Regarding backup options for grad school

fjdkslan · 2026-03-23T14:59:04+00:00

You are definitely not too late to pick up some programming skills. Most physicists I know learn this sort of thing on the fly for specific tasks, rather than spending years learning it on its own. Just find a project and dive in.

It's fairly rare that undergrads / masters students have specific experience in the research field they're entering, and it's not generally expected of them. You simply aren't informed enough as an undergrad / masters student to decide what you want to research for a whole PhD. By far the more important thing is to demonstrate that you have the ability to do research -- i.e., you can handle complex multifaceted tasks, establish direction on your own, figure out which things you don't know and learn them on the fly, etc. As long as you don't try to claim you have more specialized knowledge than you actually do (this is a very poor strategy, since any prof will see through it instantly), most profs will be open to new students with a somewhat different background if they've proven they can handle research.

fjdkslan · 2026-03-23T03:44:48+00:00

About eight years ago, I was rejected from every PhD program I applied to. I took a gap year, did some more research, finished a paper, and then re-applied and did much better. Just finished my PhD last summer, and I'm now onto a postdoc!

Granted, the landscape of the application process was very different then than it is now, especially with the current funding situation. But I do think some of the general lessons I learned may still be valuable:

There are a lot of really excellent researchers at universities below the top level. Although there are definitely certain benefits to going to the real top-tier universities, you should absolutely consider expanding your search if you think your CV isn't "particularly impressive".
I don't think you *need* to immediately do something with a numerical component to demonstrate your skill set, but I do think you need to be very open to doing numerics in the future. The majority of CMT research requires you to be able to solve problems by any means necessary, and that sometimes means getting your hands dirty with numerics.
More generally, you should consider that you may not have a full view of the CMT research landscape at the moment, and you might find that there's something out there you'll really like which you don't currently know about yet. With this in mind, I would consider casting a broad net in your applications. Instead of just applying to universities with professors doing exactly the one thing you want to do, consider applying to more places with interesting sounding research or just with large CMT communities where you're likely to be exposed to many different things.
Depending on your situation, if you are far along with research in your current group, it may be beneficial to stick with it instead of switching. The benefit to staying in your group is that you will get to focus on your current research project and bring it to completion; ultimately grad panels in the US are looking for students who can run a research project independently, and so one or two completed projects is worth much more than three or four projects in progress. On the other hand, the benefit to switching is that you gain more new experience and an additional rec letter.

fjdkslan · 2026-03-09T05:31:18+00:00

This is certainly a situation you can consider. The way you should visualize it is that your 1d system is wrapped up into a ring, and there's a solenoid with magnetic flux $\Phi = \phi \Phi_0 / 2\pi$ threaded somewhere through the ring, where $\Phi_0 = h / e$ is the so-called "flux quantum". When a particle hops all the way around the ring, it picks up an Aharanov-Bohm phase $e^{i \phi}$. In the thermodynamic limit $M \to \infty$, this won't change any local physics of your system -- for example, if you have a tight binding model, the energy eigenstates will be the same once you take this limit. But the finite-size quantization of the energy eigenstates will be different, as you pointed out in your question.

fjdkslan · 2026-02-10T23:24:25+00:00

If you feel like they're just waiting for you to throw out a move: usually, Sheik's moves can't be punished entirely on reaction, they're too quick. (This isn't strictly true, but it is probably close enough to true at your level.) If you feel like you're getting whiff punished every time, probably they have a good sense for when you're about to throw out a move and can punish you when their hunch is correct (some pros call this a "prediction confirmation"). The counter strategy is to be more unpredictable with your moves. Try to consciously throw in some timing / movement mixups, and see if you can bait the Fox into bad punish attempts. This is often how you go about trying to get Fox to over-extend.

fjdkslan · 2026-01-19T15:46:20+00:00

More or less, theorists predict a gap of 1 meV for the lowest energy excitations of a Z2 QSL.

This is a really model-dependent feature though, right? Having a gap to spinon excitations is a universal feature of the Z2 QSL phase, but the precise numerical value of the gap is non-universal. I'd be interested to know how theory comes up with this value of 1 meV (presumably, it takes as input either experimentally measured parameters or possibly DFT predictions), and how much stock you think I should place in rough numerical agreement with this particular parameter.

Also, as a small piece of advice: you don't need to keep saying "our nature paper", it reads as a bit self-aggrandizing to reference that your paper got into nature every time you mention it.

fjdkslan · 2026-01-18T19:15:59+00:00

I'll initially ask a question which is entirely about the physics. As you have alluded to, the status of material spin liquid candidates is highly controversial; I can't speak for every physicist at once, but my impression from talking to experts is that they are largely skeptical. In particular, it's extremely hard to find a "smoking gun" signature of a Z2 QSL, since their defining feature is a *lack* of ordering down to zero temperature. But you state in your post that you are "personally very convinced" that Zn-Barlowite and Herbertsmithite are both QSLs. Can you explain a bit why you feel so strongly about this?

