We've previously had some discussion about the suitability of pure math questions for this site. Currently, pure math questions - by which I mean those that have no physics content, even if they arise in a physical context - are off topic. We migrate those to Mathematics. Here are some recent exa...
We have a precedent for that in many other areas, e.g. subjective questions, like "what kind of coffee do physicists like?" (that's an extreme example but you see my point?)
No, that represents a bit of a change. Right now questions about a mathematical method are considered off topic even if the question arose in the context of applying that mathematical method to a physical problem.
with some selected exceptions for things like renormalization, which could arguably be considered physics anyway
So for example, a question like "How do I solve the Schroedinger equation for the potential V(x) = ...?" would currently be off topic, but the proposed answer would put it on topic.
I have noticed that some stack exchanges sites have different policies as compared to the stackoverflow.com. e.g. Math.SE has completely different policies for comments and home-work questions.
What is the policy of Phys.SE for asking beginner level questions, that is can unintelligent pe...
I know that that $$\dfrac{d\sqrt{x}}{dt} = \dfrac{d\sqrt{x}}{dx} \dfrac{dx}{dt}$$
In this equation there you only have 1 variable, namely $x$.
But why is the following correct?:
$$T = \frac{1}{2} m \left(v_{x}^2 + v_{y}^2 + v_{z}^2 \right)$$
$$\dfrac{dT}{dt} = m \left( v_{x} \dfrac{dv_{x}}...
ironically, it would actually be a decent question if he hadn't tried so hard to justify it being on topic here and hadn't put arbitrary restrictions on it (the note in the last paragraph).
It seems that popular textbooks on electrodynamics do not discuss how to solve the Laplace equation in ellipsoidal coordinates. I could not find any reference, but there must be references about this. Could anyone give a reference?
As an example, the question can be how to calculate the charge d...
@ChrisWhite Instead of chaotically looking into stuff, I'm now following an orderly procedure... (yeah, I'm speaking about learning Physics) :D
Then, I lost internet for about a month (by which, productivity was also lost)... (now, I have an USB modem, still a lot of connectivity problems since relocation)
Two weeks back, I moved into a new home... (which further reduced my productivity)
@ChrisWhite What would that be? ... would that be useful for me? :P
I have one question: I know that if you will act $n$ creation operators on state: $n\hat H a^+|\Psi>=Ea^+|\Psi>$ you will get $E_n = (n+\frac{1}{2})h\omega$ and if you will act on state with annihilation operator you will get 0. But i have found in internet that if you will act annihilation/creation operator on state you will get this: $a^+|n>=\sqrt{n+1}|n+1>$ and $a^-|n>=\sqrt{n}|n-1>$ but how to derive them? thanks
user54412
@Waffle'sCrazyPeanut useful? depends - do you want to simulate radiation-dominated accretion disks around black holes?
As soon as this semester ends, I've got 2-months of vacation (longest-ever vacation I've possibly had, since fifth grade)
user54412
@Gigi10012 That could go on the main site. You can work things out explicitly, using Hermite polynomials. Or there are more clever ways just using the expression of H in terms of a and a^\dagger. Or you can postulate those relations for a|n> and a^\dagger|n>, and derive what a and a^\dagger must be in terms of x and p.
Here we are taking environment like movie 'the Matrix'. Now in that movie people live in Simulated reality.Now according to Wikipedia definition for simulated reality is "the hypothesis that reality could be simulated—for example by computer simulation—to a degree indistinguishable from "true" reality, and may in fact be such a simulation. It could contain conscious minds which may or may not be fully aware that they are living inside a simulation."
Now suppose a computer simulation programmer develop a mechanism in which arrow of time is vague. Means glass falling from table and its reverse is both valid..(which is prohibited from our real world by second law of thermodynamics). Now a child is born in that simulated reality world and does not come direct touch with real world which is human used to live before that matrix like scenario.
So for that child is it possible that he can not differentiate arrow of time(difference between future and past) when bring back to real world but his parents can because they were born in the real world and then has been exported into matrix?
> Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question.
Uh, I recently got in a discussion with my GR prof about the staticness of the "k" constant in flrw (the one which can be 1,-1, or 0), and we had a rather interesting discussion.
I don't know enough to know which aspect this is. Might be mutiple
@KyleKanos The prof mentioned that the idea was interesting and would make a good project for my fourth year, in the meantime I plan to try to learn enough and read some papers
@KyleKanos sort of, yeah. Basically, if we tweak the definition of "homogeneity" to allow for it to be inhomogenous at a snapshot but homogenous as a time average, I wanted to see what we can do.
probably a very easy question for someone but for the last question on the page, why is it 'cannot be true' rather than 'could be true', when surely the summation of no forces could be 0 too?
haha ok - that's sort of worrying but logically to me if you're not touching it, there's no resultant force, just like if you had two opposing forces meaning there's no resultant force, so I guess the Mark Scheme is just wrong here
In a comment, someone posted a URL that went directly to a particular answer to a certain question. How does one find the URL of a particular answer?
I have noticed that some stack exchanges sites have different policies as compared to the stackoverflow.com. e.g. Math.SE has completely different policies for comments and home-work questions.
What is the policy of Phys.SE for asking beginner level questions, that is can unintelligent pe...
I know that that $$\dfrac{d\sqrt{x}}{dt} = \dfrac{d\sqrt{x}}{dx} \dfrac{dx}{dt}$$
In this equation there you only have 1 variable, namely $x$.
But why is the following correct?:
$$T = \frac{1}{2} m \left(v_{x}^2 + v_{y}^2 + v_{z}^2 \right)$$
$$\dfrac{dT}{dt} = m \left( v_{x} \dfrac{dv_{x}}...
