Van der Waals forces between cylinders. I. Nonretarded forces between thin isotropic rods and finite size corrections

The free energy of interaction of two long thin dielectric cylinders is evaluated in the nonretarded limit by the method of van Kampen. The result includes all nonadditive many body forces and the effects of an intervening medium. In the limit of dilute systems the result reduces to that obtained by summation of r(-6) pair potentials.