DEATH OF COSMOLOGICAL WHITE HOLES

We reexamine Eardley's analysis of the death of white holes, which sho ws that, due to the accretion of ambient matter, a white hole ceases t o radiate significantly after a time scale comparable to its mass. Whi le Eardley only vaguely provided the meaning of such a time scale, we give a precise, operational definition for the lifetime of white holes . Our expression for this lifetime is compatible with Eardley's estima te. We also show that while the present-day observation of a white-hol e explosion is very unlikely if the white hole is relatively close by, the prospect for such an observation is much enhanced if the white ho le is located at high cosmological redshifts.