The h Bar

Phase

7:00 PM

Sometimes it's literally just because it's convenient to be able to represent points by numbers

Bernardo Meurer

@BalarkaSen Yeah, $2^{2n}-1$ is always a multiple of three, I did the proof for $4^n - 1$ last week

Abcd

thermal conduction too...for fast shm

Phase

Like [gonna butcher the maths here] you can make all the axes of a 3d space imaginary, but different numbers, so the imaginary part of multiplication of two points gives you the cross product

Bernardo Meurer

Now what I don't know is whether divisibility by three implies the tiling

Balarka Sen

@BernardoMeurer True (good observation), but is your formulation equivalent to my problem?

Bernardo Meurer

7:01 PM

I don't know yet

CooperCape

@Phase You know... I think I'll stick to believing and not understanding you there :P

Bernardo Meurer

Well, the tromino is symmetric

Phase

@CooperCape let $i^2 = j^2 = k^2 = ijk = -1$

you have pretty much all you need

Bernardo Meurer

Hmm, I am not sure

Phase

its not commutative so left and right multiplication arent equivalent

CooperCape

7:02 PM

Right...

user228700

@JohnR: Are you around?

Phase

in fact its anticommutative

so ab = -ba

John Rennie

@Kaumudi.H yes ...

Bernardo Meurer

$$\neg \text{hot}(\text{man})$$

CooperCape

Oh boy... how exciting.

That's wild

Phase

7:02 PM

Fine ill stop talking : p

user228700

@JohnRennie I messed up my laptop, big time.

Bernardo Meurer

@BalarkaSen How do you like that? :P

Balarka Sen

@BernardoMeurer How about a 1x3 rectangle? # of squares there is 3, which is divisible by 3.

CooperCape

@Phase Nah it's interesting you just lost me at 'so the imaginary part of multiplication of two points gives you the cross product' cause I'm not sure how that is a thing but thanks anyways yano...

John Rennie

@Kaumudi.H unless you dropped it in the bath or out of a window it's unlikely to be irretrievably broken ...

Sid

7:03 PM

@Kaumudi.H Get a new one

Phase

well refer back to my previous message

i j and k are unique imaginary numbers

CooperCape

Right.

Bernardo Meurer

@BalarkaSen Sure, but you proposed a square, not a rectangle :P

Phase

since ijk = -1, ij = k, as kk = -1, and you can derive the other info for the table from that

Balarka Sen

@BernardoMeurer I rate this meme a shaq/10

CooperCape

7:04 PM

right okay.

Phase

theres groups in further maths right?

Balarka Sen

@BernardoMeurer Well, a square with a hole. But it does constitute a counterexample to your claim that if the number of squares is divisible by 3 it can be tiled by L-shaped trominoes, right?

CooperCape

@Phase Since the last two times you mentioned further maths, for reference, I still don't take further maths ;)

Bernardo Meurer

@BalarkaSen Yeah, that is true

John Rennie

@Kaumudi.H do you want to switch to Hangouts to avoid the chatter about tiling problems?

CooperCape

7:05 PM

And I think not iirc

Bernardo Meurer

I am mystified

I'll tell A. this one

Maybe she knows how

Balarka Sen

Coolio

Bernardo Meurer

Nice problem, thanks

Phase

@CooperCape just get FP textbooks

Decision maths sucks

Balarka Sen

It's also enlightening to do it for $n = 1, 2$ by hand

Bernardo Meurer

7:06 PM

Nice, I got loads of grid paper :P

lololol

n=1 is trivial

Yup

n=2 not so much

@Phase Ehh I roughly know what each textbook covers and I sort of swing in and out of the topics at random intervals.

Bernardo Meurer

7:06 PM

But still I can see it

Balarka Sen

Mhm

Phase

@CooperCape if I can give you any advice at all from my limited experience

Get a structure as soon as you can dont just learn bits and pieces

It will fuck you over in the long run

Bernardo Meurer

Maybe I have to smoke trees to solve this one

CooperCape

yeah I spent a lot of time un-messing up my knowledge of the A-level physics course over the past few months due to doing that.

Phase

When you're done with your A levels and if you're bored in the Intermediate time

It's my recommendation to pester 0celo7 with constant messages until he gives you a book list

Balarka Sen

7:08 PM

@Bernardo It's basically quick maffs.

Bernardo Meurer

@BalarkaSen Get a snapchat

CooperCape

@Phase or blocks me... I wonder wots first...

