title: Critical scaling properties at the superfluid transition of 4He in aerogel.
abstract: We study the superfluid transition of 4He in aerogel by Monte Carlo simulations and finite size scaling analysis. Aerogel is a highly porous silica glass, which we model by a diffusion limited cluster aggregation model. The superfluid is modeled by a three dimensional XY model, with excluded bonds to sites on the aerogel cluster. We obtain the correlation length exponent nu=0.73+/-0.02, in reasonable agreement with experiments and with previous simulations. For the heat capacity exponent alpha, both experiments and previous simulations suggest deviations from the Josephson hyperscaling relation alpha=2-dnu. In contrast, our Monte Carlo results support hyperscaling with alpha=-0.2+/-0.05. We suggest a reinterpretation of the experiments, which avoids scaling violations and is consistent with our simulation results.
authors.affiliation: Department of Theoretical Physics, Royal Institute of Technology, AlbaNova, SE-106 91 Stockholm, Sweden.
authors.forename: Marios
authors.initials: M
authors.lastname: Nikolaou
authors.forename: Mats
authors.initials: M
authors.lastname: Wallin
authors.forename: Hans
authors.initials: H
authors.lastname: Weber