Tag Archives: DoingScience

The Near and the Far: Motivations for Physics

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When I introduce myself, I often describe my job like this:

“I develop mathematical tools to make calculations in particle physics easier and more efficient.”

However, I could equally well describe my job like this:

“I’m looking for a radical new way to reformulate particle physics in order to solve fundamental problems in space and time.”

These may sound very different, but they’re both correct. That’s because in theoretical physics, like in many branches of science, we have two types of goals: near-term and far-term.

In the near-term, I develop mathematical tools and tricks, which let me calculate things I (and others) couldn’t calculate before. Pushing the tricks to their limits gives me more proficiency, making the tools I develop more robust. In the future, I can imagine applying the tools to more types of calculations, and specifically to more “important” calculations.

All of that still involves relatively near-term goals, though. Develop a new trick, and you can already envision what it might be used for. The far-term goals are generally deeper.

End of the road, not just the next tree.

In the far term, the new techniques that I and others develop might lead to fundamentally new ways to understand particle physics. That’s because a central feature of most of the tricks we develop is that they rephrase the calculation in a way that leaves out something that used to be thought of as fundamental. They’re “revolutions”, overthrowing some basic principle of how we do things. The hope is that the right “revolution” will help us solve problems that our current understanding of physics seems incapable of solving.

Most scientists have both sorts of goals. Someone who studies quantum mechanics might talk about developing a quantum computer, but in the near-term be interested in perfecting some algorithm. A biologist might study how information is stored in a cell, but introduce themself as someone trying to cure cancer.

For some people, the far-term goals are a big component of how they view themselves. Nima Arkani-Hamed, for example, has joked that believing that “spacetime is doomed” is what allows him to get out of bed in the morning. (For a transcript of the relevant parts, see here.) There are plenty of others with similar perspectives, people who need a “big” goal to feel motivated.

Myself, I find it harder to identify with these kinds of goals, because the payoff is so uncertain. Rephrasing particle physics in a new way might be the solution to a fundamental problem…but it could also just be another way to say the same thing. There’s no guarantee that any one project will be that one magical solution. In contrast, for me, near term goals are something I can feel confident I’m making real progress on. I can envision each step along the way, and see the part my work plays in a larger picture, led along by the satisfaction of solving each puzzle as it comes.

Neither way is better than the other, and both are important parts of science. Some people do better with one, some do better with the other, and in the end, everyone can view themselves as accomplishing something they care about.

Am I a String Theorist?

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Perimeter, like most institutes of theoretical physics, divides their researchers into semi-informal groups. At Perimeter, these are:

  • Condensed Matter
  • Cosmology
  • Mathematical Physics
  • Particle Physics
  • Quantum Fields and Strings
  • Quantum Foundations
  • Quantum Gravity
  • Quantum Information
  • Strong Gravity

I’m in the Quantum Fields and Strings group, which many people seem to refer to simply as the String Theory group. So for the past week or so, I’ve been introducing myself as a String Theorist. As I briefly mention in my Who Am I? post, this isn’t completely accurate.

Am I a String Theorist?

The theories that I study do derive from string theory. They were first framed by string theorists, and research into them is still deeply intertwined with string theory research. I’ve definitely had occasion to compare my results to those of string theorists, or to bring in calculations by string theorists to advance my work.

And if you’re the kind of person who views the world as a competition between string theory and its rivals (like Loop Quantum Gravity) then I suppose I’m on the string theory “side”. I’m optimistic, at least, that the reason why string theory research is so much more common than any other approach to quantum gravity is simply because string theory provides many more interesting and viable projects for researchers.

On the other hand, though, there’s the basic fact that the theories I work with are not, themselves, string theories. They’re quantum field theories, the broader class that encompasses the modern synthesis of quantum mechanics and special relativity. The theories I work with are often reasonably close to the well-tested theories of the real world, close enough that the calculations are more “particle physics” than the they are “string theory”.

