The h Bar

0celo7

00:10

@FenderLesPaul are you on campus right now?

user54412

So do other fields have April Fool's arxiv posts?

0celo7

@ChrisWhite momentum :(

user54412

> Deviations of the observed CMB [...] are obviously highly significant and deserve to be pursued more aggressively in order to discover the physical phenomena underlying them. Through intensive investigation we have discovered that there are equally surprising features in the digits of the number π [...] Putting aside the unreasonable possibility that these are just the sort of flukes that appear when one looks hard enough...

user54412

> One additional realm that hasn't been adequately considered, however, is that this large increase in exoplanets would also impact claims regarding astrology.

0celo7

01:52

@ACuriousMind that ending oO

I went with Citra

0celo7

03:19

@Slereah Haha the boring physics conjecture

>not defining the metric as a nondegenerate section of $S^2 T^*\mathcal{M}$

@Slereah is this a physics book

@Slereah shouldn't that be a $c^4$ in eq. 2.12?

kevin Tah N.

03:40

Hey

What do you guys use for latex with version control that is free

skill patrol

hi

kevin Tah N.

I Like 100% free

with version control and is private, not public

0celo7

@skillpatrol Time to write another proof on the el blog

skill patrol

have fun :-)

0celo7

@skillpatrol this is not fun

skill patrol

03:43

Never forget Einstein and The Evidence

0celo7

04:11

@skillpatrol have I mentioned that I hate topology and analysis

trying to prove obvious things "rigorously" is terrible

Secret

https://en.wikipedia.org/wiki/Paravector

I see weird stuff that I do not understand atm

0celo7

Oh, of course! The preimage of an open set is open :P

@Danu For once that definition of continuity actually came in useful :D

kevin Tah N.

04:28

any hope for a completely free latex platform with version control . I kind of want to track my changes and stuff

Slereah

hey

kevin Tah N.

hey dude

0celo7

is there something weaker than a proposition

skill patrol

conjecture?

0celo7

that's something unproven

skill patrol

04:35

what do you mean by "weaker"?

Bernard Meurer

@0celo7 youtube.com/watch?v=hKWmFWRVLlU

2

This may help you

kevin Tah N.

nice

skill patrol

in theory

;-)

kevin Tah N.

the men's zone is so true lol

Money is quite important

0celo7

tfw in the danger zone

Hmm.

kevin Tah N.

04:56

yeah I am in the no no zone lol

0celo7

@topologists If $f:X,Y$ is a homeomorphism, does $\overline{f(X)}=f(\bar X)$ generally hold?

I think it should, at least in metric spaces where we can take sequences!

kevin Tah N.

@0celo7 can you explain the question less abstractly?

0celo7

@kevinTahN. huh?

what's unclear about it

that should be $f:X\to Y$

kevin Tah N.

$\overline{f(X)}=f(\bar X)$

0celo7

@kevinTahN. is the closure of the image the image of the closure

kevin Tah N.

04:59

ah I see

hmm

Slereah

@0celo7 grid.ece.ntua.gr/sites/metamathsite/mpeuni/hmeocls.html

⊢ ((𝐹 ∈ (𝐽 Homeo 𝐾) ∧ 𝐴 ⊆ 𝑋) → ((cls ‘𝐾) ‘(𝐹 “ 𝐴)) = (𝐹 “ ((cls ‘𝐽) ‘𝐴)))

0celo7

What the fuck is that

Slereah

proofwiki.org/wiki/…

try this instead

0celo7

cool beans

Slereah

Oh yeah that's right

Topological spaces can be defined equivalently by open sets and closed sets

0celo7

05:06

@Slereah can/should I just link to that page on the blog

@Slereah Challenge: reference a metamath proof in a GR paper

Slereah

It is probably a standard proof really

Slereah

05:37

Hm

Thinking about it

A geodesic will always be either timelike null or spacelike

0celo7

thinking about what

Slereah

Since the connection is metric

I think that could be a part of the proof that $\exp_p(I^+(0)) = I^+(p)$

Any geodesic that has any tangent vector timelike will have all of them timelike

0celo7

i'm going to bed

Slereah

night

0celo7

write up the proof

skill patrol

05:40

cya later

0celo7

or the sketch

I'll take a look at it later

Physics Meta

0

Q: What can be done in order to re-open a closed question?

