= Dielectric anisotropy of a nematic
{title2=$\Delta\epsilon=\epsilon_\parallel-\epsilon_\perp$}
The dielectric response differs along and perpendicular to the <nematic director>. In Gaussian units the orientational electric contribution at prescribed field is $-\Delta\epsilon(\mathbf E\cdot\mathbf n)^2/(8\pi)$; positive anisotropy favors alignment with the <electric field>. The electric term does not receive the additional one-half convention used in writing the Frank elastic terms.
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