Theory of monolayers with boundaries: exact results and perturbative analysis

Domains and bubbles in tilted phases of Langmuir monolayers contain a class of textures known as boojums. The boundaries of such domains and bubbles may display either cusplike features or indentations. We derive analytic expressions for the textures within domains and surrounding bubbles, and for the shapes of the boundaries of these regions. The derivation is perturbative in the deviation of the bounding curve from a circle. This method is not expected to be accurate when the boundary suffers large distortions, but it does provide important clues with regard to the influence of various energetic terms on the order-parameter texture and the shape of the domain or bubble bounding curve. We also look into the effects of thermal fluctuations, which include a sample-size-dependent effective line tension.