
What's Happening in the Mathematical Sciences
What's Happening in the Mathematical Sciences is a series of publications that report on the latest mathematical research in a way that both mathematicians and nonmathematicians can appreciate. Volumes 7 and 8 are by Dana Mackenzie; Volume 6 is coauthored by Dana Mackenzie and Barry Cipra; Volumes 1 through 5 were written by Barry Cipra.
The table of contents of each and the full text of selected articles are below.

Order What's Happening in the Mathematical Sciences, Volume 8 on the AMS Bookstore
Table of Contents, Volume 8
Accounting for Taste
Netflix, a movie rental company, offered a milliondollar prize for a computer algorithm that could significantly upgrade the company's ability to predict its customers' likes and dislikes. The wildly successful competition upset some conventional wisdom in the field of machine learning and vividly demonstrated the power of "crowdsourcing."
A Brave New Symplectic World
Thirty years ago, Alan Weinstein conjectured that certain kinds of dynamical systems with two degrees of freedom, such as a pendulum that is free to stretch as well as swing, always have periodic (repeating) solutions. At the time, no one had any idea how to prove his conjecture. But that was before "symplectic camels" and a "crazy" homology theory based on the equations for a magnetic monopole. Conclusion: Periodic orbits exist. (Magnetic monopoles still don't.)
Mathematics and the Financial Crisis
In the first decade of the 2000s, investors embraced credit derivatives: a clever, formulabased method to parcel out the risk of subprime loans and profit from a booming housing market. But they forgotor chose to ignorethat a mathematical model is only as good as its assumptions.
The Ultimate Billiard Shot
In an insideout version of billiards that you can't quite fit into your garage (or even the Milky Way), two groups of researchers find different ways to sink the cue ball into a pocket at infinity.
SimPatient
Mathematical models of patient populations have begun to supplement or replace clinical trials in cases where the trials would be difficult or impossible to perform. In 2009, a public health panel used six breast cancer models to arrive at a controversial recommendation that women aged 4049 should no longer be advised to have an annual mammogram.
Instant Randomness
How long does it take to mix milk in a coffee cup, neutrons in an atomic reactor, atoms in a gas, or electron spins in a magnet? In the Ising model of magnetism, mathematicians have calculated a unique cutoff time when the system abruptly goes from essentially unmixed to almost completely mixed. The same behavior is expected for other systems described by the theory of Markov chains.
In Search of Quantum Chaos
A classical billiard ball, on a table with curved, "dispersing" sides, travels on a chaotic trajectory that essentially randomizes the ball's position over the long term. However, at low energies, quantum billiard balls are not chaotic. In a tour de force combining pure number theory with physics, mathematicians proved that quantum chaos does emerge at high energies.
3D Surprises
Even in the twentyfirst century, mathematics can still reveal new phenomena in ordinary threedimensional space. Item 1: a stunningly efficient way to pack tetrahedra. Item 2: the Gömböc, a homogeneous body that automatically rights (and wrongs) itself.
As One Heroic Age Ends, a New One Begins
John Milnor's discovery of "exotic spheres" in 1956 ushered in a new era of highdimensional topology, with powerful new tools like framed cobordism theory, stable homotopy theory, and surgery. But one question, called the Kervaire Invariant One problem, remained stubbornly unanswered for more than 40 years, until three topologists found "a shortcut to Mount Everest."


