Detecting large extra dimensions via mini black holes ?

[Coin]

Detecting large extra dimensions via "mini black holes"?

Occasionally I come across something explaining that one of the
possible discoveries at the Large Hadron Collider might be the
production of "mini black holes", which if found would demonstrate the
existence of large extra dimensions. The idea, at least as I
understand it, is supposed to be that gravity in an more-than-four-
dimensional universe could be actually much stronger than we measure
it to be; but in a way that only has any effect over very small
distances, because the gravitons leak out into the extra dimensions if
given the chance. The "very small distances", if I'm understanding all
this right, could possibly be large enough that colliding particles at
a modern particle accelerator would be able to trigger the creation of
microscopic, short-lived black holes. The reason I usually see given
for why people are excited about this possibility is that it would
provide strong experimental support for string theory, by showing one
of string theory's more controversial elements-- extra dimensions-- to
be not just a theoretical convenience but actually a physical fact.

An example of a writing on this subject, picked at random from google,
might be:

http://cerncourier.com/cws/article/cern/29199
or:
http://quasar9.blogspot.com/2006/08/new-dimensions-at-lhc.html

The thing that confuses me about this, though, is the frequent
implication that this effect-- the effect that allows for mini black
hole production in particle accelerators, that is-- wouldn't exist in
all theories of more-than-four-dimensional spacetime, or even all
variations of string theory. It's usually left very vague, however,
*which* theories would or wouldn't produce this behavior. This seems
to make it very difficult to evaluate what the detection or non-
detection of these black holes at the LHC would or wouldn't be telling
us. So, I would like to ask:

** What attributes would a string theory have to have, in order for
the extra dimensions to be in principle detectable through black hole
production in a particle accelerator? The one thing everything I find
on this subject seems to agree on is that the spacetime which the
strings inhabit must have more than four non-compact dimensions, but
are there any *other* conditions which either the spacetime, or the
string theory acting within that spacetime, must satisfy for the "mini
black hole" production to be possible? **

I have a few slightly more specific versions of this question I'd also
like to ask, but I unfortunately do not know very much about String
Theory so I am not certain I know how to ask them correctly. So please
excuse me if the following turns out to be gibberish:

1. As far as I'm aware, the preeminent variation of string theory with
"large extra dimensions" would be the "brane cosmology" models, where
ALL 10 or 11 dimensions are taken to be arbitrarily large, but the
perceived universe is lower-dimensional because the movement of
strings is restricted to the surfaces of lower-dimensional "branes".
(I somehow got the impression that the string theories with compact
extra dimensions can be approximated within this model by folding the
branes properly, but I am not sure about this.) Within a model of
braneworld cosmology, is it possible to see mini-black-hole production
at a particle accelerator within some individual brane-world embedded
in the bulk? And if so, would the mini-black-hole effect be *required*
by the use of braneworld cosmology, or is it possible to design a
brane-world where the effect which results in the mini-black-holes
does not exist?

2. If the answer to the last question is "yes, but only in a model
with the correct circumstances", then is the mini-black-hole effect a
property of the theory which describes the branes, or is it only a
property of some individual brane-world described by that theory? In
other words, would it be possible for there to be a higher-dimensional
bulk, contained within which were BOTH brane-worlds which allow the
"mini black hole" production, and also brane-worlds which do not?

3. The specific large-extra-dimensions model I seem to hear about the
most is this Kachru-Kallosh-Linde-Trivedi, or KKLT, construction,
defined by the paper the arXiv has at hep-th/0301240. My *incredibly*
limited understanding of this construction is that it assumes a
braneworld cosmology model (i.e. all ten-ish dimensions are noncompact
but strings live on a lower-dimensional brane) and then describes a
way of configuring branes within the bulk so that you create a nice de
sitter space for the strings to live on. (I somehow got the impression
that the "string landscape" you sometimes hear about specifically
refers to all the different ways of configuring the KKLT construction,
but I am not sure about this.) Does use of the KKLT construction allow
the mini black holes effect to be present within a brane-world? Does
KKLT *require* the effect be present?

Thanks!

 

[AndyW]

Thank you for your question about detecting large extra dimensions through the production of mini black holes at the Large Hadron Collider (LHC). I can provide some insight into the attributes and conditions that would allow for this effect to be observed.

Firstly, it is important to note that the possibility of mini black hole production at the LHC is still a theoretical concept and has not been observed experimentally. It is based on certain models of string theory, which is a theoretical framework that attempts to reconcile the theories of gravity and quantum mechanics. In order for the extra dimensions to be detectable through black hole production at the LHC, the following conditions must be met:

1. The spacetime in which the strings exist must have more than four non-compact dimensions. This is a fundamental requirement for the existence of extra dimensions in string theory.

2. The string theory model must allow for the production of mini black holes at energies that can be achieved at the LHC. This is dependent on the specific parameters and equations of the theory.

3. The model must also allow for the mini black holes to be stable enough to be detected. In some models, the black holes may evaporate too quickly to be observed.

To answer your more specific questions:

1. In the "brane cosmology" models, the extra dimensions are taken to be arbitrarily large, but the perceived universe is lower-dimensional because the strings are restricted to the surfaces of lower-dimensional "branes". It is possible for these models to allow for mini black hole production at the LHC, but it is not a required feature of these models. It is possible to design a brane-world where the effect that results in mini black holes does not exist.

2. The mini black hole effect is a property of the theory that describes the branes. It is possible for there to be a higher-dimensional bulk with both brane-worlds that allow for mini black hole production and those that do not.

3. The KKLT construction is a specific model within string theory that describes a way of configuring branes within the bulk to create a de Sitter space (a type of expanding universe). The use of this construction does not necessarily require the mini black hole effect to be present, but it does allow for it to exist in certain configurations.

In conclusion, the detection of mini black holes at the LHC would provide strong evidence for the existence of large extra dimensions in string theory. However,

 

[sir-pinski]

First of all, it's important to note that the production of mini black holes at the Large Hadron Collider (LHC) is just one of many possible outcomes and discoveries that could occur. It is not the main goal or purpose of the LHC, but rather a potential byproduct of the high energy collisions that are happening there.

Now, to address your questions about the detection of large extra dimensions through mini black hole production:

1. In order for mini black holes to be produced at particle accelerators, the extra dimensions in the string theory model must be non-compact, meaning they are infinite in size. This is because in order for the gravitons to leak out into the extra dimensions and create a mini black hole, the dimensions must be large enough for the gravitons to travel through. So, if a string theory model has compact extra dimensions, it would not exhibit this mini black hole effect.

2. The mini black hole effect is a property of the theory that describes the branes, rather than an individual brane-world. So, if a theory allows for the production of mini black holes, any brane-world described by that theory would also exhibit this effect.

3. The KKLT construction is just one specific model within string theory, and it does not necessarily require the mini black hole effect to be present. However, it is possible for the KKLT model to allow for the production of mini black holes if the extra dimensions are non-compact. Other string theory models, such as brane cosmology, can also allow for the production of mini black holes if they have non-compact extra dimensions.

In conclusion, the detection of mini black holes at the LHC would provide strong evidence for the existence of large extra dimensions, but it would not necessarily prove string theory to be correct. Other theories, such as brane cosmology, can also allow for the production of mini black holes. Therefore, the detection of mini black holes would be a significant discovery, but it would not be a definitive confirmation of any particular theory.