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In homogeneous phase we had

Now we divide system into layers, and with
We want to add the dependence on . Lowest order: linear dependence on . *But* this is not symmetric with respect to
. *Solution:* use

(2) |

(3) |

- 1.
- Sign of
*g*: if*g*<0, ``wavy'' structures are favored:

Therefore*g*>0. - 2.
- Value of
*g*: the dimensionality of*g*/*d*is*(Why?)*. From previous section it is clear, that this of the order of the*square of the molecular size*: Since at , we obtain . We will see that this is square of the*a*_{0}*correlation length*:

© 1997

Thu Oct 16 20:58:44 EDT 1997