The h Bar

Ramanujan

3:00 PM

3rd problem

I don't even know from where to start😥

John Rennie

Well suppose $n=1$ then the expression is just $\sqrt{2}$.

For $n=1$ (1) gives zero because $\cos(\pi/2)=0$ and (2) gives 2 because $\sin(\pi/2)=1$.

(3) gives $\sqrt{2}\cos(2\pi)=\sqrt{2}$, so the answer is (3)

Ramanujan

Lol,answer is 1

That's a problem when we substitute 1 , so we should sub 2

But I dont want to do math in this way, I am looking for full natural method

John Rennie

Oops, in my original analysis I've just spotted a mistake. For $n=1$ equation (1) is $2\cos(\pi/4)$ not $2\cos(\pi/2)$. $\cos(\pi/4 = 1/\sqrt{2}$ so (1) gives $2/\sqrt{2}=\sqrt{2}$. So (1) is correct. It's easy when you know the answer :-)

Ramanujan

Lol,right,but for n=1 (3) also gives same

John Rennie

Actually (3) also gives the right answer for $n=1$, so yes you'd have to check $n=2$ as well.

Ramanujan

3:12 PM

@JohnRennie iam looking for natural method to solve it,without substitutions,can you help?

John Rennie

@Ramanujan I'm afraid not. Sorry.

Ramanujan

@JohnRennie OMG! You are discouraged,sorry

user116211

Noted @emilio; that's a pretty good advice. Meanwhile, I'll ponder over in off-times as to what I can add more to that post.

Emilio Pisanty

3:40 PM

@MAFIA36790 Yeah, it's probably better to mull it over without rushing to fix things

it's a good post

I just feel it's shooting over the OP's head

that is in itself not necessarily a problem

but it's probably also shooting over the heads of anyone who wanders there looking to learn

user116211

@EmilioPisanty okay, I should explain each step in concluding the equations of motion like $\mathsf{Pr}\infty\mathsf{fWiki}$ does.

Emilio Pisanty

@MAFIA36790 That may or may not be what's required

user116211

Wait... I'll let you know after the edit....

Emilio Pisanty

If your reader has no idea what $\nabla$ means, then no amount of explanation of your proof will do much to help

But that doesn't need to mean that all the physics in your post will be lost to that reader

user228700

@Ramanujan: I will try those problems in my free time and let u know.

Emilio Pisanty

3:49 PM

you just need to think critically about who you're writing for

user228700

Also, @Ramanujan: I'm not exactly discouraging you from "understanding it at a deeper level", but you need to become accustomed and very comfortable with these "tricks".

user228700

Sometimes, esp. indefinite integrals, this substitution is the most preferred method.

user228700

Just, keep that in mind, I guess...

Ramanujan

@Kaumudi I will be trying substitute method, but as I have lot of time to get math in deeper,i wanted so

John Rennie

@Kaumudi or if, like me, you have absolutely no idea how to do the derivation, using a trick may be your only option :-)

0celo7

3:52 PM

what derivation?

Ramanujan

@Kaumudi at last we are studying math not for any exam, but for its beauty

user228700

@JohnRennie Haha, yes :-)

user228700

@Ramanujan OK, if u have the time to do this right now, go ahead...

John Rennie

52 mins ago, by Ramanujan

0celo7

wtf how are are you supposed to do that?

what kind of math is this?

John Rennie

3:54 PM

That's what I thought ...

Keshav Srinivasan

Can someone take a look at my question here:

1

Q: Is there a formula for the axis-angle rotation vector in terms of the angular velocity vector?

Euler's theorem of rotations states that for any rigid body motion with one point fixed is equivalent to a rotation about some axis passing through that fixed point. So let's consider a rigid body with one point fixed, and for any time $t$ let $\vec{\alpha}(t)$ denote the "rotation vector" of th...