Order What's Happening in the Mathematical Sciences, Volume 7 on the AMS Bookstore
Table of Contents, Volume 7
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Two seemingly unrelated kinds of knotsmodular knots and Lorenz knotsturn out to be the same. For number theorists, the payoff is a new way to look at an old concept, the modular surface. For dynamical systems theorists, it's a new way to understand the beginnings of chaos.
Errorterm Roulette and the SatoTate Conjecture
Fifteen years ago, Andrew Wiles proved Fermat's Last Theorem, thereby solving the most famous problem in mathematics. The aftershocks are still being felt. A team of number theorists, including Wiles collaborator, Richard Taylor, adapts Wiles' machinery to polish off another celebrated unsolved problem in number theory.
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Persi Diaconis, Susan Holmes and Richard Montgomery tell you how to get the odds in your favor the next time you flip a coin. And no, you don't have to cheat.
Dominos, Anyone?
An innocent puzzle about tiling a checkerboard with dominos leads, ultimately, to a new model of random surfaces. The theory is both simple enough to be exactly solvable, and complex enough to include phase transitions between "solid," "liquid," and "gaseous" statesa combination that has never occurred previously in statistical physics.
Not Seeing Is Believing
New "metamaterials" may soon bring invisibility cloaksand inaudibility cloaks, tooout of the realm of fantasy and into reality. Unlike Harry Potter's cloak, these devices will work strictly on the principles of mathematics, not magic.
Getting with the (Mori) Program
In algebraic geometry, the Mori Minimal Model Program is an ambitious effort to match the geometry of surfaces defined by polynomial equations to their algebra. After 100 years of carrying out the program one dimension at a time, algebraic geometers race to the top of the ladder.
The Book that Time Couldn't Erase
More than 1000 years ago, an unknown scribe copied some of Archimedes' works onto parchment. But 200 years later, another scribe erased them and wrote a prayer book over the top. Over the last ten years, hightech imaging methods have penetrated through the damage done by centuries of neglect and abuse to reveal what Archimedes, the greatest mathematician of ancient Greece, really wrote.
Charting a 248dimensional World
Racing against time and the incurable illness of one of their colleagues, a team of twenty group theorists puts together a detailed survey of "the most beautiful structure in mathematics" the exceptional Lie group, E8.
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Proving that more is not always better, mathematicians show that "sparse" or "compressible" signals, such as digital photographs and cell phone messages, can be reconstructed from many fewer measurements than engineers previously supposed. As an extreme proof of principle, engineers design the world's first singlepixel camera.


Order What's Happening in the Mathematical Sciences, Volume 6 on the AMS Bookstore
Table of Contents, Volume 6
See links to Cipra and Mackenzie talking about the subject of each chapter.
by Barry Cipra ( 1 MB)
hear the podcast interview with the author
In 2002, Grigory Perelman announced a solution to the Poincaré Conjecture, a problem in topology selected in 2000 as one of the seven leading math challenges of the millennium. After more than three years of scrutiny, mathematicians are cautiously accepting his proof, which uses a geometric partial differential equation called "Ricci flow," first studied by Richard Hamilton.
by Dana Mackenzie ( 1.62 MB)
hear the podcast interview with the author
While threedimensional topologists awaited a verdict on the Poincaré Conjecture (which deals with closed manifolds), several of them solved a suite of longstanding conjectures about the ends of open manifolds.
by Barry Cipra ( 317 KB)
hear the podcast interview with the author
Pi lovers rejoice! You can now stick your finger into pi and pluck out any digit (say, the trillionth one) without having to compute all the preceding digits. The only catch is that you have to count in sixteens.
by Barry Cipra ( 415 KB)
hear the podcast interview with the author
A question posed by an undergraduate studentcan a Venn diagram be rotationally symmetric?leads to some beautiful "doilies," intricate mathematics, and (after forty years) a solution found by another student.
New Insights into Prime Numbers
by Barry Cipra ( hear the podcast interview with the author)
numbers surprised number theorists. A team of Indian mathematicians, including two students, discovers the first polynomialtime algorithm for testing to see if a number is prime. American, Turkish, and Hungarian mathematicians collaborate to show that small gaps between consecutive primes occur much more often than anyone had previously proved. And another international collaboration finds evenly spaced (but nonconsecutive) prime sequences of any desired length.
From Rubik's Cube to Quadratic Number Fields ... and Beyond
by Dana Mackenzie ( hear the podcast interview with the author)
Manjul Bhargava started with a simple idea of putting numbers into a box. What came out of the box, eventually, was a whole new way to combine and to count objects in algebraic number theory.
Vortices in the NavierStokes Equations
by Barry Cipra ( hear the podcast interview with the author)
From Jupiter's Great Red Spot to the eddies in a stream, vortices are a familiar feature of fluid flow. Mathematicians have gained new insights into the formation and longterm survival of vortices in both two and threedimensional fluids.
by Dana Mackenzie ( 735 KB)
hear the podcast interview with the author
How do water striders move on a nearly frictionless surface? How do dragonflies hover? These and other conundrums of biology can be explained by the mathematics of the NavierStokes equations.
Brownian Motion, Phase Transitions, and Conformal Maps
by Dana Mackenzie ( hear the podcast interview with the author)
A new random process called SchrammLoewner evolution turns out to be a good model for a variety of physical phenomena, from the random jitters of air molecules to phase transitions of a magnetic material. The key mathematical property of these systems, proven in some cases and still conjectural in others, is conformal invariance.
Smooth(ed) Moves
by Barry Cipra ( hear the podcast interview with the author)
Some algorithms of computer science, such as the simplex algorithm for solving linear programming problems, work better than they are supposed to. A new measure of complexity, called smoothed analysis, shows why the standard worstcase scenarios are so misleading.


