• We have updated the guidelines regarding posting political content: please see the stickied thread on Website Issues.

Riemann's Hypothesis: anyone explain to me?

lopaka

Gone But Not Forgotten
(ACCOUNT RETIRED)
Joined
Sep 17, 2001
Messages
2,011
I read this article today in the LA Weekly (http://www.laweekly.com). This *sounds* fascinating, but my math/physics background is extremely weak. Can anybody dumb this down a level or two and try to explain the importance of this and why it's not merely theoretical riddle, but something that could have actual ramifications in RL?
-------------------------------------------------------------------------------------------------

AUGUST 22 - 28, 2003

Quark Soup
Prime Obsession
Will the greatest problem in mathematics ever be resolved?
by Margaret Wertheim


It’s been called the hardest problem in mathematics, and also the most important. Three books have recently been published about it and dozens of the world’s most brilliant mathematicians are devoting themselves to it. A million- dollar prize awaits the person who solves it. Known as the Riemann Hypothesis, no mathematical problem inspires such fear and awe — it is said that some mathematicians would sell their souls for the answer.

A decade ago, mathematics splashed onto front pages the world over when Andrew Wiles announced that he had solved another famous problem known as Fermat’s Last Theorem. The public interest in Wiles’ solution stunned the mathematics community — a member of their notoriously nerdy fraternity was now being asked to pose for Gap ads. Suddenly, “It felt almost sexy to be a mathematician,” writes Oxford don Marcus du Sautoy in his new book, The Music of the Primes (HarperCollins). And next month’s publication of David Foster Wallace’s Everything and More, a 300-page rumination on transfinite numbers, seems set to propel math into the lexicon, and onto coffee tables, of the literary cool set.

With a pedigree linking many of the greatest names in the field, the Riemann Hypothesis runs like a river through vast swaths of seemingly distinct mathematical territory. Andrew Wiles himself has compared a proof of this proposition to what it meant for the 18th century when a solution to the longitude problem was found. With longitude licked, explorers could navigate freely around the physical world; so too, if Riemann is resolved, mathematicians will be able to navigate more fluidly across their domain. Its import extends into areas as diverse as number theory, geometry, logic, probability theory and even quantum physics.

The Riemann Hypothesis is a proposal about prime numbers, the atomic elements of the number system. Primeness is one of the most essential concepts in mathematics, for primes — 2, 3, 5, 7, 11 and so on — are numbers that cannot be broken into any smaller elements. All other integers can be built up by multiplication of these basic units. So, for example, 6 is built up from 2 x 3, 15 from 3 x 5, 49 from 7 x 7. In his book The Riemann Hypothesis (FSG), science writer Karl Sabbagh makes an analogy between numbers and molecules. All of the vast plethora of molecules that inhabit our world, everything from salt and ammonia to hemoglobin, are made up of the basic elements of the periodic table — carbon, hydrogen, oxygen and so on. As Sabbagh notes, the primes may be seen as the periodic table of the number system. Yet where the elements follow a clear pattern, the primes seem to be distributed randomly.

To mathematicians, randomness is anathema. As du Sautoy writes, they “can’t bear to admit that there might not be an explanation for the way nature has picked the primes.” That would be like “listening to white noise”; what mathematicians crave above all else is harmony. They want, they need, they demand a pattern behind the apparent chaos. Du Sautoy quotes the great French mathematician and physicist Henri Poincare: “The scientist does not study nature because it is useful, he studies it because he delights in it, and he delights in it because it is beautiful. If nature were not beautiful, it would not be worth knowing and if nature were not worth knowing, life would not be worth living.”

For many mathematicians life would not be worth living if the organization of the primes did not ultimately conform to some beautiful underlying order. The Riemann Hypothesis proposes what that order might be. One of the most innovative mathematical thinkers of all time, Bernhard Riemann was a sickly German genius of the mid–19th century who also developed the non-Euclidean geometry on which Einstein based his general theory of relativity. Riemann’s life and work form the subject of John Derbyshire’s touching biography Prime Obsession (Joseph Henry Press). Though he died at 39 and his collected works amount to a single slim volume, virtually every paper Riemann wrote revolutionized a different branch of mathematics.