Bernardo Meurer

So I can provide you with daily memes

I have some real good shit

Phase

I'll bug him for a list for you if that becomes the case : P

Balarka Sen

@Bernardo Make a discord and send those over to me

Bernardo Meurer

7:09 PM

Bah

That's too much work

Balarka Sen

lol

Bernardo Meurer

I send them in the morning to everyone

lol

Sir Cumference

I once adressed an important person as "Dead Mr. X" rather "Dear Mr. X"... — peterh yesterday

@peterh Glad to know I'm not alone

CooperCape

@SirCumference Was that in an email or something? My friend emailed a uni admissions tutor I was applying to "What's poppin Val, where the links at".

DanielSank

@BalarkaSen @BernardoMeurer

3

Q: Nested integral: volume of a right simplex

Consider the integral $$I_n \equiv \int_{t_1=0}^T dt_1 \int_{t_2 = t_1}^T dt_2 \cdots \int_{t_n = t_{n-1}}^T dt_n \, .$$ I suspect the result should be $I_n = T^n/n!$ but would like to prove it. Doing the $n^\text{th}$ integral gives \begin{align} I_n &= \int_{t_1=0}^T dt_1 \cdots \int_{t_{n-1}=t...

integration

Balarka Sen

7:16 PM

Nice, someone finally made it using induction

Bernardo Meurer

@DanielSank Nice

@BalarkaSen We are noobs

We got rekd trying

Balarka Sen

I actually proposed an answer using Fubini

Maybe I can post it

DanielSank

Yeah, it's just interesting that you don't need to use Fubini.

Balarka Sen

I am a lazy ass

@DanielSank True

DanielSank

@BalarkaSen Post. I will upvote.

Bernardo Meurer

7:17 PM

@BalarkaSen Only answers using theorems created by people this tall can be used

DanielSank

By the way, that simplex integral comes up when you deal with time ordered operators.

Bernardo Meurer

@DanielSank Did you see my charger in the conference room?

@DanielSank Also, I was laughing alone in my exam this morning thinking of the email w.r.t to backpack that was left there

DanielSank

@BernardoMeurer I'm not in the office. Working at home today.

Bernardo Meurer

@DanielSank Ah, alright

DanielSank

@BernardoMeurer I sent it. It was awesome. Kunal responded saying "Oh, thanks that's mine."

Bernardo Meurer

7:22 PM

@DanielSank LOLOLOL

That reminds me I have to email him

@DanielSank You home cause of the smoke & ash?

Emilio Pisanty

@DanielSank whut

Bernardo Meurer

@EmilioPisanty Only git users understand the joke

Emilio Pisanty

@BernardoMeurer I'm a git user

much as you might not like that

Bernardo Meurer

u r a git h8r

Emilio Pisanty

@BernardoMeurer I don't hate git

DanielSank

7:26 PM

@EmilioPisanty I found a backpack left at work yesterday evening after Bernardo and I finished working on something. I looked inside to see if I could identify it. I figured I'd send a group email to the effect of "Someone left a blue backpack containing x, y, and z at work."

Emilio Pisanty

I do think it's overrated and that git evangelizers do a lot of things that actively hurt its cause, but I don't hate git

DanielSank

So I went to itemize x, y, and z.

I found a laptop, a sock, and a conference name badge.

Emilio Pisanty

@DanielSank a sock?

as in, a sock puppet?

DanielSank

So I sent the group an email: "There is a blue backpack containing a laptop, a sock, and a conference name badge reading <name of coworker> in the conference room".

A different coworker than the one named in the badge replied "Oh, thanks Dan that's mine", which was funny.

Emilio Pisanty

@DanielSank yeah, that's a bit bizarre

DanielSank

7:28 PM

Oh, by the way:

digitalphase.org

2

Emilio Pisanty

have a star, good sir

DanielSank

Why, thank you!

Did you read it?

Emilio Pisanty

@DanielSank didn't read the author intros

Narcissus jewel

Do modern physicists (meaning set remove cranks) care about the idea of multiple universes, or does such a notion belong to philosophy?

Emilio Pisanty

did read the rest

@Narcissusjewel the statement "there exist smart people that are generally recognized as not-cranks and that have wide recognition as field experts in several branches of physics, who both care about the idea of multiple universes and who think it's probably true" is true

Anonymous

7:36 PM

@Narcissusjewel Well, if you consider Greene to be a non-crank

Emilio Pisanty

whether all modern physicists care, that's a different matter

Narcissus jewel

@EmilioPisanty Sure, I wasn't careful. I was leaving that to you lovely folks.

peterh

@SirCumference :-)

Narcissus jewel

Where can I read about such a thing from a non pop-science perspective?

DanielSank

@EmilioPisanty comments? Good/bad?

how to improve...

