The h Bar

Bernardo Meurer

00:08

@ACuriousMind How can I show that $h(x)$ has a local "extreme" at x=2?

and say whether it will be a max or min

OH

if the first derivative is 0 then it's an extreme

ACuriousMind

@BernardoMeurer The proper English term is "extremum" or "extremal point". Also, your statement as written is wrong (look at $f(x) = x^3$ for a counterexample).

Bernardo Meurer

Yeah, yeah, if the first derivative is 0 and the second one is non-0

(right?)

ACuriousMind

Yep

Bernardo Meurer

and then if it's <0 it's a max and >0 it's a min

(the second derivative that is)

ACuriousMind

Yep

Bernardo Meurer

00:12

Do you have an intuitive reason why?

ACuriousMind

@BernardoMeurer If the second derivative is negative, then the first derivative is going from 0 to negative at this point, so the function itself is decreasing, so the point must've been a maximum

Bernardo Meurer

@ACuriousMind Ah! Of course!

When I graduate you might end up being the top person on the thank you list lol

Now the only thing I don't know how to do is the MacLaurin magic with the Lagrange spell

but idk if I can learn that in like, 1h

@ACuriousMind Is this stuff just applying the formula?

is MacLaurin just Taylor for f(0)?

ACuriousMind

@BernardoMeurer I have no idea what you mean by "Lagrange spell"

Bernardo Meurer

Lagrange remainder :P

ACuriousMind

@BernardoMeurer Yes

@BernardoMeurer I have neither the remainders nor their names memorized :P

Bernardo Meurer

00:25

@ACuriousMind Yeah it seems pretty "just know the formula" to me

In case your curious this is the exercise

I guess you just apply Taylor with lagrange and handwave

He uses the more-squiggle character in his solution

Sir Cumference

01:26

Oh @ACuriousMind, can you answer a question?

DanielSank

02:03

Just had a wonderful argument with a psychotic landlady (not mine).

Denise, if you're reading this, thanks for being a good landlady <3

Bernardo Meurer

@DanielSank Wat?

DanielSank

Wat?

Bernardo Meurer

Is she J's landlady?

DanielSank

Denise is mine. I wanted to make it clear that I'm not complaining about her.

Jason's landlady is one of the more unreasonable people I've met.

My hats... they're gone!

Nooooooooooo

Sir Cumference

@DanielSank What?

No!

DanielSank

02:08

They've taken our hats!

2

We need a patch script to enable our own hats whenever we want.

ACuriousMind

Order has been restored.

DanielSank

Who knows js?

@ACuriousMind Order?!

Bernardo Meurer

These Klipsch speakers are making my wallet look at me scared

DanielSank

You call this order?

Sir Cumference

@DanielSank Huh, that's actually a good idea

I'll have to wait until next year to figure out how the hats work, tho...

Then I might be able to write a script

DanielSank

02:09

Heyyyyyy that's a good idea.

Dump the page before and after the hats are deployed.

Do a diff and just copypasta the code that adds the hats!

Why didn't we think of that before!

Goodness, the fact that that's possible is part of why the internet is so scary.

Sir Cumference

Anyone still have a page open with hats?

DanielSank

^

Sir Cumference

Preferably one on the user page

Bernardo Meurer

@ACuriousMind Can I go by with 5€ a day for food?

DanielSank

@BernardoMeurer Maybe, but you won't be happy.

Bernardo Meurer

02:10

Hmpf

Maybe I can sell my body for money on the streets

Sir Cumference

@ACuriousMind Oh btw, can I ask you a question?

DanielSank

@SirCumference Just ask the question, bro.

Bernardo Meurer

@ACuriousMind Don't ask to ask, come on, you've been here long enough

ACuriousMind

@BernardoMeurer Yes, but it probably means little meat and you having to survive in a kitchen without setting fire to it ;)

Sir Cumference

@DanielSank Well I want to make sure he's here, lest I waste my finger energy

Bernardo Meurer

02:11

@ACuriousMind I have a woman now

ACuriousMind

Great, one more victim of the fire :P

Bernardo Meurer

She loves cooking, all I gotta do is go to the supermarket which she hates and I like

Sir Cumference

Ok, well here goes: can the Big Crunch happen if phantom energy exists?

