Use this tag for dimensions of a manifold, typically the space-time. DO NOT USE THIS TAG for dimension of a physical quantity.

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Questions about the existence of 5d & 6d version of 4d ${\cal N}=2$ SCFTs

Given a 4d N=2 Superconfomal field theory (SCFT) with a global flavor symmetry ( $\mathfrak{f}$ as the corresponding lie algebra), can we clam that this theory can always flow from a 5d ${\cal N}=1$ ...
2
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0answers
60 views

Could gravity be considered a dimension rather than a force? [closed]

Sorry I could have phrased this better, what I was trying to get at is the possibility that gravity is a 4th dimension, thus leaving us we 3 spatial dimensions 1 temporal dimension, and 1 ...
2
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2answers
77 views

Chern Simons action in 4 dimensions

I can not understand why we do not have a Chern-Cimons action for 4 or even forms? And why it not good theory for (3+1) dim?
3
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0answers
50 views

How one can write $\bar{\psi}$ in odd dimension?

I know that the Dirac equation in general dimensions has a form of $$ (i\gamma_{\mu} \nabla_\mu - m ) \psi =0 $$ and the action for that is written as $$ S = \int d^d x \bar{\psi} (i\gamma_{\mu} ...
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0answers
19 views

The low dimensional end of the brane scan

Common wisdom says that only the top dimensional part of the brane scan of Green-Schwarz super p-brane sigma models is quantum consistent (the critical strings and the M-branes). But by the results in ...
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1answer
123 views

Gravity in $d$ spacetime dimensions

Given the following action $$S=\frac{1}{16\pi G}\int d^4x \sqrt {-g}(R+aR^2+bR_{\mu\nu}R^{\mu\nu}+cR_{\mu\nu\lambda\sigma}R^{\mu\nu\lambda\sigma}),$$ which is in 4D. How to we generalise this ...
0
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1answer
56 views

Is the center of the universe in another dimension?

If we live in a four dimensional world and when we try to find the center of the universe (where the big bang occured) we found that there is no apparent center, could that means that the big bang ...
2
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1answer
33 views

Why does dimensional reduction of 10,6,2 to 9,5,1 have an equal number of supersymmetry?

In general, the number of supersymmetry is different for each dimension since from dimensional reduction, the number of supersymmetry is usually increased. $i.e$ 4d N=1 $\rightarrow$ 3d N=2 ...
3
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1answer
72 views

If there are 4 dimensions, shouldn't objects appear and disappear in 3D space?

If there are 4 (or more) physical dimensions, and physical objects can move through the 4th dimension in paths perpendicular to our 3 dimensions, the physical objects must pass through our ...
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3answers
138 views

Determining whether a space is really three or two dimensional? [closed]

A space purports to be three dimensional with the metric $$dl^2=dx^2+dy^2+dz^2-\left(\frac{3}{13}dx+\frac{4}{13}dy+\frac{12}{13}dz\right)^2$$ How can I show that it actually represents a two ...
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0answers
74 views

Why are there only 11 dimensions in M-theory? [duplicate]

Why is it that there are only 11 dimensions in M-theory?
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0answers
19 views

Higher dimension world possibility [duplicate]

Could it be possible that all of the unexplained phenomena (like uncertainty) in our 4D world might be originated from a higher dimension universe? If so, then of course we'll never observe the ...
2
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2answers
139 views

Is the universe 5 dimensional space-time or 4?

we've been told that in General Relativity (GR), matter tells space how to curve and space tells matter how to move. But my question is, if 3 dimensional space was curved by matter then it should be ...
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1answer
41 views

How can extra (non-curled up) dimensions be hidden from us?

Wikipedia says: If extra dimensions exist, they must be hidden from us by some physical mechanism. One well-studied possibility is that the extra dimensions may be "curled up" at such tiny ...
2
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1answer
68 views

Compactified extra dimensions and symmetry

It's my understanding that M-Theory necessitates 11 space-time dimensions (10 spatial dimensions plus 1 time dimension) in order work mathematically. This appears to jar with reality, which only ...
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1answer
48 views

Are all galaxies we see really our Milky Way? Any possibility?

