From Osher Doctorow

Wikipedia (I haven't examined Wolfram on this) doesn't do a great job
on White Holes, but that's not surprising since the literature is so
disorganized and the topic is filled with "bugaboos" and "tabus".

White holes actually have a "respectable" background and have been
studied by Linde of Stanford, Strominger (motivated by Hawking),
Thorne of CalTech, and others. Not everybody who studies them even is
talking about the same thing, though they do have in common an outward
direction rather than an inward direction (the latter toward the
singularity).

A rather curious thing does happen to physicists who study White holes
when and if (as with those mentioned above) they make important non-
White-hole discoveries. In that case, they tend to forget White
holes. This isn't too surprising because, like tachyons and
monopoles, White holes have more theoretical interest than present-day
empirical data.

I should mention than Andrei Linde's main paper on white holes was
with Renata Kallosh (1995), "Exact supersymmetric massive and massless
white holes," hep-th/9507022 v3 10 Dec 1995, 18 pages, and that Linde
has 108 papers in arXiv while Kallosh has 128 papers there (many with
Linde). As readers might begin to expect in this type of field, the
Kallosh-Linde 1995 White hole paper has a quadratic orientation or
rational function of quadratics or ratio of functions of quadratics.

Osher Doctorow