Kaluza-Klein model

[paweld]

I wonder why Klauza-Klein theory was discarded. According to the article:
www.weylmann.com/kaluza.pdf
this model reproduces almost exactly the action of gravitation field coupled
to the electrodynamic field. What are the drawbacks of this theory?
At first sight it looks very promising.

[Nabeshin]

Well there is the whole unobserved dimension thing... :rolleyes:

[paweld]

Sure, but if the equations are correct ...

[JesseM]

Well there is the whole unobserved dimension thing... :rolleyes:
That's hardly a conflict with observation, since the Kaluza-Klein theory predicts that one dimension is "compact" (rolled up like the second dimension of the surface of a hose) just like in string theory. I suppose string theory brings up one possible answer to the OP's question--the original Kaluza-Klein theory was not a quantum theory, and so it presumably couldn't reproduce the experimentally-verified predictions of quantum electrodynamics (which differ in some cases from those of classical electromagnetism).

Here's a review paper on Kaluza-Klein theory and later quantum generalizations of the idea:

http://arxiv.org/abs/grqc/9805018