Tag Archives: DoingScience

On the Care and Feeding of Ideas

I read Zen and the Art of Motorcycle Maintenance in high school. It’s got a reputation for being obnoxiously mystical, but one of its points seemed pretty reasonable: the claim that the hard part of science, and the part we understand the least, is coming up with hypotheses.

In some sense, theoretical physics is all about hypotheses. By this I don’t mean that we just say “what if?” all the time. I mean that in theoretical physics most of the work is figuring out the right way to ask a question. Phrase your question in the right way and the answer becomes obvious (or at least, obvious after a straightforward calculation). Because our questions are mathematical, the right question can logically imply its own solution.

From the point of view of “Zen and the Art”, as well as most non-scientists I’ve met, this part is utterly mysterious. The ideas you need here seem like they can’t come from hard work or careful observation. In order to ask the right questions, you just need to be “smart”.

In practice, I’ve noticed there’s more to it than that. We can’t just sit around and wait for an idea to show up. Instead, as physicists we develop a library of tricks, often unstated, that let us work towards the ideas we need.

Sometimes, this involves finding simpler cases, working with them until we understand the right questions to ask. Sometimes it involves doing numerics, or using crude guesses, not because either method will give the final answer but because it will show what the answer should look like. Sometimes we need to rephrase the problem many times, in many different contexts, before we happen on one that works. Most of this doesn’t end up in published papers, so in the end we usually have to pick it up from experience.

Along the way, we often find tricks to help us think better. Mostly this is straightforward stuff: reminders to keep us on-task, keeping our notes organized and our code commented so we have a good idea of what we were doing when we need to go back to it. Everyone has their own personal combination of these things in the background, and they’re rarely discussed.

The upshot is that coming up with ideas is hard work. We need to be smart, sure, but that’s not enough by itself: there are a lot of smart people who aren’t physicists after all.

With all that said, some geniuses really do seem to come up with ideas out of thin air. It’s not the majority of the field: we’re not the idiosyncratic Sheldon Coopers everyone seems to imagine. But for a few people, it really does feel like there’s something magical about where they get their ideas. I’ve had the privilege of working with a couple people like this, and the way they think sometimes seems qualitatively different from our usual way of building ideas. I can’t see any of the standard trappings, the legacy of partial results and tricks of thought, that would lead to where they end up. That doesn’t mean they don’t use tricks just like the rest of us, in the end. But I think genius, if it means anything at all, is thinking in a novel enough way that from the outside it looks like magic.

Most of the time, though, we just need to hone our craft. We build our methods and shape our minds as best we can, and we get better and better at the central mystery of science: asking the right questions.

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Topic Conferences, Place Conferences

I spent this week at Current Themes in High Energy Physics and Cosmology, a conference at the Niels Bohr Institute.

Most conferences focus on a particular topic. Usually the broader the topic, the bigger the conference. A workshop on flux tubes is smaller than Amplitudes, which is smaller than Strings, which is smaller than the March Meeting of the American Physical Society.

“Current Themes in High Energy Physics and Cosmology” sounds like a very broad topic, but it was a small conference. The reason why is that it wasn’t a “topic conference”, it was a “place conference”.

Most conferences focus on a topic, but some are built around a place. These conferences are hosted by a particular institute year after year. Sometimes each year has a loose theme (for example, the Simons Summer Workshop this year focused on theories without supersymmetry) but sometimes no attempt is made to tie the talks together (“current themes”).

Instead of a theme, the people who go to these conferences are united by their connections to the institute. Some of them have collaborators there, or worked there in the past. Others have been coming for many years. Some just happened to be in the area.

While they may seem eclectic, “place” conferences have a valuable role: they help to keep our interests broad. In physics, there’s a natural tendency to specialize. Left alone, we end up reading papers and going to talks only when they’re directly relevant for what we’re working on. By doing this we lose track of the wider field, losing access to the insights that come from different perspectives and methods.

“Place” conferences, like seminars, help pull things in the other direction. When you’re hearing talks from “everyone connected to the Simons Center” or “everyone connected to the Niels Bohr Institute”, you’re exposed to a much broader range of topics than a conference for just your sub-field. You get a broad overview of what’s going on in the field, but unlike a big conference like Strings there are few enough people that you can actually talk to everyone.

Physicists’ attachment to places is counter-intuitive. We’re studying mathematical truths and laws of nature, surely it shouldn’t matter where we work. In practice, though, we’re still human. Out of the vast span of physics we still pick our interests based on the people around us. That’s why places, why institutes with a wide range of excellent people, are so important: they put our social instincts to work studying the universe.

Amplitudes 2017

I’ve been at Amplitudes this week, in Edinburgh. There have been a lot of great talks, most of which should already have slides online. (They’ve been surprisingly quick about getting slides up this year, with many uploaded before the corresponding talks!) Recordings of the talks should also be up soon.

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We also hiked up local hill Arthur’s Seat on Wednesday, which was a nice change of pace.

