A note on the geometric simplicity of the spectral radius of nonnegative   irreducible tensors
  We prove that the spectral radius of even order nonnegative irreducible tensors is real geometrically simple. In the case when the order of the tensor is odd, or in the complex field, some conditions are given to guarantee the geometric simplicity of the spectral radius. 
Yuning Yang, Qingzhi Yang
math.SP