The critical geometry of a thermal big bang · HackerPapers discussions

The critical geometry of a thermal big bang — mentioned by raattgift

Sun, 12 Feb 2017 17:17:49 GMT

I'll try to answer that via a couple of concrete examples of theories that deliberately set the speed of gravity and light at different values for good reasons. The short answer is that General Relativity (GR) predicts that the speed of light is equal to the speed of gravitational waves. In order to have a difference between the speed, one needs a different theory from GR. Moreover, the equality of the speed is well-tested at solar system scales; there is good evidence that at least within a few billion light years from here the speeds are the same; and there is good evidence that for at…

Paper and discussion history. A mention is not an endorsement.

The critical geometry of a thermal big bang — mentioned by raattgift

Wed, 30 Nov 2016 10:06:55 GMT

I'd add https://arxiv.org/abs/1603.03312 too, as a link to the actual paper's arxiv version. Bimetric theories are pretty strongly disfavoured on the grounds that there is an apparent universal coupling to the single metric g_\alpha\beta which lets us treat the metric as a geometrical property of spacetime, which gives us General Relativity everywhere we can presently look, and even in places we can't (GR as an effective field theory should hold up inside the horizons of the largest black holes until fairly close to the centre of mass). One can try for a UV completion of General Relativity in…

Paper and discussion history. A mention is not an endorsement.