The Physicist Decoding the Nonbinary Nature of the Subatomic World
Rithya Kunnawalkam Elayavalli’s experience as a transgender person informs their understanding of the nonbinary world of quarks and gluons.
Emily April Allen for Quanta Magazine
Introduction
Many discoveries in physics flow from theory to experiment. Albert Einstein theorized that mass bends the fabric of space-time, and then Arthur Eddington observed the effects of this bending during a solar eclipse. Likewise, Peter Higgs first proposed the existence of the Higgs boson; nearly 50 years later, the particle was discovered at the Large Hadron Collider.
Hadronization is different. It’s the process by which elementary particles called quarks and gluons join together to form protons and neutrons — the components of atoms. No current theory can accurately describe how or why hadronization occurs.
“This is really the opposite of the norm,” says Rithya Kunnawalkam Elayavalli, a high-energy nuclear physicist at Vanderbilt University in Nashville, Tennessee.
Kunnawalkam Elayavalli spends their days observing hadronization and trying to formulate a theory that explains it. They’re part of the Sphenix and STAR experiments at the Relativistic Heavy Ion Collider (RHIC) in New York, as well as a member of the CMS experiment at CERN near Geneva. Their research studies the behavior of quarks and gluons in the aftermath of collisions, during the sub-millisecond time span in which these particles move freely before they hadronize anew.
These experiments have revealed details about the structure of quarks and gluons in that interim state, as well as the timing of hadronization. Still, Kunnawalkam Elayavalli finds it frustrating to watch without understanding even more.
The quantum realm defies binaries — gluons especially so. These elementary entities can have three different charges in multiple configurations. And they must exist in sets that bring these charges into balance. To Kunnawalkam Elayavalli, it’s similar to holding the multiplicity of genders they experience as a nonbinary person.
Kunnawalkam Elayavalli in their office on the campus of Vanderbilt University in Tennessee.
Emily April Allen for Quanta Magazine
Quanta Magazine caught up with them to discuss the mysteries of binary-bending nuclear physics, alongside their experience being transgender — in Tennessee, no less, where anti-trans legislation is some of the most regressive in the country — while doing natural science. The interview has been condensed and edited for clarity.
What do we understand about quarks and gluons?
At the Big Bang, there must have been a form of matter that existed, this primordial matter made of quarks and gluons before they converted to hadrons. The best understanding of quarks and gluons that we know comes from the theory of quantum chromodynamics, which was developed in the 1970s. We call it “chromo” because we introduced this new concept called color charge. Quarks and gluons can have three different charges, and physicists named those three things red, blue and green. You also can have antiquarks, which means you have anti-colors: anti-red, anti-blue and anti-green.
Just so I am clear, this has nothing to do with color as we know it?
There is no real connection. We needed something that came in threes that when added together becomes a zero quantity. Color was a reasonable term to use. With light, when you combine red, blue and green together, you get white light, which is neutral. And if you combine a color and its anti-color, you also get white. Similarly, quarks and gluons by themselves carry color charges, and all the hadrons are color-neutral combinations of those quarks and gluons. Everything we see in the world is color neutral.
But to make things complicated, gluons have multiple color charges; one color is going this way, the other color is going that way. Quarks have three color charges. Gluons have two color charges.
Kunnawalkam Elayavalli meets with students, collaborators and friends on Vanderbilt’s campus.
Emily April Allen for Quanta Magazine
How do we know this description is correct?
Our validation of the theory of quantum chromodynamics comes from comparisons with real collider data. We collide an electron and a positron, which is the electron’s antiparticle. We know that when matter shakes hands with its own antimatter, it explodes. That explosion of energy converts itself into a quark and antiquark pair. The probability of that process happening was [well] described by the theory of quantum chromodynamics.
That is how we know that theory can model quarks and gluons. What it cannot do is describe quarks and gluons when they group into the hadrons. At that point, the theory breaks down into the region that we call nonperturbative — noncalculable — physics. All our calculations blow up at us. They literally blow up, in the sense that the terms go to infinity. That’s where our theoretical understanding fails us.
How are you and your colleagues using particle colliders to get insight into that process?
The RHIC collides nuclei of gold atoms. When you do that, you dump so much energy into the system, because you’re colliding several protons and neutrons on several protons and neutrons. Those guys have so much energy that you kind of re-create a little bit of the Big Bang.
Kunnawalkam Elayavalli in front of Vanderbilt’s 17th and Horton Building, where their office is located. The building was originally home to the Little Sisters of the Poor Home for the Aged.