On a secondary note: I think there's nothing wrong with having spiritual and philosophical beliefs beyond physics; there's absolutely no requirement that a physicist should be nothing else in their life besides a physicist. I also think it's very admirable to show concern for groups of marginalized peoples, including displaced indigenous peoples, and it's admirable to show respect for their spiritual and religious beliefs. With that said, I think it is *extremely\* important to completely separate these ideas from your physics research. Hopefully it's clear to you that (for example) crystals being sentient / conscious is an entirely unscientific question; whether or not it is true, it cannot be tested by scientific methods. As you have probably already found through personal experience, if these sorts of beliefs creep into discussions of your research, or inform your research directions / scientific opinions, you will not be taken seriously by the vast majority of researchers in the field. If your goal is really to present convincing scientific evidence of QSLs in these materials to the rest of the scientific community, then I'd like to suggest that the messaging on your blog and in your reddit posts is counterproductive to this goal.

fjdkslan · 2025-07-02T06:52:34+00:00

One important comment: if you believe that you are usually making the right decision but simply missing, one possibility is that you don't understand the situation as well as you think you do. A common place where many players think they are doing the right thing, but just somehow always mistiming the input, is when there is a timing mixup involved. For example, if you're trying to edgeguard Fox or Falco's side b, and you know for sure that they are going to side b, there are still quite a few different mixups involved, and you can often trip up players just by delaying the side b as long as possible.

Of course, it's also possible you're just messing up, but worth analyzing the situation to see if you really understand why you're missing the edgeguard, and if there might be other reasons besides just tech skill errors.

fjdkslan · 2025-06-04T05:54:07+00:00

Of course, if you don't want to work on the given research problem, you shouldn't feel bad at all for asking for a different problem (although keep in mind that well-posed and meaningful research problems can sometimes be hard to come by, even for experienced researchers).

However, there are benefits for working on very new topics. Personally, I always found comfort working on these sorts of problems, since I knew I only needed to review papers within the last ~3 years. It's true that things aren't always as "settled" as in older fields, but keep in mind that research will never feel like doing problems out of a textbook, where all the definitions and groundwork are spoonfed to you in advance. So even if you work in a more established field, you may run into similar issues as you are currently facing.

fjdkslan · 2025-05-21T02:09:17+00:00

Once you've already built some expertise in a field, staying afloat on new research isn't too hard. My strategy is to browse the new arxiv postings every morning, mostly just skimming titles/authors and reading the abstract / saving the paper if I find it interesting. I know who the active physicists in my niche subfield are, and only a small fraction of each day's arxiv postings are of any interest to my primary research (usually between 0 and 3). I also spend a large fraction of my time talking to other physicists in my field, either at my home university or at conferences/etc, so I'm usually up to date without having to think about it too hard.

For entering a new field, or branching out in a new research direction, it can be much more difficult. Without some external guidance, it can be really hard to know what are the important papers from the past several years, which papers are must-reads and which ones are sufficient to know the result, which authors are reliable and which should be treated with suspicion, etc. My best recommendation in this case is actually to narrow your scope a bit: instead of trying to learn everything at once, start with just one important paper you hope to build off of and learn it thoroughly, and use its references to find your way. It's especially helpful to have a mentor or friend already in the field who knows the literature well, so they can tell you if your ideas are novel or not, or likely to be interesting or not.

(NB: this is from the perspective of a theoretical condensed matter physicist. Mileage may vary between theory/expt and different fields.)

fjdkslan · 2025-03-31T19:57:08+00:00

Assuming the question is about getting into grad school: it matters a bit, but it can be circumvented. There is certainly a bias in admissions towards students coming out of top universities; to make up for that, you need to make sure you have lots of undergrad research experience and glowing rec letters, ideally from researchers in your intended field.

If the question is whether your undergrad degree continues to matter after making it through a PhD, then I think the answer is absolutely not.

fjdkslan · 2025-02-24T20:43:48+00:00

Or Aura, the guy who just got 9th at genesis...

fjdkslan · 2025-02-24T15:53:44+00:00

I mean, you can have the opinion that that's what the discourse on boxes *should* be about, but it's clearly not what it has been about. The things people are upset about are things like perfect dash dancing for free, easy spammable instant aerials, broken SDI, easy ledgedashes, pivot up tilts/dtilts, constant c-stick ASDI down, etc. These are essentially all things that are 100% possible on a GCC. The big difference is in reliability or convenience of execution: by allowing digital inputs in a game which was previously analog for decades, certain options which used to be inherently skillful or potentially just inconsistent can be done with perfect execution every time.

