Mexican Hat Gravitational Lenses (2007)
Paul Haines Waseda, Paul Haines, Deon Solomons
The mexican hat function is used to model a compensated (in density) gravitational lens. First we discuss the need for compensation. Then we integrate photon orbits to construct wavefronts. One...
Bounce Conditions in f(R) Cosmologies (2005)
Carloni, Sante, Dunsby, Peter K. S., Solomons, Deon
We investigate the conditions for a bounce to occur in Friedmann-Robertson-Walker cosmologies for the class of fourth order gravity theories. The general bounce criterion is determined and...
Bounce behaviour in Kantowski-Sachs and Bianchi Cosmologies (2001)
Solomons, Deon, Dunsby, Peter, Ellis, George
Many cosmological scenarios envisage either a bounce of the universe at early times, or collapse of matter locally to form a black hole which re-expands into a new expanding universe region. Energy...
Exact Inflation Braneworlds (2001)
Solomons, Deon, Dunsby, Peter, Ellis, George
In Randall-Sundrum type braneworld cosmologies, the dynamical equations on the three-brane differ from the general relativity equations by terms that carry the effects of embedding and of the free...