question about black holes

[Puki]

In the OA universe, can a wormhole that collapsed into a black hole be turned back into a wormhole?

In principle, yes. In practice, meaning within the known technological capabilities of the Terragen archailects - no.  From the reference paper titled Wormhole Engineering in Orion's Arm: An Overview - written by Adam Getchell a physicist and the 'inventor' of OA's wormholes:

A wormhole can be constructed from a Schwarzschild black hole, if sufficient quantities
of phantom radiation exist. This process involves symmetric, precisely timed imploding pulses of
pure radiation with negative energy density, and is essentially the reverse process of wormhole
collapse to a black hole. Since the resulting wormhole throat is smaller than the Schwarzschild
radius, the collapse process involves at least 70% of the mass of the wormhole radiating away,
and the pulses must be nearly infinitely thin and precisely timed, this method of wormhole
construction is not believed to be feasible without enormous quantities of inflaton or axion fields
and exceptional computational ability. Nevertheless, this technique is widely studied for the
insights it gives to the stability problem.
Requests for interviews with transapient wormhole architects went unanswered, and
various Hider clans reputedly capable of spacetime engineering remain unavailable. Some
researchers have also noted extremely large energy signatures in intergalactic regions where
phantom energy densities would be expected to be large.

Note that - even if this were possible for Terragens, the resulting wormhole would probably not be a 'repaired connection' between the two points that the original WH connected, but just be a new wormhole/pair of WH mouths that would then have to be transported in the normal way to connect to two points. That kind of 'projecting a wormhole to where you want to go' effect doesn't appear to be possible for wormholes in the RL per existing theories and therefore isn't possible in OA.

Hope this helps,

Todd

In OA, can the Hider Clans do spacetime engineering? Where would they get the technologies and minds required to do things like that?

-Puki