There is a possibility for our universe to be the surface volume of a (higher-dimensional) hyperspace. So if this possibility is true,then is there also a possibility that the other galaxies we see ...
4
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2answers
166 views

Why M-theory has only M2 and M5 branes?

Why M-theory has only M2 and M5 branes? In string theory, depending on the type one considers, you get all kind of D-branes. What is so special in M-theory that only allows 2 and 5 branes?
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0answers
29 views

Why is space 3 dimensional and could it be different? [duplicate]

Is there any particular physical law or property which caused space to be 3 dimensional, and is there theoretical possibility of having more or less dimensions in physical space?
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0answers
62 views

Topology of a black hole

How many dimensions are theorized for a black hole, in view of the fact that black holes are not observed directly.
2
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1answer
82 views

Doubt regarding the dimension of a manifold

I'm very unsure about all this business so please forgive any inaccuracies in my question. Essentially what I'm having trouble understanding right now is how we "decide" the dimensionality of a ...
4
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1answer
90 views

Theories that predict the number of space-time dimensions

My impression in that most theories assume three spatial dimensions and one temporal dimension, though could in principle be formulated in others numbers of dimensions without inconsistencies. I know, ...
0
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1answer
101 views

Are we living in a Universe with 3 time dimensions and 1 spatial dimension? [duplicate]

If I said that we are living in a Universe with 3 time dimensions and 1 spatial dimension, would I be wrong? By that I mean if the spacetime interval was evaluated as ...
0
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1answer
22 views

Locally accessible dimensions of configuration space

I am reading a book called "Structure and Interpretation of Classical Mechanics" by MIT Press.While discussing configuration space and degrees of freedom,the authors remark the following: Strictly ...
2
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2answers
83 views

What's the degree of freedom of this kind of matrix?

We first have a unitary matrix $$\{a_{ij}\}\quad(n\times n)$$ I know how to calculate its degree of freedom, which is $n^2$ if we consider a real variable as one degree of freedom. Now we have a ...
0
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1answer
113 views

How do we know there are dimensions above the third?

Excluding the interpretation of time being the forth dimension, what mathematical evidence is there that suggests it exists? When talking about string theory they say how there is 12 dimensions and I ...
4
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0answers
72 views

Are there relativistic theories with spacetime modelled on $\mathbb C^4$ rather than real Minkowski space $\mathbb R^4$?

Does anybody know of references to theories where relativity & spacetime is modelled on a (complex/Kähler) manifold which is locally diffeomorphic to $\mathbb C^4$ rather than $\mathbb R^4$, hence ...
0
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1answer
61 views

What is dimension and how many types of dimensions are there in the universe?

What is dimension and how many types of dimensions are there in the universe? I mean how many total dimensions are there? I have only heard about 2d and 3d. Other than these two, are there any other ...
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2answers
90 views

4- dimensional space geometry, what is the point? [closed]

I just read about the 4 dimensional space. I found a nice article describing how to visualize a 4-D object into our 3-D world. This is really fascinating. However, what's the point of researching in ...
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0answers
58 views

Can spin angular momentum be understood as orbital angular momentum in extra dimensions?

It is to my understanding that in Kaluza-Klein theories the mass of particles can be understood as linear momentum in the extra dimensions. Let's consider in $\mathbb{R}^{1,3}\times{}B$ space-time a ...
0
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1answer
60 views

How are dimensions indicated in physics equations?

The universe is often described as being 4-dimensional (having 3 spatial dimensions + the dimension of time). Some theories (such as some string theories) consider the universe as having even more ...
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0answers
65 views

Are there diffrent understandings of dimensions?

If people are talking about 4 or higher dimensions they are always pictured as space dimensions. But if you have have a look at the simplest definition of a mathematical dimension it only needs to be ...
0
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1answer
783 views

Is the fifth dimension of Interstellar the same as Block Universe theory? [closed]

Is the movie Interstellar (2014) referring to Block Universe theory of space-time with its concept of a fifth dimension?
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1answer
64 views

What are the two dimensions of relativity that are added to string theory?

