The dimensions tag has no wiki summary.
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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 ...
1
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1answer
63 views
the meaning of epsilon in this operator $ \epsilon $
Consider the dimensional regularized integral
$$ \int d^{d}k (k^{2}-m^{2}+i\epsilon)^{-\lambda} $$
For positive $ \lambda $ this integral has a pole at $ k=m $. Is this the reason we we insert the $ ...
9
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3answers
461 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 ...
3
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1answer
65 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 ...
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0answers
29 views
Multiplying Dimension Result [closed]
This might be a general question but I couldn't find any information on it.
If we multiply the first dimension by the second, we get area.
If we multiply by the third, we get cubic area.
What is ...
6
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1answer
80 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 ...
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1answer
387 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 ...
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1answer
54 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 ...
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2answers
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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 $p^{\mu}$, ...
6
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1answer
160 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
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5answers
358 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 ...
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2answers
408 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 ...
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2answers
59 views
Units and Dimensions - Use of proportionality constant
In units and dimensions we learn about Establishing a Formula :
(example) : to establish a relationship between T (Time Period) , m (Mass) , l (length of the string) and g(acc. due to gravity) - ...
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4answers
393 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
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1answer
92 views
Can negative energy explain blackholes?
I think black holes are peculiar and I want to know if there is a relation to negative energy. Does negative energy have positive mass and therefore can explain the nature of black holes? IS there any ...
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2answers
160 views
Imaginary time and string theory
Is imaginary time an extra dimension?
In other words, are time and imaginary time considered two separate dimensions?
If so, does imaginary time appear (as a separate dimension) in string theory (thus ...
0
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1answer
190 views
Is imaging 10 dimension video by Rob Bryanton has any invalid/wrong information?
I just watch this youtube video and wonder that is there anything invalid/wrong in term of real physics.
I search for Rob Bryanton and it look like he has not-so-good reputation, for example here ...
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1answer
83 views
parallel=time, perpendicular=space? on multiple time dimensions
There are some discussions on more than one time dimensions, e.g., Intuition for multiple temporal dimensions and More than one time dimension.
If we define that the parallel direction is time, of ...
2
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1answer
86 views
Can we project a 4D world using 3D video technology?
Traditional movies, TV, etc, faithfully show our 3-dimensional world using 2 dimensions. So can we have a movie that shows a 4-dimensional world using 3D technology?
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2answers
112 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 ...
4
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1answer
75 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 ...
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1answer
86 views
Are more/other colors posible with other dimensions?
Like these impossible colors (yellow/blue and green/red) or these imaginary colors, for example saturated red more intense than pure spectral red can be viewed in ordinary viewing conditions. Can ...
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1answer
108 views
Do we reside in any particular dimension(s)?
In other words does it make sense to say that we live or exist in dimension x? Or do dimensions not apply to reality the universe its self?
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2answers
147 views
Dimensions of obstacle needed to block light?
How many dimensions are required minimum for an object to block light?
in 1d I doubt it's possible.
in 2d I think it could do it if only the light was limited to a dimension perpendicular to the ...
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3answers
506 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 ...
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4answers
505 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 ...
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1answer
142 views
What is the apparent diameter of the sun as seen from earth?
I know this may not be physically accurate.
For my purposes, basically 3D renders, I am assuming the sun rays are parallel rays from an infinitely far lamp. If the sky is clear, what size would that ...
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1answer
791 views
Why are electrons and quarks 0-dimensional?
Disregarding String Theory, which says that electrons and quarks are 1-dimensional, why are electrons and quarks 0-dimensional?
The way I look at it is that they have mass, and if we were the same ...
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0answers
91 views
Higher dimensions
1) How we determine whether the higher dimensions are Unstable or Unpredictable? Or on the basis of what assumption we make this prediction?
(Source of Image: Max Tegmark. See also this Wikipedia ...
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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 ...
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2answers
186 views
How exactly do superstrings reduce the number of dimensions in bosonic string theory from 26 to 10 and remove the tachyons?
In bosonic string theory, to obtain the photon as the first excited state, the ground state must have a negative mass (tachyon). By applying $1 + 2 + 3 + \cdots = -1/12$, it can be shown (in a ...
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0answers
48 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 ...
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2answers
472 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 ...
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2answers
366 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 ...
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0answers
224 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 ...
2
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1answer
155 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 ...
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1answer
163 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 ...
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5answers
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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. ...
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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 ...
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1answer
205 views
What do scientists believe about existence in dimensions? [closed]
I couldn't really think of a suitable question title, I'm not sure if it's completely related or not.
But this is as far as I know (well, I thought it all up last night and it seemed extremely ...
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2answers
190 views
Did the universe always have 4 space time dimensions?
Is the dimensionality of spacetime in all usual models constant?
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1answer
138 views
Is there a relation between the number of dimensions of space time and the number of fundamental forces?
Is there a relation between the number of dimensions of space time and the number of fundamental forces?
Also, did the universe always have 4 space time dimensions?
And could there exist a world ...
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7answers
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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 ...
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1answer
337 views
Total Number of Dimension in universe?
I read somewhere that there are many dimensions and each diff, i read the whole article but i kinda forgot it, so my question is how many dimensions are there???
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1answer
329 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 ...
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2answers
160 views
When and how do you represent a two body state as a tensor product?
I have read that in quantum mechanics, compound systems are constructed as tensor products.
But on page 177 of Griffith, for example, a two body wavefunction is introduced as
Psi ...
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1answer
103 views
what to use for mass in a 2D FEM simulation
I am trying to find the energy of a wave travelling through a solid material in a 2D Finite Element Method (FEM) - Simulation.
As a general approach I would try to use $E_{kin}=\frac{1}{2}mv^2$ at ...
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1answer
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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 ...
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2answers
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If we had three eyes, would our visual perspective be fourth dimensional?
If one covers up one eye, then he loses depth perception (two dimensional perspective). When we uncover that eye, we can now see depth (three dimensional perspective). My question is if we had four ...
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0answers
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How far from the base of the clif does the car land? [closed]
A stunt man drives a car at a speed 20 m/s of off a 30-m-high cliff. The road leading to the cliff is inclined upward at an angle of 20 degree.
How far from the base of the clif does the car land?
