A New Theory for Systems Opposing Newton’s Third Law


Feeding birds can also be seen as a breakdown of symmetry: Instead of flying in random directions, they align like magnetic spins. But there is one important difference: A ferromagnetic phase transition can be easily explained using statistical mechanics because it is a system of equilibrium.

But birds — and cells, bacteria and traffic vehicles — add new energy to the system. “Because they have a source of internal energy, they behave differently,” Reichhardt said. “And because they can’t save energy, they appear to be out of nowhere, as far as the system is concerned.”

Beyond Quantum

Hanai and Littlewood began their investigation of BEC stage transitions by thinking about ordinary, well -known stage transitions. Consider water: Even though liquid water and steam look different, Littlewood said, there is no difference in symmetry between them. Mathematically, at the point of transition, the two states are indistinguishable. In a balance system, that point is called a critical point.

Critical events appear all over the place — in cosmology, high-energy physics, even biological systems. But in all of these examples, the researchers did not find a good model for condensates to form when quantum mechanical systems were connected to the environment, undergoing constant wiping and pumping.

Hanai and Littlewood suspect that critical points and unique points should share some important properties, even if they clearly come from different mechanisms. “Critical points are an interesting mathematical abstraction,” says Littlewood, “where you can’t tell the difference between these two phases. The same thing happens with these polariton systems.”

They also know that under the mathematical hood, a laser-in the technical state of matter-and a polariton-exciton BEC have the same basic equations. on a role published in 2019, the researchers connect the dots, proposing a new and, importantly, universal mechanism by which unique points produce phase shifts in quantum dynamic systems.

“We believe that’s the first explanation for the transfers,” Hanai said.

Vitelli and Michel Fruchart, also of the University of Chicago, joined Littlewood and Hanai in extending their quantum work to all nonreciprocal systems, using the mathematical framework of bifurcation theory and relaxing common assumptions about the energy landscape.Photo: Kristen Norman/Getty Images

At the same time, Hanai said, they learned that even if they were studying a quantum state of matter, their equations did not depend on quantum mechanics. Does the event they study apply to the larger and more general event? “We started to doubt this idea [connecting a phase transition to an exceptional point] can also be used in classical systems. ”

But to keep that idea going, they need help. They approached Vitelli and Michel Fruchart, a postdoctoral researcher in Vitelli’s lab, studying the unusual symmetries of the classical realm. Their work extends to metamaterials, which are rich in nonreciprocal interactions; they may, for example, show different reactions to pressure on one side or the other and may also show unusual points.

Vitelli and Fruchart were immediately intrigued. Is there a universal principle at play with polariton condensate, some basic law about systems where energy is not stored?

Enter Sync

Now a quartet, researchers are beginning to search for general principles that support the connection between nonreciprocity and phase transition. For Vitelli, that means thinking with his hands. He had a habit of building physical mechanical systems to illustrate difficult, abstract events. In the past, for example, he used Legos to make lattices that turned into topological materials that moved differently on the inside than on the inside.

“Even if what we’re talking about is theoretical, you can show it in toys,” he said.



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