Boxing Up Sub-Atomic Particles

Let’s say you’re a nuclear physicist who – in your quest to learn more about the way the universe works – wants to learn more about the structure and angular momentum, or spin, of an atomic nucleus. However, you can’t just grab a nucleus and stick it under a microscope. What do you do?

If you’re NC State physicist Dean Lee, you put it in a box. Lee and collaborators study complex numerical lattices that allow them – with the help of extremely powerful supercomputers – to predict the movement and position of sub-atomic particles. But to study the structure and spin of an atomic nucleus, the lattice first needs to hold the particle in place. This is done by simulating a “reduced” universe: a finite cube of space with periodic boundaries. Lee and colleagues Sebastian König and Hans-Werner Hammer have now discovered a new way to use this cube. In a paper that appears in Physical Review Letters, they show that structure and spin can be probed simply by adjusting the size of the cube and measuring changes in energy.

Having some trouble picturing this? Well, think of the movie Inception, in which Leonardo DiCaprio’s character, Cobb, places a spinning brass top inside a safe. The top continues to spin unseen inside the safe. Cobb’s wife looks at the top by opening the safe. Of course, she does that in order to determine whether she’s dreaming and the top is not a sub-atomic particle, but you get the general idea.

The end result, according to Lee, is that “we’ve figured out a way to tell if the nucleus is spinning without having to look inside the box. Essentially, we turned the computer simulations into a microscope.”

Pretty nifty, huh? And no, you’re not dreaming.