0celo7

no

user228700

@0celo7 Now who's ignoring other people's feelings?

user228700

@Ramanujan: These are the kind of problems in ur chap. on Mathematical Induction, wtf?

0celo7

@Kaumudi what?

Slereah

3:57 PM

atlas.cern/colouring-book

0celo7

Nerds

user228700

2 days ago, by 0celo7

just because I present a gruff, manly exterior doesn't mean I don't have feelings...

0celo7

@Kaumudi what?

I didn't say that

user228700

@0celo7 Dude. DUDE. Idk how to screw with the transcript so it displays what u say u didn't say. U said that, omg.

0celo7

Maybe. But I don't remember it.

ACuriousMind

4:01 PM

@Slereah Cute, now I know what my children will be colouring ;)

Now, to acquire children...

user228700

@0celo7 OK.

user116211

@Kaumudi, have some sympathy. He has MDP.

ACuriousMind

@0celo7 Maybe your energy is running out. Might be time to deploy 0celo8 soon.

user228700

@MAFIA36790 Nice try, I'm not falling for that again. U said he has brain tumor. Then @0celo7 said he has a mental disorder and now he has some obscure disease called MDP?

user228700

@0celo7: Do you have any of those three things?

user116211

4:04 PM

@Kaumudi oops; I mean MPD.

John Rennie

Multiple Personality Disorder?

user228700

Okay, @0celo7: Do u have MPD?

user116211

yes :(

user116211

Sep 18 at 5:22, by 0celo7

@IceLord I have MPD.

user228700

Ah, OK... @0celo7: That sucks dude, I'm sorry :/

user228700

4:08 PM

@MAFIA36790: Then why the heck did u tell me that he has brain tumor?!

ACuriousMind

The only claim about 0celo7's medical condition I would take seriously here is the one about his eye :P

user116211

@Kaumudi Well, he also claimed that once.

user228700

@ACuriousMind I feel inclined to agree with u, for some weird reason, even tho Idk 0celo7

user116211

Oct 11 at 17:10, by 0celo7

Or a brain tumor

user228700

@MAFIA36790 Dude, that's not him saying he has brain tumor!

user116211

4:11 PM

:(

user228700

Guess @0celo7's medical condition will always remain a mystery...as it probably ought to be.

John Rennie

Don't encourage him or we'll be getting a detailed description of his haemorrhoids, and I've just eaten lunch.

user116211

0

Q: Conservation of linear momentum

Are there any restrictions to conservation of momentum of a system, or is it applicable in all cases?

newtonian-mechanics classical-mechanics

user116211

Lack of research efforts?

Slereah

atlas.cern/sites/atlas-public.web.cern.ch/files/…

>one W boson

>one Z boson

>one gluon

What pleb book is this

If you're gonna differentiate W and Z put 8 gluons

And differentiate $W^+ / W^-$

Also the two Higgs

ACuriousMind

4:24 PM

Maybe they felt they had to put four force particles but weren't comfortable putting a graviton there?

John Rennie

I like the strange quark :-)

Slereah

Well it's an ATLAS coloring book

They don't do gravitational experiments

ACuriousMind

@JohnRennie heh

Slereah

also why are all the neutrinos cool dudes

John Rennie

I might just use that as my avatar.

ACuriousMind

4:29 PM

@JohnRennie In a version hand-coloured by you, please!

Ramanujan

@JohnRennie you look handsome in your present avatar

user218912

lol

0celo7

4:45 PM

ok then.

@JohnRennie I'm actually concerned I have those.

@ACuriousMind Please quiz me on basic QM

I have an exam and don't know if I need to study more.

ACuriousMind

Can't, getting ready to go to the semester kick-off party

Emilio Pisanty

5 hours ago, by Secret

$$\text{Whole} > \sum \text{parts}$$

Sep 20 at 18:34, by ACuriousMind

For the love of the almighty potato, use \text for words that are meant to be words

0celo7

@ACuriousMind wtf is with you German and parties

ACuriousMind

Sorry for making your post non-sensical @EmilioPisanty

@0celo7 They're fun, and contrary to popular opinion, most of us like fun?

