Absence of hyperuniversality in critical films

Scaling density profiles O(N) symmetric systems confined between two parallel plates with a large separation L are analyzed by field-theoretical methods for a continuous phase transition at bulk criticality Tc,b in spatial dimension d=4-{ε}. At distances z{}L from one wall a the profile contains a perturbation Ba,b(z/L)ᵈ induced by the distant wall b. In contrast to previous expectations the ratio of the universal amplitude Ba,b and the corresponding Casimir amplitude is not hyperuniversal, i.e., not independent of both surface universality classes characterizing the walls a and b.