„Something in there is working”

Research is fascinating. Research leads us to the Unknown. Research is able to prepare a better future. Yes, all this is true. But also: research is tough work-every day; research is numerous attempts and failures; research poses a lot of challenges – until finally research leads you to what you wanted to know.

Alex, one of our group members, recently published two papers with new results which provide valuable insight into the inner workings of quantum field theories. These are the publications: Operator Product Expansion for Form Factors and An Operator Product Expansion for Form Factors II. Born level

Talking about his newest findings we decided to also offer an insight into how he got to these findings – an unpretentious and honest journey into the whirls and hurdles of theoretical particle physics research and how to overcome them.

Alex, how would you describe a research project in theoretical particle physics?

Every project starts with an idea. Sometimes these ideas are born from conversations with other people, sometimes from reading papers and sometimes they are just logical continuations of previously completed works. Each of these ideas essentially consists of answers to two questions.  

First, the “goal”: What are you trying to compute, what would be the final outcome of your work?

And second, the “path”: How are you going to reach this goal, what methods are you going to use?

Sometimes this “path” is very clear, and you can pretty much guess what the final result is going to be before you even start the project. But quite often actual research work is - for the lack of a better word - a gamble.

How does this so-called gamble look like?

Even if you are sure that your research goal is achievable, there will always be unexpected hurdles along the way. Sometimes these hurdles can be purely technical: for example, there simply isn’t enough machine power to finish the calculation you started. In this case you are forced to optimize your code, or try to reduce the generality of what you’re doing to match the capabilities of the machine. Another type of hurdles that theorists often face are the conceptual ones. During the calculation you get to a point where some parts of it are starting to fail. Something in what you’re doing is wrong, but you don’t know what exactly.

Of course, there are ways of overcoming these kinds of issues, too. For instance, you can devise a method that would test all parts of your calculation independently, to see where exactly the problem lies.

What is the secret key for you personally to get through the hurdles?

A lot of people seem to think that the work of a theorist consists of dealing with an endless stream of equations and integrals day after day, but the way I see it, research work often consists of being stuck on something you don’t understand until you finally break through. The biggest motivation booster for a theorist in a situation like this is seeing that “Something in there is working”: huge expressions simplifying into compact formulas, finding trivial solutions to equations that a-priory don’t have to have any, and so on. These kinds of things give us very a strong “This looks natural, we’re on the right track” feeling. Another type of motivation, which should not be underestimated, is “We’re too deep to give up now”. It is the combination of these that pushes me forward.

Recently this motivation boost kept you up and you succeeded. What are your findings?

We calculated an important class of observables, the form factors, in the regime, for which the interaction strength is not small. These observables are more general versions of the scattering amplitudes and, despite being computed in a modified theory, have direct connection to collider physics. They capture a certain part of the Higgs production process at any number of loops.

Why are these results special?

These results are completely out of reach of traditional approaches, as they would require evaluating an infinite number of Feynman diagrams to obtain. Thus, they provide valuable insight into the inner workings of quantum field theories outside of the narrow, weak interaction regime.

What is their contribution to future research?

We hope these results will serve as an important step towards the complete understanding of N=4 SYM, the theory in which we were working, for arbitrarily large interaction strength. Having such an understanding would undoubtedly change our perspective on the way we view quantum field theories and in the long run might lead to generalization of these results to other theories, including QCD, which describes strong interactions between the fundamental particles.

July 29, 2021