[knzhou]

Indeed, the author's 2000-page online textbook, heavily promoted on the internet, is a classic trap for unwary students.

It looks alright at first: volume I is light on math, but full of neat examples. But it's full of intuitively plausible but slightly wrong statements which fall apart in more general situations, reflecting the author's lack of technical expertise. This problem steadily gets worse: volume IV is an oversimplified introduction to quantum mechanics which contains almost no math, and serious conceptual errors on almost every page. Volume V covers a bizarre mix of particle physics, consciousness, and sexual reproduction. And volume VI is the author's almost math-free personal theory of everything. Because the change is gradual, a student can get seriously misled without noticing, like the proverbial boiling frog.

On HN, people are always asking how to get started self-learning topics like physics. The tragedy is that this has been a completely solved problem for decades: the standard textbooks are excellent. But people don't hear that message because self-promoters pollute the discourse.

[mncharity]

> the standard textbooks are excellent

A caveat. Some years ago, at a first-tier university, some physicists and mathematicians were munching. A physics professor described how days earlier he thought he had found a case of a well-respected intro physics textbook saying something wrong. But, after some hours and days of thought, he realized the textbook was very carefully worded so as to not be incorrect. Yay. Most everyone smiled and agreed it was an excellent textbook.

A bit later, there was a quiet out-of-band question: So... if you're already an expert on the topic, and do a close read, after thinking about it for days, you will escape being misled... and this is a win??

There's an old physics education research joke: If you think your lectures are working, your assessment also isn't. I've found that to apply to much science education content as well.

[lisper]

> the standard textbooks are excellent

Sorry, I have to disagree with this, at least with respect to quantum mechanics. The pedagogy of QM is atrocious because it generally focuses on the single-particle case and relegates entanglement to the sidelines while making a big deal out of the mystery of the measurement problem. This leaves students hopelessly confused. At least, it left me hopelessly confused for about ten years. Even today one hears physicists speak un-ironically of "quantum erasers changing the past" and other associated nonsense. If there's a standard text that inoculates against that, I have not seen it.

[spekcular]

Can you point to a standard textbook that does this? The ones I'm familiar with definitely don't shortchange multi-particle problems.

And is the measurement problem not a mystery? If there's convincing explanation, that's news to me.

[lisper]

> Can you point to a standard textbook that does this?

That does what? Focus on the single-particle case and punt on measurement? My two poster children are the Feynman lectures and Griffiths.

> The ones I'm familiar with definitely don't shortchange multi-particle problems.

What does your reading list look like? Maybe things have changed since I last looked.

> the measurement problem not a mystery?

It might be a mystery, but it is not the mystery most commonly presented, namely, that particles change their behavior "when somebody looks." This is nonsense. Measurement has nothing to do with "somebody looking", it is just entanglement + decoherence. The only real mystery is the origin of the Born probabilities.

See https://flownet.com/ron/QM.pdf for a complete discussion.

[spekcular]

A) I don't consider the Feynman lectures a "standard textbook." I don't think there exists any university that uses them as the primary reference in their quantum course. They're fine, as far as they go, but I think modern pedagogy is better.

Concerning Griffiths, what do you feel it lacks? You've got the hydrogen atom, fermions, bosons, helium, and probably more stuff that I'm forgetting right now. What else would you stick in an intro course? Hartree-Fock?

B) Decoherence doesn't solve the measurement problem. Even the decoherence boosters admit this. See, for example, Adler's paper on this: https://arxiv.org/abs/quant-ph/0112095.

This isn't to say the decoherence program isn't important. I think it is. It just hasn't solved the measurement problem.

[lisper]

What Griffiths lacks is an explanation of what a measurement is. He, like many other authors, explicitly avoids this because he says that measurement is an ineffable mystery, but it isn't. A measurement is a macroscopic system of mutually entangled particles. The only real mystery is why the outcomes obey the Born rule.

Decoherence does not solve the whole measurement problem. Like I said, it does not explain the Born rule. But it does solve parts of the measurement problem. Decoherence explains why measurements are not reversible (they are reversible in principle but not in practice because you would have to reverse O(10^23) entanglements). It explains why only one outcome is experienced (because you are part of the mutually entangled system of particles that constitutes the measurement, and all of the particles in the system are in classical correlation with each other). I don't know of any standard text that discusses this at all.

Whether or not Feynman is a "standard text" is quibbling over terminology. A lot of people learn QM from it (or at least try to).

[spekcular]

I'm sorry, but your description of how decoherence purportedly solves parts of the measurement problem is incorrect.

Even decoherence researchers agree that docoherence theory does not do this. You can find references and details in the Adler paper I linked, or in Schlosshauer's "Decoherence, the measurement problem, and interpretations of quantum mechanics." (Schlosshauer is the author of a main reference on docoherence: http://faculty.up.edu/schlosshauer/index.php?page=books.)

So, the reason that Griffiths avoids giving the explanation of measurement you prefer is that it is wrong. It's a virtue of the book, not a fault. He does discuss decoherence on page 462 of the third edition, though.

[hoten]

What are the standard textbooks? Could I just look at the curriculum of any physics program of a respected school and go from there?

[spekcular]

Yes. Whatever MIT uses for their OpenCourseWare is going to be fine, for example.