  Hydrodynamical simulations of galaxy formation in spatially flat Cold Dark
Matter (CDM) cosmologies with and without a cosmological constant (Lambda) are
described. A simple star formation algorithm is employed and radiative cooling
is allowed only after redshift z=1 so that enough hot gas is available to form
large, rapidly rotating stellar discs if angular momentum is approximately
conserved during collapse. The specific angular momenta of the final galaxies
are found to be sensitive to the assumed background cosmology. This dependence
arises from the different angular momenta contained in the haloes at the epoch
when the gas begins to collapse and the inhomogeneity of the subsequent halo
evolution. In the Lambda-dominated cosmology, the ratio of stellar specific
angular momentum to that of the dark matter halo (measured at the virial
radius) has a median value of ~0.24 at z=0. The corresponding quantity for the
Lambda=0 cosmology is over 3 times lower. It is concluded that the observed
frequency and angular momenta of disc galaxies pose significant problems for
spatially flat CDM models with Lambda=0 but may be consistent with a
Lambda-dominated CDM universe.