I recently asked a question that was originally put "on-hold" (you can look at the question here: SU(2) Rotation Matrices Problem from Halzen and Martin). Now, I’ve read the homework policies several times, in an attempt to edit my problem so that it is more in concurrence with the site’s polic...

user54412

07:08

@kevinTahN. git

user54412

it has its faults (there's no good manual, and the command names are magic incantations with no relation to what they do), but it is by far the best version control in existence for anything

skill patrol

07:37

@JohnRennie did they even have computers back then? :P

Slereah

82 is barely out of the punch card era

John Rennie

08:06

@skillpatrol It was a hugely exciting time for us computer nerds. The computer industry wasn't the settled place it is now and new types of personal computer were appearing every week (well it felt that way).

Slereah

How does it feel now that you're an old man

With the specter of the grim reaper looming over you

Danu

09:33

@Slereah a bit too far, Slereah

Slereah

ramsay

anyone knows where to ask questions (on SE network) related concentration, sprituality and all that stuff?

Slereah

There are several religious SE

ramsay

i am atheist, so i don't want religious SE, rather i need for the question which i had posted but it got closed (let me send question link)

David Z

09:52

If there is an appropriate site, you might find it in this list

ramsay

unfortunately i am not able to find the question :(
but crushed version of my question is : i am losing my concentration from any works,(*like studying, coding, music*) but i really love to study but when i do that i get bored to early, i don't know how will i get my dedication back ? :_(

David Z

Ahh... that one you might want to take to reddit or something. I'm not sure if it would fit on an SE site.

You could check on Academia but I really don't know if they accept that sort of thing. Start by searching. I think people have tried to ask such questions before.

ramsay

thank you! David

Slereah

There is also a health Stack Exchange

ramsay

10:08

i don't think it is health related issue, is it?(and i am 14 approaching 15 years)

skill patrol

@ramsay sounds like natural growing pains :-)

we all had to go through it

ramsay

but this makes me cry!

skill patrol

It gets better as you mature.

Hang in there.

Slereah

Or doesn't.

mb you will slowly get crushed by life until you give up all your dreams

ramsay

10:27

:_(

13 mins ago, by Slereah

mb you will slowly get crushed by life until you give up all your dreams

this ^ really sounds bad

Slereah

Welcome to my world

ramsay

haha

you world is depressive (i guess) Slereah

Slereah

could be worse

ramsay

|*afraid*|

skill patrol

11:37

you still there @ramsay?

David Z

arxiv.org/abs/1603.09496

skill patrol

perhaps an extension of the zodiac :P

ramsay

@skillpatrol yup

skill patrol

you ok?

ramsay

no!

skill patrol

11:45

come on, you've got so much to look forward to

life is just beginning

ramsay

but i don't wanna waste time, i want to make myself back, what i was in 2015 :(

skill patrol

what were you?

ramsay

i was very very muvh dedicated

skill patrol

these things go through cycles

look at the "big picture"

Slereah

@DavidZ Looks more like a vixra article :p

I suppose it's an april fool article

Too bad it was posted on the 31st!

ramsay

11:54

but our teachers says "teen period is most important and it decides whether one can be successful or not" and on other side i am wasting my teen period

skill patrol

They are lying.

Mew

groundbreaking article

Slereah

Most of what you will learn in school as a teen will not be of any use

You will probably forget most of it and, if need be, relearn it later

It is also probably wrong to some degree

For several reasons

skill patrol

enjoy your youth

Danu

Challenge: Measure the speed of sound based on this gif (stolen from reddit)

2

ramsay

11:59

"enjoy" i am in 12th grade and next year my university, lots and lots of pressure and competition

Mew

Slereah, I've never forgotten the maths and physics and chemistry I learned in school

What pressure ramsay?