0celo7

@ACuriousMind That's not English.

Emilio Pisanty

4:49 PM

@ACuriousMind wait, what?

ACuriousMind

@0celo7 right

John Rennie

@0celo7 No, no, the doctor didn't say you have a pain in the backside, he said you are a pain in the backside :-)

Emilio Pisanty

@ACuriousMind oh, I see it

0celo7

@JohnRennie It hurts when I go to the bathroom

I can send pictures if you want

John Rennie

@0celo7 Post them here!

Emilio Pisanty

4:51 PM

That's some funky messing with history right there

0celo7

I'm about to get banned.

ACuriousMind

@EmilioPisanty mod abuse!

Emilio Pisanty

@JohnRennie what are you doing?

0celo7

@EmilioPisanty Mod abuse.

ACuriousMind

For the record: Do not post pictures of your haemorrhoids!

Emilio Pisanty

4:51 PM

Yeah, imma join the chorus and cry mod abuse

0celo7

Why are you misspelling hemorrhoids constantly?

John Rennie

ae is the English spelling

0celo7

You lost the war, give it up.

John Rennie

We've lost several wars, starting in AD 43!

0celo7

America has never lost a war.

Emilio Pisanty

4:54 PM

John Oliver Never Thought He'd Have To Care About Trump

►

John Rennie

That's ... erm ... an interesting perspective though discussion of it is probably off topic here

0celo7

Name one we've lost?

Emilio Pisanty

@JohnRennie most notably some business with France on a day much like today 950 years ago?

0celo7

@ACuriousMind if I fail this test you're to blame.

John Rennie

@EmilioPisanty Don't look at me, I'm half Scots and half Welsh :-)

0celo7

4:56 PM

He only marries half the sheep.

John Rennie

What do you call a sheep with no legs?

A Welsh fleshlight?

A cloud! Boom, boom!

Oh.

I note you immediately went for the low end of the humour scale :-)

Not that I'm admitting I know what a fleshlight is ...

0celo7

4:58 PM

No, but you sure know what a Welsh fleshlight is :P

John Rennie

Traditionally Welsh condoms are made of sheep gut, for that natural feel :-)

Danu

@0celo7 lol

0celo7

@JohnRennie We're gonna get banned.

@Danu I take it you have one?

Danu

@0celo7 Oh, nehhhh :P

John Rennie

@0celo7 we should probably move on to other subjects, though I doubt a discussion of the US adventures in foreign policy is a good idea either.

Emilio Pisanty

5:04 PM

@JohnRennie also lack of any natural resources that are not sheep

@JohnRennie making fun of the Welsh, maybe?

user116211

@EmilioPisanty, done.

0celo7

Making fun? I'm stating facts.

Emilio Pisanty

@MAFIA36790 Honestly? I don't think the annotations do much to help.

user116211

hmm. I can't give much more time; I've to go back to my studies now.

user116211

Nevertheless, thanks @emilio.

John Rennie

5:07 PM

I'm sure we've discussed the prevalence of interspecies relations before and concluded that all rural areas had roughly the same incidence. I don't think the Welsh are unique in their love of animals.

0celo7

But sheep

And it doesn't change the fact you're welsh

So stop trying to get out of this.

user116211

That's why I reacted with WTH ;/ Do use \text @secret :(

John Rennie

@0celo7 Half Welsh. Actually a bit less than half as there is a bit of English ancestry in there too.

Now there's a star board worth preserving for posterity:

Emilio Pisanty

@JohnRennie quick, if you edit for the current star board we can get a recursive image

oh. Hi @DanielSank.

this is totally not awkward.

DanielSank

@EmilioPisanty ?

