The h Bar

Emilio Pisanty

19:02

booya

0

There is now some overlap between what we can do using optical elements, and the sort of photon energies that correspond to nuclear excitations. In particular, as mentioned in e.g. this paper, the 229Th nucleus has a low-lying excited state at energy $E=7.8\pm0.5\:\mathrm{eV}$, and this is low en...

rob

@EmilioPisanty Very nice. You didn't even get distracted by halfnium.

Emilio Pisanty

@rob wait, what?

what's hafnium gotta do with stuff?

rob

@EmilioPisanty Halfnium-178 has a electromagnetic excited state which is metastable with lifetime 30 years.

Emilio Pisanty

@rob huh

at what energy?

rob

There used to be proposals to chemically separate a bunch of this isomer to see whether the relaxation of one nucleus would stimulate emission on its neighbors.

Emilio Pisanty

19:12

@rob huh

rob

Difference in mass excess between isomer and ground state is 2.4 MeV. But the isomer has $J^P = 16^+$. It's slow because the transision requires a lot of angular momentum.

Emilio Pisanty

yeah, that'd be pretty neat

@rob so that'd make it hard to produce the isomer?

AccidentalFourierTransform

@ACuriousMind it wasnt me this time. Someone else accepted the flag, I didnt even have time to see it :P

rob

There's an $8^-$ state at about half the energy, lifetime four seconds, so the decay process is emission of hexadecapole photons.

AccidentalFourierTransform

it was like, an instantaneous suspension lol

Emilio Pisanty

19:15

@rob so what would be the relevant observable?

rob

@EmilioPisanty I think that if you put neutrons on Hf-177, some fraction of the new Hf-178 gets stuck in the isomeric states.

Emilio Pisanty

big cascades of photons instead of single ones?

@rob I guess the question was why is $J=16$ bad

also, if you've got references handy they'd be 'ppreciated

rob

@EmilioPisanty Probability of a transition decreases as $\Delta J$ increases. Electric dipole transitions are fastest; magnetic dipole and electric quadrupole are competitive with each other, etc.

Emilio Pisanty

@rob yeah, OK, so it's a high-$J$-makes-production-harder argument

ooooh, wait

or it's about the transition back?

rob

@EmilioPisanty Starting point: en.wikipedia.org/wiki/Hafnium_controversy

@EmilioPisanty Yes, you get ground-state and isomeric halfnium out of your reactor --- you don't pump it

Emilio Pisanty

19:20

(Aside: @Qmechanic, I changed the redaction on the latest meta post to just [user]. Language along the lines of 'X-who-shall-not-be-named' has some pretty weird resonances for folks born '85 and later.)

@rob ok, got it

so the high $J$ makes the stimulated emission harder, then?

'cause you'd need to use the hexadecapole component of the incoming photon to stimulate the transition, I'd guess

rob

@EmilioPisanty That's the idea.

Emilio Pisanty

@rob so, what's the wavelength-to-system-size ratio there?

rob

That's what I thought of when I saw that question, but I probably won't have time to answer it.

@EmilioPisanty Hmmm, good question.

Emilio Pisanty

@rob thanks, btw, that's plenty to start a lit search

> The activity is in a cascade of penetrating gamma rays, the most energetic of which is 0.574 MeV

wait

cascade?

that'd make the hexadecapole argument funky

rob

@EmilioPisanty I guess it's not a single transition. I haven't looked at a level diagram.

@EmilioPisanty See if this link works for you: nndc.bnl.gov/useroutput/…

Produced from nndc.bnl.gov/ensdf

But the NNDC website doesn't do permalinks and cached results go away after a while, so if you wait you'll have to find it again.

Emilio Pisanty

19:27

@rob works

rob

@EmilioPisanty Don't worry, it'll quit :-)

Emilio Pisanty

@rob not sure how to read it though

rob

First table is list of levels: energy, $J^P$, half-life. The $16^+$ state with the 31-year life is the last one.

