that's JEE people, right?

@Mostafa No, I am not acurious :P

@ACuriousMind good

from a deep delve into PSE history:

> By the way, I joined the math stack exchange a few minutes ago and now I'm experiencing envy. They get a lot more traffic. Things get voted up much more quickly. I wonder if that will last; surely people are more interested in the physical world than in a bunch of dusty dry theorems.

love that last line

> dusty dry theorems

My jimmies are rustled

In other news...

German letters, lol

@Slereah not even counting the copenhagen... interpretation? o_O ... (it would seem by ACMs metric, the top founder(s) of QM were quite into thinking/ debating/ studying... interpretations...)

I love how they call quantum mechanics Quantenmechanik in German....

or maybe they call Quantenmechanik quantum mechanics in English?

Things look much more...*original* in German

@Mostafa hi wondering if you have undergrad degree? are you a graduate student?

@vzn no

The copenhagen interpretation is an example of those

@Slereah ok couldnt follow the context thought it wasnt even talking about QM. what are you reading?

@Danu lol

The philosophy of quantum mechanics

By Jammer

↑ dont be afraid of a little )( interpretation o_O

@Slereah lol and you are complaining about him talking about "interpretations" with a book with that title? and am amused ACM (otherwise into philosophy as long as it has nothing to do with physics) wouldnt like it! have heard of that ref, maybe should look into it sometime...

@EmilioPisanty A wonderful phrase but I'm left wondering what the dusty theorems have to do with the reality of what goes on at math.SE :P

I'm complaining about the ambiguity

@vzn He's not complaining about the book being about interpretations. He's just expressing his dismay at the way it is written, as he does with most things he's reading. Don't jump the gun here :P

Interpretation in it refers to 4 different things

@Slereah lol, exactly. ps try studying zen sometime... how about "dancing wu li masters" by zukav! o_O :P

@vzn Hi. we talked about this with details once before....but it seems you've forgotten :(

@ACuriousMind lol sounds like philosophical hairsplitting to me :P

Nah I don't like philosophical wanking too much :p

@Mostafa sorry hard to keep it straight without profile info

Currently doing my master's degree....looking for my original idea for my thesis

@Mostafa cool, EE? what areas were you working in?

@vzn photonics

(btw I like how you added cool in the edit xD)

@Mostafa ok yeah now recall that conversation some )(, great field

More specifically, I'm working on metasurfaces (artificial structures with sub-wavelength inclusions) that can manipulate light with its spin (polarization)

Can you send photons by mail

@Mostafa lol were you involved in that swastika thread a few days ago? o_O

Yeah ( ͡ᵔ ͜ʖ ͡ᵔ )

(👁 ͜ʖ👁)

♥‿♥

@Mostafa reminds me, theres a lot of irridescence in animals/ biology incl insects...

ah, classic vzn

@ACuriousMind I request your physics help

@BernardoMeurer I request you specify the problem before I grant any assurance of assistance.

@vzn Those structures are chiral which means they behave differently for waves with various helicity

@Mostafa its a cool field & something like it may eg allow creating holograms for projection ie holographic tv someday... already experiments along those lines...

@0celouvsky Of course there is!

@BenNiehoff Hi. I emailed the corresponding author of that paper for the error (I asked you whether I should inform him). He answered a few days later and thanked me for it :)

@BenNiehoff it only works for come equations, of course

come equations are the hardest though

What is a come equation

"some" as typed by 0celo7

I blame autocorrect.

@AccidentalFourierTransform lol

I didn't see that typo until now

If force = mass times acceleration.. Then let's say a bus is going at 60mph but it is not accelerating.. there's a lot of mass there.. but acceleration is 0. It can't be that the bus would hit at 0 newtons, so how can force = mass * acceleration?

@barlop When stuff "hits" something, it decelerates rather rapidly, so acceleration is not zero there.

A very nice piece of manifold alright

@ACuriousMind but would deceleration be a negative number, so would the formula be mass * acceleration , and if negative then * by -1 to make it positive?

@barlop The sign just shows the direction of acceleration, and the force points in the same direction as the acceleration, so if you decide to measure the deceleration as negative, then the force will also be negative, there's no problem with that.