Emilio Pisanty

5:21 PM

@DanielSank cf. the current star board as in John's screenshot

DanielSank

@EmilioPisanty The one telling 0celo7 to not post pictures of hemorrhoids?

Emilio Pisanty

@DanielSank yeah

DanielSank

@EmilioPisanty How does me being here make it awkward?

Emilio Pisanty

@DanielSank any new person walking in on that

DanielSank

ah

Danu

5:24 PM

o/

Emilio Pisanty

aaaaaaaanyways

DanielSank

\o

Emilio Pisanty

0

A: Why is interference there when pulses do not overlap in space and time?

This is a very good question, because we like to think of spectrometers as black boxes, and indeed as seen from the outside there are only two clearly separate pulses going in, so how do they manage to interfere? The answer is clearest by turning the paradox on its head: whatever the interferomet...

↑ boom, killer post

always wanted to draw one of these

user116211

@EmilioPisanty How do you make this insanely amazing piece?

Emilio Pisanty

@MAFIA36790 Inkscape

user116211

5:28 PM

Ah!

Emilio Pisanty

@MAFIA36790 dl.dropboxusercontent.com/u/60184856/… knock yourself out ;-)

(editable Inkscape SVG)

Danu

@EmilioPisanty No TikZ? ;D

Emilio Pisanty

@Danu oh God no. ::shudders::

Danu

Weak, WEAK!

Emilio Pisanty

@Danu what, you fancy doing all of that in TikZ while building on top of the imported bitmap?

Danu

5:33 PM

Nice answer though

@EmilioPisanty I'm just kidding

Emilio Pisanty

@Danu yeah, I know. just thought I'd have a go right back at you ;-)

Danu

:)

GPhys

I found the gravity wave!

Danu

lol

GPhys

That took longer thane xpected

Emilio Pisanty

5:45 PM

@GPhys that is one enormously helpful x axis.

GPhys

now I gotta do the other detector Q_Q

Emilio Pisanty

I mean, look at them tick marks run

GPhys

@EmilioPisanty oh, this is just the temporary plotting show from matplotlib; it lets you mouseover to get points

(which is what I was doing to find the stuff to filter out)

Emilio Pisanty

@GPhys don't sweat it, I've seen worse

@GPhys case in point

GPhys

amazingly you only need inverse gaussian filters and a band pass to get the above image

I expected one would need more complex analysis before it would be remotely recognizable

what are the chances that all the vibrational resonances of the two LIGO detectors are exactly the same

extremely poor, apparently:

(the same filters applied to the other LIGO detector ^)

David Z

5:57 PM

shark teeth? :-P

Emilio Pisanty

I think I didn't overstep here, but if someone can give this an independent look then that'd be good

0

Q: Quantum Entanglement to convey information to Classical Computer

I have read a few similar questions on the exchange, but I don't believe they answer this particular issue. Can Quantum entanglement transfer information to a classical computer to run a set of operations. For instance this is my scenario I am thinking of. Let's say I want to operate a drone fr...

quantum-mechanics

Danu

Thank you for referring me the information. — Ed Yablecki 3 mins ago

user116211

What is Dedekind's construction of real numbers?

user116211

I have no Birkhoff :(

user116211

@DavidZ $^\smile\left(\circ_{\land\lor\land\lor\land\lor\land}\circ\right) ^\smile$

user116211

6:06 PM

Saw this somewhere today.

user116211

Pretty shark teeth.

user116211

Anyways, I need to know how the construction helps to embed naturally a chain in an order-complete chain.

user116211

Have to check Birkhoff if there is any online.

Emilio Pisanty

@MAFIA36790 A real number is defined as a set $S\subset \mathbb Q$ with the property that if $q\in S$ then for every $p<q$ you have $p\in S$.

Then informally speaking you associate $S$ with its supremum (except, of course, that this doesn't exist yet).

@MAFIA36790 not sure what you mean by that, though.

user116211

@EmilioPisanty So, real numbers are subsets of rational numbers? Ohh.

