Science

Present pictorial means of distinguishing contravariant vectors (or simply vectors) from covariant vectors (or linear forms). By Bernard Jancewicz (University of Wroclaw).

Mathematica notebook showing how to plot light cones in two plus one spacetime dimensions with a point mass. By Patricia Schwarz.

Introductory article by Gerhard Schäfer (Jena University) about the ways that rotating bodies affect spacetime (and hence the propagation of light and particles in free fall) in their vicinity.

E-print which presents the exact solution for the stress-energy tensor of a spherical matter shell of finite thickness that will patch together different metrics at the boundaries of the shell. By David Waite.