The dimensions tag has no wiki summary.
32
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5answers
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Does Coulomb's Law, with Gauss's Law, imply the existence of only three spatial dimensions?
Coulomb's Law states that the fall-off of the strength of the electrostatic force is inversely proportional to the distance squared of the charges.
Gauss's law implies that a the total flux through a ...
26
votes
5answers
1k views
Is 3+1 spacetime as privileged as is claimed?
I've often heard the argument that having 3 spatial dimensions is very special. Such arguments are invariably based on certain assumptions that do not appear to be justifiable at all, at least to me. ...
14
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2answers
485 views
Has the concept of non-integer $(n+m)$-dimensional spacetime ever been investigated by theoretical physicists?
The following image serves to aid the reader in understanding the "privileged character" of $3+1$-spacetime.
The wikipedia article on spacetime, and the sub-article "The priveleged character of ...
13
votes
4answers
531 views
Why are so many forces explainable using inverse squares when space is three dimensional?
It seems paradoxical that the strength of so many phenomena (Newtonian gravity, Coulomb force) are calculable by the inverse square of distance.
However, since volume is determined by three ...
13
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3answers
516 views
Can light exists in $2+1$ or $1+1$ spacetime dimensions?
Spacetime of special relativity is frequently illustrated with its spatial part reduced to one or two spatial dimension (with light sector or cone, respectively). Taken literally, is it possible for ...
11
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1answer
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How to define angular momentum in other than three dimensions?
In classical mechanics with 3 space dimension the angular momentum is defined as
$\mathbf{L} = \mathbf{r} \times \mathbf{p}$
In relativistic mechanics we have the 4-vectors $x^{\mu}$ and $p^{\mu}$, ...
10
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1answer
417 views
Why one-dimensional strings, but not higher-dimensional shells/membranes?
One way that I've seen to sort-of motivate string theory is to 'generalize' the relativistic point particle action, resulting in the Nambu-Goto action. However, once you see how to make this ...
9
votes
3answers
511 views
Gravity in other dimensions than 3 and stable orbits
I have heard from here that stable orbits (ones that require a large amount of force to push it significantly out of it's elliptical path) can only exist in a three spatial dimensions because gravity ...
9
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0answers
227 views
How can two time theories be compactified to 3+1 without any Kaluza-Klein remnants
I have recently been looking into the two-time theories and the implied concepts.
For me this seems slightly hard to grasp.
How can I see the basic concept in this theory in a fundamental way based ...
8
votes
3answers
557 views
Understanding counterintuitive units like s^2
One of the things I never understood but was too afraid to ask is this: how should I think of things like kg/s^2. What exactly is a square second? Square foot makes sense to me because I can see it, ...
8
votes
7answers
1k views
Why are extra dimensions necessary?
Some theories have more than 4 dimensions of spacetime. But we only observe 4 spacetime dimensions in the real world, cf. e.g. this Phys.SE post.
Why are the theories (e.g. string theory) that ...
8
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6answers
1k views
Experimental evidence of a fourth spatial dimension?
As human beings, we observe the world in which we live in three dimensions. However, it is certainly theoretically possible that more dimensions exist.
Is there any direct or indirect evidence ...
7
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3answers
736 views
Maxwell in multiple dimensions: What happens to curl?
I read this answer a while ago, and while thinking about $\nabla$, I realized something. Since the cross product can be written as a determinant, in higher dimensions we require extra vector inputs. ...
7
votes
1answer
111 views
Is the LEP B meson asymmetry evidence for higher dimensions and/or string theory?
According to this blog, new standard model calculations have changed the 3 sigma B meson forward and backward production asymmetry observed at LEP into two anomolies:
A 2.5 sigma B meson production ...
6
votes
2answers
176 views
Why would a particle in an extra dimension appear not as one particle, but a set of particles?
I was reading an article in this months issue of Physics World magazine on the three main theories of extra dimensions and stumbled across something I didn't quite understand when the author began ...
6
votes
1answer
165 views
A Game Of The Number Of Space-Time Dimensions
Holger Bech Nielsen, one of the founders of string theory, has apparently just played some sort of game between different potential dimensions for space-time and reached the conclusion that D4 wins in ...
