The interpenetration ratio

However, the result still depends on / = u/V5, which is not an observable quantity. We can eliminate this parameter in favor of the interpenetration ratio... 

The choice of no governs r for small momenta in the dilute limit where Eq. (13.21) reduces to Nr = no- We thus should consider some universal ratio, defined for c —> 0, q -+ 0 which must be most sensitive to Nr. The interpenetration ratio ip is a good candidate, since it depends on Nr even in zero-loop approximation. From Sect. 15.4, Eq, (15.54) we take the one-loop order result... 

Fig. 18.1. Fixed point value of the interpenetration ratio as funo tion of the parameter no- Pull line, one-loop result short dashes zero-loop order long dashes xfj = 0,245...

Another startling conclusion from this study concerns the interpenetration ratio 4 (cf. eq. (2.14)), and goes to the heart of polymer theory. But this requires a brief historical digression. 

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