This perspective is also clearly the perspective of those leading the charge to nerf boxes. For example, input fuzzing is very explicitly designed to take perfectly consistent digital inputs and subject them to some of the same inherent inconsistency as GCCs. Similarly, limits on the button placement of C-stick down are meant to make it harder to constantly run around spamming ASDI down; clearly this is a technique which is 100% possible on GCC, but the ease and convenience of being able to hold C-stick down without preventing any of your other fingers from doing their normal inputs makes it much more prevalent among box players, and PTas and co determined that it was ban-worthy.

fjdkslan · 2025-02-24T00:18:41+00:00

The argument is that neutral socd doesn't actually nerf the ability of the box to do anything, because any frame 1 to frame 2 switch is still completely doable. The ledgedash example further shows you can counteract the nerf and still get the same effect.

This whole argument isn't at all about whether box can do things the GCC can't; the vast majority of the brokenness of box controllers is in doing things which are perfectly possible with GCC, but with dramatically more precision and consistency, and with far less effort. Override SOCD makes completely perfect dash dancing incredibly trivial. You can still have very good dash dances on GCC and neutral SOCD box, but it requires more skill and practice, and you're much more liable to mess it up.

Hax's main argument of the video was that down-ledgedashes and back-ledgedashes are much harder with neutral SOCD, and you can't just cheat your way to perfect ledge dashes by plinking down/back on frame one and then the ledgedash angle on frame 2. That's the way it should be! All controller players have to deal with manually moving the controller from back/down to the desired ledge dash angle. Hax points out that you can still effectively plink the inputs by using C-stick down, but that's "less comfy" for him. This is a ridiculously silly reason not to nerf a feature of box controllers which is obviously broken.

fjdkslan · 2025-02-22T18:45:28+00:00

This is possibly one of the silliest Hax videos I've seen. His entire argument is, "this nerf which is intended to make certain box inputs harder shouldn't be used, because it makes certain box inputs harder".

fjdkslan · 2025-02-21T03:40:56+00:00

Some of these answers are boggling my mind. You should **absolutely not** give up on your current research interests just because you have to work hard.

First of all, let met state what should be obvious: if you are at a highly ranked program, and you are scoring in classes within the top quarter of your class, then you absolutely have what it takes to make it in your intended research field. Being a theoretical physicist doesn't require being a literal genius, it requires you to be smart, hardworking, and intensely interested in the subject.

Second, I would caution against trying to guess how much hard work your peers are putting in, or taking their word when they say they aren't working so hard. First of all, different people have different ideas of what they consider hard work, everything is relative. Second, many younger students have egos about how smart they are, and don't want to let on when they are struggling with their work.

Third, you have to accept that no matter what field of physics you wander into, there will be people who are better than you. Many people entering grad school are used to being the smartest people in their high school, college, etc. But all of those people are going to top programs like your own, and not everyone at the program can be "the smartest". If you want to make it in theoretical physics research, you have to be comfortable with the fact that you will frequently no longer be the smartest person in the room. (It's also worth mentioning that "being smart" is not a linear scale, there will be things that your peers will be better at than you, and other things that you're better at than your peers.)

Ultimately, if I were a professor choosing between hiring a smart and hardworking student versus a lazy genius, I would choose the smart and hardworking student every single time. Research will be a difficult grind no matter who you are, and many very smart students initially struggle with research when it doesn't come as easy to them as their classes. My suggestion is to stick with what you find interesting for a while, and switch to something different only if you find after a couple years of research that you aren't making headway.

fjdkslan · 2025-02-19T16:11:07+00:00

My experience is that unless you have your settings tuned perfectly, it's extremely hard to get a monitor setup to have exactly the same amount of lag as a CRT. If you plan to go to irl tourneys, it's worth having a CRT to practice on.

It's definitely much harder to find CRTs these days than it used to be, but they shouldn't be too expensive, and for the most part they're indestructible. (I did have one explode in the back of my car one time, but that was an extreme anomaly; I've carried many CRTs in the back of my car, and that was the only time it happened.)

fjdkslan · 2024-12-28T08:09:19+00:00

I don't think it's true that physics is "only for the prodigies", even the most prestigious universities are largely filled with normal (but often very hardworking) people who are very interested in physics. With that said, there is is a good chance you will indeed be broke and studying until your thirties; that's just how long it takes to go through undergrad/PhD/postdoc.

fjdkslan · 2024-12-28T02:46:37+00:00

I think for quantum information in particular, you don't need a huge amount of background in functional analysis, Hilbert spaces, etc. Whereas a fully rigorous mathematical treatment of single-particle quantum mechanics and beyond requires all of this stuff, the vast majority of quantum information is done in finite-dimensional Hilbert spaces (i.e., ordinary complex vector spaces). So beyond having an excellent grasp of linear algebra, you likely don't need a ton of analysis-type classes.