Of course, all of that could change. One of the great things about string theory is the way it connects lots of different interesting quantum field theories together. There’s a “string”, the “GKP string”, involved in the work of Basso, Sever, and Vieira, work that I will probably get involved with here at Perimeter. The (2,0) theory is a quantum field theory, but it’s much closer to string theory than to particle physics, so if I get more involved with the (2,0) theory would that make me a string theorist?

The fact is, these days string theory is so ubiquitous that the question “Am I a String Theorist?” doesn’t actually mean anything. String theory is there, lurking in the background, able to get involved at any time even if it’s not directly involved at present. Theoretical physicists don’t fall into neat categories.

I am a String Theorist. Also, I am not.

Hexagon Functions II: Lost in (super)Space

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My new paper went up last night.

It’s on a very similar topic to my last paper, actually. That paper dealt with a specific process involving six particles in my favorite theory, N=4 super Yang-Mills. Two particles collide, and after the metaphorical dust settles four particles emerge. That means six “total” particles, if you add the two in with the four out, for a “hexagon” of variables. To understand situations like that, my collaborators and I created “hexagon functions”, formulas that depended on the states of the six particles.

One thing I didn’t emphasize then was that that calculation only applied to one specific choice of particles, one in which all of the particles are Yang-Mills bosons, particles (like photons) created by the fundamental forces. There are lots of other particles in N=4 super Yang-Mills, though. What happens when they collide?

That question is answered by my new paper. Though it may sound surprising, all of the other particles can be taken into account with a single formula. In order to explain why, I have to tell you about something called superspace.

A while back I complained about a blog post by George Musser about the (2,0) theory. One of the things that irked me about that post was his attempt to explain superspace:

Supersymmetry is the idea that spacetime, in addition to its usual dimensions of space and time, has an entirely different type of dimension—a quantum dimension, whose coordinates are not ordinary real numbers but a whole new class of number that can be thought of as the square roots of zero.

This is actually a great way to think about superspace…if you’re already a physicist. If you’re not, it’s not very informative. Here’s a better way to think about it:

As I’ve talked about before, supersymmetry is a relationship between different types of particles. Two particles related by supersymmetry have the same mass, and the same charge. While they can be very different in other ways (specifically, having different spin), supersymmetric particles are described by many of the same equations as each-other. Rather than writing out those equations multiple times, it’s often nicer to write them all in a unified way, and that’s where superspace comes in.

At its simplest, superspace is just a trick used to write equations in a simpler way. Instead of writing down a different equation for each particle we write one equation with an extra variable, representing a “dimension” of supersymmetry. Traveling in that dimension takes you from particle to particle, in the same way that “turning” the theory (as I phrase it here) does, but it does it within the space of a single equation.

That, essentially, is the trick that we use. With four “superspace dimensions”, we can include the four supersymmetries of N=4 super Yang-Mills, showing how the formulas vary when you go beyond the equation from our first paper.

So far, you may be wondering why I’m calling superspace a “dimension”, when it probably sounds like more of a label. I’ve mentioned before that, just because something is a variable, doesn’t mean it counts as a real dimension.

The key difference is that superspace dimensions are related to regular dimensions in a precise way. In a sense, they’re the square roots of regular dimensions. (Though independently, as George Musser described, they’re the square roots of zero: go in the same direction twice in supersymmetry, and you get back where you’re started, going zero distance.) The coexistence of these two seemingly contradictory statements isn’t some sort of quantum mystery, it’s just a consequence of the fact that, mathematically, I’m saying two very different things. I just can’t think of a way to explain them differently without math.

Superspace isn’t a real place…but it can often be useful to think of it that way. In theories with supersymmetry, it can unify the world, putting disparate particles together into a single equation.

Stop! Impostor!

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Ever felt like you don’t belong? Like you don’t deserve to be where you are, that you’re just faking competence you don’t really have?

