  We study the specific heat scaling function of superfluids confined in cubic
geometry and in parallel-plate (film) geometry with open boundary conditions
(BC) along the finite dimensions using Monte Carlo simulation. For the case of
cubic geometry for the superfluid order parameter we apply open BC in all three
directions. We also calculated the specific heat scaling function for the
parallel-plate confinement using open BC along the finite dimension and
periodic BC along the other two dimensions and we find it to be very close to
the earlier calculated using Dirichlet instead of open BC. We find that the
specific heat scaling function is significantly different for the two different
geometries studied. In addition, we generally find that the scaling function
for a fixed given geometry when calculated with open BC is quite close to that
calculated with Dirichlet BC, while when calculated with periodic BC is quite
different. Our results for both the scaling functions obtained for the
parallel-plate geometry and for cubic geometry with open BC along the finite
dimensions are in very good agreement with the recent very high quality
experimental measurements with no free parameters.
