ON THE ANALYSIS OF TWISTED DIRECTOR CONFIGURATIONS

A twist tensor (T-tensor) is introduced, which is defined for differen tiable vector and director fields. Its eigensystem describes the local helical structure of the underlying field. It can have up to two nonz ero eigenvalues, which indicate whether the local structure is untwist ed, helical or double-twisted. The eigenvalues q(i), if real valued, a re the helical wave numbers, and the corresponding eigenvectors repres ent the local twist axes. The T-tensor can serve as a tool to analyze director configurations in chiral nematic liquid crystals, and applica tions in computational fluid dynamics seem feasible.