6
votes
5answers
361 views
More than one time dimension
We know that space-time dimensions are 3+1 macroscopically, but what if 2+2?
Obviously it is tough to imagine two time dimensions, but mathematically we can always imagine as either having two ...
6
votes
1answer
91 views
Critical dimension in quantization of p-branes
So I have what might be a fairly basic question, but my understanding that in the quantization of the the string, or the 1-brane, there are conditions on the number of spacetime dimensions to ensure ...
6
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0answers
65 views
String landscape in different dimensions
For D = 11 large (uncompactified) spacetime dimensions, the only "string theory" vacuum is M-theory
For D = 10, there are 5 vacua. Or maybe it's more correct to say 4, since type I is S-dual to ...
6
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2answers
370 views
Some questions regarding $n+m$-dimensional spacetime [duplicate]
Possible Duplicate:
Has the concept of non-integer $(n+m)$-dimensional spacetime ever been investigated by theoretical physicists?
The following image:
serves to aid the reader in ...
5
votes
3answers
581 views
How can we be so sure the universe has 3 dimensions?
I'm just a layman here so please bear with me if I don't get all the words or theories by correct name or whatever. I hope it will be clear enough what my question is. Here goes:
When I read articles ...
5
votes
2answers
138 views
Einstein Field Equations in other space-time dimensions than 3+1?
This question is apparently quite simple but I can't seem to find an answer to it, so I was hopping anyone could clarify me.
Are the Einstein field equations (EFE) only valid for a 3+1 dimensional ...
5
votes
1answer
339 views
Intuition for multiple temporal dimensions
It’s easy, relatively speaking, to develop an intuition for higher spatial dimensions, usually by induction on familiar lower-dimensional spaces. But I’m having difficulty envisioning a universe with ...
5
votes
5answers
426 views
Is time fundamentally different from space?
Note: This is a rewrite of the original question, which was titled What would time be for 2D beings?
In my current, non-physicist's understanding, every instant of our three‑dimensional world ...
5
votes
1answer
200 views
Is this explanation of “Why nine space dimensions?” correct?
In Gordon Kane's Supersymmetry and Beyond (p. 118), he states:
String theory has to be formulated in nine space dimensions or it is not a consistent mathematical theory. There doesn't seem to be a ...
5
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2answers
95 views
Is the “dimension” in dimensional analysis the same as the “dimension” in “three spatial dimensions”?
When we talk about the dimension of a quantity (e.g. the dimension of acceleration is$[ L \ T ^ {-2}]$) are we talking about the same "dimension" as when we talk about three dimensional space?
Are ...
4
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3answers
257 views
Measuring extra-dimensions
I have read and heard in a number of places that extra dimension might be as big as $x$ mm. What I'm wondering is the following:
How is length assigned to these extra dimensions?
I mean you can ...
4
votes
4answers
496 views
Could negative dimension ever make sense?
After some quick check I found that negative dimensions are not used. But we have negative probability, negative energy etc. So is it so likely that we won't ever use negative dimension(s) ?
Update
...
4
votes
3answers
588 views
Why are there 4 Dimensions and 4 Fundamental Forces?
Is it a coincidence that there are four fundamental forces and four spacetime dimensions ? Does a universe with three spacetime dimension contain four fundamental forces? Can magnetism be realized in ...
4
votes
3answers
324 views
Why (in relatively non-technical terms) are Calabi-Yau manifolds favored for compactified dimensions in string theory?
I was hoping for an answer in general terms avoiding things like holonomy, Chern classes, Kahler manifolds, fibre bundles and terms of similar ilk. Simply, what are the compelling reasons for ...
4
votes
1answer
85 views
What is the connection between extra dimensions in Kaluza-Klein type theories and those in string theories?
This follows to some extent from a question I asked previously about the flaws of Kaluza-Klein theories.
It appears to me that Kaluza-Klein theories attach additional dimensions to spacetime that are ...
4
votes
1answer
121 views
Limit on space-time dimension from susy
I read an argument saying that it would be impossible to write down a super-symmetric theory in more than 11 dimensions, this limit coming from the dimension of the Clifford algebra that goes as ...
4
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1answer
57 views
Are there real life applications for Hausdorff dimensions, specifically crack formations?
