FLUCTUATION-INDUCED COUPLINGS BETWEEN DEFECT LINES OR PARTICLE CHAINS

One-dimensional structures such as defect lines or chains of dipolar particles are generally subject to strong Landau-Peierls thermal fluctuations. Coupling between these fluctuations in parallel lines may lead to an attractive force, analogous to the London force, or to a repulsive force of entropic origin. We analyze these forces for chains of electric dipoles and for flux lines in isotropic superconductors. In the first case the force is attractive, and can significantly change the Hamaker constant, which governs the attraction between colloidal particles. In the second case, over much of the magnetic field-temperature phase diagram the force is repulsive, and dominates over the direct repulsive interaction between flux lines.