"Jay R. Yablon" wrote in message ...
Most of not all of the Kaluza-Klein models that I have seen employ a
fifth dimension which is spacelike, that is, in which the Minkowski
metric tensor signature is +----. These need to be compactified, they
run into chirality issues, need for orbifolding, etc.

I am curious if there are any reviews of theories where the extra
dimension is *timelike* rather than spacelike, i.e., with a +---+
signature, which of the problems that appear from an extra spacelike
dimension are averted, and what new perceived problems arise by
switching the extra dimension over from spacelike to timelike.

In short: what are the perceived problems / challenges of Kaluza Klein
theories that employ an extra timelike dimension, and which of the
problems / challenges that exist in theories with an extra spacelike
dimension are sidestepped or avoided?


I suggest posting your question on the moderated group sci.physics.research


--
Martin Hogbin