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Ryan Unger

12:58 AM

@AlexSok index raised with the inverse metric

4 hours later…

vzn

4:54 AM

↑ Probability distributions for the first 36 eigenstates of a particle trapped in a heart-shaped potential well! reddit.com/r/quantum/comments/lw9z9t/…

5 hours later…

Physics Meta

9:32 AM

Q: Someone other then OP adding "homework-and-exercises' tag to a question, then the question gets closed as a homework-type-question?

On this question by Kashmiri, here, it was originally posted without the "homework-and-exercises" tag. And if you look at the question itself, nothing about it seems homework-type. Later the question was edited by another user - where the H&AE tag was added - then the question was closed due to i...

2 hours later…

Slereah

11:32 AM

John Rennie

12:17 PM

Starship SN10 launches today. That the launch will be fine seems certain. Whether the landing will be fine is less so :-)

Monty

Hi Physics folks.

John Rennie

@Monty hi :-)

Monty

I wonder if anyone knows much about Kramers equation.

I'm looking for some up to date list of applications for it.

basically chapter 11 of this link.springer.com/chapter/10.1007/…. gives some applications but its quite old. Wondering if anyone has anything newer.

John Rennie

It's not an area I know anything about. Sorry :-(

Monty

moreover, and this is more of a long shot, but if anyone has any good references for the non-linear kramer equation (other than Chavanis) it would be greatly appriciated!

@JohnRennie :) just a hope

2 hours later…

Charlie

2:33 PM

What actually necessitates imposing D/N boundary conditions on open strings?

As is, is there an obvious problem with just imposing no boundary conditions?

ACuriousMind

3:05 PM

@Charlie how are you gonna solve equations of motions without boundary conditions? :P

Charlie

I think I'm missing too much background in solving generic O/PDEs. I assume an initial value or boundary condition is necessary to apply standard techniques or something?

ACuriousMind

@Charlie it's necessary so that it is meaningful to talk about "the solution"!

all the existence and uniqueness statements about solutions of differential equations are always specific to there being fixed initial or boundary conditions

Charlie

Ah I see what you mean

Sleb Lagnej

Aye

fqq

3:21 PM

are Robin boundary conditions ever considered for open strings? Are they excluded because they break conformal invariance?

Sleb Lagnej

How's life everyone?

ACuriousMind

@fqq I've never seen them used, but also never seen any argument about it

but indeed it is likely that the breaking of conformal invariance is why they're not discussed

bolbteppa

3:53 PM

@Charlie if a function $y = f(x)$ is defined by a second order differential equation, it means that you know how the second derivative, and thus all higher derivatives, will behave, but you know nothing about the first two terms of it's Taylor series. One way to fix them it to impose initial values on $y$ and it's derivative $y'$, another way is to assume you know $y$ at two 'boundary' values. This is why you need to impose e.g. boundary conditions on o/p-de's

Charlie

Oh yeah that makes sense ty

Rover

Option 2 or 4 , which will come ?

Charlie

4:34 PM

When you get negative norm states during quantisation you find that (I think) the positive/zero norm states are a subspace, but is there a name given to this larger space? Is it just an indefinite inner product space in which the physical Hilbert space can be embedded in some sense?

John Rennie

5:05 PM

@Rover the gradient is -1/RC so either (2), or (4), or both could be true.

@Rover oh, wait, no. The y intercept is the current at time zero so it's log(V/R). Since the y intercept doesn't change that means R cannot have changed. So the answer is (2) C is increased.

Physics Meta

Q: How should one ask a _physics_ question _about_ an engineered artifact?

My question was closed as being off-topic: humidity - Why do fireproof safes "capture and hold in moisture"? - Physics Stack Exchange But I'm struggling to think of why this isn't an obvious physics question. I wanted to know why some physical systems demonstrate some physical behavior? In the ...