Long awaited data from the Planck satellite was released today, papers available here. The accompanying press release leads with results about the timing of the first stars, 500 million years or so after the big bang, with little mention of the very early universe. This is also the main topic of BBC News coverage.
This paper reports a bound on r of .08-.09, exactly what Shaun Hotchkiss was predicting earlier this week here. This appears to be pretty much the end of the line for hopes that Planck would see primordial gravitational waves, with the paper seemingly pointing to other experiments being necessary to get below r=.05 (see page 35).
The BBC News story also characterizes these bounds as ruling out the simplest inflationary models, requiring they be supplemented by “exotic physics”.
What is clear from the Planck investigation is that the simplest models for how that super-rapid expansion worked are probably no longer tenable, suggesting some exotic physics will eventually be needed to explain it.
“We’re now being pushed into a parameter space we didn’t expect to be in,” said collaboration scientist Dr Andrew Jaffe from Imperial College, UK. “That’s OK. We like interesting physics; that’s why we’re physicists, so there’s no problem with that. It’s just we had this naïve expectation that the simplest answer would be right, and sometimes it just isn’t.”
For about as long as I can remember, string theorists and multiverse fans have been pointing to Planck data as the test of their ideas. For cosmic strings, the last Planck data release had a paper ruling them out. I don’t see a paper on this topic out or projected for the new data, it seems that this is now something not even worth looking for.
We’ve also been hearing for years that Planck will test supposed evidence of bubble collisions indicating other universes, see for instance this article about this paper, where the article states that
Data from the Planck telescope should resolve the question once and for all.
I don’t see anything in the new data even looking for this. Has it already been ruled out, without any publicity, or did the Planck people think it was something not worth even looking for?