The h Bar

0celo7

12:00 AM

@ACuriousMind Why does Heine-Borel work?

@ACuriousMind and I don't mean the proof

why does it work

what caused Mr. Heine to sit down and think bounded sets are precompact

Alfred Centauri

12:20 AM

@JohnRennie I do hear you John but and it's true, one can learn much from seeing a canonical problem solved well. However, being the cynical entity that I am, my gut informs me that this format is not ideal for that for reasons that I can't go into here but that I suspect almost everyone understands anyhow. I've found the, e.g., physicspages.com format helpful. Regardless, I hope the best for your endeavour.

dmckee

Anyone here comfortable enough with general relativity to tell me if I am being an idiot in this comment?

0celo7

@dmckee Maybe

But "mass" is such a loose term

Do they mean ADM mass?

gravitational mass has no meaning in GR

Bernard Meurer

@dmckee Do you know circuits?

I need salvation

dmckee

@0celo7 Damn if I know. Can I ask how the mass need to make a Schwarzschild metric match the Kerr metric of a rotating object at large distance compares to the mass the of the Kerr object?

0celo7

@dmckee ADM mass of Schwarzschild happens to be the mass in the Schwarzschild radius

dmckee

12:33 AM

@BernardMeurer Depends how complicated we're talking. Basics, yeah. And bits and pieces of other things.

0celo7

but that's a coincidence. Let me check my books for the ADM mass of Kerr black hole

ADM mass is basically the energy of spacetime measured at timelike infinity

Bernard Meurer

@dmckee It's very simple, but decoders and mutiplexers are confusing me right now

0celo7

something like that, I'd have to review it before saying more

dmckee

@BernardMeurer Ah. Discrete logic circuits in terms of gates. Yeah, I can probably do that.

0celo7

Kerr mass is Komar mass

Bernard Meurer

12:34 AM

Basically I need to build a circuit that takes in 3 bits and outputs three bits. And it is a map like this
0->1
1->0
2->7
3->5
4->4
5->3
6->2
7->1

Andras Deak

are there two 1s and no 6 on purpose?

(in the output)

Bernard Meurer

so if the input ($A_0, A_1, A_2$) is dec3, the output $Y_0, Y_1, Y_2$ should be dec 5

dmckee

@AndrasDeak There is no reason to expect the output to span the representation space.

Andras Deak

sure, but all the rest seemed unique, it was worth asking:D

Bernard Meurer

@AndrasDeak Yes, the reason is my prof said so in the problem :P

So, by building the truth table I started Identifying some patterns

dmckee

12:37 AM

Oh ... I knew how to do those once, but it's been a while.

Bernard Meurer

i.e. when $A_2$ is 0, $Y_0 = A_1$

0celo7

Ok, in a stationary spacetime, ADM = Komar

Is Kerr stationary? It's not static

Damn, I don't remember these definitions

@dmckee It depends on the angular momentum

In the $a\to 0$ limit, you get the Schwarzschild metric

So you'd need to look at the metric (in appropriate coordinates)

But that's a reasonable question

Problem is, people do Kerr in different coordinates than Schwarzschild

Bernard Meurer

@dmckee I can use MUX 4:1 and 2:1 and/or DEC 2:4, 3:8, and 4:16

dmckee

@BernardMeurer Do you have always 1 and always 0 lines available? I seem to recall working problems with those is easier.

Bernard Meurer

Always 1 and always 0? Like VCC and GND?

Or do you mean the EN control on the IC

dmckee

12:44 AM

I mean can I assume the existence of an input that is always one and an input that is always 0 to the logic. On the chip those might well be VCC and a diode to GND, but that is an implementation detail.

Bernard Meurer

@dmckee Yes, I have those lines :)

$$\begin{table}[]
\centering
\begin{tabular}{llllllll}
\hline
DEC & A_2 & A_1 & A_0 & Y_2 & Y_1 & Y_0 & DEC \\ \hline
0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\
1 & 0 & 0 & 1 & 0 & 0 & 0 & 0 \\
2 & 0 & 1 & 0 & 1 & 1 & 1 & 7 \\
3 & 0 & 1 & 1 & 1 & 0 & 1 & 5 \\
4 & 1 & 0 & 0 & 1 & 0 & 0 & 4 \\
5 & 1 & 0 & 1 & 0 & 1 & 1 & 3 \\
6 & 1 & 1 & 0 & 0 & 1 & 0 & 2 \\
7 & 1 & 1 & 1 & 0 & 0 & 1 & 1 \\ \hline

Oh, tables no worky

dmckee

Man. It's been a long time.