Emilio Pisanty

@rob yeah, but how would that one decay?

rob

Second table is gamma rays, sorted by energy in keV, labeled by originating level and multipolarity (if known)

Emilio Pisanty

19:32

ah

rob

So there's a very soft transition which is probably E3 and goes to the probably-$13^-$ state, cascading from there ...

Emilio Pisanty

So one E5 line by 587 down to the (11-) at 1859

heather

hello all

rob

@EmilioPisanty Yep

And an M4 to a (12^-) state at 1859

Emilio Pisanty

plus one M4/E5 line by 309 down to the (12-) at 2136

then

after which it'd presumably decay down much faster?

rob

19:34

Parentheses indicate doubt about spin/parity assignments.

Emilio Pisanty

so the lowest-energy one would be the 309MeV one

rob

Yes, apart from the two isomers, all the other states probably decay more or less instantaneously.

Emilio Pisanty

@rob ah, so there's possibly one E3 line down to the level just under?

'cause that would drastically change the multipolarity argument

309MeV is about 1.6 fm

12.7 is about 8fm

rob

@EmilioPisanty 309 keV is about 1600 fm, you mean.

Qmechanic

@EmilioPisanty : Ok.

Emilio Pisanty

19:37

no, wait

@rob all of these are in keV?

ah, yes

rob

@EmilioPisanty The referenced paper (2015KiAA: Phys Lett B750, 89 (2015)) may have information on the relative strengths of the different transitions --- I'm not sure why that would have been left out of the NNDC table.

Emilio Pisanty

309keV is about 640fm, 12.7keV is about 15,500fm

what size is a hafnium nucleus?

Is 1fm a reasonable figure?

rob

@EmilioPisanty You're off by 2π: 309 keV is 4000 fm

Emilio Pisanty

@rob hmmm, right you are

rob

@EmilioPisanty Nuclear radius is a few femtometers, but adjacent nuclei are separated by a few angstroms.

@EmilioPisanty As penance, we'll change the name of the chat room to "the h" for a week

Emilio Pisanty

19:43

@rob but this is about the transition between states of the same nucleus, right? so the matrix elements are between states of the extent of a few fm

rob

@EmilioPisanty Are we back on lasers yet? If we want stimulated emission, we would want many isomers to decay in phase with each other.

Emilio Pisanty

@rob sure, but this is just the transition probability of the thing happening to begin with

right?

rob

All electromagnetic transitions in nuclei have wavelength longer than the diameter of the nucleus, because no nuclei are bigger than a few femtometers and no nuclei have more than a few MeV of nucleon separation energy.

Emilio Pisanty

@rob sure, but that doesn't mean that the nucleus isn't sensitive to the spatial derivatives of the mode

it just makes it less sensitive

by something like $a/\lambda$, where $a$ is the size of the system

rob

@EmilioPisanty The rule I remember is that there's a term in the transition probability like $(a/\lambda)^{\Delta J}$, where $a$ is nuclear size and $\lambda$ is transition wavelength.

Emilio Pisanty

19:48

@rob yeah, precisely

rob

The E3 transition is so soft, at 12 keV, that it kind of makes sense for it to compete with the 20x more energetic E5 and M4 transitions.

Emilio Pisanty

for those transitions, I make $a/\lambda$ to be 2.5E-4 for the 309keV E5 transition, and 1E-5 for the 12keV (E3) transition

by that measure, the 12keV E3 transition would come out ahead by about 10^5

0celo7

What on earth is going on here

This sounds like physics

AccidentalFourierTransform

ugh, disgusting

Emilio Pisanty

because $(a/\lambda_{12\mathrm{keV}})^3\approx 10^{-15}$, and $(a/\lambda_{309\mathrm{keV}})^5\approx 10^{-18}$

@0celo7 pretty much

we're discussing metastable hafnium

just, you know, because.

