i don't follow all the math, but i can pick up what i need to in most spots.
Anonymous
@heather MIT OCW has a lecture series which follows the book by Hecht an the one by Goodman (including readings and assignments from those two books). I'm using it at present and am finding it quite useful. The best part is that in the OCW they specify the exact amount of time you need to learn each topic.
@heather Yeah, and also it will be helpful if you learn a bit of differential equations and take a basic electromagnetism course before starting that. Good luck with your studies!
This has bothered me for some time, and since bad tags are on the table, I think this is a good time to do it.
There are currently 60 questions tagged general-physics of which roughly fifteen have that as their only tag (and of those, five are closed). The tag is absolutely terrible and it is ab...
@EmilioPisanty fwiw, I already asked this question (A generally terrible tag) which Qmechanic marked as a duplicate of an old "list tags to burninate" post. i do agree though, with your meta post.
Please burninate general-physics.
It is no more descriptive of a question than the fact that it was posted in this site. If absolutely no other tags apply to the question then it is very, very unlikely to be on-topic here.
Unless anyone objects I'll start to slowly de-tag the current 54 mistagg...
@user685252 : This is my first feed creation, so I don't know if I did it correctly. However, if it works, it will not be in form of a drop-down, but as a comment.
presumably OP means deriving the wave equation from the Maxwell equations
but frankly it's such a low-effort question that any external help will just encourage OP to ask more terrible questions
so, e.g., OP is clearly referencing a derivation that works in reduced dimensionality, as is usually done in intro texts, but which is a very simplified version of the full derivation you can do. That's OK if OP references the text where they got this from.
@heather Oh, that's great! You might want to check out our blog chat room, then. It's a bit busier during the week. Monica Cellio's probably the go-to person if you want to submit a story.
Does anyone know (or know a link to) the precise statement of Schrodinger's equation in an electromagnetic field, using connections? In http://www.ihes.fr/~celliott/Dirac_quantisation_talk.pdf they use $$i \frac{\partial \psi}{\partial t}= (\nabla+iA)^2 \psi$$ but this is a type error since $A$ as a $1$-form here ( they later talk about $A+d\chi$).
@Alyosha $\Omega^1(M)$ is naturally a $C^\infty(M)$-module. Multiplication of $\psi\in C^\infty(M)$ by a 1-form is well-defined.
Hmm, the other side doesn't make much sense in that case.
Anonymous
@Abcd How can the accelerations be still $a_r$ and $-a_r$ ? Won't they become $g+a_r$ and $g-a_r$ ? That is because now P is falling down with accn $g$. So the net acceleration of the blocks can be found by superposition of P's accn and their accn w.r.t pulley P.
@Alyosha That's one possibility, and then contract with the metric... But usually one sees $(\nabla+\mathrm i A)^2$ in the contex of Yang-Mills, where you get the curvature. So that's a 2-form. That equation does not make sense as written, I see your point now.
OK. I'm not really happy to assume Yang Mills stuff because I'm trying to find out from foundations how much of it is physical assumptions and how much is maths. Thanks for the input!
Metrics don't really appear in Maxwell's equations, though, so I'm not sure if it's good to use one.
@Alyosha As a mathematician, most of these equations seem to be well-motivated in a classical setting or whatever, and then by some version of the Equivalence Principle are greatly generalized.
@Alyosha They do.
Curvature appears.
Maxwell's equations are $\mathrm dF=0$ and $\delta F=0$. Defining $\delta$ requires a metric.
I just voted to close this question over on physics and I'm confused with the result.
When I was shown the question in the review queue, it had four close votes as off-topic, but I disagreed with that assessment - the way I see it, the question is a clear duplicate of this other question, and th...
@Alyosha It's still inconsistent because $A^2$ there should be $A\wedge A$, which is $0$ for a $\mathrm U(1)$ gauge theory. In QM you have an $\mathbf A^2$ though, I think.
Many physics papers now have dozens of authors per paper. Experimental physics may have multi-organizational and multi-country contributing staffs, but I'd guess that most of the names don't contribute a word or equation to a paper, yet they get individual authorship credit.
My question is who de...
Does physics address the topic of consciousness?
For instance, does physics say anything about how it might arise or what might be its qualitative properties?
I'm wondering because it's interesting how certain combinations of particles are conscious (at least apparently) while others are not.
Are there are any mathematical expressions in physics that will always be equal one or to a number which is almost equal to one.
If there are any I would highly appreciate if you could show me and tell me the name of it/them.
@EmilioPisanty I'm going to mildly disagree with that - 1. There are physics-y people that talk about consciousness and 2. Asking 'Is there a known classical [non-quantum], relativistic law that allows massive particles to travel faster than light' isn't off topic, it's just that an answer that isn't no isn't 'mainstream'
@Mithrandir24601 I think the question is off topic. You apparently think it is on topic. You have a perfectly legitimate right to think it is on topic. I have a perfectly legitimate right to think it is off topic. I don't see what else there is to discuss.
@heather yeah, I agree. I voted to delete but it won't do much, community deletion only works for negatively-scored posts.
@EmilioPisanty Because I wanted a short discussion/explanation of why you think it's off topic and thought that the easiest way to get that started was to explain why I felt that it was on topic :P
"There are physics-y people that talk about consciousness" doesn't make a question about physics. There are physics-y people that overstep the boundaries of what they can intelligibly talk about and talk all sorts of nonsense about philosophical topics that they should really stay out of.
Generally, when I say physicists I suppose I tend to mean someone with a job that involves publishing papers in mainstream physics, but it's not something I've thought much about
@Mithrandir24601 unless you have something specific to discuss, I would rather not go into rambling-rant territory just for the sake of rambling rants.
Erm... OK. My main point is that (if this makes any more sense, which it probably won't) asking something along the lines of 'is x mainstream physics?' isn't a non-mainstream physics question (although I don't actually know if such a question is on or off-topic here) regardless of whether or not x is mainstream physics
@ACuriousMind Consider the following... $\Omega\subset\Bbb R^n$ with $\partial\Omega\in C^1$ so we have a geometric outer normal field $\nu$. Suppose $\bar\Omega$ has a Riemannian metric $g$ and a Riemannian outer normal $n$. For $w\in T_p\partial\Omega$, we have $g_{ij}w^i n^j=0$. But the geometric normal gives $w^i\nu^i=0$. Since $w$ is arbitrary we are left to conclude $n^j=g^{ji}\nu^i$, no?
@Kaumudi.H you might find this interesting, it answers a huge question that was on my mind lately after reading other movie reviews of Dunkirk thedailybeast.com/… ps my uncle was here en.wikipedia.org/wiki/Omaha_Beach