Riemann’s Hypothesis is not easy to state in any language. In essence it links the distribution of prime numbers to a complicated equation called the Riemann Zeta Function. For some values this equation equals zero, and it turns out there are an infinite number of such values, which mathematicians refer to as the “zeros” of the zeta function. Riemann demonstrated that there is a beautiful and unexpected link between these “zeros” and the pattern of the prime numbers.

Each Riemann zero can be represented as a point on something called the complex plane, one of mathematics’ most truly enchanted places. Formed from the intersection of the “real” and the “imaginary” numbers, the complex plane is also where the fabled Mandelbrot Set lives. To his astonishment, Riemann discovered that on this plane the zeta-function zeros seemed to lie in a strict vertical line, which is now called the critical line. Why this might be so is one of the deepest questions in mathematics. It was Riemann’s intuition, his hypothesis, that all the zeta zeros must lie on this line.

Riemann did not prove his proposition, however, and neither could the finest mathematicians since. John Nash, the hero of A Beautiful Mind, was known to be working on the problem just before he started receiving messages from aliens. Alan Turing, one of the founders of modern computing, attempted to build a cog-and-gear mechanical device for calculating zeta zeros. One prominent Riemannologist was promised a Ferrari by his father if he ever managed to solve the question. Over the years, a number of people have claimed to have proofs, but none have withstood scrutiny.

In 2000, the Riemann Hypothesis was selected by the Clay Mathematics Institute in Boston as one of the seven “Millennium Problems,” each of which is now attached to a million-dollar prize. But money may not be enough — some mathematicians suspect the problem may simply be beyond human capability. Or worse still, that it is unprovable. Another option would be to disprove it, for the discovery of a single zeta zero not on the critical line would immediately render the proposition false. On the surface this would appear an easier row to hoe — all one has to do is to start at the first zero and keep on calculating. Sooner or later, if exceptions exist they must reveal themselves. Though mathematicians would still want to understand why the hypothesis wasn’t true, at least the basic question would be laid to rest.



The idea that there might be exceptions to Riemann’s rule has inspired one of the more quixotic enterprises in the history of mathematics, a project that might also be ‰ included among the great conceptual works of our time. For the past 25 years, Andrew Odlyzko has been calculating Riemann zeta zeros — to date he has recorded some 30 billion of them! If you go to his Web site, you can download a list of the first 100,000 Riemann zeros accurate to nine decimal places, and another of the first 100 zeros accurate to 1,000 decimal places. During his calculations, Odlyzko estimates he has used 250,000 hours of computer time, and has generated 640 gigabytes of data. This vast haul of unadulterated zeta zeros constitutes one of the largest caches of pure mathematical information ever assembled.

Originally from Poland, Odlyzko still speaks with a strong but gentle East European accent after 40 years in the U.S. Bespectacled and balding, he looks every inch the classic nerd. As a mathematician Odlyzko has had a lifelong interest in computation, and his research interests have ranged across a wide variety of fields from cryptography and error-correcting codes to number theory, combinatorics, communications networks and electronic publishing. More recently he has become an expert on the economics of e-commerce. Until 2001, Odlyzko was a leading researcher at AT&T’s Bell Labs in New Jersey. Two years ago he moved to the University of Minnesota to take up an appointment in the mathematics department and to head their new Digital Technology Center. Finding zeta zeros is what he does in his spare time.

Speaking by phone from Minneapolis, Odlyzko seems a man of Zen-like patience. His search for Riemann zeros dates back to 1978, when Bell Labs became the first private company to acquire a CRAY-1 supercomputer. Most of the machine’s processing power was devoted to company research, but Bell offered small, five-hour chunks for worthy scientific hobby projects. Odlyzko put in a proposal to calculate the first million zeta zeros. “In the end,” he notes, with typical understatement, “I used up quite a bit more time than that.”