Emily April Allen for Quanta Magazine
We call it the Little Bang. And from the Little Bang, you get a very short amount of time, 10−22 seconds — yoctoseconds. In that short time frame, a fluid called the quark-gluon plasma shows up, and all the quarks and gluons talk to each other. It’s a fireball. Then it evolves. It expands. It cools down. At some point, it reaches the temperature at which quarks and gluons convert to hadrons.
So we start with hadrons that we collide. Then we go to quarks and gluons, and then we come back to hadrons. Hadronization is happening in front of us every time we run our colliders at any single collider in the history of physics. The fact that we can’t understand it at a quantitative level or even a qualitative level — it’s infuriating! One of the main driving forces of my research is to look at it and try to figure out what is going on here.
In my head, I am imagining you all taking a photo with a little camera and studying the explosion.
Well, basically yeah.
Here is a simple analogy. Say you work in car safety testing. You put a dummy in the car, accelerate the car, hit a block, and then look at what happens to the dummy’s body to determine if it’s safe and if the airbags are working.
Now imagine you only have a photograph of the crash test site several years later. And a photograph of the undamaged car before the crash.
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That multiyear time lag in the analogy reflects the yoctosecond time lag between the collision and your ability to capture it, correct?
Yes, it is happening in a very short amount of time, and there is no way to stop it.
So you look at those two photographs, and you say: I know the dummy’s hand started here and ended up here. What are some of the other clues in the photograph I can use to re-create the dummy’s hand’s path?
I create a reconstruction algorithm. From here, the hand goes back to over here, and then I gather some more information, and then I go back further. I can estimate what happens in theory through a simulation.
We have an iterative process where we learn. We make a prediction; the data disagrees. We update the prediction; we compare it with newer data. Maybe it matches.
Doing this at the smallest levels of matter around us truly is what particle and high-energy nuclear physics is all about.
What have you found out?
We measure jets, which are conelike structures consisting of a spray of hadrons and other particles and particle fragments shooting away from a collision. We reconstruct and study the substructure of these jets.
Emily April Allen for Quanta Magazine
Looking at the particle distribution within the jet, if I look at particles that are far away from each other, that is a very calculable region of the jet. As the distance scale gets closer, that goes into the incalculable or nonperturbative region. We’ve identified a specific scale where quarks and gluons can no longer be talked about as quarks and gluons; they have to be talked about as hadrons.
In our long-term quest to identify how hadronization happens, we have discovered with our data and our calculations that hadronization seems to happen at that fixed distance scale, called the transition region. I can convert that distance to a time. So we’re finally getting to the point where we know exactly when hadronization is taking place.
Do the properties of quarks and gluons resonate with you as a nonbinary person?
Yes, I think the simple fact that gluons carry multiple color charges means they are fundamentally nonbinary creatures. And they are the cornerstone of everything around us.
This is a more colorful aspect of nature. It tells us that there’s something more than just the binary positive or negative charge. You have a lot more color choices. You have a lot more flavors in the soup.
Kunnawalkam Elayavalli stands beside a display on the Vanderbilt campus, titled Freehand Carving, by Nancy DuPont Reynolds. The text below reads: “Scientific research forms many paths / From atom to cosmos / Reaching ever into mystery.”
Emily April Allen for Quanta Magazine
What does it mean to you to look at these particles?
I am on the journey to self-discovery alongside my intellectual journey into understanding quarks and gluons and how they evolve. Everything, in my view, has a path of evolution.
I started out in a society [in southern India] that was very binary in its visual representation. There were clear gender roles that were defined. Coming to the United States and spending 15 years in this country, it has taken me a long time to realize what I might understand to be myself. The idea of nonbinary, of not belonging to a certain representation — that took a long time to realize.
My initial realization that this is a possibility, that transition might happen, was at CERN. My colleague just showed up wearing a dress. And I was like: Oh, you can do this!
In the physics world, there are not that many people who are queer or who are trans. Representation matters a lot to me, and showing up and being there as an openly trans person, representing my field, my area of study — which is fundamentally nonbinary in its nature — is a very important aspect of my day-to-day work.
But it’s hard. Our Tennessee representative in Congress just filed a bill that removes federal funding from any institution that facilitates “the disassociation of any individual from his or her sex.” That is the wording of the bill.
They’re coming after insurance. They’re coming after universities.
How can you think about physics when you are thinking about all of that?
Fifty percent of my brain is thinking about this, how can I survive, and in the remaining 50% of the brain, I can think about physics.
I am a physicist, but before that, I’m a person. If someone wants to just chat physics with me, you can’t just get my physics, you also get the fact that I’m a trans person and hear about the environment I’m being asked to do my research in.