Danu

@ramsay And yet, when you look back in say 5-7 years you'll sigh and say: "Damn, back then life was so freaking easy"

Mew

Physics is easy to get into

hardly anyone wants to do it

Danu

(at least that's how it goes for almost everyone)

Mew

Life is always easy mate

Much easier than physics anyway

Ramsay after reading a few of your posts it sounds like you have internet addiction

too much internet makes u lose ur concentration because ur always jumping about to different pages

give yourself an internet ban for a week and just read books and youll be better mate

Danu

12:02

Armchair psychologist confirmed

Mew

yeah mate

i can dabble in any field

Danu

Australian confirmed

Mew

using the problem solving skills i have developed

through the study of physics and mathematics

yeah I'm an Aussie too

ramsay

@Mew i will definitely follow his step in few minutes

Slereah

Danu

12:03

lol

Mew

WTF

lol

ramsay

lol

skill patrol

nice @Slereah :D

ramsay

bye! see you guys maybe after a week , thanks @skillpatrol ,@Danu, @Slereah, @Mew

skill patrol

yup, it's tough growing up in this Internet age

Mew

12:05

np ramsay

all the best

skill patrol

Cya

o/

2 hours ago, by skill patrol

Hang in there.

Danu

@skillpatrol Honestly, we've got a really nice life.

I'm worried about the future ~50 years though.

Slereah

Hopefully by that point we will all be dead

skill patrol

I'm sure they said that 50 years ago too. @Danu

Danu

I'm not so sure.

I feel like 1966 was a pretty chill time in terms of future prospects

skill patrol

12:14

Ask someone old enough to remember.

Danu

I did, and they agreed

skill patrol

Wasn't that the hippie era?

Vietnam war etc

Slereah

1966 was the cold war

People thought that the world might be destroyed by then

skill patrol

Right.

Slereah

Still the case today

Except more global warming than nuclear annihilation

skill patrol

12:19

World War III will be fought with sticks and stones.

Danu

WWIII won't be fought.

skill patrol

Oops, I meant IV

:P

Danu

Game theory keeps us all in check

Slereah

Nowadays the nations powerful enough to actually wage world war don't have that much interest in conventional warfare

Even Russia barely tries anything

And they're not really capable of waging a world war

skill patrol

Why fight a real war when you can run a simulation on the Internet :P

Slereah

12:28

Quite unfortunate, really

Cold war would boost those research budgets :V

Yes mister general, I am working on a convex normal neighbourhood bomb

Bass

Hi guys! When talking about the $U(1)$ gauge transformation of QED, Maggiore distinguishes between the electron's charge $e$ and the parameter of the $U(1)$ representation $q$. I can see that there's a difference, because he lets $\Psi$ transform to $e^{iqe\theta(x)}\Psi(x)$ and $A_\mu\mapsto A_\mu+(i/e)(\partial_\mu U)U^\dagger$, where $U(x)=e^{ie\theta(x)}$, so $\Psi$ transforms in a specific representation of $U(1)$, whereas $A_\mu$'s transformation does not depend on $q$.

Is that correct so far?

Slereah

I'd say so?

Each particle can have its own charge, after all

Bass

@Slereah But since $q\in\mathbb Z$, the charge of every particle would be a multiple of $e$?

Slereah

The coupling can be arbitrary, I think?

It just happens that in the standard model all couplings are $\propto e/3$

Bass

Or maybe they redefine $e$ to be $1/3$ of the electron's charge, then the electron and positron are in the $q=3$ rep, the up quark in $q=2$ and the down quark in $q=1$.

@Slereah Yep. Makes sense. But is that related to the $U(1)$ representation?

Bass

12:56

Do the down quark, the up quark and the electron transform in the $q=1, 2, 3$ representation of $U(1)$ respectively?

Physics Meta

13:10

0

Q: Guidelines for *answering* homewore-like questions

I was looking for guidelines, but the best I could find is this. Is there a better statement somewhere? That was hard enough to find. Perhaps a entry could be put in the help to make it easier to find. I thought this was a settled issue, but the comments to the answer I linked suggest ot...

feature-request homework answers

Slereah

13:36

homewhore questions?

Slereah

14:41

In the neighbourhood, is a point joined to $p$ by a timelike curve an exponential mapping of a timelike vector?

Pretty sure it is but how to prove it

0celo7

14:55

@Slereah why don't you @ me

@Slereah It is!

Slereah

Apparently there's a theorem $\langle d \exp_p(v_x), d \exp_0(v_p) \rangle = \langle v_p, w_p\rangle$

Because other people might know, you ego monster

0celo7

That's the Gauss lemma

Do you even know any Riemannian geometry?