0celo7

you broke chat

dmckee

@BernardMeurer I don't think MathJax will like a table environment, but it might process just the tabular.

Andras Deak

your first row is inconsistent, though

it should be dec1 according to your original message, right?

Bernard Meurer

12:52 AM

@AndrasDeak Yeah, I'm just saying that the row is the DEC representation of the binary

I guess the fact that the first one is the DEC of A and the second of Y is implicit

Andras Deak

I'm saying that you said 0->1

dmckee

^ that.

Bernard Meurer

Oh! Ny bad, it should've been 0->0!

Good observation @AndrasDeak, thanks!

Andras Deak

no worries, I can't be of help otherwise:D

dmckee

Anyway, I recall that the trick is to pick out the smallest set of rectangles that are homogeneous (all 0 or all 1) and cover all cases in the output, then to figure out the logic for each one.

Andras Deak

12:55 AM

Well, does it help that most of it is a reverse+cyclic shift? My hunch is "no"

dmckee

But the data you've been given is nasty. The biggest blocks are 1x3 or 3x1.

0celo7

what on Earth are you people doing

Bernard Meurer

@0celo7 Digital systems

@dmckee It is nasty indeed

0celo7

you could learn string theory instead

Bernard Meurer

@AndrasDeak It's (2+A)%8

@0celo7 String theory won't get me as much pussy as this in the long run

Andras Deak

12:57 AM

@BernardMeurer ah...

Bernard Meurer

@AndrasDeak :P

0celo7

mmmm

38GB used on the music app

not even a quarter done

Andras Deak

but (2+2)%8==4?

dmckee

Ah, wait. This isn't the write table.

You need three tables like

Bernard Meurer

@AndrasDeak yes, and 4 is mapping to 4

0celo7

12:58 AM

@dmckee Write? :P

Bernard Meurer

@AndrasDeak OH, wait, nah I'm talking about something else

Andras Deak

but you said (2+A)%8, then (2+2)%8 would refer to A==2? :D

@BernardMeurer OK then:)

don't worry about me, I'm just being nosy and curious, but it doesn't really matter if I stay confused

Bernard Meurer

@AndrasDeak I'm just a lost freshman. I wish my course involved more Linux on calculators

@0celo7 Today my calculator played music btw

0celo7

@BernardMeurer Has Michelle mentioned Bob lately?

dmckee

Nope. I'm going to have to read before I can recall how to do this. And I'm suppose to be grading intro physics papers.

0celo7

1:01 AM

@BernardMeurer wtf those things have speakers?

Or have you tortured it enough

Bernard Meurer

@0celo7 Not more than making an analogy about bob in skinny jeans. Why?

0celo7

it now plays music through the circuits

@BernardMeurer He's not doing well

Bernard Meurer

@dmckee "Dear students. Your grades will be late because I have spent my weekend helping a freshman with a simple MUX/DEC problem. Love, David"

:P

@0celo7 I added a USB soundcard and connected it to speakers

@0celo7 Oh shit, what's up with the ungermaster?

0celo7

Bad back

Bernard Meurer

@0celo7 Ah, ageing must suck

0celo7

1:04 AM

Yup

Bernard Meurer

If I was a prof I'd always end my emails with "Love, Bernardo" to lure them into thinking I was a sweet prof

Then RAM THEM with some exam where they have 45 minutes to rewrite the 0.01 Kernel from scratch

Andras Deak

by the time you get there all your joints hurt from all the paperwork, and you only sign BM

Bernard Meurer

@AndrasDeak Lol, so that's why :P

0celo7

I would love to write an analysis test

it would be 15 "easy" problems

ACuriousMind

@BernardMeurer I bet it played the "don't hurt me" part of this over and over again :P

2

0celo7

1:06 AM

lol

1: Prove Cauchy sequences are bounded

Bernard Meurer

@ACuriousMind Woke up, got out of bed, turned his computer on, just to say that :P

0celo7

That result is so basic but there's a trick that no one knows

2: R is complete

@AndrasDeak Ok

51GB used on my new phone

40 of that is music

Still have 200GB free :)

ACuriousMind

@BernardMeurer I never miss a chance to link that song in the h bar :P

Bernard Meurer

@0celo7 Dood, $\mathbb N$ is neither closed nor open

0celo7

What does that even mean?