If not, it may surprise you to learn that this is a very common feeling among successful young academics. It’s called impostor syndrome, and it happens to some very talented people.

It’s surprisingly easy to rationalize success as luck, to assume praise comes from people who don’t know the full story. In science, we’re surrounded by people who seem to come up with brilliant insights on a regular basis. We see others’ successes far more often than we see their failures, and often we forget that science is at its heart a process of throwing ideas against a wall until something sticks. Hyper-aware of our own failures, when we present ourselves as successful we can feel like we’re putting on a paper-thin disguise, constantly at risk that someone will see through it.

As paper-thin disguises go, I prefer the classics.

In my experience, theoretical physics is especially heavy on impostor syndrome, for a number of reasons.

First, there’s the fact that beginning grad students really don’t know all they need to. Theoretical physics requires a lot of specialized knowledge, and most grad students just have the bare bones basics of a physics undergrad degree. On the strength of those basics, you’re somehow supposed to convince a potential advisor, an established, successful scientist, that you’re worth paying attention to.

Throw in the fact that many people have a little more than the basics, whether from undergrad research projects or grad-level courses taken early, and you have a group where everyone is trying to seem more advanced than they are. There’s a very real element of fake it till you make it, of going to talks and picking up just enough of the lingo to bluff your way through a conversation.

And the thing is, even after you make it, you’ll probably still feel like you’re faking it.

As I’ve mentioned before, there’s an enormous amount of jury-rigging that goes into physics research. There are a huge number of side-disciplines that show up at one point or another, from numerical methods to programming to graphic design. We can’t hire a professional to handle these things, we have to learn them ourselves. As such, we become minor dabblers in a whole mess of different fields. Work on something enough and others will start looking to you for help. It won’t feel like you’re an expert, though, because you know in the back of your mind that the real experts know so much more.

In the end, the best approach I’ve found is simply to keep saying yes. Keep using what you know, going to talks and trying new things. The more you “pretend” to know what you’re doing, the more experience you’ll get, until you really do know what you’re doing. There’s always going to be more to learn, but chances are if you’re feeling impostor syndrome you’ve already learned a lot. Take others’ opinions of you at face value, and see just how far you can go.

“China” plans super collider

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When I saw the headline, I was excited.

“China plans super collider” says Nature News.

There’s been a lot of worry about what may happen if the Large Hadron Collider finishes its run without discovering anything truly new. If that happens, finding new particles might require a much bigger machine…and since even that machine has no guarantee of finding anything at all, world governments may be understandably reluctant to fund it.

As such, several prominent people in the physics community have put their hopes on China. The country’s somewhat autocratic nature means that getting funding for a collider is a matter of convincing a few powerful people, not a whole fractious gaggle of legislators. It’s a cynical choice, but if it keeps the field alive so be it.

If China was planning a super collider, then, that would be great news!

Too bad it’s not.

Buried eight paragraphs in to Nature’s article we find the following:

The Chinese government is yet to agree on any funding, but growing economic confidence in the country has led its scientists to believe that the political climate is ripe, says Nick Walker, an accelerator physicist at DESY, Germany’s high-energy physics laboratory in Hamburg. Although some technical issues remain, such as keeping down the power demands of an energy-hungry ring, none are major, he adds.

The Chinese government is yet to agree on any funding. China, if by China you mean the Chinese government, is not planning a super collider.

So who is?

Someone must have drawn these diagrams, after all.

Reading the article, the most obvious answer is Beijing’s Institute of High Energy Physics (IHEP). While this is true, the article leaves out any mention of a more recently founded site, the Center for Future High Energy Physics (CFHEP).

This is a bit odd, given that CFHEP’s whole purpose is to compose a plan for the next generation of colliders, and persuade China’s government to implement it. They were founded, with heavy involvement from non-Chinese physicists including their director Nima Arkani-Hamed, with that express purpose in mind. And since several of the quotes in the article come from Yifang Wang, director of IHEP and member of the advisory board of CFHEP, it’s highly unlikely that this isn’t CFHEP’s plan.

