12:00 AM
@Danu Thanks!

The rules about cursing are, in effect, set network wide simply because flags go out network wide.

@Danu I have not sworn in weeks
I am a changed man
What the hell is a vitriol? — Bernard Meurer 25 mins ago
@BernardMeurer srs?

It is true that many physicists will use adult language among themselves, or at least tend to overlook the use of it by others, but we represent a fairly small subset of the population.

@0celo7 Changed boy? :)

@BernardMeurer I have something for you
Thm. Subsequences of a convergent sequence converge to the same limit as the original sequence. Proof. Assume $(a_n)\to a$ and let $(a_{n_k})$ be a subsequence. Given $\epsilon>0$ there exists $N\in\Bbb N$ such that $|a_n-a|<\epsilon$ when $n\ge N$. Because $n_k\ge k$ for all $k$, the same $N$ will suffice for the subsequence, that is, $|a_{n_k}-a|<\epsilon$ when $k\ge N$.
So, if you have a sequence, say $a_n=(-1)^n$, and you can produce two convergent subsequences that converge to different limits, the original sequence cannot converge.

12:19 AM
@0celo7 I'll look at it in the morning, I'm exhausted right now. Thanks a lot though

@0celo7 Or so you think

@Danu you're 5 years older.

12:42 AM
@BernardMeurer I'm going to take credit for popularizing that phrasing, for better or for worse.

Howdy

@HDE226868 I knew you'd have something to do with this

@BernardMeurer I'll gratuitously interpret that as a backhanded complement.
Also, how's school university going?

@HDE226868 Meh.
I really like analysis but my prof has crap notation and it makes it super confusing (ask @0celo7)
I hate chemistry because it's basically guessing since we don't know calc yet and this dude is teaching QM
Digital Systems is fine
Linear algebra is pretty cool

@BernardMeurer It seems like someone messed up badly there.
@BernardMeurer I'll concur with that.
What QM stuff are you doing?

12:56 AM
@HDE226868 Schrodinger's eq, De broglie, an electron trapped in a 1-dim infinite potential box or w/e it's called in english
stuff like that
all without us knowing any calc
he just integrates and derivates stuff
and says that eventually we'll understand it
which is so, so stupid

My friend at another school's doing pretty much the same thing in her chem course, but she has a good calc background. Some of her classmates don't, and they're struggling pretty badly.
You professor doesn't sound too sympathetic, though.

1:26 AM
how can linear algebra be cool?

@0celo7 It is cool.
I proved that to you a few days ago.

no, it really isn't

Remember the $k$-dimensional Pythagorean theorem?
@BernardMeurer We have Puritan cultural history. Everything is screwed up.
A movie can have someone machine-gun down a hundred "bad guys" and be rated for teenagers, but if there's a woman's breast for more than a couple seconds it's rated R.

2:23 AM
@Danu yes you will, for 30 mins
@DanielSank yes, pornography and alcohol has been corrupting the youth
@DanielSank Yes, I didn't think that was particularly cool.

@DanielSank A point that has been made very publicly a number of time in the last century but seems to have no effect on the "sex-is-sin" crowd.
BTW Is there someone present who feels confident about the vector forces of sailing? I did a kind of historical narrative for physics.stackexchange.com/questions/283760/… but it needs a more nitty-gritty answer as well, and I am only vaguely familiar with the subject.

@dmckee There's a course at UCSB called "The physics of sailing".
Sadly, I did not take it.

2:38 AM
Ahhh!. They didn't offer than when I was there. I feel cheated!

that would be a physics class I'd take

I hear it's rather a difficult course.
::shrugs::

^ I'll bet.
It's all bloody fluid dynamics!

since when are you british?

Never. I just borrow slang that I like without fear or favor, mate.

2:41 AM
I like to try to work in British stuff, especially when @JohnRennie is around.
Heh, here's an excellent example of that terrbiel parametrization of the harmonic oscillator equations I was complaining about a few days ago.

that's what I don't get

Because it doesn't look like a harmonic oscillator until after you've diddled it a couple of ways for one thing. Yuck.

Huh?

Thanks for fixing that, @dmckee.
It's bad because it's full of a bunch of irrelevant constants.
I'd much rather work with e.g. $$H = \hbar \omega \left( \frac{1}{2}X^2 + \frac{1}{2}Y^2 \right) \qquad [X,Y]=i/2 \, .$$
Then we'd have e.g. $a = X + i Y$.

I'm still confused. What's wrong with defining $a=something$, then carrying on with your life?

