Fluids close to two-dimensionality
Prof. i.R. Rolf Schilling (Johannes Gutenberg-Universität Mainz)

Confined fluids allow to approach the two-dimensional limit by decreasing the confinement length. For a strongly confined fluid in slit geometry with accessible width L and 2D number density n the transversal degrees of freedom can be eliminated, leading to an effective 2D fluid and a shift of a 2D phase transition point by order L². We prove that the influence of the transversal degrees of freedom on the 2D behavior can systematically be elaborated by a thermodynamic perturbation theory with nL² as smallness parameter. The leading order corrections of thermodynamic and structural quantities are calculated analytically and discussed. We also study the dynamics which simplifies for L → 0 since the transversal degrees of freedom decouple and become Knudsen-gas-like.