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arXiv 1906.09232cond-mat.softmath.AP
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一种新的四次弹性Landau-de Gennes模型

A Novel Landau-de Gennes Model with Quartic Elastic Terms

Dmitry Golovaty, Michael Novack, Peter Sternberg

摘要:

在广义Landau-de Gennes理论的框架内,我们确定了一个基于$Q$张量的能量,当考虑到可定向单轴双光子态时,该能量可简化为四常数Oseen-Frank能量.虽然通常考虑的朗道-德热讷理论在$Q$ -张量及其导数的分量中具有至多立方的弹性贡献,但这里提供的替代方案是这些变量的四次。一个明显的优势,我们的方法超过立方理论是,相关的最小化问题是适定的弹性常数的一个显着更广泛的选择。特别是,四次能量可以用来模拟向列相到各向同性相变的高度不同的弹性常数。除了证明适定性的建议版本的Landau-de Gennes理论,我们建立了一个严格的连接,这个理论和它的Oseen-Frank对应通过$Γ$收敛参数的限制消失的相关长度。我们还证明了强收敛的相关极小。

英文摘要:

Within the framework of the generalized Landau-de Gennes theory, we identify a $Q$-tensor-based energy that reduces to the four-constant Oseen-Frank energy when it is considered over orientable uniaxial nematic states. Although the commonly considered version of the Landau-de Gennes theory has an elastic contribution that is at most cubic in components of the $Q$-tensor and their derivatives, the alternative offered here is quartic in these variables. One clear advantage of our approach over the cubic theory is that the associated minimization problem is well-posed for a significantly wider choice of elastic constants. In particular, quartic energy can be used to model nematic-to-isotropic phase transitions for highly disparate elastic constants. In addition to proving well-posedness of the proposed version of the Landau-de Gennes theory, we establish a rigorous connection between this theory and its Oseen-Frank counterpart via a $Γ$-convergence argument in the limit of vanishing nematic correlation length. We also prove strong convergence of the associated minimizers.

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