scholarly journals Bifurcation analysis of the twist-Fréedericksz transition in a nematic liquid-crystal cell with pre-twist boundary conditions

2009 ◽  
Vol 20 (3) ◽  
pp. 269-287 ◽  
Author(s):  
FERNANDO P. DA COSTA ◽  
EUGENE C. GARTLAND ◽  
MICHAEL GRINFELD ◽  
JOÃO T. PINTO
Keyword(s):  
Magnetic Field ◽  
Liquid Crystal ◽  
Boundary Conditions ◽  
Nematic Liquid Crystal ◽  
Pitchfork Bifurcation ◽  
Critical Magnetic Field ◽  
Twist Boundary ◽  
Freedericksz Transition ◽  
Diamagnetic Anisotropy ◽  
Fréedericksz Transition

Motivated by a recent investigation of Millar and McKay [Director orientation of a twisted nematic under the influence of an in-plane magnetic field. Mol. Cryst. Liq. Cryst435, 277/[937]–286/[946] (2005)], we study the magnetic field twist-Fréedericksz transition for a nematic liquid crystal of positive diamagnetic anisotropy with strong anchoring and pre-twist boundary conditions. Despite the pre-twist, the system still possesses ℤ2 symmetry and a symmetry-breaking pitchfork bifurcation, which occurs at a critical magnetic-field strength that, as we prove, is above the threshold for the classical twist-Fréedericksz transition (which has no pre-twist). It was observed numerically by Millar and McKay that this instability occurs precisely at the point at which the ground-state solution loses its monotonicity (with respect to the position coordinate across the cell gap). We explain this surprising observation using a rigorous phase-space analysis.

scholarly journals Bifurcations analysis of the twist-Fréedericksz transition in a nematic liquid-crystal cell with pre-twist boundary conditions: the asymmetric case

2016 ◽  
Vol 28 (2) ◽  
pp. 243-260 ◽  
Author(s):  
FERNANDO P. DA COSTA ◽  
MARIA ISABEL MÉNDEZ ◽  
JOÃO T. PINTO
Keyword(s):  
Liquid Crystal ◽  
Boundary Conditions ◽  
Nematic Liquid Crystal ◽  
Dirichlet Condition ◽  
Liquid Crystal Cell ◽  
Phase Plane Analysis ◽  
Twist Boundary ◽  
Freedericksz Transition ◽  
Crystal Cell ◽  
Fréedericksz Transition

In the paper, Bifurcation analysis of the twist-Fréedericksz transition in a nematic liquid-crystal cell with pre-twist boundary conditions (2009 Eur. J. Appl. Math.20, 269–287) by da Costa et al. the twist-Fréedericksz transition in a nematic liquid-crystal one-dimensional cell of lenght L was studied, imposing an antisymmetric net twist Dirichlet condition at the cell boundaries. In the present paper, we extend that study to the more general case of net twist Dirichlet conditions without any kind of symmetry restrictions. We use phase-plane analysis tools and appropriately defined time maps to obtain the bifurcation diagrams of the model when L is the bifurcation parameter, and related these diagrams with the one in the antisymmetric situation. The stability of the bifurcating solutions is investigated by applying the method of Maginu (1978 J. Math. Anal. Appl.63, 224–243).

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