Helical defects in smectic-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>A</mml:mi></mml:math>and smectic-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mi>A</mml:mi><mml:mo>∗</mml:mo></mml:msup></mml:mrow></mml:math>phases
Physical review. E, Statistical, nonlinear and soft matter physics