This paper shows that the mass-sheet degeneracy and other degeneracies in lensing have simple geometrical interpretations: they are mostly rescalings of the arrival-time surface. Different degeneracies appear in Local Group lensing and in cosmological lensing, because in the former the absolute magnification is measured but the image structure is not resolved, whereas in the latter the reverse ...

The accelerating expansion of the universe suggests that an unknown component with strongly negative pressure, called dark energy, currently dominates the dynamics of the universe. Such a component makes up ;70% of the energy density of the universe yet has not been predicted by the standard model of particle physics. The best method for exploring the nature of this dark energy is to map the re...

The Olivetti Research Laboratory has developed an experimental system based on intelligent peripherals connected directly to an ATM network. As well as multimedia modules (e.g. audio and video) the system also includes a directly connected RAID-3 storage server called the “Disc Brick”. This paper describes the architecture of the Disc Brick, and discusses some of the hardware and software issue...

In this paper, we propose SiLo, a novel energy efficient shifted logging storage architecture, for write-oriented workloads. By organizing free storage space of redundant mirrored disks in a RAID10 system into a logical logging space pool and shifting logger among different mirrored disk pairs, only one or few mirrored disk pairs are used as the on-duty logger at a time and all the other off-du...

In a classical Symbolic Perturbation scheme, degeneracies are handled by substituting some polynomials in ε for the inputs of a predicate. Instead of a single perturbation, we propose to use a sequence of (simpler) perturbations. Moreover, we look at their effects geometrically instead of algebraically; this allows us to tackle cases that were not tractable with the classical algebraic approach...

We prove sharp L estimates for oscillatory integral and Fourier integral operators for which the associated canonical relation C ⊂ T ∗ΩL × T ∗ΩR projects to T ∗ΩL and to T ∗ΩR with corank one singularities of type ≤ 2. This includes two-sided cusp singularities. Applications are given to operators with one-sided swallowtail singularities such as restricted X-ray transforms for well-curved line ...

We show that in the worst case, (n d) sidedness queries are required to determine whether a set of n points in IR d is aanely degenerate, i.e., whether it contains d + 1 points on a common hyperplane. This matches known upper bounds. We give a straightforward adversary argument, based on the explicit construction of a point set containing (n d) \collapsible" simplices, any one of which can be m...