In article ,
Yousuf Khan writes:
I was watching a program which were comparing various Big Bang theories
against each other. In it, they said one way to falsify Inflation vs.
Cyclic Universe theories is that a Cyclic Universe will *not* produce
gravity waves.

"Gravity waves" and "Gravitational waves" are two very different
things, but a little searching says it's the latter that is meant.
Sadly, even some otherwise credible web sites seem to get the two
mixed up.

Does anybody know why this would be the case?

There are other sources of gravitational radiation in the early
Universe, but those all lead to E-mode polarization. It's
specifically the B-mode polarization that is the signature of
inflation.

There's an overview at
http://www.b-pol.org/bpol-science.php
and more illustration at
http://cosmology.berkeley.edu/~yuki/CMBpol/CMBpol.htm
(Read "gravitational waves" where these sites write "gravity waves.)

The short answer (as far as I can tell, not being an expert on this
subject) is that the origin of the polarization is quantum
fluctuations, which are initially tiny but magnified by inflation.
Without inflation, there's no such magnification or at least not
enough to make the signature observable.

If anyone has a clearer (or more accurate!) explanation, I'd love to
see it.

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