Starship Asterisk*

The lecture video is embedded below.

Additionally, slides used in the lecture are embedded below, or can also be downloaded directly from here.

Questions after the lecture? Please feel free to post them in the same thread.




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Can a graviton (which is still not prooved to exist) have a negative mass?
Theoretically, of course.

If they exist, gravitons would have to have zero rest mass.

I think that since gravitons need to be able to travel FTL to escape a black hole (or, more generally, an event horizon), they possess "imaginary mass" as mentioned briefly in the lecture.

So, they should be some kind of tachyons, right?

A "real" graviton in general relativity cannot escape from a black hole. It travels at light speed and therefore has insufficient velocity. The problem is avoided by recourse to virtual gravitons. A virtual graviton can travel at any speed.

The same "loophole" applies to the interaction of a charged black hole with its surroundings. Virtual photons mediate the electromagnetic force and they can escape the black hole. Thus a charged black hole does "express" this charge in its environment.