ACuriousMind

@SirCumference I have to wonder why you thought anything qualifies me to answer that question.

Bernardo Meurer

@SirCumference Only if you carve away the grumbo well while manufacturing the plumbus

Sir Cumference

02:13

@ACuriousMind Well you like GR, right?

ACuriousMind

I also have to wonder how you got that impression :P

Sir Cumference

Er...well, you answered some of my old cosmology questions

Bernardo Meurer

@SirCumference He doesn't like any physics involving things larger than 5nm or so

3

:P

Sir Cumference

Oye, where's @0celo or Chris when you need them

Bernardo Meurer

PLEASE RETURN CHRIS WHITE

Sir Cumference

02:15

@BernardoMeurer AND HATS

Bernardo Meurer

How many hats seasons must go by without thy presence

DanielSank

@BernardoMeurer Ehhhh, you know... males can cook too ::points at self::

Bernardo Meurer

If I am elected moderator I will build a Chris White to keep out hats in our chat

DanielSank

@BernardoMeurer Dude, your hero is gone. Deal with it.

Bernardo Meurer

@SirCumference You had to ruin the subtlety

@DanielSank You're my hero

Sir Cumference

02:16

@BernardoMeurer Ok then

DanielSank

@BernardoMeurer :D

Bernardo Meurer

Chris White was just like, the Robin

ACuriousMind

@BernardoMeurer I vaguely feel as if I should be offended by that :P

DanielSank

Why?

Bernardo Meurer

@ACuriousMind Lol

DanielSank

02:17

It's probably true. In fact, 5nm is likely a massive overestimate.

I feel naked without my hats.

Bernardo Meurer

at 5nm tunneling can be observed, no?

Sir Cumference

The top hat added a bit of elegance to my pie gravatar...

Chris W knew GR better than anyone else ;-;

Bernardo Meurer

Okay kids, time for me to go to bed

analysis exam tomorrow

heather

@SirCumference did you see Emilio Pisanty's comment a bit ago?

Bernardo Meurer

a lot of black magic awaits

Sir Cumference

02:20

@heather No?

heather

@BernardoMeurer best of luck =) and good night

@SirCumference lemme see if i can find it

Bernardo Meurer

See you all after I get assblasted by a senile professor

Goodnight!

Sir Cumference

'Night

heather

@BernardoMeurer good night =)

how can you look through all things said by a user?

Bernardo Meurer

Stop stalking me @heather

ACuriousMind

02:22

@heather Define "said"

heather

@BernardoMeurer, sorry =P

DanielSank

@heather Use search box.

heather

@ACuriousMind stated at the hbar

DanielSank

Use search box.

heather

@DanielSank, i tried various wordings, none of them were right

i can't find the statement i'm looking for

Bernardo Meurer

02:23

Is it from me?

heather

and just putting the username and hitting enter doesn't work.

DanielSank

11

Q: Search for all chat messages by a particular user?

Is it possible to search for all messages by a particular user in the chat search, at http://chat.stackexchange.com/search? I tried searching with the 'search for' field empty, but got no results... and with '*', the same.

heather

@BernardoMeurer, nope, EP

ACuriousMind

@heather In that case you cannot do that

Bernardo Meurer

@heather Try more general wording

the search box is like dumb google

very dumb google

heather

02:24

@BernardoMeurer I've tried, i'll go again

Bernardo Meurer

TRY HARDER

Sir Cumference

Wait, ACM, do you know some GR?

heather

ah, here we go

that recent tab helped, thanks @DanielSank

ACuriousMind

@SirCumference Yes. I don't know much about cosmology, though.

heather

yesterday, by Emilio Pisanty

Have folks seen this?

Sir Cumference

02:24

Ok, can you tell me where this equation comes from?