When considering Riemann’s critical line, it is helpful to imagine a narrow cliff face, an infinitely high but very thin vertical wall stretching straight up into the stratosphere. The question can then be stated thus: Is there any place where this vertiginous face deviates from its seeming perfection? Seen in this light, Odlyzko might be viewed as a kind of mathematical rock climber, a minuscule speck inching his way ever higher up an endless, flat escarpment. As he climbs, the numbers defining each zeta zero get progressively larger and his calculations ever more lengthy. The higher he goes, the more computational power he needs.

Odlyzko could have kept on calculating zeta zeros from the bottom up forever. There is indeed an open-source computer project called ZetaGrid in which volunteers around the world donate spare cycles on their PCs to check that every Riemann zero really does lie on the critical line. (See http://www.zetagrid.net.) Since August 2001, when the project was initiated, participants have checked the first 470 billion, and they are currently progressing at around a billion zeros a day. But Odlyzko had a hunch that if exceptions exist, they would only be found at very high altitudes. He realized that if he was ever going to find a counterexample, he’d have to give up the idea of traversing the entire critical line and restrict himself to exploring small slices. So in 1990 he leapt ahead to the billion billionth Riemann zero and began calculating in that vicinity. Still, the cliff face was perfectly flat.

At this point Odlyzko was calculating with 12-digit numbers, plus all the decimal places. Just to do the calculations, he had to invent new computational algorithms. At the time, he says, 1012 was “the highest order of zeros that we could reach with the calculation methods available to us.” Still, he suspected it wasn’t high enough. “The wildness of the zeta function grows extremely slowly,” Odlyzko tells me. Only when the “wildness” comes to the fore are deviant zeros likely to reveal themselves. In a sense, Odlyzko is searching for monsters, aberrations of the normal taxonomy whose location — like all good mythical beasts — is off the edge of any current map.

A decade later, he and a colleague invented a much better algorithm, and in one mighty bound Odlyzko leapt up the critical line to the 1020 Riemann zero. Now he was operating in a zone where no human had ever set foot. “To calculate all the zeros up to this point would require more computational time than there’s been in the history of humanity,” Odlyzko notes. Another jump brought him to the 1021 zero, then the 1022, and finally the 1023. At each step, billions more zeros fell to his computational scythe. But still the wild things eluded him.

“If I could do 1050, I would do it,” Odlyzko says. Yet he now suspects that even this would not be good enough. So slowly does the “wildness” grow, he believes that if exceptions exist off the critical line, they will probably not be found until around the 10100 Riemann zero. At present that region is beyond any currently conceivable computing power. And even if he could reach that high, Odlyzko notes philosophically that “counterexamples are likely to be extremely rare.” His chances of finding one are essentially nil. Nonetheless, he keeps on climbing.



In the mathematical universe, Odlyzko is applying what is known as a brute-force approach — the more computer power he can bring to bear, the more zeta zeros he can calculate, hence the more likely he is to find aberrations. On the whole, mathematicians disapprove of computational approaches; a widespread attitude, especially among older mathematicians, holds that the only “real” proof is an analysis derived from fundamental axioms. All else is hack work.

Odlyzko is aware of this bias among his colleagues, but he likens himself to an explorer venturing into a new land. “I am really going out there and looking at this wild universe and finding things that I hope will eventually lead to proofs,” he says. He is just now beginning to analyze his mammoth cache of zeros. “We simply don’t know what surprises the data might hold,” he declares. Odlyzko notes that this explorational view of mathematics is very much part of the subject’s tradition. Indeed, a marvelous new book by Amir Alexander, Geometric Landscapes (Stanford University Press), traces the history of the idea of the mathematician-explorer and shows how the rhetoric of discovery was integral to the way in which mathematicians of the scientific revolution conceived of themselves and their work.

