and the average solvent density is given as, (ps(y))w+,w-, where
^ / r∙ , n <HnQs[⅛,+ + w_]
z⅛⅛+ + u>-]) = →⅛ ^wt+w-∣ ■ (8 3S)
Clearly, there are two important aspects for particle-to-field transformation. One
is the introduction of the auxiliary chemical potential lw, fields that serve to decouple
the interaction among the molecules, replacing them with the interactions between
each molecule and the field variables. The second aspect and the advantage of such
a transformation is that the resulting field theory sidesteps the many-body problem
- only the partition function of the (ə[w] of a single polymer or solvent molecule
experiencing the auxiliary fields need to be computed.
8.3 Formalism of self-consistent field theory
The field-theoretic models express the relevant partition function as a functional
integral over one or more chemical potential fields, w(r),
Z — J Dw exp(-7∕[w]). (8.37)
The observable properties are calculated as an ensemble average,
(G[w]) = Z~1 [ Dw G[w] exp (—H[w]). (8.38)
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