The application of speckle interferometry to infra-red astronomy

Imperial Users onl

Actions of higher-rank lattices on free groups

If $G$ is a semisimple Lie group of real rank at least 2 and $\Gamma$ is an irreducible lattice in $G$, then every homomorphism from $\Gamma$ to the outer automorphism group of a finitely generated free group has finite image.Comment: 11 pages, no figures. Final version. To appear in Compositio Mat

Convergence in a multidimensional randomized Keynesian beauty contest

We study the asymptotics of a Markovian system of $N \geq 3$ particles in $[0,1]^d$ in which, at each step in discrete time, the particle farthest from the current centre of mass is removed and replaced by an independent $U [0,1]^d$ random particle. We show that the limiting configuration contains $N-1$ coincident particles at a random location $\xi_N \in [0,1]^d$. A key tool in the analysis is a Lyapunov function based on the squared radius of gyration (sum of squared distances) of the points. For d=1 we give additional results on the distribution of the limit $\xi_N$, showing, among other things, that it gives positive probability to any nonempty interval subset of $[0,1]$, and giving a reasonably explicit description in the smallest nontrivial case, N=3.Comment: 26 pages, 4 figure

A comparison of methods for mapping golf greens

Several golf greens were mapped using a RTK GPS, Riegl 3D-Laser Mirror Scanner and Trimble S6 Robotic Total Station systems to determine the most appropriate method for this task. The RTK GPS was the easiest methods for data capture but was insufficiently accurate for mapping at a contour interval of 0.05 m or less in this situation. The laser scanner level data accuracy was slightly more accurate than the robotic total station but both produces results that were suitable for golf green mapping. However, the ease of use of the robotic total station determined this as the preferred methodology for golf green mapping with a 0.05m contour interval

The Douglas-Peucker line simplification algorithm : an introduction with programs

CISRG discussion paper ;