Already Odlyzko’s forays into the stratospheric zone of the Riemann zeros have verified something astonishing. It turns out these zero points are not arranged randomly on the critical line. Mysteriously, they follow the same statistical pattern that physicists have found in some kinds of atomic systems — specifically, what are known as “quantum chaotic systems.” Thus, what seems at first a purely abstract discovery has turned up in nature. Nobody has the slightest idea why this might be so. But the revelation suggests the incredible possibility that we might be able to find (or build) a quantum system — perhaps some bizarre kind of atom — that would prove the Riemann Hypothesis. A number of physicists are now working toward that goal.

The interplay between mathematics and the material world has fascinated philosophers and scientists alike. “God ever geometrizes,” Plato declared. “All is number,” Tierry of Chartres concurred in the Middle Ages. Riemann himself developed his radical non-Euclidean geometry because he was convinced there must be a geometric explanation for the force of gravity. Fifty years after his death, Einstein demonstrated the truth of that insight. The link between Riemann’s zeta zeros and quantum mechanics suggests that understanding these zeros will help to illuminate the deeper mysteries of atoms, molecules and atomic nuclei.

Though Riemann’s Hypothesis was originally stated merely as an aside, it has turned out to be one of the most profound mathematical statements ever uttered. The deeper mathematicians go into it, the more connections they continue to discover. As Sabbagh writes, “The Riemann Zeta Function extends its tentacles into so many branches of mathematics it’s impossible to say where a solution might come from.” After so many years on the cliff face, no one has a greater investment in the problem than Odlyzko. I ask him if he thinks it will be resolved in his lifetime. Before answering, he pauses and on the other end of the phone I can hear a slow intake of breath. Yet his answer, when it comes, is full of optimism: “For all we know, it may have been done yesterday,” Odlyzko says. “It may be done tomorrow.”

Then again, he adds, “It may take another hundred years.”
 
I don't understand the mathematics of it either, but if, like the article says, this hypothesis was proven it might be some key to understanding more about the distribution of the Primes. That would be like grabbing a couple of pages from the the Reality Technical Manual.
 
Can anybody dumb this down a level or two and try to explain the importance of this and why it's not merely theoretical riddle, but something that could have actual ramifications in RL?
Short Answer: No.

Long Answer: Still no! It's something too specialist really for discussion on a message board like ours, fascinating though I find the subject myself.

A very interesting article, BTW, but one that has already dumbed things down quite a bit!

As for RL connections, these often do take decades or even centuries to emerge from pure maths research into practical scientific explanations, and there's often no way of predicting where those applications might lie.

I came across an example of this recently, when preparing a talk for my local astro-soc about orbits and space craft operation. Mission engineers now are starting to use Dynamical Systems Theory to plan space craft trajectories, as opposed to cobbling together pieces of conic section orbits (as had been done up until the 1990s). But DST was invented over 100 years earlier by the mathematician Poincare. But as he discovered it in the context of gravity fields, this is not much of a change of direction.

But when the space scientists resurrected and advanced his work, they found that researchers in other disciplines were ahead of them - the same maths was being used by chemists studying molecules, and by people researching ocean currents!

(DST, btw, was really the first discovery of what we now call Chaos mathematics, but let's not get into that here! :) )
 
You'd think that after Mr Odlyzko had calculated a billion billion of the things and they still hadn't deviated one jot or tittle, that would be proof enough. I guess it's a monument to human endeavour that he's still carrying on looking. But what if he does get up to the 10100 Riemann zero, and they still don't deviate? I mean, at some point, you would have to call it a day.
I mean, some things in maths just are. For example, all perfect numbers (number equal to the sum of its own integral factors) end in either 6 or 8. The value of Pi will never recur, ever. And so on.
Prime numbers are fascinating, however. Is it not amazing that a number with over a million digits can have no integral factors?
In the pre-Internet days of the '80s, I was proud of the fact that I knew some very large Mersenne primes from memory. Anyway, monster primes are ten a penny now that the Internet is here.