Hafnium controversy

The hafnium controversy is a debate over the possibility of 'triggering' rapid energy releases, via gamma ray emission, from a nuclear isomer of hafnium, 178m2Hf. The energy release is potentially 5 orders of magnitude (105 times) more energetic than a chemical reaction, but 3 orders of magnitude less than a nuclear reaction. In 1998, a group led by Carl Collins of the University of Texas at Dallas reported having successfully initiated such a trigger. Signal-to-noise ratios were small in those first experiments, and to date no other group has been able to duplicate these results. Peter Zimmerman...

rob

19:55

@EmilioPisanty Hmmm, I did different.

I used $a = (178)^{1/3}\rm fm = 6 fm$

For the 12 keV E3 transition I get $(a/λ)^3 = 2\times10^{-13}$

for the 590 keV E5 transition I get $(a/λ)^5 = 2\times10^{-13}$

Emilio Pisanty

yeah, I get the same

wait, so the 590 keV is more likely than the 309keV?

duh, yes, of course

rob

The 309 keV transition is a competition between M4 and E5. The magnetic transitions go like $(a/λ)^{\Delta J + 1}$, which is why the M4 and E5 compete. So I think that's the winner by a factor of some small power of two.

No, you're right --- the larger-energy one is the winner.

Emilio Pisanty

ok, but I'm sold on the fact that this is a pretty damn unlikely transition

rob

The 309 keV transition is in third place intensity-wise.

Bernardo Meurer

What are you guys up to?

rob

20:01

This was fun. Got to go. Cheers, all.

Emilio Pisanty

@BernardoMeurer we were estimating nuclear transition amplitudes, but we're mostly done

Bernardo Meurer

@EmilioPisanty Every day I do something cool at uni and feel smart, I come to the h-bar and get put back into place and feel stupid :P

Emilio Pisanty

@BernardoMeurer emphasis on 'estimating'

Bernardo Meurer

@EmilioPisanty Hilbert spaces are dope af

0celo7

@BernardoMeurer what is a Hilbert space

Bernardo Meurer

20:13

@0celo7 generalisation of an Euclidean space

we basically saw an Euclidean space with infinite dimensions

and showed how a transform on a hilbert space is continuous everywhere iff it's continuous at 0

heather

@ACuriousMind, finally bit the bullet and (mostly) finished my meta post (there are still a few sections to be written):

0

A: Chat and the moderation thereof

A brief summary of the arguments in this post: That there was given a complete lack of explanation of thought process in the days leading up to and even after this meta post by mods - especially a poor announcement of the situation (meta post made after the mods started deleting posts). That t...

0celo7

@BernardoMeurer generalization of Euclidean space?

That's not a definition

Bernardo Meurer

@0celo7 If you want a rigorous definition go google it

0celo7

I would like for you to tell me

Bernardo Meurer

@0celo7 Quit being an asshole

I can take out my notes on it

0celo7

20:17

I'm afraid that's impossible

Bernardo Meurer

I did a mini-course on it, and I thought it was cool, that's all

0celo7

@BernardoMeurer well, I was going to tell you that you don't need a Hilbert space for what you said

Bernardo Meurer

@0celo7 You don't need a Hilbert space for an infinite dimensional function space with an inner product?

0celo7

@BernardoMeurer nope. A Hilbert space is much stronger than that

You don't even need an inner product for the continuity

heather

whew, i've already gotten an upvote and a downvote on my meta post. ::shakes head:: contentious issue.

Bernardo Meurer

20:21

@0celo7 What?

0celo7

And hilbert spaces aren't necessarily function spaces, but in many cases they are

Bernardo Meurer

Not necessarily, but I gave the example we used

0celo7

For an inner product space to be a Hilbert space, you need completeness

Bernardo Meurer

@0celo7 When did I say you needed an inner product for continuity?

Sure, so you can use Calculus techniques on it

0celo7

@BernardoMeurer here

@BernardoMeurer no

You can do a lot of calculus without completeness

Bernardo Meurer

20:22

@0celo7 I don't say inner product once in that sentence

@0celo7 But not all of it

0celo7

You said Hilbert space

@BernardoMeurer like what?

Bernardo Meurer

@0celo7 Dude, you want to be mean to people go gangbang, leave me alone

David Z

@BernardoMeurer "gangbang"? ...

