This paper considers an alternative to black holes, gravastars, in which different types of spacetimes are glued together with appropriate junction conditions. One nice feature is that gravastars do not need to involve event horizons.
The topic is mathematically rather opaque and not within my expertise by a stretch. It deserves a mention for the spelling mistake ‘cut and past technique’ which appears twice in this paper.
Best accidental pun in an academic paper award!
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