We present extensions to the GRJunction computer algebra program, which allow the study of null boundary surfaces and thin shells in general relativity. We summarize the null formalism due to Barrabès and Israel and highlight those steps which differ from the timelike/spacelike cases. GRJunction has been used to verify a number of results from the literature. We then present two new results cal...

We present strongly stable finite difference approximations to the quarter space problem (x > 0, t > 0) for the first order in time, second order in space wave equation with a shift term. We consider space-like (pure outflow) and time-like boundaries, with either second or fourth order accuracy. These discrete boundary conditions are a first step for the construction of stable finite difference...

INTRODUCTION: Skeletal metastases frequently occur in patients suffering from breast cancer, the spine being the most common site. An improved survival rate of breast cancer has led to a rise in the incidence of skeletal metastases, resulting in serious morbidity (e.g. collapsed vertebrae) and a marked decrease in quality of life. The management of spinal metastatic lesions currently involves i...

* Graduate Student in Finance, University of Alberta School of Business, Edmonton, Alberta, Canada, T6G 2R6. Email [email protected]. ** Stephen A. Jarislowsky Distinguished Professor of Finance, School of Business, University of Alberta, Edmonton, Alberta, Canada, T6G 2R6.Tel: (780) 492-5683. E-mail [email protected]; Research Associate, National Bureau of Economic Research, 1050 Massach...

This work was supported by ESPRIT Basic Research Action P3020 \Integration", by CICYT under grant TIC 91-0425, and by \Progetto Finalizzato Sistemi Informatici e Calcolo Parallelo of C.N.R." under grant n.9100880.PF69 Departamento de Sistemas Inform aticos y Computaci on, Universidad Polit ecnica de Valencia, Camino de Vera s/n, Apdo. 22012, 46020 Valencia, Spain. Dipartimento di Informatica, U...