= Good-solvent concentration-blob scaling
{title2=$\xi\sim a\phi^{-3/4},\quad g\sim\phi^{-5/4}$}
In a three-dimensional semidilute <good solvent>, take $g$ statistical segments per blob with size $\xi\sim ag^{3/5}$ and concentration matching $\phi\sim ga^3/\xi^3$. Eliminating $g$ gives the displayed relations. A developed blob regime requires $1\ll g\ll N$ and a <volume fraction> well below close packing. Within a blob the chain retains isolated swollen statistics; on larger scales interpenetrating chains screen excluded-volume effects. The exponents use $\nu=3/5$ and the site-volume assumption. For general $\nu$, $\xi\sim a\phi^{-\nu/(3\nu-1)}$.
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