Seemingly accelerating motion of an exponentially truncated Airy wave packet in free space. The initial wave packet is ψ = C exp(0.2 x)Airy(x), where C is a normalization constant. The evolution of this wave packet according to Eq. (1) with V(x,x′) = 0 is plotted, and natural units m = ħ = 1 are used in the figures. (a) The evolution of |ψ(x,t)|². The density profile undergoes a seemingly accelerating motion. (b) and (c) The mean position ⟨x⟩ and acceleration a. The mean position of the wave packet keeps still, and the acceleration is 0 all the time, thus in fact the wave packet does not accelerate.