Can negative mass be considered in General Relativity ?
  We show, through Newtonian approximation, that shifting to a bimetric model of the Universe based on a suitable system of coupled field equations, removes the preposterous runaway effect and gives different interaction laws, between positive and negative masses, that bring new insights into the alternative VLS interpretations previously proposed by several authors, and strengthening their assumptions. 
Jean-Pierre Petit and Gilles dAgostini
physics.gen-ph