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| -rw-r--r-- | main.tex | 2 |
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@@ -204,6 +204,8 @@ coupling to linear order is \begin{equation} f_\i=-b^{(i)}\epsilon_\X^{(i)}\eta. \end{equation} +Many high-order interations are permitted, and in the appendix another of the +form $\epsilon^2\eta^2$ is added to the following analysis. If there exists no component of strain that transforms like the representation $\X$ then there can be no linear coupling. The next-order coupling is linear in strain, quadratic in order parameter, and the effect of this coupling at a |