So what’s going on here? On one level, it could be a problem on the journalists’ side. News editors love to rewrite headlines to be more misleading and click-bait-y, and claiming that China is definitely going to build a collider draws much more attention than pointing out the plans of a specialized think tank. I hope that it’s just something like that, and not the sort of casual racism that likes to think of China as a single united will. Similarly, I hope that the journalists involved just didn’t dig deep enough to hear about CFHEP, or left it out to simplify things, because there is a somewhat darker alternative.

CFHEP’s goal is to convince the Chinese government to build a collider, and what better way to do that than to present them with a fait accompli? If the public thinks that this is “China’s” plan, that wheels are already in motion, wouldn’t it benefit the Chinese government to play along? Throw in a few sweet words about the merits of international collaboration (a big part of the strategy of CFHEP is to bring international scientists to China to show the sort of community a collider could attract) and you’ve got a winning argument, or at least enough plausibility to get US and European funding agencies in a competitive mood.

This…is probably more cynical than what’s actually going on. For one, I don’t even know whether this sort of tactic would work.

Do these guys look like devious manipulators?

Indeed, it might just be a journalistic omission, part of a wider tendency of science journalists to focus on big projects and ignore the interesting part, the nitty-gritty things that people do to push them forward. It’s a shame, because people are what drive the news forward, and as long as science is viewed as something apart from real human beings people are going to continue to mistrust and misunderstand it.

Either way, one thing is clear. The public deserves to hear a lot more about CFHEP.

Feeling Perturbed?

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You might think of physics as the science of certainties and exact statements: action and reaction, F=ma, and all that. However, most calculations in physics aren’t exact, they’re approximations. This is especially true today, but it’s been true almost since the dawn of physics. In particular, approximations are performed via a method known as perturbation theory.

Perturbation theory is a trick used to solve problems that, for one reason or another, are too difficult to solve all in one go. It works by solving a simpler problem, then perturbing that solution, adjusting it closer to the target.

To give an analogy: let’s say you want to find the area of a circle, but you only know how to draw straight lines. You could start by drawing a square: it’s easy to find the area, and you get close to the area of the circle. But you’re still a long ways away from the total you’re aiming for. So you add more straight lines, getting an octagon. Now it’s harder to find the area, but you’re closer to the full circle. You can keep adding lines, each step getting closer and closer.

And so on.

And so on.

This, broadly speaking, is what’s going on when particle physicists talk about loops. The calculation with no loops (or “tree-level” result) is the easier problem to solve, omitting quantum effects. Each loop then is the next stage, more complicated but closer to the real total.

There are, as usual, holes in this analogy. One is that it leaves out an important aspect of perturbation theory, namely that it involves perturbing with a parameter. When that parameter is small, perturbation theory works, but as it gets larger the approximation gets worse and worse. In the case of particle physics, the parameter is the strength of the forces involves, with weaker forces (like the weak nuclear force, or electromagnetism) having better approximations than stronger forces (like the strong nuclear force). If you squint, this can still fit the analogy: different shapes might be harder to approximate than the circle, taking more sets of lines to get acceptably close.

Where the analogy fails completely, though, is when you start approaching infinity. Keep adding more lines, and you should be getting closer and closer to the circle each time. In quantum field theory, though, this frequently is not the case. As I’ve mentioned before, while lower loops keep getting closer to the true (and experimentally verified) results, going all the way out to infinite loops results not in the full circle, but in an infinite result instead. There’s an understanding of why this happens, but it does mean that perturbation theory can’t be thought of in the most intuitive way.

Almost every calculation in particle physics uses perturbation theory, which means almost always we are just approximating the real result, trying to draw a circle using straight lines. There are only a few theories where we can bypass this process and look at the full circle. These are known as integrable theories. N=4 super Yang-Mills may be among them, one of many reasons why studying it offers hope for a deeper understanding of particle physics.

