A negative answer to the question of the linearity of Tate's Trace for   the sum of two endomorphisms
  The aim of this note is to solve a problem proposed by J. Tate in 1968 by offering a counter-example of the linearity of the trace for the sum of two finite potent operators on an infinite-dimensional vector space. 
Julia Ramos Gonz\'alez, Fernando Pablos Romo
math.RA