2:52 AM
@0celo7 Several things.
1) More constants = more mistakes.
2) The dimensions are confusing. What are the dimensions of $\sqrt{\hbar m \omega}$?
3) It's fantastically stupid to learn to deal with the harmonic oscillator by always using the constants that make sense for a massive block on a spring.

@DanielSank That makes zero sense. $\hbar$ is not classical.

@0celo7 Who said a massive block on a spring is classical?
I have no idea what you mean by that comment.

I have no idea what your comment means.

@0celo7 That's because you don't know quantum mechanics.

Whatever.

2:56 AM
What part do you not understand?

I don't know QM, it's ok.

The "harmonic oscillator" is a generic system, i.e. any one in which the Hamiltonian is a sum of two squared operators whose commutator is an imaginary number.

No, the SHO is something that has oscillating classical solutions.

@DanielSank That. We certainly use the mass on spring as a model for other harmonic oscillator during the first year, but by the time students are doing the harmonic one in the commutator and ladder operator framework they've seen lots of them. Time to put the idea on a pedestal as an ideal that has nothing to do with springs and everything to do with quadratic terms for both kinetic and potential energy.

Learning about that system by always using the "particular case" of a mass on a spring is stupid.
@dmckee FWIW I have a set of notes where I write the quantum oscillator like this: $$\hat{H} = \frac{1}{2} \alpha \hat{u}^2 + \frac{1}{2} \beta \hat{v}^2 \quad [\hat{u},\hat{v}] = i \gamma \, .$$
Then I work out all the things in terms of those constants.

2:59 AM
You should hat $H$ to be consistent.

It's super-turbo useful.

@DanielSank Yeah. I saw your link the other day. I was planning on stealing at least part of that framework to improve my own handout. I'll give you credit.

@dmckee Yay!
Note that the github repo uses a submodule, so if you clone it, you have to use --recursive.
Alternatively just steal the tex documents you want.
...and don't forget to steal the macros from the submodule ;)
By the way, @dmckee you made my day! I live to have my writeups called useful.

I want @dmckee to use one of my writeups :(

@0celo7 I';d love to, but first I have man up on the abstract math front enough to understand them.

3:01 AM
^ Ha

Luckily our math department is planning on starting a grad program and next term they are offering advanced abstract algebra as one of the the first class for it.

cool

Oh, I don't know any algebra

I quit algebra at the Sylow theorems.
I was the last third of that course plus a seminar away from a math minor.
Couldn't take it any more.

But this weekend I wrote a two-page memo on the point-set topology of manifolds
Proved they are paracompact, sigma compact, separable, metrizable.

3:03 AM

@DanielSank It's a part of a larger document that I am preparing
Although I can't get the correct formatting.
@DanielSank I need some thing that acts like a blog, but I can just write TeX directly too. I had a blog but it was terrible because I had to TeX everything separately
and it didn't have any packages, macros or what have you
@dmckee I think I have a relatively complete "physicist math" course on complex analysis typed out
somewhere
goes through basic facts of life like contour integration, Cauchy's theorem

@0celo7 Now that's a fun subject.

I had hoped to make it my calc BC final project but the teacher had never heard of calculus with complex numbers.

oh gosh
I have a writeup on manifolds on there lol
that website

3:14 AM
@0celo7 ?!?
All the math teachers who didn't only teach remedial math at my high school had masters degrees and one had a Ph.D.

None of mine had anything more than a BS in math
MS in education presumably

I suddenly feel even more privileged than I knew. This was at a public high school. Mind you the "all" there was three (or four if you counted the computer science teacher who reported to the math department (her MS was from UCSB and it turned out I took a class from her advisor)).

3 precalc
then maybe 4 teachers for the rest
probably more
@dmckee I grew up in a poor neighborhood well-off DC suburb
hmm

Everything below pre-algebra was considered remedial at my high school (grades 9-12).

I don't understand how my high school was so terrible
@dmckee what the hell is pre-algebra?

3:28 AM
That was actually the fault or Ross Perot. The same guy who ran for president. He forced a school reform bill through the Texas legislature about a decade before.

My teachers were excellent at teaching the tests.
But anything beyond that -- no clue

@0celo7 Order of operations. Make sure you know about the propeties of raising things to a power or taking nth roots.
That sort of thing.

Hmm

Skills you'll need in algebra. But assuming you already knew how to do your arithmetic.

I didn't learn that until 9th grade I guess
I had a math tutor in middle school
I wasn't in remedial math when I got to America
"algebra 1"

3:30 AM
You basically has to pass algebra to get a "proper" high school diploma in Texas at the time. And you were only required to take two years of math. So you had to be almost ready for algebra when you got to high school.

although I think we still did order of operations in algebra 2

I heard they relaxed things later.
@0celo7 I did too, but by then it was "I'm handing out a sheet on the order of operations. Make sure you remember it."

