Method of the asymptotic limit

Method of the asymptotic limit. The figure shows the asymptotic behaviour of f,(q) for q - oo. Let us note that the random noise is large. 

It is admitted that asymptotically the coherent contribution reaches a constant limit when the transfer wave number q becomes much larger than the inverse of the correlation length of the system. This correlation length is, in dilute solutions, the size of the chains in semi-dilute solutions, the screening length. In 

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