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Relativity Finally Meets Quantum Theory?
prion86 writes "Physisist Fotini Markopoulou Kalamara (try saying that 3 times fast) believes she has found a way to blend relativity with quantum theory. The article can be found on the Scientific American site."
Just like to point out that what she's doing is combining relativistic gravitation with quantum physics to produce the physicist's holy grail - quantum gravity.
Merely mixing relativity and quantum theory has been done for years and years - the form of the strong nuclear force was found by Yukawa to be a solution of the Klein-Gordon equation - which was proposed in 1924. The relativity papers were published in 1905, 1908.
OK, so I haven't actually clarified anything at all, have I?
I don't really think it's supposed to be a sterotype. It's simply a comparison. The average person would consider cooking to be easier then quantum physics. Although judging by the fact that I have burned cereal, this might be wrong.
I may still be a plain old physics student, but even I know that using the standard interpretation of quantum mechanics, as she appears to, to create an entire cosmology, is very problematic. The standard interpretation is beset by massive difficulties in the form of the measurement problem, and most other intepretations are far more successful in dealing with this. The Everett interpretation (sometimes referred to as the 'Many-Worlds' interpretation, although this ascription is inaccurate in several ways) is the one most commonly used by quantum cosmologists, and with good reason, as it does actually allow for a quantum state vector to be applied to the universe. The standard intepretation, however, does not allow for such an assignation, it is nonsensical to talk about it in the standard interpretation, a point which seems lost on the writer and perhaps even the obviously very intelligent physicist. Maybe they both should have attended philosophy of physics 101.
There's one thing I don't get. Here's the relevant snippet:
But a spin network represents the entire universe, and that creates a big problem. According to the standard interpretation of quantum mechanics, things remain in a limbo of probability until an observer perceives them. But no lonely observer can find himself beyond the bounds of the universe staring back. How, then, can the universe exist? "That's a whole sticky thing," Markopoulou Kalamara says. "Who looks at the universe?" For her, the answer is: we do. The universe contains its own observers on the inside, represented as nodes in the network. Her idea is that to paint the big picture, you don't need one painter; many will do. Specifically, she realized that the same light cones she had used to bring causal structure into quantum spacetime could concretely define each observer's perspective.
Because the speed of light is finite, you can see only a limited slice of the universe. Your position in spacetime is unique, so your slice is slightly different from everyone else's. Although there is no external observer who has access to all the information out there, we can still construct a meaningful portrait of the universe based on the partial information we each receive. It's a beautiful thought: we each have our own universe. But there's a lot of overlap. "We mostly see the same thing," Markopoulou Kalamara explains, and that is why we see a smooth universe despite a quantized spacetime.
So my boggle is this: Until the first "observer" evolved, nothing observed the universe, so it existed in all quantum states simultaneously. If so, how did that first observer ever evolve? Or is she posutlating that the universe's existence is its own observation?
... is whot bwings os tugevza tsuzay.
Maybe the folks at Scientific American just needed to find one person that they could write a nice story about. You could check out John Baez's web page too, or Dan Christensen's page for example.
http://arxiv.org/abs/gr-qc/0203036 for those of you that have advanced degrees in physics... could the rest of us have a translation? Of course I could be off with the publication, but it is hers and it's the only one Perimeter Institute had for her, and the introduction implies gravity with quantum physics... just a disclaimer. I don't have that advanced physics degree yet.
...can be found in the arXiv database. A search for Fotini gives ten results between 1997 and 2002, most of them published in well-known journals, such as Phys. Rev. D, Nucl. Phys. B etc. Not that I understand any of it, by the way...
Some of the players in loop quantum gravity (LQG) before Kalamara are Abhay Ashtekar, Lee Smolin, Carlo Rovelli, John Baez and Chris Isham. Also, Julian Barbour has written a cute semi-popular book called The End of Time on the subject as has Lee Smolin---Three Roads to Quantum Gravity
Anand Rangarajan anand@cise.ufl.edu
Other article with picture and her interests as well as her phone number are here. :-)
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Money for nothing, pix for free
John Baez is a well-known mathematician/math. physicist who works in, among other things, quantum gravity. He is also very well known for the Usenet column This week's finds in mathematical physics, which is certainly worth a look a t if you're at all interested in these things and have a bit of a mathematics background.
One of the great things about TWFiMP is the writing style: when reading it, one really does get the idea that one understands what's going on. Of course this tends to wear off soon after leaving the computer, but. At any rate, many of the TWFiMP talk about spin networks and quantum gravity, including for example week 43 and week 55. Week 110 talks specificially about Penrose's spin networks. He mentions some of Markopoulou's work in week 99, week 114 and week 133. These might provide a bit of a middle-ground between the very fluffy SciAm article and the hard stuff on arXiv.
Of course there is also Markopoulou's recent expository article, which is a great introduction!
Especially if certain very fundamental basic patterns arise at the strangest places. Take the algebra of rooted trees, a mathematical object dealing with special graphs. In 1963, is was shown that they relate to numerical approximation methodes. In 1998/1999 they were shown to relate to feynman graphs (high energy physics). In 2002 we see them in Fontini's work.
That such an elementary math object appears in such different places certainly is something amazing. Realizing that your field of work had such a structure really requires more "intuition/feeling" then purely analytic skills. Art isn't far away.
I intend to live forever, so far so good.
First, the article was written by a woman--perhaps that's where the 'chick stuff' came from. On closer reading, there is also evidence to suggest that the promising young physicist herself introduced the cooking analogies, which were only extended by the journalist. Remember, SciAm is targetting a popular audience (smarter than PopSci, but still). Articles like this will always try to make the person and his or her work seem more human. Scientific American ran a review of a biography of mathematician Paul Erdos a few years ago. The article emphasized his personal eccentricities and some funny anecdotes from his life--should we take SciAm to task for presenting a stereotypical view of the socially inept and out-of-touch mathematician?
Lastly, why the hell is cooking still considered women's work by the sexism police on Slashdot? I'm male and I make my living from physics, but I'm also a pretty good chef. Among my friends, the best cooks are 1) a database designer, 2) a nanomaterials chemist, and 3) a molecular biologist. Two are female, one male. I'll let the guy know he shouldn't be doing that girly stuff, but I'm sure going to miss his creme brulee.
~Idarubicin
There are many contenders
Loop Gravity (this article) & Spin Networks (the easiest to quantize space time with)
Noncommutative Geometry (IMO the most promising)
Stochastic Gravity (the most humble)
And I am sure that I am forgeting more. But string theory gets the most attention and the most money. This is odd to me because string theory has/had some of the ugliest assumptions (particles are strings, supersymmetry) and introduces the most extra stuff (lots of extra Kaluza-Klein style dimensions, all kinds of extendend objects, excessive parameters).
If string theory ever reaches current holy grail, then I think it will end up being a completely different theory.
A Usenet Troll Triumphs on Slashdot
> 4th dimension: Time
I would argue that time is only half a dimension. It only goes one way.
No, just we can only travel one way through it. (t least, at the moment)
c - a blessed +5 grain of salt