“…; a n j Þ 2 R n , (j = 1, 2, 3), are three distinct constant vectors, and ðU À a 1 ; U À a 2 Þ P n i¼1 ðU i À a i 1 ÞðU i À a i 2 Þ means the Euclidean scalar product of vectors (U À a 1 ) and (U À a 2 ) and $ 2 = D = o 2 /ox 2 + o 2 /oy 2 + o 2 /oz 2 is the Laplace operator, a, b are real constants. In the scalar case, when n = 1, a = 0, and in the one space dimension, for different choices of parameters a 1 , a 2 , a 3 the model reduces to the well-known nonlinear diffusion equations appearing in a different fields sometimes with different names: the Fitzhugh-Nagumo equation (a 1 = 0, a 2 = 1, a 3 = a) arising in population genetics [9] and models the transmission of nerve impulse [10], autocatalytic chemical reaction model introduced by Schlögl [11,12], generalized Fisher equation [2], Newell-Whitehead equation [13] or Kolmogorov-Petrovsky-Piscounov equation [14] (a 1 = 0, a 2 = 1, a 3 = À 1), Huxley equation (a 1 = a 2 = 0, a 3 = 1).…”