Bernard Meurer

1:08 AM

@0celo7 OH

HAHAHA

0celo7

I mean it's closed as a subset

Bernard Meurer

PWND

ACuriousMind

???

Bernard Meurer

MC Hammer - U Can't Touch This

►

0celo7

That sentence doesn't make sense unless you say with respect to which topology it's not closed

Bernard Meurer

1:09 AM

This is the topology of $\mathbb N$ to @0celo7 right now

0celo7

it's closed as a subset of $\Bbb R$

as a subspace, it's trivially closed and open

in no scenario is it neither

@ACuriousMind Agreed?

ACuriousMind

yes

0celo7

good

@BernardMeurer I got a new phone with 0.25TB internal storage

how is such a thing even possible?

Bernard Meurer

@0celo7 iPhone 7, sweet

@0celo7 NAND technology is very advanced nowadays

specially with TLC cells

0celo7

when you pick it up and look at it, it turns on

it's watching...

Bernard Meurer

1:13 AM

Samsung?

0celo7

iphone

Bernard Meurer

Dude you're such a spoiled kid :p

0celo7

I bought it myself.

I do have a job

Andras Deak

@0celo7 that's not so bad

Obliv

hey @bernard you there?

Bernard Meurer

1:14 AM

@0celo7 Then you're just stupid dawg :P

@Obliv Yessir

0celo7

@BernardMeurer No argument here

Obliv

Could you help me with some configuration settings in eclipse?

if you're not busy that is

Bernard Meurer

@Obliv I don't use Eclipse, nor do I recommend it :/

@Obliv Ask away though, maybe I know the answer

But why Eclipse?

Obliv

Well I'm running windows and I figure an IDE is easier to use than a text editor

Bernard Meurer

@Obliv Which lang.?

Obliv

1:16 AM

eclipse isn't recognizing 'cout' and I'm not sure why. It's c++

using mingw

Bernard Meurer

@Obliv jetbrains.com/clion/?fromMenu

Use this

It's free for students

It's the best IDE there is, I use it on Linux

Works on all OS's

@Obliv Did you declare the namespace? If not did you do std::cout?

Obliv

I tried std::cout it doesn't work. declaring the namespace doesn't work either lol

omg..

it works now.

Bernard Meurer

See, I have this effect on computers

Obliv

Wtf.. lol @bernard u have the magic touch

THANKS MAN.

0celo7

@BernardMeurer they scream in pain?

Andras Deak

1:19 AM

@0celo7 nuff said (OK, might be bogus, but this one's legit)

user218912

@0celo7 you bought an iphone 7???

Bernard Meurer

@Obliv Love ya

@0celo7 They work in fear that I'll try and fix them

0celo7

@obe I was in the mall looking for some new shoes (@BernardMeurer) and thought it was time to upgrade

user218912

@0celo7 which colour?

Bernard Meurer

@0celo7 What was your old one?

0celo7

1:20 AM

5s

Bernard Meurer

@0celo7 Wanna give it to me?

0celo7

I sold it to pay for apple care, sorry

@obe matte black

Bernard Meurer

@0celo7 Dang it

user218912

coool

user218912

i want jet black :(

0celo7

1:21 AM

no you don't

user218912

why

0celo7

it get scratched

so you have to put a case on it

and that just defeats the purpose

user218912

you're right but it still looks cool

0celo7

@BernardMeurer jk it was my bd present, but I did pay for it

Bernard Meurer

@0celo7 I knew it!

That shit cost 900 bucks dawg

ain't no uni job that pays for that

You'd have to work a decade

0celo7

1:23 AM

Um.