Emilio Pisanty

6:15 PM

@MAFIA36790 in Dedekind's construction.

user116211

@EmilioPisanty Well, it's what is written in Kelley; he tells to check Birkhoff for further details.

Emilio Pisanty

You can also say that they are equivalence classes of Cauchy sequences in the rationals.

@MAFIA36790 that doesn't help much

if you define chain and logical chain I might be able to help more

user116211

@EmilioPisanty I know, I'm myself confused; I'm checking if there is Birkhoff in the archive.

user116211

@EmilioPisanty Oh, chain is a set ordered by linear order.

Emilio Pisanty

@MAFIA36790 any set?

is this still inside the reals?

user116211

6:18 PM

@EmilioPisanty No, the general definition.

Emilio Pisanty

@MAFIA36790 then what does "linear order" mean?

user116211

@EmilioPisanty Total order.

Emilio Pisanty

@MAFIA36790 As in, a chain is a set equipped with a total order?

user116211

There should not be any non-comparable pairs.

user116211

@EmilioPisanty yes.

Emilio Pisanty

6:21 PM

@MAFIA36790 Then you say that, instead of a self-referential, incomplete sentence.

but anyways.

what's an order-complete chain?

one where every set has a supremum?

user116211

@EmilioPisanty If, every non-void subset of the chain having an upper bound, has a supremum.

Bernard Meurer

@MAFIA36790 Chem help?

user116211

Then the chain is order-complete.

Emilio Pisanty

@MAFIA36790 Yeah, then you can apply Dedekind's construction directly.

user116211

@BernardMeurer Halp @JohnRennie!

user116211

6:23 PM

@EmilioPisanty Don't tell!!

user116211

Let me figure this out myself.

user116211

@BernardMeurer Nevertheless, at least jot down the query; I'll respond if I can.

Bernard Meurer

"Determine the wavelength of the photoelectrons removed from a rhodium anion (Rh-) with a radiation of 488nm, knowing that the electroaffinity of Rh is 110,27 kJ/mol"

How the fuck do I do this?

user116211

@BernardMeurer phd level T__T

Bernard Meurer

What am I doing?

user116211

6:27 PM

@BernardMeurer You should sue your prof.

Bernard Meurer

@EmilioPisanty You're a PhD now, halp

Emilio Pisanty

@BernardMeurer So you know the photon energy and the work function, right?

Use that to get the kinetic energy

from there to the momentum

0celo7

@MAFIA36790 you're turning into me + Trump

Emilio Pisanty

and from there to the de Broglie wavelength

user116211

@0celo7 ._.

Bernard Meurer

6:29 PM

@EmilioPisanty You haven't been filled in on the state of my general chemistry course, have you? :P

Also, is electronegativity inversely proportional to electroaffinity?

0celo7

What are those words?

Emilio Pisanty

@BernardMeurer no idea

from a dumb physicist perspective, it just looks like you've been given the work function

Bernard Meurer

@EmilioPisanty My course is literally insane. The guy tried to teach us 3-dim schrodinger on spherical coords. and we don't even know calculus

I'm freaking out

user116211

@BernardMeurer yes, that's why I told to report you in the chem dept. against your prof.

Bernard Meurer

@MAFIA36790 They know the man is crazy

Emilio Pisanty

6:32 PM

@BernardMeurer That is in fact suboptimal.

Bernard Meurer

I think it's a social experiment or something, it must be

user116211

@BernardMeurer Why are they tolerating him then :(

Bernard Meurer

Well, last year a freshman jumped off the chemistry tower, maybe that was it

user218912

should I fail my calc midterm because I don't feel like walking to the exam room which is 35 mins away?

user218912

it's only worth 5%.

