What fun! Today I get to post about my two favourite subjects one after the other.
This link will lead you to a fairly lengthy review of issues around the possible production of black holes at the Large Hadron Collider at CERN. It's by physicist Greg Landsberg, to whom I give some credit for actually answering some emails sent to him by James Blodgett, the author of the Risk Evaluation Forum site (see link in my blogroll.) Blodgett's site got me interested in this whole topic.
Landsberg does not think there is anything to Blodgett's concerns, but at least he was respectful in his answers.
Anyway, Landsberg's article above is interesting in several respects:
1. He confirms clearly that Hawking Radiation is never going to be observed directly at astronomical distances (it is far too weak - see pages 8 to 9.)
2. The entire article makes it clear how many different ideas there are about what exactly would happen in the decay process of a micro black hole.
3. Landsberg notes this:
Given the current lower constraints on the fundamental Planck scale in the model with large extra dimensions of ≈ 1 TeV [8], the black holes that we may be able to study at colliders and in cosmic rays will be barely transplanckian. Hence, the unknown quantum corrections to their classical properties are expected to be large, and therefore it is reasonable to focus only on the most robust properties of these mini black holes that are expected to be affected the least by unknown quantum gravity corrections.
Later, he writes:
In quantum gravity, it is expected that there is a fourth, Planckian stage of black hole evaporation, which is reached when the mass of the evaporating black hole approaches the Planck scale. The details of the Planckian stage are completely unknown, as they are governed by the effects of quantum gravity, which should be dominant at such low black hole masses. Some authors speculate that the Planckian stage terminates with a formation of a stable or semi-stable black hole remnant with the mass ∼ MPl. Others argue that the evaporation proceeds until the entire mass of the black hole is radiated. The truth is that no predictions about the Planckian regime are possible, given our lack of knowledge of quantum gravity.
This has been said before: I just thought that it is nice to see such a blunt and direct statement of ignorance.
4. Despite this, Landsberg expresses no doubts at all about Hawking Radiation applying to micro black holes. (It is expected to occur before the black hole reaches Planckian scale and its behaviour becomes guesswork.)
5. Landsberg notes that it has been suggested that instead of (or as well as?) mini black holes, the LHC could create other things such as string balls (don't ask me) or this:
Another possibility is a production of higher-dimensional objects, e.g. black p-branes, rather than spherically symmetric black holes (p = 0) [48].
First time I have heard of that. Did the safety review of the LHC take these into account?
6. The article appears optimistic on the possibility of the by products of naturally occurring mini black holes being detected in neutrino telescopes being built. If this is confirmed, then any of my concerns about Hawking Radiation not occurring would be gone.
7. Landsberg raises one point in such a way that I cannot understand whether it is a potential danger to the LHC or not. This is heavy going, and I refer the interested reader to section 10 of the paper on page on page 27. It seems to me that he may be saying that, on some models, it may be possible for a mini black to evaporate quickly with the equivalent energy of a few hundred pound bomb. This sounds dangerous to me, but as I say, I could be misunderstanding him here. (I would be happy to hear what other reader's think he means.)
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