On spacetimes dual to spherically symmetric solutions

By defining a duality transformation which implies interchange of active and passive electric parts of gravitational field, it is possible to construct spacetimes dual to solutions of the Einstein equation. Under the duality transformation a fluid spacetime maps into a fluid spacetime with density and pressure transforming as ρ→ (ρ + 3p)/2 andp → (ρ -p)/2. On the other hand a vacuum solution will acquire a global monopole charge. The remarkable feature of spherically symmetric solutions is that it is possible to give a general prescription for writing dual solutions. We demonstrate its application by writing dual solutions to the McVittie solution for a Schwarzschild particle in an expanding universe and to Vaidya’s radiating star solution.