$T^{\mu\nu} = \frac{\hbar^2}{m} (g^{\mu \alpha} g^{\nu \beta} + g^{\mu \beta} g^{\nu \alpha} - g^{\mu\nu} g^{\alpha \beta}) \partial_{\alpha}\bar\phi \partial_{\beta}\phi - g^{\mu\nu} m c^2 \bar\phi \phi$

I have it written in my notes but I didn't have time to write any context

heather

yesterday, by Emilio Pisanty

Not sure if it's the same person as before, but it's definitely interesting.

ACuriousMind

@heather Last seen in 2015, what's the big deal?

DanielSank

@BernardoMeurer this is for you

Sir Cumference

I'm not even sure if it's GR

heather

@ACuriousMind ::shrugs:: Sir mentioned CW, which just made me think of it.

Sir Cumference

02:26

Sigh, this stuff is getting too fast

ACuriousMind

@SirCumference Judging from the symbols used it appears to be a stress-energy tensor for a complex scalar field

Sir Cumference

OK, thanks

ACuriousMind

Wait, why is it written so weirdly, that there is just a silly way to write $\partial^\mu \bar\phi\partial^\nu\phi$

Sir Cumference

I don't know if I got it down perfectly...

I was rushing, he talks at 1 million words per minute

Also, this formula

$g = -\frac{GM}{R} + \frac{1}{3}\Lambda R$

I know this is for the acceleration of the universe, but I can't find it online

ACuriousMind

$g$ is usually used for the determinant of the metric

Sir Cumference

02:30

@ACuriousMind Sigh, that was dumb of me

@ACuriousMind You talking about the second formula or the first?

ACuriousMind

@SirCumference Hmm, no, it's not exactly that. However, it is the standard stress-energy tensor for a complex scalar field.

@SirCumference the second. I don't recognize that equation, though, I'm just guessing

Sir Cumference

@ACuriousMind Okay. The prof used an analogy where he compared it to gravitational acceleration in Newtonian mechanics (hence, $g$)

ACuriousMind

@EmilioPisanty Sorry to disappoint you, but didn't you see that that user was last seen in 2015?

Sir Cumference

Ugh, I'm losing sleep over all this

Howdy @Ramanujan

Ramanujan

@SirCumference I am good and how are you doing?

Sir Cumference

02:40

All right

heather

02:51

good night everyone

Sir Cumference

'night

Hey @AlfredCentauri

They took our hats

Alfred Centauri

@SirCumference Life's a beach...

Sir Cumference

@AlfredCentauri Huh?

What up?

@AlfredCentauri Oh, think ya meant to reply to the hat thing

Alfred Centauri

@SirCumference Just briefly checking in to see if I have any comments to address. I'm taking a break from the exchange for a bit (I think they call it a 'Wikibreak' over at Wikipedia). How are you?

Sir Cumference

Tired

But good in general

Alfred Centauri

03:02

@SirCumference I feel more or less the same way. Everything good here?

Sir Cumference

Yep

Physics is starting to confuse the hell out of me

Thank god for this site

Alfred Centauri

@SirCumference It only gets worse... I (think) I miss my 'arm chair physicist' days when I could convince myself I actually had some competence in this. My QFT class last semester pretty much convinced me otherwise.

Sir Cumference

@AlfredCentauri Pff, I thought Newtonian mechanics and high school geometry were my thing

Then all this GR stuff comes in

I'm losing sleep studying over all this, plus the other classes I have

@AlfredCentauri On a side note, I have a question

You go on astronomy SE at all?

Alfred Centauri

@SirCumference I'm going to try the 2nd semester of GR for grins. Heck, you just never know what might happen. Losing sleep isn't good but I know what you mean. It seems like one can't escape the problem sets even in sleep.

@SirCumference I haven't tried the astronomy.SE site. Do you recommend it?

Sir Cumference

@AlfredCentauri Exactly, I'm having nightmares about forgetting the important stuff on a test

@AlfredCentauri Yeah, definitely

Then again I have over 4k rep there so I might be a bit biased

Well anyways, my next question is, do you have tampermonkey?

