# Tagged Questions

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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### What does it mean for an integral's differential to be raised to a power, like e.g. $d^3r$ or $d^3u$?

I was reading Zwelfel's book on reactor physics and saw the following notation: Notice that the differential of the integral is raised to the third power. What is the meaning of this notation? ...
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### String Theory Vs. Holographic Theory of the Universe. Compatibility [on hold]

String Theory claims strings to be one dimensional objects vs. dimensionless point particles of the Standard Model. String Theory also needs 10 or possibly more spatial dimensions to operate in. ...
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### Force and dimension is the same? [on hold]

I read somewhere that maybe we have 10 dimensions. We know that we have four dimensions (3 dimensions of space plus one of time). There are also four forces: gravity, electromagnetism, the strong ...
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### What is the fifth dimension? [on hold]

What is known as the fifth dimension, and if the fifth dimension is not defined (yet), are there theories? Which? I have heard about the fifth dimension being gravity but that doesn't seem to make ...
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### Significance of electrical fields of infinite objects

I've noticed a pattern with the electric fields of charged objects of infinite dimensions. A point charge, which can be considered a charge of 0 dimensions, has an electric field that goes as $r^{-2}$...
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### What is the measure of distance in higher dimensions?

In our world we are using kilometers to measure distance. What measurement is used to measure distance in higher dimensions?
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### Clarification on the 11 dimension in the M-theory [closed]

In the book the Grand Design by Stephen Hawking, he wrote about the M-theory, and how in that theory it has 11 dimensions. I do not quite get that, so can someone explain it to me a little bit. I ...
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### Why do strings need 9+1=10 spacetime dimensions to exist? [duplicate]

Why do strings need 9+1=10 spacetime dimensions according to previous theory, or equivalently, 11 dimensions as per M-theory? Why cannot they exist in the 4-dimensional world?
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### Is there any experimental evidence that Universe has more than 3 spatial dimensions?

Someone asked about proof of higher dimensions. But discounting time as a dimension, along with the hyper-dimensional GUTs/Supersymmetry theories, has this possibility been tested and what did the ...
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### Ising simulation-dimensionless

My question is about dimensions in Ising model.When we want to simulate Ising we use dimensionless parameter as you know.We choose J to be 1 and also K equal 1 and when temperature is 2.26 then it's ...
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### What would a universe with 2 time dimensions be like? [duplicate]

In a universe with 2 dimensions of time, and 3 spatial dimensions, the equation for finding the change in time is: $\Delta T= \sqrt{(\Delta \alpha_1)^2+(\Delta \alpha_2)^2} \geq 0$ Where $T$ is the ...
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### Purpose of the multidimensional NLSE/GNLSE

I know the purpose of the NLSE (Evolution of a complex field envelope in a nonlinear dispersive medium). Usually I am solving the 1d-GNLSE when simulating the propagation of a light pulse through a ...
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### Multidimensional Area and Volume

In 3D the volume is $xyz$, the product of three coordinates. But in $N$ dimension ,how to define area and volume?
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### How can time be a dimension when it is relative? [closed]

I understand that by definition dimension is defined by just another coordinate to pin-point something in space-time. Therefore we need to know not only where but when. At the same time, this somehow ...
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### Is “time” a singular dimension or multiple dimensions? [closed]

We know of x, y, and z dimensions. We also know of "time"... Another dimension we are aware of, which is a "non-physical dimension" called a "temporal dimension". Now, we all look at "time" as a "...
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### Why are dimensions regarded as square/perpendicular?

Starting from the second dimension, the dimensions are basically represented by a square, cube, tesseract, and so on. I don't know if this is a stupid question or not, but is there an obvious or less-...
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### Could a 3+1 space be embedded in a 4+1 space and retain its 3+1 characteristics? [closed]

I'm confused because I can conceptualize this embedding scenario in two seemingly incompatible ways. Which of the following scenarios are possible?: 1) 4+1 space automatically enforces 4 dimensions ...
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### Is there a limit in dimension?

