On the real rank of monomials
  In this paper we study the real rank of monomials and we give an upper bound for the real rank of all monomials. We show that the real and the complex ranks of a monomial coincide if and only if the least exponent is equal to one. 
Enrico Carlini, Mario Kummer, Alessandro Oneto, Emanuele Ventura
math.AC math.AG