The Big Gasp.
It's all about the O.
Posted on 08/04/2006 4:26:21 AM PDT by PatrickHenry
The question of what happened before the Big Bang long has frustrated cosmologists, both amateur and professional.
Though Einstein's theory of general relativity does an excellent job of describing the universe almost back to its beginning, near the Big Bang matter becomes so dense that relativity breaks down, says Penn State physicist Abhay Ashtekar. "Beyond that point, we need to apply quantum tools that were not available to Einstein."
Now Ashtekar and two of his post-doctoral researchers, Tomasz Pawlowski and Parmpreet Singh, have done just that. Using a theory called loop quantum gravity, they have developed a mathematical model that skates right up to the Big Bang -- and steps through it. On the other side, Ashtekar says, exists another universe with space-time geometry similar to our own, except that instead of expanding, it is shrinking. "In place of a classical Big Bang, there is in fact a quantum Bounce," he says.
Loop quantum gravity, one of the leading approaches to the unification of general relativity with quantum physics, was pioneered at the Institute of Gravitational Physics and Geometry at Penn State, which Ashtekar directs. The theory posits that space-time geometry itself has a discrete "atomic" structure, Ashtekar explains. Instead of the familiar space-time continuum, the fabric of space is made up of one-dimensional quantum threads. Near the Big Bang, this fabric is violently torn, and these quantum properties cause gravity to become repulsive, rather than attractive.
While the idea of another universe existing prior to the Big Bang has been proposed before, he adds, this is the first mathematical description that systematically establishes its existence and deduces its space-time geometry.
"Our initial work assumes a homogenous model of our universe," Ashtekar acknowledges. "However, it has given us confidence in the underlying ideas of loop quantum gravity. We will continue to refine the model to better portray the universe as we know it and to better understand the features of quantum gravity."
***
Abhay Ashtekar is holder of the Eberly family chair in physics and director of the Institute for Gravitational Physics and Geometry in the Eberly College of Science. He can be reached at ava1@psu.edu.
The finding reported above was published in Physical Review Letters in May 2006. The research was sponsored by the National Science Foundation, Alexander von Humboldt Foundation, and the Penn State Eberly College of Science.
A million monkeys and Hamlet...
An undetermined number of universes and this one supports life...
Never happened to notice a parallel before.
Cheers!
.
Remember Feynman: "It doesn't matter how smart you are, it doesn't matter how good your theory is. If it doesn't agree with experiment, it's *wrong*."
What does one do when the predicted results are quite subtle, vastly different theories all reduce to current results, and experiments to decide between the theories haven't been done yet.
You just gotta wait...
Cheers!
No, that would be Goddess...as if Ann Coulter hadn't claimed that title with her book (which had an unfortunate typo on the cover and ended up saying "Godless" instead.)
Cheers!
Careful, there.
If you can't measure something (i.e. by its interactions with other things) then the question is, "Does it exist, or not?"
Apparently neutrinos are predicted by conservation laws. Angels are not.
The standard model therefore includes one but not the other....
A couple of nitpicky questions, since it sounded like he was handwaving...
"The answer is that, in quantum theory, particles can be created out of energy in the form of particle/antiparticle pairs. "
I was under the impression that the lifetime of the particle/antiparticle pairs was inversely related to their mass.
IF I remembered that correctly,
AND IF it applies in this context,
...how does such a massive universe have such a long lifetime?
"In the case of a universe that is approximately uniform in space, one can show that this negative gravitational energy exactly cancels the positive energy represented by the matter. So the total energy of the universe is zero."
This sounds like hand waving. How 'uniform' is 'approximately enough' uniform for the cancellation to be exact?
Did the uniformity of the Universe change since the big bang, due to inflation?
And (just to be annoying) what happens if the uniformity of the Universe exceeds the threshold for the cancellation of negative and positive energy? Do you get an analogy to the "time traveler shooting his own grandfather" paradox?
And two more questions, in the vain hopes of getting someone to post a picture of Lisa Randall:
1) Are these predictions affected at all by the number of extra dimensions predicted in various string theories (as certain dimensions are "rolled up" into really, really, tiny volumes)?
