Skip to comments.The Beauty of Branes [Cosmology & Lisa Randall]
Posted on 09/30/2005 6:38:27 PM PDT by PatrickHenry
It was the summer of 1998, recalls Harvard University physicist Lisa Randall, when extra dimensions finally pulled her in. Extra dimensions -- beyond the four we encounter every day (three of space plus one of time) -- have been an ingredient of theoretical physics for decades: mathematician Theodor Kaluza proposed a fifth in 1919, string theory requires 10 of them, M-theory needs 11. But Randall hadn't much use for them, she says, until that summer when she decided they might be helpful to supersymmetry, one of the conundrums she was pondering.
Randall contacted Raman Sundrum, a Boston University postdoctoral student with whom she had previously collaborated, and asked him if he would like to brainstorm about extra dimensions and membranes -- "branes," as they are called for short. Branes are domains or swaths of several spatial dimensions within a higher-dimensional space. The everyday world we live in could be a three-brane, for example, and it is anyone's guess as to what dimension brane it might be embedded in. "Raman had already thought about branes and extra dimensions, and he was an obvious person to join forces with," Randall explains.
But Sundrum was a little worried. He was on his third postdoc, didn't have a job lined up and was considering leaving physics for finance. But he liked the way Randall thought and decided to set off on what might be his final physics adventure. The fruits of that collaboration, as fueled by caffeine and ice cream as by heady equations, were papers known as RS-1 and RS-2, two of the most cited in physics for the past five years.
The papers, which appeared in 1999, offered novel ways to think about gravity, branes and extra dimensions, and they suggested that the universe might have evolved differently in the beginning than it did later. "For me and a lot of people interested in cosmology and particle physics, it meant that there was this whole new set of possibilities of what could be going on in the early universe," says James Cline of McGill University. For Sundrum, now a professor at Johns Hopkins University, it meant seven job offers. "She is somebody with a marvelous instinct," he laughs.
This instinct often draws Randall to problems she knows little about. While at the renowned Stuyvesant High School in New York City, Randall decided to work on perfect versions of complex numbers called Gaussian integers for the then Westinghouse science talent search. (In perfect numbers such as 6, the factors -- in this case, 1, 2 and 3 -- add up to the number itself.) "The project was looking for and seeing if there were any patterns. And there aren't very many. Basically, I always do this. I don't know anything and take on a big project," she says. Nevertheless, Randall's musings on these numbers tied for first place -- a fitting precedent for her subsequent mathematical forays into a host of arcane physics fields: technicolor, charged parity symmetry violation, flavor structure and baryogenesis, to mention a few.
Although they did not intend to, Randall and Sundrum ended up using extra dimensions to offer a solution to what is called the hierarchy problem. It can be framed in several ways, but the problem is essentially this: Why is gravity so puny, so many billion on billions of times weaker compared with the other forces -- electromagnetism and the weak and strong nuclear forces? Discrepancy in strength makes it impossible to combine gravity with the other three forces, a unification thought to have existed during the early phase of the big bang.
But rather than invoking supersymmetry -- a popular solution that argues for the existence of as yet undetected partners to all the known particles--Randall and Sundrum posited that gravity could reside on a different brane than ours, one separated from us by a five-dimensional spacetime in which the extra dimension is 10-31 centimeter wide. In this RS-1 model, all forces and particles stick to our three-brane except gravity, which is concentrated on the other brane and is free to travel between them across spacetime, which is warped in a negative fashion called anti-De Sitter space. By the time it gets to us, gravity is weak; in the other brane it is strong, on a par with the three other forces.
String theorists had looked at the idea of confining all forces to a brane and having gravity leak, but they had not worked out the mechanism, says physicist Joseph Lykken of Fermilab in Batavia, Ill. Randall and Sundrum, he remarks, "changed people's thinking about this stuff entirely."
As Randall and Sundrum refined their idea, they realized that if the extra dimension of spacetime were warped in anti-De Sitter fashion, it could be infinitely large and what we observe about gravity could still be true. This model came to be known as RS-2. "Working that out was mind-blowing," Sundrum recalls. "We had reason to be dead scared. In each of these cases, there was a distinct fear of making complete fools of ourselves."
"It was counterintuitive," notes theorist Michael J. Duff of Imperial College London. "It came as a surprise even to those working in extra dimensions that even though the extra dimension is very large, we wouldn't be aware of it. Newton's law would still be an inverse square law, not an inverse cube law, which is what you might naively expect."
It took a while for many physicists to realize what Randall and Sundrum were suggesting, but the time was right for such thinking. Anti-De Sitter space was popping up in some models, branes were thriving, and in 1998 Nima Arkani-Hamed of Harvard, Georgi Dvali of New York University and Savas Dimopoulos of Stanford University (or ADD, for short) had postulated a three-brane within two large extra dimensions.
Some of the recent models, be they RS, elaborations of ADD or others, will be put to the test when the Large Hadron Collider (LHC) at CERN near Geneva fires up in 2007. "If there is any solution to the hierarchy problem, it should be revealed at the energies the LHC will explore," Randall enthuses. Evidence could include gravitons, supersymmetric partners or evanescent, tiny black holes. "Even if we don't know the answer, it should tell us what the answer is," she adds.
In typical fashion, Randall recently took on two things new to her. The first was writing a book about physics, released last month. The second was participating on a task force formed by Harvard president Lawrence Summers after his comments about women in science. She says she is nervous about the reception of the first project and dislikes talking about the second one. "I like to solve simple problems like extra dimensions in space," Randall declares. "Everyone thinks [women in science] is a simpler issue, but it is so much more complicated."