Order What's Happening in the Mathematical Sciences, Volume 5 on the AMS Bookstore
Table of Contents, Volume 5
New Heights for Number Theory
Progress proceeds apace in the postFermat world of elliptic curves and modular forms.
A Mathematical Twist to Protein Folding
Powerful statistical methods are helping researchers elucidate the threedimensional structure of life's most important molecules.
Nothing to Sphere But Sphere Itself
A centuries old problemthe Kepler conjecturehas yielded to new insights and some dogged computation.
Is the universe finite? Observations of the cosmic microwave background and a new mathematical algorithm may provide an answer.
The Mathematics of Traffic Jams
Computer models are helping researchers understand where traffic jams come fromand maybe what to do about them.
Plimpton 322 is one of mathematicians' favorite cuneiform tablets. But what did it mean to the scribe who composed it?
It's a Small, Big, Small, Big World
Researchers have found a short distance from theory to applications in the study of small world networks.
A Celestial Pas de Trois
New methods have revealed a multitude of solutions to an old problem in celestial mechanics: the orbital motion of three bodies.
The Clay Mathematics Institute has singled out seven important problems in mathematics, with a $1 million dollar prize for each.
Ising on the Cake
A new theorem helps explain why statistical physics has had such a hard time with one of its central problems.


Order What's Happening in the Mathematical Sciences, Volume 4 on the AMS Bookstore
Table of Contents, Volume 4
A BlueLetter Day for Computer Chess
Deep Blue's victory over Garry Kasparov is the end of a long road in computer chess, but the mathematical study of "perfect" play in combinatorial games has an even longer ways to go.
Quantum chaologists and analytic number theorists have their sights set on a mysterious mathematical object: the Riemann zeta function. (Please Note: This article is available in PDF format.)
Proof by Example: A Mathematician's Mathematician
Paul Erdős, the "Johnny Appleseed" of mathematics, inspired hundreds of colleagues and left a rich legacy of mathematical problemsand solutions.
Computers Take Algebraic Geometry Back to Its Roots
Computer power has brought algorithmic questions in algebraic geometry back to the fore.
As Easy as EQP
An automated theorem prover succeeeds in settling a decadesold conjecture in symbolic logic. What's left for human minds to do?
Beetlemania: Chaos in Ecology
A collaboration between mathematicians and biologists has led to the first experimental evidence for chaotic dynamics in a population.
From Wired to Weird
Mathematical discoveries are shaping research in a potentially revolutionary kind of computing, based on principles of quantum mechanics.
Tales from the Cryptosystem
A breakthrough in the theory of computational complexity has implications for cryptographic systems with "guaranteed" security.
But Is It Math?
Mathematics and art have more in commmon than is commonly supposed. Two twentiethcentury artists, M. C. Escher and Marcel Duchamp, used mathematics as an inspiration for works of art.
Mathematical Discovery (by Henri Poincaré)
Henri Poincaré's thoughts on thinking, written near the beginning of the twentieth century, are well worth repeating at century's end.


