A mean-field model for semiflexible chains

We derive a mean-field model for a semiflexible chain using a functional integral approach. The resulting model satisfies the global constraint 〈u2(s)〉=1 rather than the hard constraint that u2(s)=1 for all s. The function u(s) is the tangent vector ∂r/∂s, where r(s) represents the conformation of the chain and s is the arc length.