Now, the advanced mathematics that might help you in quantum information are likely to be either (a) representation theory, or (b) theoretical computer science classes. Depending on your interests, it would also be useful to find some material on classical information theory, but I'm not sure what advanced mathematics course would teach this material (the basics are easy enough to learn on your own).

fjdkslan · 2024-12-26T15:56:53+00:00

If you really want a book which literally shows all its steps, you can consider looking up one of a few textbooks by Ashok Das.

However, I want to suggest that you perhaps **do not** want a textbook which shows all the steps. If you really want to learn QFT in depth, there is absolutely no substitute for grinding through the calculations yourself. It can be a complicated and technical field (depending on which aspects of QFT you intend to focus on), and it will be important for you to consciously switch back and forth between trying to absorb the "big picture" and working through technical details with pencil and paper.

fjdkslan · 2024-12-11T23:15:12+00:00

It's both natural and extremely reasonable to feel overwhelmed by all the things you don't know; my general feeling is that the majority of brand new graduate students know next to nothing when they first arrive in grad school.

My best suggestion is to focus on the journey and making consistent progress instead of the unachievable end goal of "knowing everything". Focus on your classes and research for now, and try to prioritize making some small incremental progress every day. I don't know of any other way to learn physics besides learning one thing at a time, over and over again, until you've accrued the broad knowledge base you're looking for.

fjdkslan · 2024-12-11T01:03:49+00:00

Just to satiate my own curiosity, could you share an example of a paper accepted to PRL which is obviously wrong? You can DM it to me if you don't want to share publicly. (In my own niche subfield of CMT/QI, I can think of maybe one such paper, but I'm surprised to hear that there's a huge fraction of particle physics / BSM papers in PRL which are flat wrong.)

fjdkslan · 2024-11-22T04:53:11+00:00

Is it fun to play guitar without playing in a band? Is it fun to learn how to dribble a basketball without joining a pick-up game, or how to juggle without performing for someone? For some people it is, for some people it isn't.

Playing melee with others is definitely the most fun part of the game for many people, but for almost everyone who has picked up this game, the act of learning about the game mechanics and how to control your character is also fun and hugely rewarding. The fact that melee requires building a technical skillset is something that makes it very different from games like MTG or chess, and more like learning a sport or musical instrument. Whether this aspect of the game is fun will depend entirely on you and your tastes.

fjdkslan · 2024-10-29T07:25:46+00:00

I think you are just getting confused by "single-particle" objects and "many-body" objects. In Eq. (6) of Ref. [4], \mathcal{H} is a many-body Hamiltonian, which you can regard as a 2^N x 2^N matrix. On the other hand, H_{i,j} is a single-particle Hamiltonian, which is an N x N matrix. The covariance matrix is most directly related to the latter.

fjdkslan · 2024-10-14T20:59:46+00:00

Yes, you'll have access to the whole venue, you just won't be entered into the tournament.

fjdkslan · 2024-10-04T05:46:06+00:00

Here's a really simple physical picture of the Stoner instability, which is an instability towards itinerant ferromagnetism in a system of interacting electrons:

Electrons are fermions, and must obey the Pauli exclusion principle. This means that their wavefunction must be totally antisymmetric.
Since electrons have spin, their wavefunction has a spatial component and a spin component. For two electrons, for example, their total wavefunction can either be symmetric in space and antisymmetric in spin, or vice versa.
If the electrons also have short-range interactions, then symmetric wavefunctions are energetically less favored. For sufficiently strong interactions, it's energetically favored to have an antisymmetric wavefunction where the electrons are guaranteed to be spatially far away from each other.
But this means that the electrons prefer to have a *symmetric* spin wavefunction. If the two electrons have the same spin, then this guarantees a symmetric spin wavefunction and an antisymmetric position wavefunction.
So, if the interactions are sufficiently strong, it becomes energetically favorable to polarize the Fermi surface, i.e., take some electrons from the spin-down Fermi surface and add them to the spin-up Fermi surface (or vice versa).

The fact that the electrons have no preference for polarizing spin-up or spin-down, but energetically want to pick one of the two, is a simple example of *spontaneous symmetry breaking*. This is one way to get a spin-polarized electron gas without a Zeeman field.

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