Nah, I remember crazy things being on tests

We did complex number in that class because getting to the fundamental theorem of algebra was one of the big goals.

like triple fractions with roots and powers and sorts of fun
I did complex numbers as a sophomore

3:32 AM
@0celo7 Which is fine, but it is simple application stuff. Still on the third tier of Bloom's taxonomy.

I don't remember if we saw FTA that year or in precalc
of course we didn't prove it

user116211
WTH does this symbol $\exists !$ mean?

exists a unique

We proved it in a simplified sort of way. Wave away the difficulties of showing the fisrt degree case and then show that given the nth degree case you can prove the (n+1)th degree. Tada!

user116211
@0celo7 Gotcha.

3:34 AM
@dmckee I'm fairly sure you can't prove FTA by induction.
The hard part is actually 5th order polynomials.
Anything below that you can write down the solutions explicitly.

Hmmm .. that's how I recall it. It was done in matrix form assuming non-zero determinant and making a lot of arguments that amount to Gaussian elimination.

wth, Gaussian elimination in high school?
matrix form?

I wouldn't put it pass them to have slipped in a ringer. Something that wasn't quite rigorous.
No. Thant can't be right. I'm jumbling things together.

@dmckee you're gonna have to find those notes

user116211
Isn't this a homework post @dmckee

user116211
3:37 AM
0

Consider that harmonic oscillator with $$H\psi_n(x)=(n+1)\hbar\omega$$ with $$\int_{-\infty}^{\infty}dx|\psi_n(x)|^2=1 \, .$$ We want to show that $$\int_{-\infty}^{\infty} dx |a_+\psi_n(x)|^2=(n+1)h\omega \, .$$ where $$a_+=\frac{1}{\sqrt{2\hbar m \omega}}(-ip+m\omega x) \, .$$ I'm using Griff...

user116211
?

how does Gaussian elimination work for nonlinear equations

@JohnRennie: Hi sir, morning :-) I have a Chem. question; I've asked it at the CSE chat. The first part is again, related to the levelling and differentiating effect of solvents, while the second part is about Ostwald's dilution law for weak electrolytes...

@MAFIA36790 I thought so. But I have been not casting votes on any but the most flagrant cases until others weigh in.

user116211
@dmckee okay.

3:39 AM
@0celo7 It doesn't. Like I said, I seem to be mixing things up. That was about 28 years ago.

hmm
28 years is a long-ish time
my memory is so poor you probably remember more about high school than I do

::blinks:: I just realized that saying Perot was the same guy who ran for president might not have given you any context at all.

I know who Ross Perot is

Well, that's something.

I'm uneducated, but not that badly.

3:41 AM
Some of your peers are that ... well let's say "connected to their own moment in time".
Which reminds me that I haven't looked at this years Beloit mindset list yet.

what's that?

Always worth a groan. Or three.
A list of facts about the incoming class compiled to help professors understand who their new students are. Or at least understand a little better.
It's been copied elsewhere, but the one at Beloit is the original one to make a splash on the internet.
Don't know if it actually the first of its kind, however.

grrrr

the book I learned frame bundle connections from used $\omega$ as the connection and $\theta$ as the solder
now this book uses $\omega$ as the solder and $\phi$ as the connection
@dmckee huh
"Grandpa has always been able to reach for the Celebrex."
What?
> Among those who have never been alive in their lifetime are Frank Sinatra, Phil Hartman, Matthew Shepard, Sonny Bono, and Flo-Jo.
I know one of those people!
> Newt who?
Gingrich.

3:48 AM
@0celo7 But we have already establish that you are a cultural literate.

> Deceased men have always been able to procreate.
Ok what the hell?
Deceased men can procreate?
Oh my god I'm stupid

Sperm on ice,

the soldering form is defined by $\mathrm d\pi(t)=\omega(t)$
so of course on the horizontal spaces we get an isomorphism through the solder
@dmckee that's just stupid
@dmckee Not a fan of this list.
Clearly the students they're talking about are bottom of the barrel Neanderthals.

It's not for you. It's to remind old people like me about what changed between my childhood and theirs.
Beloit is a highly selective school.

No one my age things about "sperm on ice."
@dmckee But this is not my mindset.