(I know what it means, I'm just questioning your judgment in posting that)

Bernardo Meurer

@DavidZ Don't google it

Ah

Well, it's a mean thing

0celo7

@BernardoMeurer I'm not being mean

I was genuinely wondering what you did in the class

Sorry for asking

Bernardo Meurer

20:25

@0celo7 You're trying to show off how much more maths you know. Don't worry, I know that, we all do.

0celo7

I've got a thermo test, bye

@BernardoMeurer Nope

Bernardo Meurer

@DavidZ Fair enough, sorry for that.

Skyler

@vzn in a nutshell I'd say this guys hit a few good points, people have already wasted so much energy before inauguration day that tiring out is already apparent

@vzn also, so is the formulation of gravity as MFT the correct way to think about this theory in my head

heather

@BernardoMeurer, thanks for the comment on my post; that's exactly what I meant.

AccidentalFourierTransform

hey @heather, I think youre being unfair in 5.

mods did not "have an impressively poor stance in discussing this"

heather

20:37

@AccidentalFourierTransform I can tone down the language, but I do think they haven't done the best job of communicating.

AccidentalFourierTransform

@heather yes, I agree that they didnt do the best job, but thats far from having an impressively poor stance...

heather

@AccidentalFourierTransform, I'm editing that, I'm not sure why I wrote it that way.

AccidentalFourierTransform

yeah, the tone was a bit harsh IMO

heather

you're right, i went a bit far.

sorry about that; thank you for pointing it out.

Skyler

A bit

Also would I be allowed to discuss immigration if I tried to incorporate renormalization groups into its analysis

heather

20:43

you're allowed to discuss immigration period now @Skyler =)

renormalization groups or no renormalization groups.

Skyler

yay, not really being challenged to hack the rule requirements but hey im all for more allowed speech so i cant complain

theNamesCross

Ill be flooding the forum with political opinions now too. If others do it, why not me.

heather

@theNamesCross, hello. I found your opinion rather interesting.

Balarka Sen

To be honest, 0celo's got a point here but - socially inept as he is - he's not communicating it very well to a person who's just started learning about Hilbert spaces. The really cool thing is that Hilbert spaces are "complete". As a warm-up example, consider the space of continuous functions $[0, 1] \to \Bbb R$, denoted as $C[0, 1]$. Suppose you take a sequence of functions $f_n$ "pointwise converging" to a function $f$, by which I mean that $f_n(x)$ converges to the value $f(x)$ as $n \to \infty$, for any $x \in [0, 1]$. But limit functions of sequences need not stay in $C[0, 1]$; it can…

Skyler

How do you quote stuff here?

Balarka Sen

20:54

In the end it's all about having enough structure so that limit of a sequence of functions, where the sequence is "accumulating" converges to a limit in the space. Eg, $1, 1/2, 1/3, \cdots$ converge to $0$ in $[0, 1]$ but to nothing in $(0, 1]$ (because the limit 0 isn't there!).

heather

use an arrow > and then a space

> like this

> like this

Balarka Sen

(Also, I don't think he's trying to show off, he's just horribly miscommunicating)

Skyler

> socially inept as he is

savage

there we go

Balarka Sen

I think half the chat would agree with me about that, we just shrug off it because we're so used to it.

So, not really.

Skyler

still need some water for application purposes

DanielSank

21:05

@Skyler Right angle bracket

> like this

@heather yo

AccidentalFourierTransform

11 mins ago, by heather

> like this

DanielSank

Did you see the photo I pinged you with?

heather

@DanielSank no...? I don't think so.

i finished my meta post =)

DanielSank

@heather link?

heather

you can read it if you want here @DanielSank it's a bit long though.

DanielSank

21:10

3

heather

=D

DanielSank

@heather my desk army ^

heather

=D =D that's awesome!

you have a good variety of characters too.

DanielSank

Thanks!

Yeah I'm happy with my little collection.

IG88 is one of my favorites.