Alfred Centauri

03:10

@SirCumference Alright, on the strength of your recommendation, I'll take a looksee.

@SirCumference <sigh> what on Earth is a tampermonkey? Hold on, Google is my friend... OK, the answer is no, I don't have tampermonkey. What will it do for me?

Sir Cumference

Okay then...you ever heard of a userscript?

Alfred Centauri

@SirCumference Many moons ago, I remember trying something called greasemonkey to manage userscripts but my aged memory might be faulty.

Sir Cumference

@AlfredCentauri Ok, so you know what JavaScript is?

Alfred Centauri

@SirCumference for the sake of argument, let's say yes...

Sir Cumference

@AlfredCentauri Right, so JS is what websites use

Alfred Centauri

03:15

@SirCumference yep, this is sounding familiar...

Sir Cumference

A userscript is a piece of JS code that lets you modify any website you want

It's basically a browser extension/plugin that you write for yourself

Alfred Centauri

@SirCumference OK, do you mean modify a website locally or actually modify a website?

Sir Cumference

Tampermonkey is a chrome plugin that installs a userscript you wrote into the website, so you can modify the website for youself

@AlfredCentauri locally

That way, you can fix any petpeeves you have with the site or add a design/feature

Alfred Centauri

@SirCumference This is really beginning to ring a bell now; I think I remember looking into this back when I was experimenting with Gentoo Linux. Go on...

Sir Cumference

So I was gonna ask you if you were willing to test out a userscript I wrote

Alfred Centauri

03:19

@SirCumference What's in it for me? :)

Sir Cumference

Uh, I dunno. You bored?

Alfred Centauri

@SirCumference Is it nefarious?

Sir Cumference

Nah

It just adds a design to Astronomy SE

Alfred Centauri

@SirCumference dang, now I'm bored :-)

Sir Cumference

Needed an opinion on how it looked

@AlfredCentauri Well if you're up for it, you'll need to download tampermonkey

Alfred Centauri

03:23

@SirCumference Done

Sir Cumference

@AlfredCentauri Okay, then click this to install the script

Wait, crud

There, try clicking that

Now do you see anything change on Astro SE?

@AlfredCentauri Uh, you there?

Alfred Centauri

@SirCumference Yeah, I got the warning about malicious stuff etc. and the install button doesn't seem to do anything. I went to the Astro SE site and then I got the deleting your hard driv...

Sir Cumference

@AlfredCentauri wait wtf

You didn't get something that looked like this?

@AlfredCentauri Uh, everything okay?

Sir Cumference

03:50

@AlfredCentauri You there...?

Alfred Centauri

04:41

@SirCumference I'm back - I've created an astronomy.se account, made sure the script is active (as best as I can tell) by Tampermonkey, and I'm not seeing anything out of the ordinary. What am I looking for?

FenderLesPaul

06:32

@ACuriousMind @0celo7 Hiii

John Rennie

→ 1 message moved to Trash

@SirCumference that's the proper acceleration of a stationary observer in the Schwarzschild-de Sitter metric. The symbol $g$ means the gravitational acceleration in the sense we teach it to schoolchildren i.e. $g = 9.81$ m/s$^2$ at the Earth's surface.

user223506

07:12

hello @JohnRennie!

user223506

i had 18 hats in the end ....

John Rennie

Congrats :-)

The hats are surprisingly good fun for such a basically silly idea.

user223506

they are indeed!

user223506

they made gravatar gorilla even more of a touch of class!

user223506

hey @JohnRennie - meaning to ask, what is your field in Physics?

John Rennie

07:24

That's ... complicated :-)

user223506

lol - now I am even more intrigued

John Rennie

Cambridge doesn't do separate physics, chemistry, etc degrees. Everyone does a single Natural Science degree and you choose the courses that suit you. I ended up doing mostly quantum chemistry.