I did pay for it using my money.

Bernard Meurer

@0celo7 That someone gave you?

user218912

then how is it a bd present?

0celo7

No, from my job

Andras Deak

doesn't getting a new iphone involve ritually camping for three weeks?

user218912

you bought yourself a bd present?

0celo7

1:24 AM

@obe I'm getting reimbursed

@AndrasDeak only if you get it day 1

user218912

ok

Andras Deak

@0celo7 like all the cool kids, eh?

0celo7

I got my iPhone 4s day one

back in the day

Bernard Meurer

@0celo7 Spoiled

Andras Deak

heh:D

0celo7

1:25 AM

I camped for 15 minutes

user218912

I have a galaxy s5

0celo7

@BernardMeurer was my first phone

Andras Deak

You payed for somebody to camp for you, didn't you?

Bernard Meurer

@0celo7 Mega-Spoiled

0celo7

@BernardMeurer Was my 5th phone

@AndrasDeak Yeah, a servant

Bernard Meurer

1:25 AM

@0celo7 Called it

Andras Deak

knew it!

0celo7

One of the shoe shiner boys

user218912

@0celo7 I can't believe I made it this far in QFT, I'm basically halfway done the course and I have an A+

user218912

I deserve an iphone 7

0celo7

good job

user218912

1:26 AM

thanks :D

0celo7

@obe not from me, I dropped too much money today lol

user218912

lol

user218912

I'll beg my parents.

user218912

lol...

user218912

that's sad right

user218912

1:28 AM

I don't have a job

Bernard Meurer

@0celo7 My music wouldn't fit on your phone

0celo7

how do you have more than 0.25TB

unless you just have a lot

that's cheating

Bernard Meurer

Oh shit, it would

0celo7

lol

rekt

user218912

I can live off 32gb

user218912

1:30 AM

I only listen to like 15 songs...

0celo7

I need to make my phone not watch me

how do I do this

Bernard Meurer

@0celo7 Get another phone

0celo7

Do you want mine?

Bernard Meurer

Yes

user218912

@0celo7 what?

0celo7

1:31 AM

when you pick it up and look at it, it turns itself on

which means the camera is on all the time

or at least when you pick it up

Obliv

@bernard puu.sh/s1gmr/c02dc0c594.png you think there should be more configurations than this?

user218912

oh

Bernard Meurer

@Obliv Please try CLion dude

Eclipse is nuts

Andras Deak

good night

Obliv

@bernard I'm in too deep..

Bernard Meurer

1:33 AM

@Obliv Really. Don't

Also, that's what she said

Obliv

ALL I NEED TO DO IS WRITE A PROGRAM THAT CHECKS IF DD/MM/YY THE DATE ENTERED IS SUCH THAT YY = MM * DD

AND I HAVE TO GO THROUGH ALL THIS BS

Bernard Meurer

@Obliv Use

Clion

Or go install Linux and be happy

Andras Deak

~~python with datetime~~

Bernard Meurer

@AndrasDeak lol

Obliv

actually i'm going to try editplus really quick I think it should compile fine.

0celo7

1:36 AM

@AndrasDeak Time to figure out what my reddit password is.

Bernard Meurer

@Jim When you are around could you, please, make us a private room. I have some things I wanted to talk to you

user218912

@0celo7 this scattering stuff is difficult

0celo7

yes it is

there's a reason why physicists are smarter than mathers

QFT filters out the <125 IQ crowd

ACuriousMind

@BernardMeurer Private rooms are for moderation purposes only, Jim cannot create one.

Bernard Meurer

Dammit, @ACuriousMind halp plox?

ACuriousMind

1:39 AM

At least if by private you mean "not readable for others"

0celo7

@BernardMeurer check texts

Bernard Meurer

@ACuriousMind Yes. are you on Skype?

Obliv

@bernard okay editplus works. It's basically atom except without all the fancy stuff you mentioned before

screw eclipse.

