Re: How could extra dimensions be tested?
- From: Lester Zick <dontbother@xxxxxxxxxxx>
- Date: Sat, 31 Mar 2007 19:25:03 -0700
On 30 Mar 2007 18:49:49 -0700, "nuny@xxxxxxxx" <Alien8752@xxxxxxxxx>
wrote:
On Mar 30, 10:34 am, Lester Zick <dontbot...@xxxxxxxxxxx> wrote:
On 29 Mar 2007 20:42:21 -0700, "n...@xxxxxxxx" <Alien8...@xxxxxxxxx>
wrote:
On Mar 29, 7:30 pm, Lester Zick <dontbot...@xxxxxxxxxxx> wrote:
On Thu, 29 Mar 2007 23:16:14 +0000 (UTC),
carlip-nos...@xxxxxxxxxxxxxxxxxxx wrote:
STJensen <RecreationalPo...@xxxxxxxxx> wrote:
I hear about lower and higher dimensions, but I wonder if any
scientist is currently trying to come up with a way to see if they
exist. Is anyone? If so, who and how? If not, what do scientists
speculate such a test might involve?
There's an *enormous* amount of work on this. For example, the
1999 paper by Lisa Randall and Raman Sundrum that triggered much
of the current interest is referred to by 762 papers listed as
"experimental" in the Spires database. You can go to Spires at
http://www.slac.stanford.edu/spires/hep/andlook for these
yourself.
For example, some recent review papers:
-- many theories with extra dimensions predict that black holes
could be created at particle accelerators; see, for example,
http://arxiv.org/abs/hep-ph/0702187forhow to test this.
-- many theories with extra dimensions predict new phenomena in
particle physics coming from new "Kaluza-Klein" particles
that appear because particles can have momentum in the new
dimensions; see, for examplehttp://arxiv.org/abs/hep-ph/0510418.
-- many theories with extra dimensions predict deviations from
the inverse square law for gravity at short distances; for
current tests, seehttp://arxiv.org/abs/hep-ph/0307284.
-- many theories with extra dimensions predict observations that
can look like nonconservation of momentum, from gravitons
carrying momentum away into the extra dimensions; see, for
example,http://arxiv.org/abs/hep-ex/0105039.
For a review specifically directed towards particle physics tests,
go to the Particle Data Book (http://pdg.lbl.gov/), the standard
reference for the field, and under "Reviews, Tables, and Plots"
find the pdf file "Extra Dimensions."
These are fairly technical sources. If you want something less
technical, you could start with Randall's book, _Warped Passages_.
You could also look at, for example,
http://d0server1.fnal.gov/users/gll/public/edpublic.htm
http://physicsweb.org/articles/world/13/11/9
http://www.symmetrymagazine.org/cms/?pid=1000237
http://focus.aps.org/story/v3/st15
http://www.stanford.edu/group/kgb/Research/gravity2.html
You can find plenty of others with a few minutes on google.
Are there any experimental tests for whether higher dimensions than
three are even mathematically possible?
Do you read what you write?
No. I can't stand rereading the obvious.
If they can be empirically shown to
exist physically mathematicians will just have to accept them as
reality. If they are not empirically shown to exist, one of two
situations obtains:
1) the experiments were not exhaustive and new experiments will be
devised, in which case the mathematicians may carry on as they will,
or
2) the experiments were exhaustive and the mathematicians will have to
do a lot of blackboard-erasing.
Hey, Mark, it's good to hear from you after several years. Too bad you
weren't a participant in my threads on gravitational doppler and takin
out the trash. I could have used your level headed perspective.
So many posts, so little time. ;>)
I don't know many (read any) experiments that are exhaustive. The
point is experiments are never exhaustive. If they were we wouldn't
have to do them except to confirm what we already understand.
They can indeed confirm what we _think_ we already understand, or we
can get surprises. The actual point is to devise experiments that have
a chance of providing unambiguous results. Some of the experiments
referenced above have indeed disproved the possibility of certain size
ranges of compactified dimensions, and others will explore the
remaining ranges. Note that the mathematical theories that used those
empirically disproved dimensions are _still mathematically valid_
because they're self-consistent.
Hmmmm. So as long as we can add 1 to exponents we're ok?
As for extended dimensions, string theorists postulate them but
AFAIK have no solid ideas how to test for them.
We do have three extended physical dimenions postulated from
Euclid's human-sensorium-level experience, but over the last couple
millennia we've come to understand that our senses are pitifully
inadequate.
Mathematically, there's no good reason to assume any number of
dimensions other than what we think we see. Nor is there any good
reason to not assume any number of dimensions; there's nothing that
says we can see all there is to see which is what string theorists
say.
Well mathematically there's no good reason to assume or not assume
anything we feel like assuming or not. Personally I prefer to assume
things that are true.
Mathematical axioms are just empirical assumptions and subject to
experimental verification just like any other empirical assumption. If
higher dimensions are mathematically possible we should be able to
confirm that experimentally and if not we should dismiss them both
mathematically and physically.
The words "axiom" and "empirical" are about as close to opposites as
is possible. Axioms are assumptions made in order to have something to
work with; empiricals are what we see.
Axioms are assumptions we assume and empiricals are assumptions we
assume we see. Close enough for government work I expect.
You may be conflating them because Euclid liked right angles and
divided the visible world that way. BTW, note the same root in
"dimension" and "divide".
Mathematically any number of dimesnions are "possible" as long as
the system that includes them works out consistently regardless of
whether it matches reality. Physically, IOW empirically, a given claim
as to how many dimensions exist must be tested against reality. At
some point empiricism demonstrates that beautifully self-consistent
classes of theories do not apply to reality despite their
_mathematical_ validity.
Sorry I asked.
~v~~
.
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