Lassas, Gunther Uhlmann
math.AP math-ph math.MP