Brane cosmology and naked singularities

Brane-world singularities are analysed, emphasizing the case of supergravit y in singular spaces where the singularity puzzle is naturally resolved. Th ese naked singularities are either time-like or null, corresponding to the finite or infinite amount of conformal time that massless particles take in order to reach them. Quantum mechanically we show that the brane-world nak ed singularities are inconsistent. Indeed we find that time-like singularit ies are not wave-regular, so the time-evolution of wave packets is not uniq uely defined in their vicinity, while null singularities absorb incoming ra diation. Finally, we stress that for supergravity in singular spaces there is a topological obstruction, whereby naked singularities are necessarily s creened off by the second boundary brane. (C) 2001 Elsevier Science B.V. Al l rights reserved.