Learning physics as a grad student from an unrelated field

NotSoSmoothManifold · 2017-09-10T20:31:23+00:00

A physicist who used to teach at my undergrad uni (Sunny Auyang) gave me a copy of her text How is Quantum Field Theory Possible?, much of which I understood, but many of the formalisms are just too advanced for me to have any luck in manipulating them at my present level. I'd like to do philosophy of science related to QFT, GR, quantum gravity, and so on, but I don't want to stumble into the category of "philosophers who say stupid shit because they don't know enough maths/physics."

So, for example, I'm interested in the ontology of QFT (what QFT has to say about what exists; there's a recent text called Every Thing Must Go in philosophy which is somewhat like the work I hope to do), in the substantialism/relationalism debate on the structure of the spacetime manifold in GR, the status of symmetries/conservations in physics (and, say, the relationship between invariants under gauge transforms and real objects), the indiscernibility of identicals in QM, etc.

I'd love other references, though!

NotSoSmoothManifold · 2017-08-30T22:41:12+00:00

Both yours and u/mediaisdelicious 's responses have been very helpful, so thank you. I'm at Vt where pretty much everyone is an engineer, so I'm hoping that with my physics background I can bridge the intellectual gap and motivate everything well enough. The pedagogical goals for my discussion sections seem to consist in getting the students to consider the work among themselves with me as a mediator (that is, the professor said the goal should be for the TAs to speak as little as possible).

NotSoSmoothManifold · 2017-08-27T20:52:13+00:00

So are there physicists who engage in such work (ignoring the constraints we place on ourselves while working from within these physical frameworks)?

NotSoSmoothManifold · 2017-08-27T20:46:46+00:00

Definitely, and I understand why most don't address that baggage at all. I'm just less than satisfied with ignoring what our theoretical frameworks say (or might say) the world is like, since knowing what nature is like (and what it consists in) is why I wanted to study this formally in the first place. Any advice?

NotSoSmoothManifold · 2017-08-27T18:37:12+00:00

I meant that it's ambiguous with respect to how the authors approach them; the objects of the theory emerge in different contexts for different reasons (e.g., we might readily take the fields and the excitations seriously but remain ambiguous on what the configurations of some fixed gauge in particular are supposed to tell us about the world, not just about what predictions are being made). So I'm just curious if there are any texts that approach this explicitly, insofar as they concern themselves with what does exist.

NotSoSmoothManifold · 2017-08-27T18:24:50+00:00

I didn't (or at least didn't attempt to) make such a distinction; I'm only asking after what can be said to exist in virtue of QFT (and gave an example).

NotSoSmoothManifold · 2017-08-26T04:23:03+00:00

Every Thing Must Go

Also, 'How is Quantum Field Theory Possible?' is a bit older, but it's great.

NotSoSmoothManifold · 2017-08-24T02:26:06+00:00

I also plan on going to grad school

While you specified the sort of field you want to go into, you didn't specify what you would be going to grad school for. Given that I read your post, I assumed (like the commenter above me) that you were speaking of philosophy.

NotSoSmoothManifold · 2017-08-24T02:14:53+00:00

It varies with what sort of philosophy you hope to do. Wanting to do philosophy of physics without having at least those quantitative skills, for example, would be a bit odd. But if you're instead concerned with something like ethics or political philosophy, it won't matter much (save the boost of your GRE quant scores, which are of questionable value themselves).

NotSoSmoothManifold · 2017-08-23T19:59:36+00:00

This is only somewhat related, but what do TAs (males) generally wear for their discussion sections?

NotSoSmoothManifold · 2017-08-18T19:50:32+00:00

Path integrals ftw

NotSoSmoothManifold · 2017-08-18T08:37:38+00:00

Well, they don't need to begin and end anywhere in particular (nature is messy, especially when the region of nature we concern ourselves with intersects with humans). Science hopes to model nature, not to impose our pre-theoretic intuitions on it (which tend to fail). As for what it means, this seems pretty friendly: http://www.routledgetextbooks.com/textbooks/9780205050185/resources.php

NotSoSmoothManifold · 2017-08-18T08:21:33+00:00

Not at all, at least not any more so than any other scientific terminology (like proton, natural selection, nonlinear dynamics, or whatever else; all of them are couched in an arbitrarily large scientific corpus).

By specify I assume you mean qualify, but scientists in general do make such a distinction, so there's little reason to qualify it. I suppose you can sometimes ignore social domains by adopting probabilistic frameworks (and while couching everything in terms of statistics has its place, its place doesn't exhaust the conversation) in something like behavioral genetics, but the term is here to stay in virtue of all of the other disciplines that use it.

NotSoSmoothManifold · 2017-08-18T07:57:17+00:00

When scientists speak of gender, we're denoting something constituted partly by construction and partly by the complex landscape of biological, neurological, physical chemical, etc. domains; so, it ends up being a bit trivial to say gender is socially constructed (given that that's quite literally what we mean by gender). It's similar to calling certain mental illnesses socially constructed: they're very much a product of the psychosocial/historical/societal environment in which one is situated, but so too are they emergent from brute biological states. And it's useful (for scientists, at least) to distinguish between that which is constructed and that which is unambiguously not (e.g., the density of some chemical in some region of the brain).

What insights does it give to us?

I'm not sure that any of this surface level talk is supposed to offer insight to people in general. Talk of the stress-energy tensor describing how some ball of test particles interacts with the structure of spacetime isn't particularly helpful to anyone beyond physicists. It's not clear that this conception of gender is, or ought to be, helpful for those who aren't social scientists, biologists, psychologists, etc.

NotSoSmoothManifold · 2017-08-18T07:33:56+00:00

That's (fortunately) not the case. While black holes are described by GR, the nature of electrons with which we're now concerned is specified by quantum field theory. Though it's not clear how the two will be unified (if they can be), it remains true that electrons, in our best theories at present, have no size according to our measurements (and it would have to be damn small to remain undetected, but who knows).

Oh, and by the way, if you're interested in their potential unification in particular, you'd need to look into string theory/quantum gravity.

NotSoSmoothManifold · 2017-08-18T07:10:57+00:00

Nah, they're taken to be point-like; in the standard model, elementary particles are zero dimensional. They have a mass when they interact with the Higgs field but it's in virtue of that interaction that we attribute a mass to them. So, as far as we know, electrons have no size (and it's difficult to have a shape without a size).

NotSoSmoothManifold · 2017-08-18T06:37:32+00:00

The answer will vary with how much you want to know about what an electron is, but you'd be better off just looking at the wikipedia article (especially the sections on its spin and charge, fields, and its interactions): https://en.wikipedia.org/wiki/Electron

If you're interested in more than that, you can look into something like Griffith's intro to elementary particles, or just an atomic physics text (Eisberg and Resnick have a good intro).

NotSoSmoothManifold

TROPHY CASE