Slereah

No :(

0celo7

@Slereah go read do Carmo

Slereah

All the GR I do is from

amazon.com/Einstein-Matrix-Form-Derivation-Relativity/dp/…

0celo7

14:56

@Slereah I am proving it right now on the blog

Slereah

O'neil has a proof of it

Is that the lemma I want to prove that thing I was talking about

Feels pretty good about it

0celo7

$J^+(p,\mathcal U)=\mathcal U\cap\exp_q \overline{\mathcal T^+}$

@Slereah I'm going to prove this now.

Slereah

15:12

I should look into the proofs of the various CTC theorems

Tipler, hawking, rigidity theorem

FenderLesPaul

15:41

@0celo7 nah I just got back from MIT visit

I'm at my home in Long Island

and I'll be heading to Berkeley tomorrow

why?

0celo7

@FenderLesPaul I need you to tell me if you can access rd.springer.com/book/10.1007%2F978-3-319-26654-1 from your fancy Ivy League internet

my school doesn't appear to have purchased the 2016 grad texts in math stuff yet

and I don't want to shell out $80 for the hard cover

Slereah

Too bad there are no legal ways to get it

( ͡° ͜ʖ ͡°)

0celo7

@Slereah if you have a legal copy, send it via skype pls

of the newest edition

I have the 2nd

Slereah

Second not fancy enough for you?

0celo7

nope

there's 100 pages of new stuff in the 3rd

David Z

15:47

@0celo7 I find that highly ironic :-P

FenderLesPaul

@0celo7 I can access it when I'm at Berkeley

Oh wait

I can access it even now

0celo7

Oh come on!

Time to email the librarian

@FenderLesPaul Unless you want to send me the mycopy :)

FenderLesPaul

When's your birthday again?

The Dark Side

14

A: Examples of math hoaxes/interesting jokes published on April Fool's day?

[only borderline mathematical] Today Ali Frolop and Douglas Scott published a paper (http://arxiv.org/abs/1603.09703) in which they found: ... there is a remarkable correspondence between each type of peculiarity in the digits of π and the anomalies in the CMB.

0celo7

@FenderLesPaul Way too far down the road, I can pay you

The Dark Side

15:52

@joro: here are two proofs. 1. Permute the letters of "Ali Frolop". 2. Look here: arxiv.org/abs/1504.00108 — potentially dense yesterday

arxiv.org/find/astro-ph/1/au:+Frolop_A/0/1/0/all/0/1 — Tobias Kienzler yesterday

^

0celo7

@FenderLesPaul OH

I can send you the money via snapchat

That's a thing, right?

@DavidZ what do you mean

I would never want an illegal copy ofc

No no, everything has to be legal Mr. Mod

David Z

@0celo7 I mean that, given that you're asking someone to give you a copy of something, it's ironic that you're so particular about the person you're asking having a legally obtained copy when the method by which they would get it to you is presumably illegal.

0celo7

@fellow americans, is "theatre" the common spelling of "theater" in the south?

@DavidZ Preposterous! Everything is legal!

David Z

Copyright infringement (with respect to distribution) is a matter of how you get the copy. There isn't an attribute "legal" or "illegal" that is attached to a copy of a work and follows it around as it passes from person to person.

lol :-P

(not a lawyer, BTW)

(but I do have a 100% HNQ hit rate on law.SE so there)

0celo7

@DavidZ I'll let you in on a secret

"legal copy" is a code so the N S A doesn't raid this place

David Z

15:59

I don't care about your business with the NSA

For the record, we don't actually care about copyright here - I mean, we don't take it upon ourselves to enforce other people's copyright agreements. There's no rule against discussing copyright-infringing files. No rule against posting links to them.

0celo7

what?

I thought it was heavily discouraged

David Z

Well, it's against the law, sure, but we're not going to pile more discouragement on top of that.

0celo7

@DavidZ :P

David Z

Actually: I probably shouldn't say we don't care about copyright. What I should say is that whatever is in the SE terms of service regarding copyrighted material is what we go by.

Slereah

Please @DavidZ

We would never break copyright

@0celo7 is a good boy

David Z

16:03

But if you're going to get in trouble for copyright infringement, that trouble will come from the police, not from the mods.