She should know: she was the first female captain of her high school math team, and even though Stuyvesant is famous for cultivating science and math whizzes, she did not find it supportive of girls. "There was one teacher who kept saying that Stuyvesant was much better when it was all boys, even though the two best students in his class were girls, and he liked us both. It was this weird cognitive mismatch," she says. Regarding Harvard and the task force, Randall is reticent: "I just want to see a whole bunch more women enter the field so these issues don't have to come up anymore."
The 43-year-old Randall is now collaborating with Andreas Karch of the University of Washington, investigating some of the cosmological implications of branes and extra dimensions. According to Randall, we may live in a three-brane, but "there are regions beyond the horizon that look really entirely different. And we haven't fully explored them yet."
If her ideas don't feel obvious to you, don't fret. You are in good company. "I often don't understand her," Karch confesses. "When she says things, they don't make sense and I first think 'she is crazy.' But I don't say anything, because she is usually right. Lisa just knows the answer."
(Just LOOK at the MIND on that woman!)
I wonder if she knows she has a fan club here.
It's ten dimensions and 26. The strings vibrate clockwise in ten, counterclockwise in 26.
I dreamed I was trapped in an anti-DeSitter space once.
Yeah, she knows.
Yes, but does she have a family? children?
This is your brain on S-T-R-E-T-C-H!
Good post, but a little unfair on a Friday night.
Will have to check out her book. This is definitely interesting material! Thanks!
that's what *my* college experiences were like...
I wonder what her politics are?
Wow. Reading that was like the Blue Angels screeching right over my head.
I'm going to read everything she has written, and if I can't understand it, I'll ask her to help me.
Bookmarked under "physics - extra dimensions" and "beautiful women".
Really deep people such as she and I would never quibble over such matters.
If I were a woman, I'd be soooo jealous! Beautiful and brilliant, what could top such gifts? Wouldn't a long lunch with this Lady discussing 'stuff' be a dream come true?
Lisa Randall, Professor, Harvard:
John Kerry $210
Only $210? Bah, I can forgive that. :) Had she given to the limit, now that's a different story.
Well, one thing is for sure, if she ever wants to play "hide the eigen-vector," I'm game!
The number is telling. So the decision is not just $200 or $250, but it's either $200 or I don't buy lunch today so I can give $210 instead of $200.
Agreed, on all points.
I just looked at the pictures.
Note to self: read the article tomorrow.
Given what I read in the article, I have a feeling that the number 210 has a particular significance for her that would frankly escape pretty much all of us. (And I say this as a Ph.D. holder in a mathematical field.)
So please enlighten me about this.
Oh, sorry, I guess I didn't make myself clear. I'm basically saying that, most likely, the woman is heads and shoulders above any of us, including me, on issues of number theory.
And thus, to her, the number "210" might have some obscure property or feature that we'd have to go to the library to look up---and then we'd still not understand it :)
But maybe I'm just dreaming :)
But maybe I'm just dreaming
LOL. I think you are. I don't think someone that smart would waste that much effort to make that kind of subtle statement to the world through a campaign contribution. And if it's because she's superstitious, my point still holds.
Oh, no, it's not because she's superstitous. It's just that to you and I, multiples of 10 or 100 are nice, round, convenient, obvious numbers, but to a number theory freak, others are.
$200 is the reportable quantity boundary. She wanted to make sure the donation was posted.
Thanks for the ping!
I hadn't been over to Seattle in a while, and when I was driving on I-5 over the ship canal recently I noticed a lot of new building construction over at the U. I wonder if the Physics building is still near Frosh pond. Better go check it out next week, say around noon or so. ;)
hrmn... maybe I ought to woo her with the WAGs I have developed concerning multiversal harmonics and skewed co-spatial planes.
I can cure her apparent dalliance with reflexive Leftism (she IS an intellectual from NYC, after all) by the simple expedient of taking her shooting one fine day.
The fed rule says >=$200 I'm pretty sure. $200 though, often doesn't appear. :)
Still, it's distressing that she gave anything at all. One of our goals in having all those evolution threads is to make it respectable for intellectuals to be conservatives. Then, Lisa can come out of the closet and announce that she's one of us, and has been freeping all along. (I have other fantasies ...)
Lyman alpha forest:
Lyman Alpha Forest.
Nuclear decay and half-life:
Geological Time Machine.
Galaxy Formation and the Intergalactic Medium Research Group.
Introduction to Starbirth.
Earth/ Moon tides and lunar recession:
The Recession of the Moon and the Age of the Earth-Moon System.
Dating rocks by radioactive decay.
Continental Drift and Plate Tectonics.
Supernova and SN1987A:
The Distance to Supernova SN1987A and the Speed of Light.
And lastly here is a good overall site:
Ned Wright's Cosmology Tutorial.
It figures that women like this weren't in school when I was. :(
Her office is right next to that of physics professor/conservative blogger Lubos Motl. Maybe his politics will eventually rub off on her, making her an absolutely perfect human specimen :-d
210 factors into 2*3*5*7, the first 4 primes.... FWIW.
Aha! Longshadow, you da man. ml1954 and others, I submit Longshadow's post #43 as evidence of my suppostion in post #25 :)
You could ask her to come back to your la-BOR-a-tory and pet "Plato" your pet Platypus.........
In fairness, my observation of the composition of "210" doesn't rule out the possibility that it was all she had in her checking account at the time she was writing the check.... which is certainly a viable is less intellectually satisfying explanation for the numerical value of her contribution.
210 is 666 x pi (rounded off a bit). I see that contribution as a glorious insult to Kerry.
Hmmmm ...... maybe after you divide by 10....
The list of digits is a list of the names(3) of the spacial coordinates of this world, her cosmology. This could mean she thinks Kerry epitomizes the timeless spacehead and this is the real message she'd like to send.