offer hints to the pre-big-bang universe
Over the weekend, and that means in the US at the start of a long summer July 4 holiday when it’s hard to reach people to explain very baffling things, Penn State’s press office thumped for a tough one from the journal Nature Physics. Maybe the Big Bang was, after all, a big bounce. More important: an emerging mathematical exercise called loop quantum gravity hints that it did not entirely erase evidence of a before. That is, if there was a before in any way understandable by the average schmo (most of us).
A PSU-based team asserts that two parameters in the equations of lqg conspire to prevent the universe ever to have had zero dimension, or infinite energy density, or other such logical, math-killing conundrums that slam the door on any sniff of pre-big-bang reality. The universe had size from the start, and through that tiny window some info from Before may have leaked. But, not so fast. In a manner perhaps similar to the dueling parameters of the uncertainty principle, they also introduce a “cosmic forgetfulness” about most and perhaps all details of T-minus time. So add this to the ekpyrotic scenario (that’s the one with colliding branes) and various multiverse hypotheses of Origin via oscillations or other multiplicities. As with those (and string theory), it doesn’t say here exactly how to test this latest wrinkle in the space time argumentuum. Not much ink on it either so far. But there is some from the specialty news services and from Brit dailies.
-CP
Stories:
Daily Mail (UK) David Derbyshire gets the gist in, describes a bit of conventional theory, says nothing about other bouncing-ball cosmologies, and then understandably tells readers he cannot provide details on this one as “Loop Quantum Gravity is almost impossible to understand without a crash course in advanced physics.” How true; Scientific American JR Minkel has it with plenty of caveats that add up to — there was an earlier universe, and we can’t tell what it was like ; BBC;
Grist for the Mill: Penn State Press Release (via EurekAlert);
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July 2nd, 2007 at 1:45 pm
Sean Carroll gives some reasons not to get too excited; this is one of those times when I wish the actual paper became available at the same time as the press release.
Of course, since Carroll’s argument hinges on entropy, nobody will follow it anyway. (Legend has it that John von Neumann told Claude Shannon to name a quantity in his information theory “entropy,” because nobody knows what “entropy” is and it would give Shannon a great edge in debates.)
July 2nd, 2007 at 2:00 pm
Thanks. First thing I checked this morning was CVariance. Nothing there early — glad you looked for yourself!
July 3rd, 2007 at 12:58 pm
Glad to be of service.
June 8th, 2009 at 12:38 pm
[...] Against the languor of the Independence Day weekend, a tiny bit of media attention has managed to focus itself on a new paper by Martin Bojowald. (The paper doesn’t seem to be on the arxiv yet, but is apparently closely related to this one.) It’s about the sexy topic of “What happened before the Big Bang?” Bojowald uses some ideas from loop quantum gravity to try to resolve the initial singularity and follow the quantum state of the universe past the Bang back into a pre-existing universe. [...]