Bill Robinson
 
IT'S A CARD GAME - AND IT'S MATHS

This just swam into my ken today, so I thought I'd mention it here:
http://www.sciencenews.org/20030823/mathtrek.asp
SET Math
Ivars Peterson

The card game known as SET® is deceptively simple. Its object is to identify, as quickly as possible, a grouping (SET) of three cards, selected from 12 cards laid out face up on a table.

A SET deck has 81 (34) cards. Each card displays a design with four attributes: shape, number, shading, and color. Each attribute has three possible values.

Attribute Values
Shape {oval, diamond, squiggle}
Number {one, two, three}
Shading {striped, solid, open}
Color {red, green, purple}

For the purposes of the game, three cards are called a SET if, with respect to each of the four attributes, the cards are either all the same or all different. For example, the following three cards would constitute a SET because the cards are different for all attributes.

[diag]

Invented in 1974 by population geneticist Marsha Jean Falco (see http://www.setgame.com/set/history.htm), the game has become a popular, even addictive pastime for both children and adults. It has also attracted mathematical attention.

"Although children often beat adults, the game has a rich mathematical structure linking it to the combinatorics of finite affine and projective spaces and the theory of error-correcting codes," Diane Maclagan of Stanford University and Benjamin Lent Davis of Saint Mary's College of California remark in the current issue of the Mathematical Intelligencer. "Last year, an unexpected connection to Fourier analysis was used to settle a basic question directly related to the game of SET, and many related questions remain open."

One obvious mathematical question about the game concerns the number of cards that must be dealt to guarantee the presence of a SET.

Anyone who has played the game knows that 12 cards are sometimes not enough to find a SET. Indeed, the rules specify that, if no SET is found, three additional cards must be dealt for the game to continue. This is repeated until a SET makes an appearance.

One way to find out how many cards are needed is to do an exhaustive computer search of all the possible combinations. Such a search would reveal a collection of 20 cards that has no SET. Every collection of 21 cards does contain a SET.

It's also possible to picture each card as a point in four-dimensional space, where each of a point's four coordinates assumes one of three possible values. Three cards form a SET if and only if the three associated points are all on the same straight line in this finite four-dimensional space.

In effect, Maclagan and Davis note, players of SET are searching for lines contained in a subset of this space. They then define a cap to be a subset of the space not containing any lines and ask for the maximum possible size of a cap in the given space, which is equivalent to asking for the maximum numbers of cards that would have no SET among them.

Interestingly, this question was answered in a mathematical context in 1971, 3 years before SET was invented.

It's also possible to extend the problem in various ways. "Although SET cards are described by four attributes, from a mathematical perspective there is nothing sacred about the number four," Maclagan and Davis write. "We can play a three-attribute version of SET, for example, by playing only with the red cards. Or we can play a five-attribute version of SET by using scratch-and-sniff SET cards with three different odors."

You can then ask how the size of the maximal cap, a, depends on the number of attributes (dimension, d). The answer for five dimensions was only recently worked out, and the value for six dimensions isn't yet known exactly.



There are many more possible generalizations. For example, you could add another color, shape, form of shading, and number to the cards. Such generalizations prompt a host of new mathematical questions.

SET cards can also be used for other pursuits in recreational mathematics. For example, you could look for SET magic squares. The idea is to arrange selected cards in a three-by-three array so that any line on the square yields a SET.

In fact, you can start with any three cards, and there will always be a way to fill in the rest of the blanks to make a SET magic square. You can find out more at http://www.setgame.com/set/magicsquare.htm.

In the meantime, you can visit the official SET Web site at http://www.setgame.com/set/index.html and try the SET daily puzzle to get yourself warmed up for deeper mathematical challenges.
Full article has diagram, links, etc.
 
Back
Top