And Ackbar, obviously.

heather

yeah, I'm glad you have Ackbar =) he's cool.

AccidentalFourierTransform

21:13

@DanielSank cant read the google thing

whats written there?

> thank you for filing...

DanielSank

@AccidentalFourierTransform Oh, that's a little desk ornament for having filed a patent.

@heather :-D

AccidentalFourierTransform

@DanielSank you did? sweet :-)

DanielSank

Yeah, second one pending...

AccidentalFourierTransform

Ackbar is the "its a trap!" one, right?

Skyler

@DanielSank nobody here to say whats IG88 this itime

DanielSank

21:25

@AccidentalFourierTransform Yes.

@heather @AccidentalFourierTransform

Admiral Ackbar Cereal | Robot Chicken | Adult Swim

►

AccidentalFourierTransform

> now with brine shrimp

yummy

heather

wat?

lol

first time i've ever heard oatmeal called "a trap"

DanielSank

That clip makes me laugh every time.

@heather show you're dad (assuming he is a StarWars fan).

Bernardo Meurer

@heather I've got you bro

heather

@BernardoMeurer, with what?

Bernardo Meurer

21:35

1 hour ago, by heather

@BernardoMeurer, thanks for the comment on my post; that's exactly what I meant.

@heather You gotta eat more vegetables, it improves memory

heather

@BernardoMeurer, I probably should eat some more veggies.

AccidentalFourierTransform

lettuce is the worst vegetable

it makes no sense, its stupid

DanielSank

^ False

Bernardo Meurer

These chips I got have so much onion and garlic it's driving me crazy

it's good though

Lettuce is great

AccidentalFourierTransform

no taste, no texture, no nutrients

Bernardo Meurer

21:39

@AccidentalFourierTransform Just like you

:-)

AccidentalFourierTransform

(and please dont flag that one)

Bernardo Meurer

@AccidentalFourierTransform Lol <3

AccidentalFourierTransform

(ill delete in a couple of seconds)

lol, ive been banned twice today

Bernardo Meurer

@AccidentalFourierTransform Like a pro

AccidentalFourierTransform

I mean, the last one was uncalled for

Bernardo Meurer

21:41

@AccidentalFourierTransform The mods are watching you

DanielSank

I'm offended by this

Agreeable..? Not exactly @DanielSank, it seems to me you went out of your way to be a smart a$% in proving your point instead of simply saying, "I respectfully disagree." — theNamesCross 1 min ago

I offended and I have rights.

Bernardo Meurer

@DanielSank Refresh the page

heather

eesh.

theNamesCross seems more of the one who "went of [their] way"

Bernardo Meurer

21:59

@heather Yeah, well, he trashed his credibility doing so

AccidentalFourierTransform

cows & cows & cows

►

Bernardo Meurer

@AccidentalFourierTransform I love that video

AccidentalFourierTransform

a classic

Bernardo Meurer

@heather Want to hear my latest evil plan?

(I want to tell someone and usually you're the only person who wants to hear the crazy useless crap I work on)

DanielSank

@BernardoMeurer I did. Now what?

Bernardo Meurer

22:07

@DanielSank I responded, that was all

DanielSank

@BernardoMeurer good comment

Bernardo Meurer

@DanielSank You've instructed me well in the arts

heather

@BernardoMeurer, sure, yeah.

potato computers...running linux?

in league with your graphing calculators?

::runs away::

Bernardo Meurer

@heather So, when you want to multiply ridiculously large numbers, you need very specific algorithms

heather

@BernardoMeurer makes sense.

Bernardo Meurer

22:11

Such as Schönhage-Strassen, Fürer, or Karatsuba (most famous ones)

0celo7

@BernardoMeurer I was going to tell you about the Riesz representation theorem and why bra-ket notation works

and how it relates to Hilbert spaces

Sir Cumference

@BernardoMeurer Didn't you say you wanted me to test something for you, a while back?

0celo7

that's why I was asking

I should have asked if the lecturer talked about completeness, sorry.

