In the course of this very enjoyable press announcement, it is mentioned that inflation can create gravity waves by amplifying gravity fluctuations.
I do not properly understand this statement. I always thought that quantum fluctuations (fluctuation of the metric in this case?) should occur pretty randomly whereas waves are rather coherent motions.
So I understand somehow that inflation can amplify quantum fluctuations, but I don't see how it can convert these random "microscopic" processes into "macroscopically" observable coherent phenomena called gravitational waves. For example, how are the sources of these gravitational waves distributed? Does each point in space-time behave as some kind of a point source? And what is observed at a specific point as the superposition of all these excitations?
In addition, in the same video it is said that not all inflation models produce gravitational waves, the ones that have them are favoured by the data now, etc.