I was curios about Hausdorff dimensions. They seem to neatly describe rough surfaces. So I was wondering if there are common applications of Hausdorff dimensions in things like complicated friction ...
4
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2answers
400 views
Consequences for causality if superluminal neutrinos were explained by extra dimensions
One suggestion for explaining superluminal neutrinos (assuming for the sake of argument that the OPERA results should hold up) is that the neutrinos have taken a route through extra dimensions, with ...
3
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2answers
334 views
How can one imagine curled up dimensions?
Actually I'm learning String Theory, and one of its proposals is that there are actually 25+1 dimensions of which only 3+1 are visible to us-- and the remaining are curled up. However, superstring ...
3
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1answer
86 views
What does the Reynolds Number of a flow represent physically?
What does the Reynolds Number of a flow represent physically?
I am having trouble understanding the meaning and the utility of the Reynolds number for a certain flow, could someone please tell me how ...
3
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2answers
197 views
About space-time and its four dimensions
I explained to someone I know about General Relativity (as much as I know).
He said that he didn't see how it could be correct.
He argued:
How is 4-dimensional space-time space different to ...
3
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2answers
146 views
What is the minimum number of co-ordinates used to perfectly describe the shape,orientation and position of an n-dimensional object?
What is the minimum number of co-ordinates used to perfectly describe the shape,orientation and position of a n-dimensional object? How do I make an approach to this problem? I am confused with the ...
3
votes
1answer
455 views
How many types of chirality are there?
My question arise and is connected to the "strange" fact
that many things seem to come in pair or in number of two
similar "objects".
3
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2answers
660 views
Why does string theory require 9 dimensions of space and one dimension of time?
String theorists say that there are many more dimensions out there, but they are too small to be detected.
However, I do not understand why there are ten dimensions and not just any other number?
...
3
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2answers
495 views
Why does the force of gravity get weaker as it travels through the dimensions?
Some theories predict that the graviton exists in a dimension that we of course can't see, and that is why the force of gravity is so weak. Because by the time gravity has got from the dimension in ...
3
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2answers
503 views
Do we live in a world with 4 or more dimension?
A NOVA show have told the audience that we are live in 3 dimensional world, the world we lived in is compose by 3 element: the energy, matter, space. By the time Einstein have invented the ...
3
votes
1answer
97 views
Scaling of Static Electric Field
The electric field of a point charge goes like $\displaystyle\frac{1}{r^2}$
The electric field of an infinite line goes like $\displaystyle\frac{1}{s}$
The electric field of an infinite plane is ...
3
votes
1answer
188 views
Why does the universe exhibit three large-scale spatial dimensions? [duplicate]
Possible Duplicate:
Is 3+1 spacetime as privileged as is claimed?
Regardless of your favorite theory of how many dimensions the universe has in total, the universe seems to have a deep ...
2
votes
4answers
332 views
Does time have a special status in general relativity?
In a lot of laymen explanations of general relativity it is implied that the four dimensions of the space-time are equivalent, and we perceive time as different only because it is embedded in our ...
2
votes
2answers
727 views
Electric potential due to a point charge in Gaussian/CGS units
I learned electrostatics in SI units. In SI, the electrostatic potential due to a point charge $q$ located at $\textbf{r}$ is given by
$\Phi(\textbf{r}) = \frac{q}{4 \pi \epsilon_0 |\textbf{r}|}$.
...
2
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2answers
118 views
Do we live in an integer dimension?
I have read that there exist non-integer fractal dimensions and the images generated from these dimensions look organic and they seem to provide a new way of describing the world around us, which ...
2
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2answers
73 views
What's the meaning of dimensionality?
I got amazed with this answer and as you can see, I had a little talk with joriki. He suggested me some examples such as the 2DEG. I'm stuck with some aspects on dimensionality, see this line:
A ...
2
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1answer
112 views
String theory: why not use $n$-dimensional blocks/objects/branes?
I have a basic question: if we use 1d string to replace 0d particle to gain insight of nature in string theory, and advanced to use 2d membranes, can we imagine that using $3$- or $n$-dimensional ...
2
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1answer
177 views
Why is the candela dimension J, not W?
According to the table at the bottom of the Wikipedia page for the candela, the dimension for candelas is J (joules). Why is this not W (watts)?
The luminous intensity for light of a particular ...