I’ll have more time to write about the talks later, a few of them were quite interesting. For now, take a look at some of the slides if you’re curious.

Visiting LBNL

I’ve been traveling this week, giving a talk at Lawrence Berkeley National Laboratory, so this will be a short post.

In my experience, most non-scientists don’t know about the national labs. In the US, the majority of scientists work for universities, but a substantial number work at one of the seventeen national labs overseen by the Department of Energy. It’s a good gig, if you can get it: no teaching duties, and a fair amount of freedom in what you research.

Each lab has its own focus, and its own culture. In the past I’ve spent a lot of time at SLAC, which runs a particle accelerator near Stanford (among other things). Visiting LBNL, I was amused by some of the differences. At SLAC, the guest rooms have ads for Stanford-branded bed covers. LBNL, meanwhile, brags about its beeswax-based toiletries in recyclable cardboard bottles. SLAC is flat, spread out, and fairly easy to navigate. LBNL is a maze of buildings arranged in tight terraces on a steep hill.

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I forgot to take a picture, but someone appears to have drawn one.

While the differences were amusing, physicists are physicists everywhere. It was nice to share my work with people who mostly hadn’t heard about it before, and to get an impression of what they were working on.

PSI Winter School 2017

It’s that time of year again! Perimeter Scholars International, Perimeter’s Master’s program in theoretical physics, is holding its Winter School up in Ontario’s copious backwoods.

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Ominous antlered snowmen included

Like last year, the students are spending mornings and evenings doing research supervised by PI grad students, postdocs, and faculty, and the afternoons on a variety of winter activities, including skiing and snowshoeing.

Last year, my group worked on the “POPE”, a proposal by Basso, Sever, and Vieira, and we ended up getting a paper out of it. This year, I’ve teamed up with Freddy Cachazo on a gravity-related project. We’ve got a group of enthusiastic students and are making decent progress, I’ll have more to say about it next week.

Next Year in Copenhagen!

As some of you might be aware, this is my last year at the Perimeter Institute. It’s been great, but the contract was only for three years, and come August I’ll be heading elsewhere.

Determining that “elsewhere” was the subject of an extensive job search. Now that the search has resolved, I can tell you that “elsewhere” is the Niels Bohr International Academy at the Niels Bohr Institute in Copenhagen, where I’ll be starting a three-year postdoc job in the fall.

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Probably in the building on the left

There are some pretty stellar amplitudes people at NBIA, so I’m pretty excited to be going there. It’s going to be a great opportunity to both build on what I’ve been doing and expand beyond. They’re also hiring several other amplitudes-focused postdocs this year, so overall it should be a really fun group.

It’s also a bit daunting. Moving to Canada from the US was reasonably smooth, I could drive most of my things over in a U-Haul truck. Moving to Denmark is going to be quite a bit more complicated. I’ll need to learn a new language and get used to a fairly different culture.

I can take solace in the fact that in some sense I’m retracing my great-grandfather’s journey in the opposite direction. My great-grandfather worked at the Niels Bohr Institute on his way out of Europe in the 1930’s, and made friends with the Bohrs along the way, before coming to the US. I’ll get a chance to explore a piece of family history, and likely collaborate with a Bohr as well.

Hexagon Functions Meet the Amplituhedron: Thinking Positive

I finished a new paper recently, it’s up on arXiv now.

This time, we’re collaborating with Jaroslav Trnka, of Amplituhedron fame, to investigate connections between the Amplituhedron and our hexagon function approach.

The Amplituhedron is a way to think about scattering amplitudes in our favorite toy model theory, N=4 super Yang-Mills. Specifically, it describes amplitudes as the “volume” of some geometric space.

Here’s something you might expect: if something is a volume, it should be positive, right? You can’t have a negative amount of space. So you’d naturally guess that these scattering amplitudes, if they’re really the “volume” of something, should be positive.

“Volume” is in quotation marks there for a reason, though, because the real story is a bit more complicated. The Amplituhedron isn’t literally the volume of some space, there are a bunch of other mathematical steps between the geometric story of the Amplituhedron on the one end and the final amplitude on the other. If it was literally a volume, calculating it would be quite a bit easier: mathematicians have gotten very talented at calculating volumes. But if it was literally a volume, it would have to be positive.

What our paper demonstrates is that, in the right regions (selected by the structure of the Amplituhedron), the amplitudes we’ve calculated so far are in fact positive. That first, basic requirement for the amplitude to actually literally be a volume is satisfied.

Of course, this doesn’t prove anything. There’s still a lot of work to do to actually find the thing the amplitude is the volume of, and this isn’t even proof that such a thing exists. It’s another, small piece of evidence. But it’s a reassuring one, and it’s nice to begin to link our approach with the Amplituhedron folks.

This week was the 75th birthday of John Schwarz, one of the founders of string theory and a discoverer of N=4 super Yang-Mills. We’ve dedicated the paper to him. His influence on the field, like the amplitudes of N=4 themselves, has been consistently positive.