[pdonis]

> A black hole at the center of a gaseous body would mess with the fusion cycle would it not?

Not necessarily. That's the sort of question the paper investigates, and it finds models for which fusion can continue in the star's core for an extended period of time.

> There’s no pressurized core at the center.

Yes, there is, because, as I noted, the matter falling into the hole radiates strongly, and the radiation has pressure.

[hinkley]

How do you capture a PBH unless there’s substantial, fast mass (momentum) transfer from the star to the black hole? Otherwise the ballistic trajectory would carry it out and through. Wouldn’t you be more likely to find a PBH orbiting a main sequence star? Or gone altogether?

[hinkley]

It came to me while doing some housework that this feels like “what if the moon crashed into the earth?” The moon cannot crash into the earth. Any alien that could make that happen would be so terrifyingly powerful they wouldn’t have to crash the moon into the earth. It would be the twentieth most interesting way to doom us. Tidal waves would be easier.

[pdonis]

While your statement about the ballistic trajectory is true in the short term, over longer time scales (my off the cuff guess is thousands of years, much shorter than the time scale covered by the numerical simulations in the paper), there will be momentum transfer due to the PBH perturbing the star's matter as it passes through, and the PBH will settle into the center of the star if there are no other perturbations (i.e., no other massive bodies near enough to affect the process). The paper doesn't discuss the capture process in any detail, but I suspect that something like that is what they have in mind.

[pointlessone]

I thought infalling matter radiates because of friction in accretion disc. Does a similar structure form in a much denser interior of a star?

[pdonis]

Matter falling into a spinning black hole surrounded mostly by vacuum forms an accretion disc. But friction and heating and radiation will occur in infalling matter no matter how it is falling in. A black hole inside a star would probably not just have an accretion disc, it would have accretion happening in all directions. But the accretion would still involve friction and heating and radiation.

[hinkley]

Would there be a disk at the center of a star? Not a lot of angular momentum there.