Based on the Ramanujam's modular functions, somehow these magic numbers 10 and 26 spacetime dimensions appear in string theory. The dimensions can be viewed as 8 + 2 and 24 + 2. The number 2 is added ...
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2answers
47 views

How would the representation of a circle in 4 dimensions? [closed]

We know that the representation of a square in three dimensions is a cube, and in four dimensions is a tessaract or, hyper cube. With this, How would be the representation of a circle in four ...
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3answers
702 views

Have we proven that higher dimensions exist? [duplicate]

Have we proven higher dimensions exist?
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0answers
47 views

Regarding Randall Sundrum model

In Randall Sundrum model 2, that is the one with non compact fifth dimension, there is only one brane, which is the Planck brane. The TeV brane is removed by taking the radius of the fifth dimension ...
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0answers
50 views

My idea on parallel universes [closed]

I have a question I've long wanted to ask somebody and I see no place better than here to do it! I am not a physicist in any way, Im just a big fan :) So, I have an idea of parallel universes in my ...
0
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1answer
209 views

Do we exist in multiple dimensions?

I have heard that there are 12 spatial dimensions. Does this mean that this many are possible, or that 12 dimensions actually exist? If the latter, then do the same things that exist in 3 dimensions ...
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1answer
106 views

Why & What extra dimensions in M-theory?

I am not into String or M theory. Recently I am again reminded that M-theory "requires extra dimensions" beyond the usual string theories, beyond the usual space-time dimensions. To me, dimensions ...
4
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1answer
93 views

In 2-dimensional and 3-dimensional universes, stellar systems and galaxies are flat and disky. But what about in 4-dimensional universes?

I just watched that interesting video: https://www.youtube.com/watch?v=tmNXKqeUtJM In 2 dimensions a cloud of particles rotating in a plane is flat by definition since it's in 2 dimensions. ...
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3answers
6k views

If I squeeze something really hard, will it ever become two-dimensional?

A mosquito just wanted to bite me! Päng - and it stuck to my hand, hardly recognisable anymore. I said to my girlfriend: "Just reduced the dimension of the mosquito by one!" Therefore the question: ...
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1answer
83 views

Space curvature based on net energy = 0

In Neil DeGrass Tyson's epic video, at 2:26:50 ...
3
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1answer
86 views

Describing Objects in the First Dimension

The "third" dimension is the one we experience day-to-day. An example of the "second" dimension is the shadow of a three-dimensional object. How do we describe the "first" dimension? What would be an ...
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2answers
48 views

Is there a “forwards” and “backwards” in one dimension?

Take a displacement in three dimensions and reduce the number of dimensions by one. The original displacement loses one degree of freedom; giving it two parameters to specify a magnitude and an ...
0
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2answers
62 views

Are string theories extra dimensions required to be “higher” than the four we know of? [closed]

Does the mathematics of string theory require extra dimensions to be "higher" than our own? Is it possible that extra dimensions are lower that that the four we currently know? Could our four be ...
3
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3answers
291 views

Is it time or duration? [closed]

Taking this post: "Is there a proof of existence of time?", as a starting point. Therein was mentioned that there is confusion between: "time" and "flow of time". There was a comment (of mine) that ...
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0answers
58 views

Could a fourth dimension be “spatially simulated” one point at a time by using movements?

I wonder if time and movement can be translated into a simulation of an extra spatial dimension. At least in one point at a time. I'll try to explain. Imagine a fixed probe which measures the ...
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1answer
91 views

Instantons as a -1 dimensional object

I don't know much about Instantons, and looking through the Wiki page it seems like one must have a lot of knowledge about QFT to understand them. However recently I've encountered a statement (which ...
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1answer
64 views

Robertson-Walker metric and stable orbits [closed]

The RW metric is defined using 4 spatial dimensions, but stable planetary orbits require 3 spatial dimensions. Does this indicate a problem with the assumption of the RW metric to describe the cosmos? ...
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1answer
44 views

Coordinates of the extra dimensions

If we live in more than three spatial dimensions, is it not right to conclude that all matter observable to us shares almost the same coordinates of extra dimensions. Or is it just that ordinary ...