0celo7

the popo

@DavidZ don't worry, emailing the math librarian right now

David Z

Hey, like I said, I don't care ;-)

FenderLesPaul

Very cool paper

for those interested

0celo7

modular forms D:

David Z

@FenderLesPaul better to link to the abstract page than the PDF file

FenderLesPaul

16:06

arxiv.org/abs/1603.08925

David Z

That's like the One Rule of citing arXiv. Use the URL of the abstract page, not the download link for the PDF.

The Dark Side

@DavidZ and check the possible permutations of author names, at this time of the year! :P

David Z

Well, you have to check a lot of things :-P

The Dark Side

Ali Frolop wakes up every March/April :D

David Z

I always hope for a new epic joke paper to appear on arXiv for April Fool's Day, and I'm nearly always disappointed. Though the astrology of exoplanets one was pretty good, I thought.

The Dark Side

16:08

arxiv.org/find/astro-ph/1/au:+Frolop_A/0/1/0/all/0/1 — Tobias Kienzler yesterday

0celo7

@DavidZ why

David Z

because it's way more inconvenient to download and open a PDF file than it is to read an abstract

And you can get from the abstract to the PDF, but not the other way around

(not without manually rewriting the URL, anyway)

0celo7

@DavidZ that's what I do

David Z

And the abstract page has links to INSPIRE and ADS and so on, as well as blog trackbacks, and you can use it to find other works by the same authors, check publication info, etc.

@0celo7 yeah, nobody else wants to do that

0celo7

It's always the highlight of my day

FenderLesPaul

16:10

gr-qc is so sad to scroll through

these days anyways

0celo7

why

FenderLesPaul

it's hard to see a field dying before your eyes

0celo7

why is it dying

FenderLesPaul

gr-qc is populated by papers that scream "we're trying our best to keep classical GR research alive by publishing papers on rehashed toy problems or poking very very very deep holes into problems no one cares about"

0celo7

@FenderLesPaul are you sure it sent correctly

FenderLesPaul

16:12

@0celo7 I mean classical GR is just so well understood that at this point the gr-qc papers are either papers of the above form or very dry papers on modified theories of gravity

Yes I am

0celo7

> so well understood

NO ONE knows how to smooth curves

FenderLesPaul

what a tragedy

Slereah

@FenderLesPaul hasn't that always been the case for GR

I mean all the big GR effects that we can check experimentally have been discovered within the first 15 years of GR

0celo7

@FenderLesPaul If you can prove that causal relations are transitive, I will become your slave

@Slereah no

Shapiro, that thing with gyroscopes

g waves

Slereah

This Shapiro?

Jim "The Hammer" Shapiro video # 4

►

FenderLesPaul

16:17

@Slereah well that's definitely not true; GR didn't become really popular until the 60s and 70s

0celo7

No, the one from Breitbart

FenderLesPaul

and GR research was definitely still going strong in the 90s and early 2000s

but it's slowed down considerably now

Slereah

Well yeah but most GR things outside of cosmology have been pretty niche

FenderLesPaul

which sucks for me

ok but that doesn't change the fact that there were still a lot of relevant GR papers being published in the aforementioned period

but no so much anymore

anything relevant now tends to just come from Andy Strominger and his army of grad students

Slereah

heh

FenderLesPaul

16:19

hehe

Slereah

It would be nice if some decent experimental results came out

Not much since Gravity Probe B

0celo7

@FenderLesPaul if you get me the mycopy I will send you the money however you like!

god, the typesetting in this book is terrible

what was he thinking oO

Slereah

"Money!"

0celo7

well it went from nice computer modern to that crappy springer latex stuff

FenderLesPaul

god damn I've been on hold with Jet Blue for 20 mins

0celo7

16:25

I wonder if the equation $f_{**}=fg$ has interesting solutions

I stuck my headphone thing into the USB port

it made a noise in the headphones oO

Physics Meta

0

Q: Should we suggest that authors of complete solutions to homework-like questions delete them?

This week I've seen several complete solutions posted to homework-like questions. One author asked if he should delete his answer. I'm inclined to answer yes, he should delete it, but I'm putting the question up here to see what others think. Ah ... the author deleted it on his own, so I can't...

discussion homework

Slereah

Well yes

USB port has current running

0celo7

16:49

@Slereah Would you happen to have a proof of that?

Slereah

of what

Transcript for