The last days I was at the conference Strangeness in Quark Matter, which was strange indeed. It was nice to meet all the people, and surprising how many I knew. Walter Greiner's 70iest birthday was an occasion to tell some funny stories. As so often, I got the impression that the Heavy Ion community is actually a large family, where people stick together even though they can not stand each other, and bad habits get passed on to the next generation.
Anyway, before I begin to wonder why I kicked myself out of the field, let me come to the reason of this post. My PhD adviser Horst gave a talk about Black Hole production at the collider. I had an earlier post 'Risky Black Holes' where I told you about the governmental guy who was concerned about the danger of Black Hole production at the LHC. He wrote back several times, asking for exact probabilities for every possible scenario, and circled around the question what probability to destroy the whole planet when LHC is switched on is acceptable? 0.001% ? 0.000000000000000000000000001 % ?
Also, last week I received an email from a guy writing for a German newspaper who apparently is about to plan an article about extra dimensions and black holes for the Sunday edition.
Some of you might know that the reasons I worked on black holes are quite obscure, and that I repeat at least twice a year that I don't want to work on it any more. What's so complicated about quitting is that the interest in the topic is so large! Black holes always make a good topic at BBQs, and everyone thinks he has something to say about extra dimensions. Even though I appreciate the discussion, I can't avoid having the impression that the scientific content is in most cases entertaining but doubtful. E.g. I learned that cosmic rays are black holes that are created on our brane, then go into the extra-dimensions, grow there, then come back to our brane and make an ultra high energetic cosmic ray. Sounds exciting, huh? But is that scientific?
So here is a quite general statements:
If the Hierarchy problem (the gap between the Elektroweak and the Planck scale) is only an apparent problem and the Planck scale is much lower, then black hole production is one of the most general predictions that we can make about what is going to happen. The assumptions are plain and simple, too much energy in too little space leads to a collapse.
However, though we think we know how the Hawking radiation looks like, we have no idea what the final decay looks like. Therefore, most details of the black hole's signature are strongly model dependent and should be treated carefully.
In addition to this, the required models with extra dimensions are not really understood, esp. regarding the stabilization, the evolution in the early universe (or time dependence in general), and at least I don't feel comfortable with the mechanisms to confine particles to the brane. Also, extra dimensions are surely not a theory of everything, so there should be more about it.
This is not to say that one should not investigate speculative ideas, just that one should try to stay as close as possible to reliable assumptions. I don't think there is any point in examining weird and even weirder scenarios on shaky ground. That's nice for a BBQ party but not really scientific.