3:52 AM
But a big fraction of all incoming students are very much people of the media environment they're grown up in.
@0celo7 No, because you are weird. Otherwise you wouldn't be hanging our in The h Bar

What? I'm not weird. I'm definitely not reading a classic reference text on differential geometry for the hell of it.
::puts Bishop-Crittenden away::

My students are generally a little more mechanically adept and knowledgable about getting by on very little money, but less knowledgable about the politics from that ancient era of mammoths and mummys the 1990s.

None the less that list lets me know that all my jokes and examples are getting always a little more out of date and some need to be replaced.

have you referenced Harambe lately?

3:55 AM
@0celo7 Than the ones Beliot recruits. Very much upper-middle class, pay to get things done rather than the farm kids I teach.
@0celo7 No. I'm up to date. I talk about the Emperor Nero!

...what?
maybe I am weird
I don't get your references and I don't get contemporary ones either

4:16 AM
interesting
one can always find a torsion-free connection on the frame bundle

4:28 AM
$$R_{st}(u)=-b(\Phi(\bar s,\bar t)b^{-1}(u))$$
That's a new definition of the curvature tensor!

4:56 AM
crazy

user116211
@0celo7 WTH!

user116211
In a typical SE page, ABP blocks 2-3 ads.

@EmilioPisanty did you have a tooth-ache while we were having this exchange?
It's funny to me in retrospect that while after our first interaction there, where I was given to think you were kind of hostile and had an overdeveloped sense of "ownership" about content on SE, you later gave me a huge bounty and some kind words.
I was, to put it mildly, surprised.
I bring it up because it's kind of fascinating that now looking back, my first impression was just flat out bogus. It's amazing how quick we are to form an impression of a person based on just a few words exchanged via the internet.

user116211
As far as consistency goes: the platform here is not TeX, it is markdown + MathJax. I also find it curious that you're being so aggressive on other people's source consistency when you started this thread with a proposal that's terrible MathJax standards. — Emilio Pisanty Aug 3 '15 at 17:53

Yeah, it's funny how differently I perceive that comment now.

user116211
5:09 AM
@DanielSank Valid point and seems to be a heavy truth.

Wow, the hbar transcript is hilarious. Looking back I'm finding some really great views into the past.
Feb 9 at 2:48, by 0celo7

user116211
stares at 0celo7

@MAFIA36790 Well actually, I'm not sure I expressed what I'm thinking properly.
I didn't really form an "impression" of Emilio as a whole. It's more just that I identified that exchange as somewhat unpleasant.
I think what I'm trying to say is that it's interesting how the tone shared between two or more people can change considerably. I think the real point is that tone is important.
I dunno, I'm just rambling now...
Feb 9 at 2:48, by 0celo7
LOL
Feb 9 at 2:55, by 0celo7
@DanielSank I don't troll.
I wonder how many times @0celo7 has written that exact message.
I count four.
(continuing previous line of thought) Maybe making judgments reasonably quickly is sensible as long as they're not too firm.

user116211
@DanielSank yeh, that's legit; in the course of time, nothing remains rigid.

o/
@MAFIA36790 I do not think I can converse with you until we have done our ritual.

user116211
5:21 AM
@DanielSank Holy hell! How I could forget that ;P

user116211
\o

It's ok. You've trained me well! Now I can initiate the ritual.
So @MAFIA36790, we are alone here. Tell me about yourself.

user116211
But @Daniel, I didn't have any intention to make it a ritual; you appeared here very few times earlier; that's why I addressed you with that o/.

@MAFIA36790 Ahhh, but a ritual it is!
This is how the best rituals are invented.

user116211
@DanielSank I'm currently majoring in Physics, minoring in Maths and Statisitics.

5:23 AM
A casual interaction, but one which I now find familiar and somehow satisfying :D

user116211
But now, I have more interest in Maths.

@MAFIA36790 cool!
Math is very useful. It makes physics a lot easier.

user116211
@DanielSank Yeh, now that it has become a ritual; let us make a cult; with 0celot being our first member ;P

@MAFIA36790 But has @0celo7 done the ritual?

user116211
@DanielSank It has become a habit to address you and yuggib with o/ ;))

user116211
5:25 AM
@DanielSank Nope ;D

@MAFIA36790 Then he is not qualified to join the cult.
Not even to be our chaiwalla.
For that he must perform the ritual at least once.

user116211
Well, he always remains in the chat; at least his gravatar does. So, didn't ever think to address him with o/.

I see. The o/ is designed to attract the less-frequent chatters?

user116211
@DanielSank yes.

I think it works.

user116211
5:28 AM
But surely, it has become a ritual ;P

@DanielSank Ha, you know Hindi?