Bernard Meurer

6:33 PM

@bl00 No

user116211

@BernardMeurer Are you in Indian Hill? Because all weird experiments of Gotham were done in that center ;/

Bernard Meurer

@EmilioPisanty I don't know what the work function is, googley googley

@MAFIA36790 Lol, I wish

user218912

@BernardMeurer but what if idc what mark I get in the course?

user116211

@bl00 You should go.

user218912

._.

user116211

6:34 PM

It's not about the marks. Test yourself how fast you can solve the paper.

user218912

it's trivial.

user116211

Be like Flash.

user218912

it's not even analysis

user116211

@bl00 :(

Bernard Meurer

Okay, I have 0 clue how to solve this

user116211

6:35 PM

Then don't need to go.

user218912

lol I like how that changes your mind.

Bernard Meurer

@bl00 God bless it's not analysis, I have to prove even my name on my analysis exams

user116211

@BernardMeurer You were doing logic then.

user218912

@BernardMeurer just write "proof is trivial, left as exercise for grader"

user218912

I'm gonna take analysis next year because I don't want to let down 0celo7.

user218912

6:37 PM

and I'll be free next year too, so I have time.

user116211

Hey @0celo7, Bourbaki is not that hard.

Bernard Meurer

Letting @0celo7 down generally means you're doing the right thing with your life

user116211

I was reading Algebra I today.

Emilio Pisanty

@BernardMeurer Google "photoelectric effect"

user116211

It was quite interesting to read.

Bernard Meurer

6:38 PM

@MAFIA36790 I'm doing Analysis taught by a madman

0celo7

@BernardMeurer what?

He's not a madman

If you had my prof you could complain

Bernard Meurer

@0celo7 His notation?

user116211

There were nice theorems of homomorphisms of monoid.

user116211

I can tell if you want @0celo7.

user116211

@BernardMeurer Holy crap ;/ You seemed to be doomed T__T

user218912

6:39 PM

@BernardMeurer you mean letting down?

Bernard Meurer

@bl00 yes, thank you

@MAFIA36790 I'm doing uni the hardcore way

0celo7

Shitty notation is shitty notation, not a madman

user116211

@BernardMeurer Using bad notation is not that bad. However, abusing them is bad.

0celo7

@BernardMeurer wait what?

What's wrong with you

user116211

@0celo7 I have flagged that; no worries.

user218912

6:43 PM

it's offensive?

user116211

yes.

0celo7

Extremely.

@BernardMeurer explain yourself

user116211

ARTofCode must be in his way.

user218912

I thought it was just a friendly joke but okay.

0celo7

I'd block him but I need to flag his other messages

user218912

6:45 PM

he didn't get banned.

user218912

guess you guys didn't flag for real xP

user116211

@bl00 ARTofCode didn't come ?! Probably, he spared him.

user218912

or you didn't flag it.

0celo7

@BernardMeurer GitHub is being DDOS'd

Is this the potato army's first target?

user218912

wait so did they actually ignore that flag, even though it was extremely offensive to 0celo7?

0celo7

6:53 PM

Yes

I'm actually crying.

user116211

@0celo7 Your eye is okay still? You can cry? WoW! Doc's magic.

user218912

really?

user218912

I think bl00 is a really retarded name, why did I choose it?

user218912

guys choose a new name for me that I actually keep.

user116211

Blue Wizard.

user116211

6:55 PM

Cobalt Blue.

user218912

can it not involve blue please?

user218912

because

user218912

I am currently giving myself exposure therapy to lose my obsession with blue.

user116211

@bl00 REALLY?

user218912

yes I need to be more accepting of other colours.

user116211

6:56 PM

Red Lord.

user218912

that doesn't mean I become obsessed with a different colour xP

user116211

Okay.

user218912

I like the lord part but think of something to go before that.

user218912

idk

user116211

Alchemy.

user116211

6:58 PM

QFT Lord

user116211

Ultracool Lord.

user218912

I am far from being a qft lord

user218912

lol...

0celo7

@bl00 that's what we said.

user218912

@0celo7 :(

Transcript for