Then I did a PhD in solid state photochemistry, which more or less follows from my degree.

user223506

excellent!

user223506

technically speaking, I am a photobiologist - having originally being a geologist

John Rennie

But after that I left academia and went to work for Unilever where I worked in colloid science. This was a complete change of subject (financial considerations!!) and is really physical chemistry rather than physics.

I'm retired now and have gone back to physics just as a hobby. I had always wondered how general relativity actually worked, and now I know :-)

user223506

07:28

that is actually awesome!

John Rennie

Being retired has its advantages :-) The time it takes to learn this stuff now my brain is wearing out it remarkable. I've been at GR (part time) for the better part of a decade!

If I was still working there just wouldn't be enough hours in the day.

user223506

that be true!

user223506

my academic trail is like a drunken meandering torrent

user223506

hello @DanielSank - I made it to 18 hats before they took them away!

user223506

@JohnRennie do you still publish?

John Rennie

07:35

@Doc No. It's all just for fun these days.

user223506

@JohnRennie excellent!

user223506

meanwhile, I work 5 jobs (2 are research based) and the associated cat herding

user228700

Ello :-)

DanielSank

@Doc Very good.

user223506

@Kaumudi.H hello!

DanielSank

07:47

@Doc That's too many jobs.

user223506

@DanielSank gave my gorilla gravatar a touch of class

DanielSank

yah

user223506

@DanielSank yup, i work 40-70 hours a week

DanielSank

My octo was enjoying the top hat and specs quite a bit.

user223506

average of about 60 hours

DanielSank

07:49

I mean... I probably hit that too, but that doesn't mean I have five jobs!

Five jobs is nutty.

user223506

@DanielSank 3 of them pay the bills

DanielSank

U crazy.

You must have a lot of bills.

user223506

nah, not many

user223506

@DanielSank very crazy

user223506

3 paid and 2 volunteer jobs

Lu Bu

07:52

You must really like what you do then.

user223506

love it

user223506

keeps me in and out mischief at the same time... sort of a Schrodinger's work ethic

Lu Bu

@Doc Good for you. I think doing something you don't like makes no sense, given that one has a choice.

user223506

@LuBu absolutely and most of them are outdoors and 4 of them are on my own terms

user223506

i get to walk 10+ km a day for my ework

user228700

07:58

Wow, u walk 10+ Kms everyday?

user223506

yup, can't drive

user228700

Whoa. Can't u cycle or something?

Lu Bu

Why can't you drive though? Walking might be fun, if you're not in a hurry. But you might not always be in the mood for walking.

user223506

I have partial paralysis, car would need to be modified (too much $$)

Lu Bu

@Doc Sad to hear.

user223506

08:01

as for cycling, I am about as coordinated as a drunken swan on an oil slick

user223506

@LuBu eh, I have adapted to it - the condition doesn't really stop me

user228700

@Doc That's awesome :-)

user223506

"Stand tall, fall proudly, fail graciously, but never give up"

2

user223506

and now I don't fall anymore

John Rennie

My favourite motivational quote is:
"We are all in the gutter but some of us are looking at the kerb"
I like to have modest targets :-)

2

user228700

08:10

@JohnR: Ello! :-)

Lu Bu

I think quotes are usually just corny. =)

user228700

@Doc :-)

John Rennie

@Kaumudi.H Morning :-)

Lu Bu

This one i like though: “If you can't explain it to a six year old, you don't understand it yourself.” Just because it brings up the fact that trying to teach a concept to someone challenges your understanding about the concept.

John Rennie

That's a worthy target to aim at, but sometimes understanding something requires a level of background knowledge that six year olds just don't possess. I much prefer Einstein's (alleged) quote Everything should be made as simple as possible, but no simpler.

Lu Bu

08:20

That's true, but atleast it brings up the fact that trying to explain something might end up teaching you.

user223506

so true!

Ramanujan

If someone is interested can come in mathematics chat room I need some strange help

Lu Bu

I'll check the room out, but i won't be able to help though.

