The incorporation of matter into characteristic numerical relativity

A code that implements Einstein equations in the characteristic formulation in 3D has been developed and thoroughly tested for the vacuum case. Here, we describe how to incorporate matter, in the form of a perfect fluid, into the code. The extended code has been written and validated in a number of cases. It is stable and capable of contributing towards an understanding of a number of problems in black hole astrophysics.Comment: 15 pages + 4 (eps) figure

Simple method for estimating the surface area of layered graphene-based thin films

Thin films, papers, or foils produced from graphene-based materials have been the focus of considerable research interest in recent years. They have a range of applications including energy storage, selective filtration of liquids, and gas storage. For all of these applications, the critical attribute of the films is their pore volume. However, there remains a considerable challenge around characterizing the accessible microscopic surface area of the materials in their intended state of application. In this work, an image-processing-based approach is presented for estimating the lower threshold of specific surface area for graphene-based films that have a typical multilayered structure. Canny edge detection is used together with tortuosity measurements to infer sheet areas from layer edges. The method serves as a simple independent characterization technique. Specific surface area values predicted for a range of similar films vary by less than 4× the reported values, which vary by >1.1×103 in range.Michael R. Horn, Fraser Williams, Deepak Dubal, Jennifer MacLeod, and Nunzio Mott