Dresden 2017 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 11: Critical phenomena
DY 11.4: Talk
Monday, March 20, 2017, 16:15–16:30, HÜL 186
Ensemble dependence of the critical Casimir force — •Markus Gross1,2, Oleg Vasilyev1,2, Andrea Gambassi3, and Siegfried Dietrich1,2 — 1Max-Planck-Institut für Intelligente Systeme, Heisenbergstraße 3, 70569 Stuttgart, Germany — 2IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany — 3SISSA -- International School for Advanced Studies and INFN, via Bonomea 265, 34136 Trieste, Italy
Confining a near-critical fluid leads to critical Casimir forces acting on the boundaries. Critical Casimir forces have been studied so far in the grand canonical ensemble, in which the confined fluid exchanges particles with the surroundings. However, the canonical ensemble, in which the total number of particles in the confined fluid is fixed, is also relevant in certain circumstances. It is well-known that these ensembles are not equivalent in finite systems. This carries over to the critical Casimir force, which behaves significantly different in the two cases: for instance, for so-called (++) boundary conditions, the canonical force is repulsive instead of attractive and it decays algebraically instead of exponentially upon increasing the temperature scaling variable in the supercritical regime [1]. While these features can be rationalized within mean field theory, additional differences emerge upon accounting for fluctuations. These latter aspects are discussed within a statistical field theory in the canonical ensemble.
[1] M. Gross, O. Vasilyev, A. Gambassi, S. Dietrich, Phys. Rev. E 94, 022103 (2016)