Does Science have Fads?

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97% of climate scientists agree that global warming exists, and is most probably human-caused. On a more controversial note, string theorists vastly outnumber adherents of other approaches to quantum gravity, such as Loop Quantum Gravity.

As many who disagree with climate change or string theory would argue, the majority is not always right. Science should be concerned with truth, not merely with popularity. After all, what if scientists are merely taking part in a fad? What makes climate change any more objectively true than pet rocks?

Apparently this wikipedia’s best example of a fad.

People are susceptible to fads, after all. A style of music becomes popular, and everyone’s listening to the same sounds. A style of clothing, and everything’s wearing the same thing. So if an idea in science became popular, everyone might…write the same papers?

That right there is the problem. Scientists only succeed by creating meaningfully original work. If we don’t discover something new, we can’t publish, and as the old saying goes it’s publish or perish out there. Even if social pressure gets us working on something, if we’re going to get any actual work done there has to be enough there, at least, for us to do something different, something no-one has done before.

This doesn’t mean scientists can’t be influenced by popularity, but it means that that influence is limited by the requirements of doing meaningful, original work. In the case of climate change, climate scientists investigate the topic with so many different approaches and look at so many different areas of impact (for example, did you know rising CO2 levels make the ocean acidic?) that the whole field simply wouldn’t function if climate change wasn’t real: there’d be a contradiction, and most of the myriad projects involving it simply wouldn’t work. As I’ve talked about before, science is an interlocking system, and it’s hard to doubt one part without being forced to doubt everything else.

What about string theory? Here, the situation is a little different. There aren’t experiments testing string theory, so whether or not string theory describes the real world won’t have much effect on whether people can write string theory papers.

The existence of so many string theory papers does say something, though. The up-side of not involving experiments is that you can’t go and test something slightly different and write a paper about it. In order to be original, you really need to calculate something that nobody expected you to calculate, or notice a trend nobody expected to exist. The fact that there are so many more string theorists than loop quantum gravity theorists is in part because there are so many more interesting string theory projects than interesting loop quantum gravity projects.

In string theory, projects tend to be interesting because they unveil some new aspect of quantum field theory, the class of theories that explain the behavior of subatomic particles. Given how hard quantum field theory is, any insight is valuable, and in my experience these sorts of insights are what most string theorists are after. So while string theory’s popularity says little about whether it describes the real world, it says a lot about its ability to say interesting things about quantum field theory. And since quantum field theories do describe the real world, string theory’s continued popularity is also evidence that it continues to be useful.

Climate change and string theory aren’t fads, not exactly. They’re popular, not simply because they’re popular, but because they make important contributions and valuable to science. And as long as science continues to reward original work, that’s not about to change.

The Many (Body) Problems of the Academic Lifestyle

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I’m visiting Perimeter this week, searching for apartments in the area. This got me thinking about how often one has to move in academia. You move for college, you move for grad school, you move for each postdoc job, and again when you start as a professor. Even then, you may not get to stay where you are if you don’t manage to get tenure, and it may be healthier to resign yourself to moving every seven years rather than assuming you’re going to settle down.

Most of life isn’t built around the idea that people move across the country (or the world!) every 2-7 years, so naturally this causes a few problems for those on the academic path. Below are some well-known, and not-so-well-known, problems facing academics due to their frequent relocations:

The two-body problem:

Suppose you’re married, or in a committed relationship. Better hope your spouse has a flexible job, because in a few years you’re going to be moving to another city. This is even harder if your spouse is also an academic, as that requires two rare academic jobs to pop up in the same place. And woe betide you if you’re out of synch, and have to move at different times. Many couples end up having to resort to some sort of long-distance arrangement, which further complicates matters.

The N-body problem:

Like the two-body problem, but for polyamorous academics. Leads to poly-chains up and down the East Coast.