According to wikipedia Dimension In physics and mathematics, the dimension of a mathematical space (or object) is informally defined as the minimum number of coordinates needed to specify any ...
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### Is there an underlying reason why some forces are inversely proportional to the square of the distance? [duplicate]

This is the first time I'm studying those subjects (I'm still in high school) and my teacher couldn't give me an answer. I'm referring specially to Newton's law of gravitation and Coulomb's law of ...
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### Black hole's singularity: Does it has to be multi-dimensional?

We assume that there is an infinite density at the center of a black hole. But we also know that if it was really infinite, it would apply an infinite gravitational force to masses even if they were ...
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### Are path integrals integrals with countable or uncountable infinite dimensions?

Path integrals are integrals with infinite dimensions. But I recently became confused about if the number of dimensions are discrete/countable or continuous/uncountable. I always thought it should be ...
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### In what ways is four dimension relevant to modern physics?

In what fields can the consideration of four perpendicular vectors be useful to making theories and models in physics? Is the concept of four dimension restricted to spatial dimensions?
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### Connecting the diffusion coefficient in 2-dimensions and 3-dimensions?

Say the diffusion coefficient of the concentration of a particle in a fluid in 3-dimensions is $D_{3\textrm{d}}$. Can we estimate the diffusion coefficient of the same particle in the same fluid, in a ...
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### On the c-theorem

I have been reading a few papers on CFT and AdS/CFT regarding the c-theorem and I have a few questions regarding c-theorems: a) Why is it that the c-theorem is usually considered for only unitary ...
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### Gravitational waves in other dimensions

I know this question is purely speculative, as we don't know if more dimensions do exist and also we do not know if gravity is indeed stronger in other dimensions (if they were to exist). But, one of ...
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### General Relativity, Curvature, and extra dimensions

Setup of idea I had somewhat of a thought question regarding general relativity. Consider a simple situation of a sphere and arrow. You hold the arrow and walk from the equator to the north pole. ...
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### How does a black hole's gravity affect other dimensions? [closed]

Given the extreme gravitational force of a black hole, can it have affects on other higher dimensions? Does it continue to warp space-time regardless of the number of dimensions? In fact, can a ...
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### How to determine the size of other galaxy's/The dark matter problem

From what i understand there are two methods (well as far as i know) to determine how much mass there is in a distant galaxy. First, Luminosity. By measuring the amount of light produced from a ...
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### How many legs (minimum) would a chair need in 4 spatial dimensions for you not to fall?

I was reading another post in physics.SE about chairs when this question arose. My guess is we would need more than in 3 dimensions as in 2 dimensions you would just need 2 (I think). I've been trying ...
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### Theoretical implications of multidimensional Time [duplicate]

While the idea of extra spatial dimensions has been around for quite a while now, is there a possibility or any theory which proposes extra time dimensions? If so, what could be theoretical ...
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### Could there be a -1 dimension? [duplicate]

This might be a silly question as it just doesn't make sense to me - but could we have a dimension lower than one? Could we have a 0th dimension? Could we have a -1th dimension? Are we supporting the ...
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### How confident are we that we live in a universe that has at least a 4th spatial dimension?

Modern pop culture would have us believe that there is such a thing as the 4th spatial dimension. And yes it's easily shown that $n$ dimensions is possible using math alone and 3 just happens to be ...
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### Is time created by movement through a higher dimensional object? [closed]

In a comment I read on this page, someone mentions a theory where time is created by moving through and slicing "moments" of a higher dimensional object. For analogy, a 2-D creature living on a plane ...
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### What is the basic concept of four-dimensions in physics?

I have been reading a few books lately and browsing the internet for an explanation on the concept of "four-dimensional" space (or, space-time, as some of them have been calling it). But, what those ...
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### In Newton's gravity, is the inverse square law related to the fact that our Universe has (apparently) 3 dimensions? [duplicate]

I read, long ago, a book, whose title I can't remember but I think the author was Carl Sagan. In the book was saying that gravity follows the inverse square law because of our Universe was 3 ...
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### do we live in 3.5 dimension? [closed]

After watching interstellar movie i came to know that time is 4th dimension and watch some videos and read articles which says there is there is around 10 dimension(11 also). As x,y,z are 3 dimension ...
To study $S$-duality in more detail, i tried to read, Electric-magnetic duality and the Geometric Langlands Program. In section 2.1, there is a comment about 10d SYM. Excerpt from the paper above, ...