=)

ACuriousMind

11:35

@FenderLesPaul Wow, hey, long time no see!

anonymous

12:00

Anyone here knows reduced mass technique in classical mechanics ?

ACuriousMind

12:13

Arrrgh, why on earth would you write "We use the same convention as in ref. [11]" and not just write down the damn convention?! Why do reviewers let this crap pass? :P

Balarka Sen

Oh well

user228700

12:42

@JohnR: Hi, again! :-P How's ur day going? (Gah, I just found out that I'm totally screwed, BTW, with regard to the exam and all)

John Rennie

Good. I've got a lot of work done. Now I'm sat looking at the rain wondering if it will ever stop :-)

@Kaumudi.H Exam woes? What's up?

user228700

Ooh, rain! :-)

John Rennie

@Kaumudi.H I believe you had a bit of a storm a few weeks ago :-)

user228700

@JohnRennie Oh, just that, u know, I've got 14 (6 Phy + 8 Math) chapters to finish in 24 days, etc etc.

John Rennie

If you're under time stress prioritise. Decide what areas you're likely to do best in and do those first.

user228700

12:45

@JohnRennie :-P Yeah, no, the weather over here is just fine as is. I don't wish for it to rain...it would be nice to have it rain for just like, half an hour or something though.

John Rennie

Then if you have time left over go for the less interesting chapters.

user228700

Yeah, I wrote a mock exam today and figured that stuff out; what to finish, what to leave for later, etc.

John Rennie

So you're not totally screwed then :-)

user228700

:-) Don't u know me well enough by now to know that u should never take everything I say completely literally? Especially suspiciously hyperbolic stuff like "TOTALLY screwed" :-P

user228700

Oh, crap, "hyperbolic" was the wrong word to use :-P Hyperbolic: Relating to a hyperbola.

user228700

12:48

Huh. What's the word relating to "hyperbole" then?

John Rennie

No, hyperbolic is the correct term.

Sir Cumference

Morning

John Rennie

It can mean of or pertaining to hyperbole as well as the mathematical meaning.

user228700

Ohh, wokay, thanks!

user228700

@SirCumference Yello :-)

user228700

12:49

So yeah, 24 days and 14 chaps is not exactly a joyride so I am kinda screwed but yeah, hopefully I'm able to get it done. Dyou wanna know what the best part is, @JohnR x'D ?

John Rennie

The best part? Is there a good part to being totally screwed (leaving aside the more obscene interpretations of that phrase :-)

user228700

x'D I was being sarcastic. The best part is that all of the 6 chaps. (that I've got to get done) in Phy is electrodynamics stuff.

John Rennie

Ah ... wonderful

Though some people like electrodynamics

user228700

:-P Yep. So good. But thankfully, I passed with 95/100 in physics last year (I had electrodynamics among some other stuff in my final year of high school) so I know most of this electrodynamics stuff and even kinda like it. It's the thermo and the mechanics I was having problems with and those parts are OK, for now.

John Rennie

So you've finished the hard bits and have the easy (well, easier) bits left to do? Life is looking up.

user228700

12:55

:-P Yeah, but still, the next few months are going to be rough.

John Rennie

> I know most of this electrodynamics stuff and even kinda like it

With the great advances modern medicine is making there is hope for a cure one day :-)

user228700

x'D Sure sure.

John Rennie

We're here to help, though I'm probably not the first person to turn to with electrodynamics problems.

Secret

@ACuriousMind Trust me, they do this a lot more often in maths papers

John Rennie

And there seems to be lots of people willing to help with the maths, though again that isn't one of my strengths

user228700

12:57

@JohnRennie :-) This place is my only hope, really.

user228700

Gosh, I cannot wait till June. Dyou know that my life has been this way for...the past 3 years?!

John Rennie

> This place is my only hope, really

Ok, you're doomed :-)

user228700

:-P You're way too modest. I'm pretty sure u'd be able to help me with electrodynamics. We don't have advanced stuff in our syllabus. Well...that is, of course, if u want to :-P

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