Emilio Pisanty

7:38 PM

@DanielSank well, the mission statement sounds like the blog will be something the internet would benefit from having

Balarka Sen

I heard a good argument about the acceleration of expansion of space getting larger than the speed of light at points so some galaxies that were in the observable universe at some point in the past may not more be in the observable universe anymore. I don't know the authenticity of this argument though

Emilio Pisanty

I don't particularly care about audiophilia

DanielSank

@EmilioPisanty I don't either, but I like signals ;-)

Emilio Pisanty

past a certain reasonable level of audio equipment quality, I don't really hear the differences / care that much about them

Balarka Sen

These escaped objects should form the "other universes", whatever that means, or so I heard

DanielSank

7:39 PM

I expect that I'll start caring about audio equipment soon though.

Anonymous

@BalarkaSen Yes, that's quite a well established argument

Anonymous

I don't the math behind it. But I read it in many places

Anonymous

Perhaps even Wikipedia discussed that

Emilio Pisanty

@Narcissusjewel scientificamerican.com/article/… as an example

@DanielSank is that a healthy thing to be doing?

wallet-wise, I mean

DanielSank

@EmilioPisanty Sure.

Anonymous

7:43 PM

@BalarkaSen Hmm, wouldn't that just be a part of the universe, beyond the observable universe?

DanielSank

I have a real job. I'm not planning to go crazy, maybe just acquire nice speakers etc.

Emilio Pisanty

I mean, kinda like the advice that Japanese people give not to become a Wasabi connoisseur unless you have deep pockets

Anonymous

I'm not sure your second statement is true @BalarkaSen

DanielSank

@EmilioPisanty hahaha haven't heard that one.

Emilio Pisanty

... but then again, yes, you're the guy with the cushy industry job, aintja

DanielSank

7:44 PM

^

Balarka Sen

@Blue I mean, the functional definition of universe is the observable universe.

Emilio Pisanty

¬¬

DanielSank

I don't plan to go nuts. The only thing I spend too much money on is vintage video games.

Emilio Pisanty

@DanielSank that is a reasonable way to spend money

DanielSank

Agreed

That's why I do it.

Emilio Pisanty

7:45 PM

have you bought a lego Saturn V yet?

DanielSank

wut

no

how to do?

Anonymous

@BalarkaSen I don't think so. en.wikipedia.org/wiki/Observable_universe and en.wikipedia.org/wiki/Universe. Astronomers normally consider the universe only to be the observable portion. But as far as theorists are concerned, pretty sure, no

Emilio Pisanty

@DanielSank shop.lego.com/en-ES/LEGO-NASA-Apollo-Saturn-V-21309

it's already gone out of stock once, if you want one you should order soon

as in, damn soon

Balarka Sen

@Blue shrug

Anonymous

String theory has a notion of multiverse too, I think. You could ask ACM :P

Emilio Pisanty

7:47 PM

Adam Savage Builds the LEGO NASA Apollo Saturn V!

►

DanielSank

That's cool, but I could get a good condition Mega Man 4 for that much money.

Emilio Pisanty

@DanielSank indeed, but a Mega Man 4 isn't a meter-tall user-assemblable sculpture of the largest rocket flown by mankind

Narcissus jewel

Yeah, as Blue suggests, that's not the definition I was hoping to be used. My friend was talking about escaping the heat death of the universe by moving to another universe. I wondered if the candles (universes) were all burning out together (dying to entropy), or if we can move to another candle and light it nice and fresh.

(Motivated in part by the [in my opinion excellent] short story 'The Last Question' by Asimov)

DanielSank

True, but it is an episode in one of the greatest video game series of all time.

Narcissus jewel

(Before considering this though, it'd make sense to find out what the notion of other universes could even mean. Hopefully determining if there is moral reason to assume that these have to start at the singularity or something.)

Anonymous

7:56 PM

@Narcissusjewel Wikipedia has a nice article on multiverse. You could start with that. Most of what I know about this is from "The Book of Universes" by Barrow

Anonymous

I have forgotten many of the details tbh

Anonymous

But that is a real nice book

Emilio Pisanty

@DanielSank ¯\ _(ツ)_/¯

Balarka Sen

8:31 PM

@DanielSank I have posted my tome.

Abcd

8:48 PM

I am trying to derive the relation $A = A_o e^{-bt/m}$ for damped harmonic motion.
I have reached $m\dfrac{dv}{dt}= -kx -bv$. What do I do next? Anyone?

$A= A_o e^{-bt/m}\sin(w't+\delta)$ **

Anonymous

@Abcd That's a second order differential equation. There are standard ways to solve it. Just google

Abcd

@Blue Couldn't find the derivation on google.

Anonymous

That's not possible.

Anonymous

math.psu.edu/tseng/class/Math251/…

Anonymous

tutorial.math.lamar.edu/Classes/DE/IntroSecondOrder.aspx

Anonymous