Scaling of Confined 4He at the Superfluid Transition

4He at the superfluid transition has been well studied and has yielded valuable checks on aspects of critical behavior ranging from scaling, universality and explicit predictions of critical exponents and amplitude ratios. The most detailed results have been obtained in the thermodynamic limit, i.e., in situations where the smallest confining dimension for the helium sample is much larger than the magnitude of the critical correlation length, ξ. Since this length diverges at the transition, there are many experimental realizations, such as helium films or helium confined in pores, where the effect of confinement to dimensions comparable to ξ manifests itself as a modification of the properties realized in the thermodynamic limit, or as completely new behavior associated with a lower spacial dimension.