The 2+N-body problem:

Alternatively, add a time dimension to your two-body problem via the addition of children. Now your kids are busily being shuffled between incommensurate school systems. But you’re an academic, you can teach them anything they’re missing, right?

The warm body problem:

Of course, all this assumes you’re in a relationship. If you’re single, you instead have the problem of never really having a social circle beyond your department, having to tenuously rebuild your social life every few years. What sorts of clubs will the more socially awkward of you enter, just to have some form of human companionship?

The large body of water problem:

We live in an age where everything is connected, but that doesn’t make distance cheap. An ocean between you and your collaborators means you’ll rarely be awake at the same time. And good luck crossing that ocean again, not every job will be eager to pay relocation expenses.

The obnoxious governing body problem:

Of course, the various nations involved won’t make all this travel easy. Many countries have prestigious fellowships only granted on the condition that the winner returns to their home country for a set length of time. Since there’s no guarantee that anyone in your home country does anything similar to what you do, this sort of requirement can have people doing whatever research they can find, however tangentially related, or trying to avoid the incipient bureaucratic nightmare any way they can.

 

Experimentalist Says What?

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I’m a theoretical physicist. That means I work with pencil and paper, or with my laptop, or at most with a computer cluster. I don’t have a lab, and even if I did I wouldn’t have any equipment to store there.

By contrast, most physicists (and most scientists in general) are experimentalists, the people who actually do experiments, actually work in labs, and actually use piles and piles of expensive equipment. Naturally, these two groups have very different ways of doing things, spawned by different requirements for their jobs. This leads to very different ways of talking. We theorists sometimes get confused by the quaint turns of phrase used by experimentalists, so I’ve put together this handy translation guide:

 

Lab: Kind of like an office, but has a bunch of big machines in it for some reason. Also, in some of them they don’t even drink coffee, some nonsense about toxic contaminants. I don’t know how they get any work done with all those test tubes all over the place.

PI: Not Private Investigator, but close! The Primary Investigator is the big cheese among the experimentalists, the one who owns all the big machines. All of the others must bow before him or her, even fellow professors must grovel if they want to use the PI’s expensive equipment. Naturally, this makes experimentalists very hierarchical, a sharp contrast to theorists who are obviously totally egalitarian.

Poster: Let me tell you a secret about experimentalists: there are a lot of them. Way more than there are theorists. So many, that if they all go to a conference it’s impossible for them all to give talks! That’s where posters come in: some of the experimentalists all stand in a room in front of rectangles of cardboard covered in charts, while the others walk around and ask questions. Traditionally, these posters are printed an hour before the conference, obviously for maximum freshness and not at all because of procrastination.

Group: Like our Institutes, but (because there are a lot of experimentalists) there isn’t just one per university and (because of the shared lab) they actually have something to talk about. This leads to regular group meetings, because when you’re using expensive equipment you actually need to show you’re doing something worthwhile with it.

IRB: For the medical and psychological folks, the Internal Review Board is there to tell you that, no, you can’t infect monkeys with flesh-eating bacteria just to see what happens. They’re also the people who ask you whether a grammatical change in your online survey will pose risks to pregnant women, which is clearly exactly as important. Theorists don’t have these, because numbers are an oppressed underclass with no rights to speak of. EHS (Environmental Health and Safety) fills a similar role for those who only oppress yeast and their own grad students.

Annual Meeting: Experimentalists tend to be part of big organizations like the American Physical Society. And that’s all well and good, occupies a space on the CV and so forth. What’s somewhat more baffling is their tendency to trust those organizations to run conferences. Generally these are massive affairs, with people from all sorts of sub-fields participating. This only works because experimentalists have the mysterious ability to walk into each other’s talks and actually understand what’s going on, even if the subject matter is very different from what they’re used to. Experts suggest this has something to do with actually studying real things in the real world, but this is a hypothesis at best.

How do I get where you are?

