TY - UNPB

T1 - A Renormalized Newton Method for Liquid Crystal Director Modeling

AU - Gartland, Jr, Eugene C.

AU - Ramage, Alison

N1 - This item has been published inthe SIAM Journal of Numerical Analysis (Vol. 53 No. 1, 2015) in a shortened version, plus supplementary material. This research report contains the same material in a single document.

PY - 2014/12

Y1 - 2014/12

N2 - We consider the nonlinear systems of equations that result from discretizations of a prototype variational model for the equilibrium director field characterizing the orientational properties of a liquid crystal material. In the presence of pointwise unit-vector constraints and coupled electric fields, the numerical solution of such equations by Lagrange-Newton methods leads to linear systems with a double saddle-point form, for which we have previously proposed a preconditioned nullspace method as an effective solver [A. Ramage and E. C. Gartland, Jr., SIAM J. Sci. Comput., 35 (2013), pp. B226–B247]. Here we propose and analyze a modified outer iteration ("Renormalized Newton Method") in which the orientation variables are normalized onto the constraint manifold at each iterative step. This scheme takes advantage of the special structure of these problems, and we prove that it is locally quadratically convergent. The Renormalized Newton Method bears some resemblance to the Truncated Newton Method of computational micromagnetics, and we compare and contrast the two. This brings to light some anomalies of the Truncated Newton Method.

AB - We consider the nonlinear systems of equations that result from discretizations of a prototype variational model for the equilibrium director field characterizing the orientational properties of a liquid crystal material. In the presence of pointwise unit-vector constraints and coupled electric fields, the numerical solution of such equations by Lagrange-Newton methods leads to linear systems with a double saddle-point form, for which we have previously proposed a preconditioned nullspace method as an effective solver [A. Ramage and E. C. Gartland, Jr., SIAM J. Sci. Comput., 35 (2013), pp. B226–B247]. Here we propose and analyze a modified outer iteration ("Renormalized Newton Method") in which the orientation variables are normalized onto the constraint manifold at each iterative step. This scheme takes advantage of the special structure of these problems, and we prove that it is locally quadratically convergent. The Renormalized Newton Method bears some resemblance to the Truncated Newton Method of computational micromagnetics, and we compare and contrast the two. This brings to light some anomalies of the Truncated Newton Method.

KW - liquid crystals

KW - director models

KW - unit-vector constraints

KW - saddle-point problems

KW - reduced hessian method

KW - renormalized newton method

UR - http://www.strath.ac.uk/mathstat/research/researchreports/

M3 - Working paper

SP - 1

EP - 27

BT - A Renormalized Newton Method for Liquid Crystal Director Modeling

PB - University of Strathclyde

CY - Glasgow

ER -