@KaumudiHarikumar I wish.

user116211
@KaumudiHarikumar I do understand hindi; but am not fluent in it.

Even in the US we use this "-walla" as a sort of joke.
At least, my friends and I do.

@MAFIA36790 Oh! I thought u were from North India :/
@DanielSank Ohh, OK...

user116211
5:35 AM
@DanielSank It's in urban dictionary.

@MAFIA36790 I just noticed that.

user116211
@KaumudiHarikumar I'm a Bengali.

We joke about people being the "Xwalla" where X could be anything.

@MAFIA36790 Ohh. I figured that Bengalis would be fluent at Hindi. I was mistaken, sorry.

user116211
@KaumudiHarikumar Well, don't make a generalised remark just seeing a single person.

5:37 AM
For example, @BernardMeurer says he would do anything to work in my lab. He would even mop the floors, or bring people coffee, etc. So he'd be the coffeewalla.
Hear that, @BernardMeurer? :D

user116211
@DanielSank ;P

user116211
0

Which material is the best for HDD. Since from begining to untill now material is developed by different company. Which material is going to be a best selection for HDD.

user116211
How it can be classical mechanics ._.

Not a particularly well posed question.
...and I'm not actually sure what is being asked. Does OP want speculation about what materials will be used for hard drives in the future?

3 hours later…
8:46 AM
I have something confused...
the process a excited electron emit photon is spontaneous, therefore, taking the average of momentum, we will get zero. However, why will we take average of the time it takes (from excited to excited state and emitting photon) rough equal to $10^{-3}$s?

9:06 AM
I mean... it is kind of weird, since it is spontaneous, how come if I take the average of life time, it iconvey to some definite value?

9:23 AM
um... sorry for my lousy English, I found the way it is presented is confusing, basely I would like to ask, "Why will we get a definite time average for a spontaneous process - electron emit photon from a excited state?" (while we get zero if we take the average value of momentum)

1 hour later…
10:43 AM
(NB all are old news)

user116211
11:30 AM
UN announces its first ever space mission: The United Nations has revealed that it will be launching a global... http://bit.ly/2dTEdtp

@0celo7 You around?

12:23 PM
@BernardMeurer Not really

::This is the automatic response system for Jim. I am currently not around and will get back to you the moment I stop pretending to be an automatic response system::

@ACuriousMind people who tuck in their shirts are probably psychopaths.

@0celo7 try to wear them untucked with braces (suspenders for you 'murikan ?)

12:38 PM
Wtf is a brace
You know it's America when there's people handing out bibles on campus

suspenders?

What barbarians call them braces??

english people

@yuggib Stuff like this is why we think we're the only civilized people out there.

@0celo7 "Stuff like this is why we wrongly think we're the only civilized people out there."

12:45 PM
braces? Only cute girls got them on their tooth here.

@0celo7 wouldn't anyone who wants a bible already own a bible?

@Jim Right.
People are either not interested or genuinely already have one.
Maybe it's a cult bible.

@0celo7 I am not interested in the bible, but I own one to know my enemy better

Delicious edge
Aren't you a little too old for that?
14 was a while ago for you

@0celo7 ?

12:50 PM
What is confusing

the last couple of sentences
in particular what is supposedly characteristic of a fourteen-year-old person

The hardcore atheist stance
Or whatever that is
Holy crap
College kid
Some dude is helping them
"Can I pass some out to non believers"

I am actually not an hardcore atheist, but I am against every form of organized church, christian ones in particular

so all you are atheists?

No
@yuggib Why?

12:54 PM
@Shing I don't really care. For sure the set of all sets is a logical inconsistency

Huh?

@0celo7 because organized religion has never, throughout all history, led to good things
especially the christian church(es)

@innisfree Take a second look at this one physics.stackexchange.com/review/suggested-edits/148097.

And believe me, I know from experience, I actually am in the city with the highest density of christian priests in the world

Italians are not good people tho (proof: mafia)

12:58 PM
@DanielSank No, I stand by what I said in that thread. But the tone did get strangely rough, which is why I was trying to defuse it (with only mild success).

@0celo7 almost all the exponents of organized crime in italy are fervent catholics

@Shing I'm atheist but I'm very pro organized religion
I am a Jim, your argument is invalid

@yuggib Frechet and Gateaux derivatives in analysis today
@JohnDuffield Get out, you're banned

@0celo7 yeah? just for the sake of it or to use them in applications?

@0celo7 play nice

1:12 PM
@0celo7 one year ban is a long one

1:43 PM
he must have done something nasty
or many many many many many many many many unpleasant things