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I’ve mentioned before that this blog will be undergoing a redesign this summer, transitioning from 4gravitons.wordpress.com to just 4gravitons.wordpress.com. One part of that redesign will be the introduction of new categories to help people search for content, as well as new guides like the ones for N=4 super Yang-Mills and the (2,0) theory for some of those categories. Of those, one planned category/guide will discuss careers in physics, with an eye towards explaining some of the often-unstated assumptions behind the process.

I’ve already posted on being a graduate research assistant and on what a postdoc is. I haven’t said much yet about the process leading up to becoming a graduate student. In this post, I’m going to give an overview of a career in theoretical physics, with a focus on what happens before you find an advisor. This is going to be inherently biased, based as it will be on my experiences. In particular, each country’s education system is different, so much of this will only be relevant for students in the US.

Let’s start at the beginning.

A very good place to start.

If you want to become a theoretical physicist, you’d better start by taking physics and math courses in high school. Unfortunately, this is where socioeconomic status has a big effect. Some schools have Advanced Placement or International Baccalaureate courses that let you get a head-start on college, many don’t. Some schools don’t even have physics courses at all anymore. My only advice here is to get what you can, when you can. If you can take a physics course, do it. If you can take calculus, do it. If you can take classes that will give you university credit, take them.

After high school, you go to college for a Bachelor’s degree in physics. Getting into college these days is some sort of ridiculous popularity contest, and I don’t pretend to be able to give advice on that. What I can say is that once you’re in college, coursework is important, but research is more important. Graduate schools will look at how well you did in your courses and how advanced those courses were, but they will pay special attention to who you get recommendations from, and whether you did research with them. Whether or not your college has anyone who you can research with, you should consider doing summer research somewhere interesting. With programs like the NSF’s Research Experience for Undergraduates (or REU) you can apply to get hooked up with interesting projects and mentors. In addition to looking good on an application to grad school, doing research helps boost your self-confidence: knowing that you can do something real really helps you start feeling like a scientist. Research also teaches you specialized skills much faster than coursework can: I’ve learned much more about programming from having to use it on projects than from any actual programming course.

That said, coursework is also useful. You want courses that will familiarize you with basic tools of your field, physics courses on classical mechanics and quantum mechanics and electromagnetism and math courses on linear algebra and differential equations. You want to take a math course on group theory, but only if it’s taught by a physicist, as mathematicians focus on different aspects. More than any of that, though, you want to try to take at least a few graduate-level courses in while you’re still in college.

That’s important, because grad school in theoretical physics is kind of a mess. You’ll be there for around five years in total (I was in at the low end with four, some people take six or seven). However, you take most if not all of your courses in the first two years. In general, during that time you are paid as a Teaching Assistant. The school pays your tuition and a livable (if barely) wage, and in return you lead lab sections or grade papers. Teaching experience can be a positive thing, but you don’t want to keep doing it for too long, because the point of grad school isn’t teaching or courses, it’s research. Your goal is to find an advisor who is willing to pay you out of one of their (usually government) grants, so that you can transition from Teaching Assistant to Research Assistant. This is hard to do while you’re still taking courses: you won’t have time, and worse, you won’t know everything you need. Theoretical physics requires a lot of background, and much of it gets taught in grad school. Here at Stony Brook, you’d be taking graduate-level quantum mechanics, quantum field theory, and string theory. Until recently, each one of those was a one-year course, and the most logical way to take them was one after the other. Add that up, and that’s three years…kind of a problem when you want to start research after two. That’s why getting ahead in courses, however and whenever you can, is so important: not so much for the courses themselves, but so you can get past them and do research.

Research is what you do for the rest of your time in grad school. It’s what you do after you graduate, when you become a postdoc. It (and teaching) are what you do as a professor, what you are judged on when they decide whether or not you get tenure. Working through research is going to teach you more than any other experience you will have, so get as much of it as you can. And good luck!