@ACuriousMind Can we close for dumb question?

@ACuriousMind i'd think the deceleration is tiny though.. of e.g. a bus hitting a tennis ball.. If a bus went 300mph then the ball would go much further than if it went at 60mph. But the deceleration on hitting the ball would be tiny and I doubt it'd be more when the bus is going at 300mph

@0celouvsky No, but you can downvote. (I can see an argument for closing that question as unclear, though, but unless someone else sees it too, I'll not do that)

Done

@barlop Sure, the deceleration a massive object experiences when hitting a much lighter object is tiny. What's your point?

Also, note that the final speed of the ball tells you nothing about the force it experienced unless you stopped the time it was in contact with the bus, since the change in momentum is the integral of the force over the time the force acts.

@ACuriousMind Please humor me on this. So, consider the elliptic operator $L=\Delta+\mu$, where $\mu$ is some constant. Consider $D\subset M$ a compact submanifold with smooth boundary. I can solve $Lf=0$ in $D^\circ$, $f=0$ on $\partial D$ just fine, with $f\in C^\infty(D)$. In particular, $f$ is bounded in $D$. So with an appropriate constant $\alpha$, consider $g=\alpha f+1$. I claim that I can pick $\alpha$ such that $Lg=0$, and $g=1$ on $\partial D$, and $g>0$ in $D$. Make sense?

Yes

Good, thanks. I think that's what Yau does in his original paper, but Li's proof of the same result uses some weird spherical harmonic thing that I don't really get.

Well, I assumed you can solve for any choice of $\mu$, not just for one, right?

Because if for some reason $\mu$ is fixed, then I might object/ask how exactly you intend to pick

Hmm. I guess $\mu$ would have to be an eigenvalue for this to work.

@ACuriousMind Is that what you're saying?

Upon closer inspection I don't know what Li is doing.

Well, examining your claim, we have that $L(\alpha f + 1) = 0$, so $\alpha \Delta f = -\mu f- 1$

How are you proposing to pick $\alpha$?

I'm not sure about $f$ right now.

@ACuriousMind Pick $a$ large enough so that $|\alpha f|<1$.

idk something like that

I mean small enough

From $Lf = 0$, we know that $\Delta f = -\mu f$, so we get $(\alpha + 1) \mu f = -1$?

That...doesn't seem right, or even possible unless $f$ is constant to begin with

So I'm not sure how I propose to get $f$ in the first place

But suppose $\mu$ is an eigenvalue

Then $f$ doesn't have to be constant

Ohhhh

$L$ does not annihalate constants :(

Wait, what I wrote there is nonsense

You're right that there is an issue. The issue is that $L(1)=\mu$.

Last night I dreamt about watching presentation on quantum gravity, where one of the slides has a gravity well of spherical geometry. I end up only paid attention to the final slide where they said if the effect exists, then it is expected that any light that travels out from the well will be blueshifted, thus in effect the well act as a light accelerator. The next slides detailed how the team have done large scale experiments such as inferometery and atomic experiment and found a null result of

Yep, that's it. Somehow I failed to express that in a coherent manner and wrote a bunch of weird stuff instead :D

the effects, and proposed they have to go to the Planck scale to see it

@ACuriousMind The first issue is that $\mu$ doesn't have to be an eigenvalue so I can't even get $f$ in the first place.

I'm not sure what's going on here now

Yeah, if it's not an eigenvalue, then that equation has no solutions

And if it is an eigenvalue, then you have $L(\alpha f + 1) = \alpha L(f) + L(1) = \mu \neq 0$ for non-zero $\mu$.

Clearly. So I have to solve $Lf=0$, $f=1$ on $\partial D$ directly.

Anyway, is the speed of light also constant in an accelerated frame, I recall it get blueshifted due to unruh effect?

@ACuriousMind So what I do know is that there is a $\lambda>0$ s.t. $Lg=-\lambda g$, $g=0$ on $\partial D$.

Namely the first Dirichlet eigenfunction for $L$.

So maybe bumping up $g$ appropriately gives me what I want...

$L(g+1)=-\lambda g+\mu$...no good.