Bernardo Meurer

They are all very complex, but basically what they do is divide the large multiplication into many smaller ones, then use a dark magic called Fast Fourier Transform to perform the actual operations.

@SirCumference I got it tested using 4 VMs, thanks :)

Sir Cumference

What was it, out of curiosity?

Bernardo Meurer

22:13

@0celo7 Sorry I blew up on you, you just worded things in a way that it sounded like you're doubting things or quizzing me and I dislike that.

0celo7

@BernardoMeurer I was quizzing you, I wanted you to say "complete inner product space"

I didn't want an essay

AccidentalFourierTransform

@BernardoMeurer try implementing an algorithm that multiplies matrices in $\mathcal O(n^{2.36})$ time

Bernardo Meurer

@SirCumference A script that builds a toolchain for an x86_64 cross compiler to build a Kernel

0celo7

The point being that completeness is why quantum mechanics works

Bernardo Meurer

@AccidentalFourierTransform Sounds like a pain in the ass

heather

22:14

@BernardoMeurer FFT is used in Shor's algorithm too, right?

no, QFT, nvm

Bernardo Meurer

@heather Yes, but the fancy quantum version of it

heather

quantum version of FFT

0celo7

@AccidentalFourierTransform what is the time for matrix multiplication?

is it not $n^2$?

AccidentalFourierTransform

number of operations, whatever

Bernardo Meurer

complexity...

0celo7

22:15

I know what you mean

AccidentalFourierTransform

the naive algorithm is $n^3$

0celo7

Oh, really

why?

AccidentalFourierTransform

Matrix multiplication algorithm

Because matrix multiplication is such a central operation in many numerical algorithms, much work has been invested in making matrix multiplication algorithms efficient. Applications of matrix multiplication in computational problems are found in many fields including scientific computing and pattern recognition and in seemingly unrelated problems such counting the paths through a graph. Many different algorithms have been designed for multiplying matrices on different types of hardware, including parallel and distributed systems, where the computational work is spread over multiple processors...

heather

my system of bookmarks for webpages is madness

AccidentalFourierTransform

well, you have to perform $n^2$ operations, $n$ times

or rather, $n$ operations $n^2$ times

Bernardo Meurer

22:16

@heather So what I'm working on, is writing the algorithm in a way where we can slice the arbitrary precision number into all the slices to be multiplied using FFT, then do all the multiplications in parallel using the GPU, and it'll be uber fast

0celo7

oh, I forgot to count up the dot products

yeah, $n^3$

AccidentalFourierTransform

its a very cool fact that there are better algorithms

Bernardo Meurer

@AccidentalFourierTransform If the faster method is easily parallelizable I might take a look at it. I want to do parallelization with GPU

heather

@BernardoMeurer wow, that sounds cool

and hard

AccidentalFourierTransform

it seems an operation that is so basic that it cannot be optimised

Bernardo Meurer

22:18

@AccidentalFourierTransform Think about multiplication, that's super easy but just in 2012 we found a way to do it faster (fürer algo)

0celo7

@AccidentalFourierTransform agreed

Bernardo Meurer

@heather It's just busy work

heather

@BernardoMeurer oh. well it still sounds super cool.

Bernardo Meurer

@AccidentalFourierTransform Jesus, I might actually try implementing Coppersmith–Winograd

Sounds hard af

I'll do Strassen first though

My intention is to build a GPU-aimed arbitrary precision library throughout college

AccidentalFourierTransform

I wish I had time to learn how to code

I loved it when I learnt the basics in uni

Bernardo Meurer

22:20

@AccidentalFourierTransform It's very easy to learn Python, but it is very time demanding

AccidentalFourierTransform

c++ is great

Bernardo Meurer

Your major is physics?

