Not Yet for Us: the Nascent Black Hole

Abstract

In the second half of the last century the "frozen star" or "collapsed star" models of black hole formation were largely abandoned. The result is that later models appear to either assume that black hole event horizons already exist (such as in Hawking's 1975 paper on radiation from black holes), bypass the relative frames altogether (such as in Mirabel's 2017 paper on the formation of stellar black holes), or use coordinate systems that essentially ignore the remote viewer's point of view (Kruskal 1960). This paper attempts to re-establish the concept of a "nascent black hole" as the correct approach for modelling black holes from remote reference frames. It uses, and only needs to use, Schwarzschild metrics and presents some example scenarios to demonstrate the concepts through worked examples. Alternatives such as Eddington-Finkelstein coordinates and Penrose's local collapsing frames are not disputed; the Schwarzschild metrics must still be valid outside the event horizon and this paper is largely concerned with "remote viewers" for various meanings of "remote". For most astrophysical or cosmological questions the difference between "actual" and "nascent" black holes is largely irrelevant as they behave similarly for most practical purposes. However the difference becomes critical for effects that require an event horizon to interact with the remote viewer, such as Hawking-Zel'dovich radiation and the related information problems outlined by Susskind. That is: if there are no possible observable paths from a nascent event horizon to any remote viewer then there also cannot be any evaporation to the remote viewer