Monday, April 03, 2006

Mini Black Holes

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.


  1. 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.

    BTW, I have found "the source" of this story, it is mentioned in a recent book by some Stephen Webb,
    Out of This World: Colliding Universes, Branes, Strings, and Other Wild Ideas of Modern Physics, on page 262 - in case your amazon "look inside" works, it is the 9th hit when searching for "cosmic rays"; that is how I have found it.

    That book, from the table of contents, treats an amazingly wide range of topics, including M theory and the holographic principle. I always wanted to understand what this AdS/CFT/holography stuff is all about. Maybe I should try to read it ;-)...

  2. Hi Uli,

    yes, it is definitely rewarding! That is why I DON'T quit doing the black hole stuff. I also think its in general a good thing to communicate the stuff I am doing to other people, physicists or not. Not so much to advertise it, but because it actually is inspiring and feedback is always useful.

    As far as I know black holes were originally named 'frozen stars', which sounds more poetic (but would have spoiled our joke with the black holes in the governmental budget for the xmas-party movie...).

    Stefan, thanks for the book info. I ordered the book at amazon to see how bad it is... Will let you know.

    Uli, BTW, have a look at Lisa Randall's book, its really nice and says something about black holes as well.



  3. Stefan, thanks for the book info. I ordered the book at amazon to see how bad it is...

    Why do you assume it is bad?

  4. Seems the amazon package arrived already last week. I put it on my fridge and forgot it. Still have not read the book, sorry, no news.

    So, I can't tell whether its good or bad, that's why I want to have a look at it. From what I have heard so far, it seems to be very speculative. Though I would say I am fairly open minded for new ideas, I don't think its so good to mix up serious research with weird ideas in popular science books. The avergage reader won't be able to tell the difference.

  5. just think about how much energy it takes to run the LHC...

  6. Micro Blackholes

    Walter there is more on this topic by Bee there.


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