C++ is a necessary evil :P

AccidentalFourierTransform

yep, theoretical physics

I had so much fun learning c++

heather

python is amazing

AccidentalFourierTransform

possibly, the only class that I really enjoyed

heather

22:22

<3 python

0celo7

can we talk about math

heather

0celo7 sure

oh, guess what? I've got half of your proof, I think

0celo7

let's see

heather

it's probably complete junk, but i tried =)

Bernardo Meurer

@AccidentalFourierTransform I can recommend a good book to go more in depth if you're interested. But I'll say that the best way to learn is to pick up small projects and work on solving them

0celo7

22:23

what is FFT

I've heard it thrown around but never followed up

heather

Proposition: R is closed under $\cup$ and $\Delta$.

Bernardo Meurer

Fast Fourier Transform

0celo7

@BernardoMeurer that much I knew

AccidentalFourierTransform

@BernardoMeurer maybe this summer, when I have time. When learning c++, I spent months building a class on matrix operations

Bernardo Meurer

@0celo7 I just know how to use it :/

AccidentalFourierTransform

22:23

diagonalisation, system solving, etc

0celo7

@BernardoMeurer what does it do?

Bernardo Meurer

@AccidentalFourierTransform That's a nice project

AccidentalFourierTransform

yeah, it was fun. I learnt a lot about specific algorithms, optimisation...

Bernardo Meurer

It does the discrete fourier transform of a sequence. All I know is I use it when implementing multiplication algorithms :)

heather

Proof: Let $A, B \in R$. $A\cup B \in R$ by the definition of $R$. Therefore R is closed under $\cup$. $A-B\in R$ by the definition of $R$. Therefore R is closed under $-$. Therefore, $(A-B)\cup(B-A)\in R$, or $A\Delta B\in R$, so $R$ is closed under $\Delta$.

@0celo7 ^

0celo7

22:25

Yes, good.

You did the easy part :)

heather

i'm still very happy I got it =)

0celo7

The intersection is tricky

heather

yeah, i'm figuring that out =P

i'll keep working though.

0celo7

So you need to write $A\cap B$ as a bunch of unions and differences

heather

yeah, that's what I figured. I'm paging through Halmos to see what I can use.

Bernardo Meurer

22:27

@0celo7 We should give her Chub n' Tuck problems

heather

Chub n' Tuck? that's a strange name.

0celo7

@BernardoMeurer she will hate math!

Bernardo Meurer

It's our endearing nickname to my analysis prof

@0celo7 True, better not show her the true face of it yet :P

0celo7

@heather ok this might be too difficult, now that I look at it

you need a combination of $\cup,-,$ and $\Delta$

draw a venn diagram first

you need to get an intuitive feeling for what $\Delta$ is

Hint: $A\cup B=(A\cap B)\cup (A\Delta B)$

Prove that first, then use it.

heather

prove that $A\cup B = (A\cap B) \cup (A\Delta B)$?

0celo7

22:30

yeah

I hope it's true :P

heather

@BernardoMeurer ah. Well, I don't know analysis, so that'd probably be a bad idea.

@0celo7 lol okay, I'll give it a go.

Bernardo Meurer

@heather These problems are just really hard calculus

github.com/bemeurer/hard-calc

heather

@BernardoMeurer probably still not a good idea.

Bernardo Meurer

You can find some of them translated to english here

Take a look if you're brave

heather

maybe later =) but okay.

AccidentalFourierTransform

22:34

kbye

mhchem

Hi! I just dropped by from Chemistry to ask if a unit-formatting extension would be of interest for you physic's guys. meta.physics.stackexchange.com/a/9610/144840

9

0celo7

@heather do you need help?

for something like this you might need classical propositional calculus

Note that $A\cap B\supset (A\cap B)\cup (A\Delta B)$ should be very easy

heather

@0celo7 i haven't started my stab at it, because I have to finish up some geometry homework real quick. (two problems)

Sir Cumference

@mhchem @DavidZ You might want to super star this before it gets lost

0celo7

@ACuriousMind I don't like how physics from a math book makes more sense than physics from physics books and classes.

Balarka Sen

22:49

How about math from physics books duck

0celo7

@BalarkaSen you can learn differential geometry from Wald's GR book just fine

not all of the details of course, but it's very good

heather

okay, done with geometry homework

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