# Experimental evidence that confirms or points toward extraspatial dims

#### Universe_Man

Is there any experimental evidence that confirms or points toward extra spatial dimensions? I have been looking around for a bit, couldn't find anything.

#### Severian

No there isn't. It is one of the things they will be looking for at the Large Hadron Collider, but so far all searches have been negative.

#### reasonmclucus

What do you mean by a "dimension". In the strict mathematical sense a "dimension" is a variable. A "physical dimension" would be a physical variable or characteristic.

One difficulty in dealing with the issue is that we are conditioned early in our education to believe that physical dimensions must be something like length, width and height. There is no logical reason that other physical characteristics cannot be dimensions. For example, force or energy characteristics are variables that could be treated as physical dimensions other than the 3 Euclidean dimensions. Gravity is an obvious characteristic that isn't consistent with length, width and height. The sun is larger than earth and has stronger gravity, but a black hole could be smaller than a basketball and still have much greater gravity.

#### arivero

Gold Member
Note the original posting asks for "spatial dimensions", not plainly "dimensions" or "spaces"

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#### arivero

Gold Member
Now, the closest thing to experimental evidence is that the representations 1+5+10 of SU(5), and thus the representation 16 of SO(10), can be built from five fermionic generators (an idea from Wilczek and Zee). One could argue if these five generator are related to at least five extra dimensions, but such argument has never been written down in a formal paper.

The next "experimental" argument is from Witten, who argued, around 1981-83, than the minimal space to incorporate an action of SU(3)xSU(2)xU(1) is seven-dimensional. You can call this argument "experimental" in the sense that it starts from the standard model group and not from any mathematial requisite of quantisation of an abstact setup (as string theory, for instance). Note that Witten argument requires a total of 11 dimensions instead of the 10 of string theory, so it was a justification for SuGra (in 11 dimensions) and a motivation for M-theory.

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#### Dcase

In the applied mathematics of Game Theory, dimensions are considered alternative strategies.

I have been reading a classic from the Society of Industrial and Applied Mathematics [SIAM]: Tamer Basar and Geert Jan Olsder. 'Dynamic Noncooperative Game Theory', revised 1999 from 1982. The authors refer to this as a type of representation theory.

Since this is mathematics, the language is similar, but not identical to representation theory used in physics.

Some differences include using C* for cost-to-come and G* for cost-to-go,

Similarities include index sets, infinite topological structured sets, mappings and functionals in discrete time.

There is substitution for some of these items in continuous time such as time intervals, Borel sets, trajectory, action and informational topological spaces.

Tme appears to be treated as a duality.
There may or not be stochastic influences.
The Isaacs condition for the Hamiltonian is used.

Types of such games include:
for discrete time -
OL - open loop
CLPS - closed loop perfect state information
CLIS - CL imperfect state
FB - feedback perfect
FIS - feedback imperfect
1DCLPS - one-step delayed CLPS
1DOS - one-step delayed obsevation sharing
for continuous time -
OL
CLPS
eta-DCLPS - eta-delayed DCLPS
MPS - memoryless perfect state
FB

If players are allowed to be entities capable of exchanging enegy quanta or longevity then this might considered enegy economics?

The stochastic game may be consitent with the probablistic nature of QM.

Is phyisics failing to use a valluable tool of representation theory from applied mathematics?

#### mjsd

Homework Helper
If extra spatial dimensions exist, they must be smaller than 45 um.
This is if you assume that extra-dimensions are compactified and that gravity is not confined. In the warped spacetime of Randall and Sundrum, you can have "large extra-dimensions" without violating Newton's law.
see for example: Phys.Rev.Lett. 83 (1999) 4690-4693 [hep-th/9906064]

#### JediLukas

Kaluza-Klein Dimensions

Hi,

Could someone please tell me how many extra dimensions are needed to incorporate the strong and weak forces into the Kaluza-Klein model which has gravity at 4 dimensions and electro-magnetism at 5 dimensions?

Thanks
:-)

#### VOLVORacr

IMHO the masses are looking to far ahead, into the 6th, 7th, 8th, etc. Dimensions rather than focusing on the next obvious evolution.

And to answer the original question.

This is interesting-
http://twm.co.nz/hologram.html [Broken]

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#### arfa

Think of a cause of quantum entanglement. So that this would be a cause that can act without varying at any distance between entangled quantum components so as to maintain the measured correlations in their forms of behaviour.

Such a cause could not be described as surrounding objects in 3D space so where could it act but from additional spatial dimensions?

#### Chronos

Gold Member
This [quantum entanglement] is a bug in the wax of Einstein's universe. But in defense of DrE, QM was not yet a player. And QM does not diminish the importance of his 'new and improved' version of classical mechanics.

#### A/4

This is if you assume that extra-dimensions are compactified and that gravity is not confined. In the warped spacetime of Randall and Sundrum, you can have "large extra-dimensions" without violating Newton's law.
see for example: Phys.Rev.Lett. 83 (1999) 4690-4693 [hep-th/9906064]
The DGP baneworld model also loosens the constraint on compactified extra dimensions, adding an extra infinite 5th bulk dimension:

http://arxiv.org/abs/hep-th/0005016

#### mjsd

Homework Helper
sure.... there are many models out there.. perhaps one day we can create our own

#### A/4

sure.... there are many models out there.. perhaps one day we can create our own
Sure! Randall-Sundrum, by the way, does show departures from Newtonian gravitation. It's effectively a Yukawa-like potential due to the "warp factor" that attenuates the leakage into the bulk, albeit the deviations arise only at extremely small length scales (and not "sub-millimetre" as with the ADD model).

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