content_image/342525.jpg content_image/342523.jpg
<img src='content_image/342525.jpg'>

can be effectively considered additive. A nice example of this, a case in which a front driven by multiplicative noise is found to belong to a universality class described by an additive noise stochastic equation, is described in [19]. 

The analysis of the exact solutions to Eq. (4) for γ > 1 /ζ and long times shows the diffusion term is irrelevant in the large scale | θ − θ $^{′}$|  ≫ t 1 /ζ − γ and the correlation becomes [15, 16] 

<img src='content_image/342523.jpg'>

where C ( θ, θ $^{′}$, t ) = 〈 ρ ( θ, t ) ρ ( θ $^{′}$, t ) 〉 . In terms of arc-length differences ℓ − ℓ ′ ∼ t $^{γ}$( θ − θ $^{′}$) one 