0celo7

don't Skype without me pls

Bernard Meurer

@Obliv Use. Clion. Ir makes C++ reasonable

0celo7

1:40 AM

I'll use my new headph...shit

user218912

lol

0celo7

I'll use Skype on my phone

After I remember the password

@heather ;(

user218912

can I join too? I'm pretty lonely :'(

Bernard Meurer

No. I need to actually talk to the man

Or, message at least

0celo7

check your damn texts

user218912

1:42 AM

guys let's do a skype call for fun

user218912

plz :(

ACuriousMind

@BernardMeurer After I have reset my password, I will be, and I would prefer messages over a call

0celo7

Hah!

Bernard Meurer

@ACuriousMind Thanks. I can't call right now, lucky you :P

ACuriousMind

@0celo7 I always forget my Skype password, that's almost a ritual by now :P

0celo7

1:46 AM

@ACuriousMind I'm resetting mine right now lol

I changed it the other day to something I could remember

@obe I can't find any good wallpapers

user218912

for your phone?

0celo7

si

user218912

what do you like?

0celo7

pokemon

Bernard Meurer

@Jim Nevermind that, just send me an email when you can, meurerbernardo@gmail.com. @ACuriousMind Can attest it's a legit reason :P

user218912

1:51 AM

do you really?

ACuriousMind

@BernardMeurer Right, there are totally no brain-eating potatoes involved

user218912

I've been using ice cave wallpapers @0celo7

0celo7

Yes, I love pokemon

@ACuriousMind can confirm

@BernardMeurer is the i7 at a new resolution?

ACuriousMind

An i7 is a processor, how can it have a resolution? :P

user218912

@0celo7 ice cave

0celo7

1:53 AM

no, apparently not

@ACuriousMind iPhone 7, smartass

Bernard Meurer

@0celo7 Nope

@ACuriousMind Depending on the i7 it comes with a built-in graphics chip that has a recommended resolution

rekt

ACuriousMind

:O

0celo7

lol

@obe uhhh

user218912

cool wallpaper

Bernard Meurer

2:03 AM

@obe We will skype if you talk

0celo7

Hmm. Anime wallpapers

0celo7

2:16 AM

@BernardMeurer let's skype about QM

@ACuriousMind can watch and comment

Bernard Meurer

@0celo7 Yep, gimme 5 mins

0celo7

Ok you can help me with my bullshit EM homework

@ACuriousMind ?

Bernard Meurer

@0celo7 Ready, skype bitch

0celo7

hold on let me clear some RAM

I'm using 15

user228700

2:38 AM

Hi everyone :-)

user228700

Belated Happy Halloween..? :-P

0celo7

belated?

what day is it in India o.o

user228700

1 Nov.

0celo7

Mind = blown

Are you guys a day ahead of us?

user228700

Wtf, no!

0celo7

2:41 AM

It's October 30th where i live

Right now

user228700

Oh, crap, sorry, it's 31st. Happy Halloween :-P

0celo7

Tomorrow is the 31st I'm pretty sure

Ok, ok

My world was falling apart for a second

user228700

Sorry about that :-P

user228700

@JohnRennie: Morning :-) In the following post, I had asked about the K.E of photoelectrons in the PE:

user228700

3

Q: Kinetic energy of photoelectrons

I came across the following question: A photon of energy $h\nu$ is absorbed by a free electron of a metal having work function $W<h\nu$. Then: The electron is sure to come out The electron is sure to come out with kinetic energy $h\nu-W$ Either the electron doesn't come out or it ...

user228700

2:44 AM

And u wrote that the formula is actually given by $K.E=h\nu -W- \delta E$ where $\delta E$ is the energy lost by the electrons due to scattering.

user228700

But I googled the definition of the term work function and found that it is the catch-all term for the total energy required for the electron to be ejected-doesn't this include the energy lost due to scattering?

user228700

If we use the above definition of work function, the equation $KE_{max}= h\nu -W$ makes sense. This, as u see, is the $KE_{max}$ and not simply $KE$. Hence, the $KE$ of an ejected electron can vary b/w 0 and $KE_{max}$

user228700

(The probability that an electron will be ejected with a kinetic energy given by $KE_{max}$ is next to 0, correct?)

0celo7

What's the distribution look like?

user228700

I...dunno. Lemme google it.

user228700

2:53 AM

It has used strange terms that I'm not familiar with :/

user228700

I found (an oversimplified version):

user228700