Dark and gray solitons in nematic liquid crystals

The dark and gray solitons in nematic liquid crystals with defocusing nonlinearities were theoretically analyzed by a variational approach. It was found that the nonlocal nonlinearity drastically affects the width of the dark and gray solitons and also affects the velocity of the gray solitons. Our results also show that an increase of the degree of nonlocality leads to a decrease of the soliton width in the weakly nonlocal limit, while nonlocality has the opposite effect in the nonlocal limit.