2) Why did inflation (apparently) only affect the specific macroscopic dimensions we see now, and not the others?
Full Disclosure: Yes,I'm procrastinating on my exercise again. Buhler?....Buhler?
Cheers!
Cheers!
Ask Jim Croce.
What he didn't say...is it's a Klein bottle.
Cheers!
Spellcheck is *your* friend too, Quark.
I've been there many, many times, myself :-)
Cheers!
I can't let you get away with that, Dimensio. You're beginning to sound like me. :-)
Cheers!
Full Disclosure: Was that a microKelvin squared? And don't, don't don't, reply "An ice box" (pun on Kelvinator...)
Cheers!
1) Are these predictions affected at all by the number of extra dimensions predicted in various string theories (as certain dimensions are "rolled up" into really, really, tiny volumes)? If you read Randall's book (Warped Passages) you will find info on this rolled up dimension effect that may be detectable when the LHC comes on line. Basically, if the indication of KK particles (Kaluza Klein particles) pans out it will be a strong indicator of extra dimensions.
2) Why did inflation (apparently) only affect the specific macroscopic dimensions we see now, and not the others? At least two dimensions, both of which are experienced on macroscopic and microscopic levels, were 'effected' by the inflation period (three, four, or five variables of those two dimensions) ... space and time became intertwined and energy was bound in space and time as subatomic particles, manifesting as particles and as the quantum field in which all of space and time exist now.
Your post 291 could get you busted for "Kitty" Porn.
The Big Gasp.
It's all about the O.
Pamela Anderson PING!
Not true. Many (even if not a plurality) wish to improve or extend existing ideas.
Or at least write grant proposals or start businesses to *use* said ideas.
Cheers!
Except of course for Calvin and Hobbes. Calvin knew dinosaurs!
Cheers!
Robert A. Heinlein, Time Enough for Love, 1973
My goodness! You can quote Scripture Heinlein! It does make a pretty convenient substitute for thinking, doesn't it?
(Apologies to Junior, c/o post 444).
Cheers!
OK, but my question was with respect to Hawking's claim about for a nearly uniform universe, the gravitation potential (which may be treated as a negative engergy yada yada...). Is the Universe still uniform enough? Or is it not, and there is therefore something 'missing' in cosmology (no, I don't mean God, I mean something physical. I have hazy and probably very inaccurate memories of Einstein's cosmological constant...)
If you read Randall's book (Warped Passages) you will find info on this rolled up dimension effect that may be detectable when the LHC comes on line.
I am at least two years from getting the time to read her book. Besides, I'm waiting for the autographed swimsuit version. (Still trying to get time to finish private postings from another anonymous Freeper on renormalization, which were written in Fwench.)
At least two dimensions, both of which are experienced on macroscopic and microscopic levels, were 'effected' by the inflation period (three, four, or five variables of those two dimensions)
Yes, but do we have a reason yet? Or is it just as (for the moment) (seemingly) arbitrary as the Higgs and "spontaneous symmetry breaking" ?
Full Disclosure: I am obviously outside the light cone of recent physics--my most recent reading on anything even remotely resembling this has been a book by Kip Thorne on Black Holes, and Gary Taube's book Nobel Dreams about Carlo Rubbia. And the only tidbits I really remember about that book are these three:
1) The Christmas party skit with the "high-Z" anomaly which insulted him.
2) His graduate students once calculating that during a particular time period (semester? year?) he had an average speed of 40 mph due to his extensive air travel.
3) His haste to publish the findings of (either a Z or W) without checking the work, and telling a female colleague later "It was a Z, just not a perfect Z. You don't know how to play poker"--and a comment in the book that the point was that the apparatus won the Nobel for demonstrating its ability to distinguish Z-like events.
4) Anecdotal stories that as a younger student, Rubbia could put his finger in an electrical socket and guess the voltage to within 10%.
So if I've got some of the facts wrong, I freely admit that I'm not even an amateur at this.
Cheers!
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