Order What's Happening in the Mathematical Sciences, Volume 3 on the AMS Bookstore
Table of Contents, Volume 3
Fermat's TheoremAt Last!
Andrew Wiles has completed the astonishing tour de force that resolves the most famous problem in mathematics. His proof is the realization of a boyhood dream.
A Tale of Two Theories
A breakthrough in theoretical physics has simplified a notoriously difficult theory in 4dimensional geometry, and given mathematicians a lot to think about.
Computer Science Discovers DNA
Will computers of the future be bioengineered? It's a possibility.
Thomas Nicely set out to study prime numbers that occur in pairs. Along the way, he discovered that Intel's Pentium chip couldn't divide. (Please Note: This article is available in PDF format.)
The Gentle Art of Control
Modern technology relies on mathematical control theory to keep things on an even keel. How do the equations know what to do?
Computational Fluid DynamicsVerging on Turbulence
Mathematical techniques, faster computers, and better algorithms are gaining ground in the study of complex fluid flows. For some researchers, computtational turbulence is literally a pipe dream.
Cellular Automata Offer New Look on Life, the Universe, and Everything
The continuously increasing power of computers has enabled researchers to take a discrete look at the world. Theorists seek to explain the complex patterns that are often seen.
Are Group Theorists SimpleMinded?
Researchers are working hard to simplify one of the most complicated proofs in mathematical historythe classification of simple groups.
The Secret Life of Large Numbers
A computational challenge in number theory has been met, considerably sooner than the 20,000 years it was expected to take.
In Math We Trust
A theorem about multivariate integration may find a home on Wall Street. You could call it a getrichquick scheme.


Order What's Happening in the Mathematical Sciences, Volume 2 on the AMS Bookstore
Table of Contents, Volume 2
"A Truly Remarkable Proof"
The announcement last year of a proof of Fermat's Last Theorem stunned the mathematical world. Andrew Wiles's proof, though currently incomplete, has nonetheless drawn rave reviews.
From Knot to Unknot
What's the quickest way to untie a knot? Researchers have untangled a good part of the answer.
New Wave Mathematics
Will compact waves cruise the information superhighways of the future? In theory, it's possible.
A team of mathematicians, computer scientists, and engineers has designed a new medical imaging technology based on the safe application of electric current
Parlezvous Wavelets?
Mathematicians and scientists are rapidly learning to speak a new language. The results are making a big splash.
Random Algorithms Leave Little to Chance
Computer scientists will do anything to avoid bottlenecks and speed up computations. But gamble on the results? You bet!
Soap Solution
Undergraduate students at a summer mathematics research program have found some slick answers to some old problems about the geometry of soap bubbles.
Straightening Out Nonlinear Codes
A complicated class of errorcorrecting codes has suddenly gotten much easier to use.
Quite easily Done
A combinatorial problem, long thought to be difficult, has finally been solvedwith surprising ease.
(Vector) Field of Dreams
A clever construction "pulls the plug" on a 40year old conjecture about the topology of vector fields.


Order What's Happening in the Mathematical Sciences, Volume 1 on the AMS Bookstore
Table of Contents, Volume 1
Equations Come to Life in Mathematical Biology
Mathematicians are working with biologists to delve into some of the most challenging problems in biology today, from understanding the human immune system to "computing" the human heart.
New Computer Insights from "Transparent" Proofs
Can a computer be trusted when it produces a proof so long and complicated that no human can check the details? Theorists have cooked up a new way to tell whether or not a computer proof is right.
Can you hear the shape of a drum? is a famous problem that asks if two drums that look different can make the same sound. After decades of headscratching, mathematicians have come up with the answer.
Environmentally Sound Mathematics
Mathematicians have been teaming up with scientists to work on solving environmental problems, from ocean modeling to dealing with hazardous waste.
Disproving the Obvious in Higher Dimensions
Intuition about our threedimensional world can be surprisingly misleading when it comes to higher dimensions, as two recent results in geometry show.
Collaboration Closes in on Closed Geodesics
An unusual blend of differential geometry and dynamical systems has led to an important theoretical result about the number of closed "geodesic" curves on distorted spheres.
Crystal Clear Computations
Growing crystalson a computer? Mathematicians are helping materials scientists to better understand the nature of crystals, while picking up some challenging mathematical problems along the way.
Camp Geometry
A group of talented and inquisitive undergraduates "camped out" last summer at the Geometry Center. Using sophisticated computer graphics and their own imaginations, they came up with some fascinating mathematics.
Number Theorists Uncover a Slew of Prime Imposters
Strange as it may sound, there are composite numbers that "masquerade" as primes. A group of mathematicians trying to hunt down these prime imposters ended up proving there are infinitely many of them.
MapColoring Theorists Look at New Worlds
How many colors are needed to distinguish neighboring colors on a map? The famous Four Color Theorem notwithstanding, this is a challenging problem in graph theoryespecially when your maps aren't flat.


