Fluids close to two-dimensionality
R. Dr. Rolf Schilling (Institut für Physik, Uni 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 \(L^2\). 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 \(nL^2\) 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 \(L\to 0\) since the transversal degrees of freedom decouple and become Knudsen-gas-like.