Bagel, pretzel or cinnamon bun? After announcing the Nobel prize in physics on Tuesday morning, Thors Hans Hansson turned to a selection of baked goods to help explain the physics.
“The concept of topology may not be familiar to you,” he said at a press conference in Stockholm, brandishing a cinnamon bun, a bagel and a Swedish pretzel. “Now for us these things are different. One is sweet one is salty, they are different shapes. But if you are a topologist there is only one thing that is really interesting with these things. This thing (the bun) has no holes, the bagel has one holes, the pretzel has two holes.”
Possibly adding to the general sense of mystery, Duncan Haldane, who was named a co-winner of the Nobel prize, later mentioned: “It’s great when you see the coffee cup turn into a doughnut again.”
Struggling with the doughnut and bun analogies? Keep reading.
This year’s physics laureates are theorists, starting in the 1970s, laid the foundations of the mathematical framework that scientists now rely on to explain weird electrical properties that are being observed in certain materials.
When some materials are cooled, for instance, they suddenly switch from being a normal electrical conductor to a superconductor, which allow electrons to flow through encountering almost no resistance. Other materials can be an electrical insulator on the inside but a conductor on the surface.
Prior to the work of David Thouless, Duncan Haldane and Michael Kosterlitz, there was no theory in physics that could properly explain these exotic behaviours.
Today’s Nobel trio showed that electrical properties of a large class of materials can be understood by mapping real physical quantities (say, the interactions of electrons) into an abstract mathematical (or topological) space.
This is where the doughnuts come in. The scientists found that when the electrical properties were plotted out, they produced topological “objects” - something akin to Henry Moore sculptures, with a fixed number of holes. When a material undergoes a phase transition, say from a conductor to superconductor, an experimental scientist would see a sudden spike in the electrical current.
For the topologist, this would be the equivalent of a bun suddenly transforming into a doughnut.
The real use of this is that it allows scientists to understand and predict how new materials are likely to behave. If you can show, theoretically, that a material’s topological representation can go from bagel to pretzel, you can then work out what its corresponding electrical properties would be in real life.
Scientists believe that the work of Thouless, Haldane and Kosterlitz could pave the way for revolutionary technologies, such as quantum computers, underpinned by new classes of exotic materials.
