N-body simulations show that when infall reorientates the outer parts of a galactic halo by several degrees per Gyr, a self-gravitating disk that is embedded in the halo develops an integral-sign warp that is comparable in amplitude to observed warps. Studies of angular-momentum acquisition suggest that the required rate of halo reorientation is realistic for galaxies like the Milky Way.

In many distributed computations it is necessary to ensure that the causal order in which events occur (a partial order) conforms to a total order that is derived from a correctness constraint on the computation. For example, the events of a distributed simulation must appear to be processed in simulation-time order. The Time Warp mechanism [Jeflerson 841 uses the notion of global virtual time ...

Bridge sampling, a general formulation of the acceptance ratio method in physics for computing free-energy difference, is an effective Monte Carlo method for computing normalizingconstantsof probabilitymodels.The methodwas originallyproposedfor cases where the probabilitymodels have overlappingsupport. Voter proposed the idea of shifting physical systems before applying the acceptance ratio met...

Previous Work: Several prior algorithms attempt to provide a deformation-invariant distance measure. Tangent distance [2] uses a planar approximation to a local image manifold, allowing small spatial transformations to be modeled in pixel space. Because of the planar approximation, tangent distance does not work well for large deformations. The “shape context” method [1] is good at obtaining de...