# Questions tagged [kaluza-klein]

Kaluza-Klein theory is a classical theory that unifies gravity and electromagnetism by showing that general relativity in 5-dimensions reduces to the equations of 4-dimensional general relativity and the Maxwell equations in 4 dimensions.

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### Why Dirac's spin-$\frac12$ theory proves wrong Kaluza-Klein theory?

I recently saw Sabine's short video that mentions that Dirac's spin-$\frac12$ theory proves wrong Kaluza-Klein theory unless supersymmetry is amended to the Kaluza-Klein. Is there a more detailed ...
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### Approximation of solution for Laplace's equation in 5d (Kaluza-Klein)

I apologize for the following question because it will seem like a cheap please help me with my homework one. I just want a hint as to what direction to follow. Suppose we have a 5d space where the ...
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### Gauge transformation and Kaluza-Klein metric

The Kaluza-Klein metric, by reduction, can be written as a $(4+m) \times (4+m)$ symmetric matrix, where $m$ is the dimension of the additional spacetime (if we decompose $M_D = M_4 \times M_m$). It ...
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### Scalar spherical harmonics in $S_n$

In the Kaluza klein reduction we can "decompose" the spacetime $M_n$ as $M_n = M_4 \otimes K_d$, in which $K_d$ is a compact spacetime. So, functions like a scalar $\phi(x,y)$ can be ...
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