The h Bar

Danu

20:02

@DanielSank Nice "worst title ever" here:

"Where else could they be?"

0

Ok, let's assume for a second that the "thing" interfering star KIC 8462852 is a large array of solar panels, confirming the existence of a way more advanced than us alien civilisation. Remember that the star is about 1500 light years away, so as Pope Leo 1 was talking Attila the Hun out of sack...

0celo7

they?

the ayy lmaos?

Danu

Also a terrible question

ACuriousMind

@0celo7 What?

No close votes left.

Danu

@ACuriousMind The indigenous people of "ayy lmao"

ACuriousMind

@Danu What? :D

user54412

20:05

@Danu Oh no, I googled, and apparently this is a conspiracy theory started less than a day ago.

user54412

Gaining traction rapidly

Danu

@ChrisWhite Noooooooooooooooooo

They're on to us!

Ghost

@Danu is that your home sphere?

user54412

2

Danu

@ChrisWhite I saw this :(

user54412

20:06

I give up. Switching to astrology.

13

Danu

@Ghost Who knows...

Ghost

@Danu did you lose your home sphere???

Danu

arxiv.org/abs/1509.03622v1

What a sensationalist title!

Planet Hunter X: Where's the flux?! Coming, SOON, to theaters near you!

ACuriousMind

@Danu Can I follow the plot without having watched Planet Hunter I - IX?

user54412

@Danu Four hot DOGs in the microwave, posted today.

Manish Kumar Singh

20:12

Hellow, here I require a little clarification, Suppose I am in my room and observe the motion of a particle, I have two option either Cartesian or cylindrical. Now my friend moves with a constant speed wrt my room and measure motion say in cartesian. Now how many inertial reference frames are there? 2 or 3

Danu

@ACuriousMind Only if you know where the flux went.

Btw, some guy from Heidelberg gave a talk here today, Walchers or something... You know him?

@ChrisWhite ...wow.

Are they bored to the point of focusing all their attention on funny titles? :P

ACuriousMind

@Danu Into the flux compensator, obviously.

@Danu No, he's new.

Danu

@ACuriousMind compactifier

I had my first class for String Theory 1 by Lüst yesterday

Memorable quotes: "At least we get a prediction... that's wrong!" and "We must overcome the predictions!".

ACuriousMind

@Danu GDi, just found out it's the flux capacitor in English so I didn't make a Back to the Future reference :(

Danu

Classic string theorist :D

@ACuriousMind Don't worry, I don't know anything about those movies anyways ;)

ACuriousMind

20:19

@Danu Hehe...funny, and a bit scary.

0celo7

Never watched them either

Danu

20:38

@ACuriousMind I did kind of rip those out of context, I must admit.

0celo7

20:51

@ACuriousMind sigh

no culture...

@ACuriousMind ok, I think I understand what's going on in that proof now

I'll still stop by Alex's office and see what he has to say about it

maybe he can give me some ~~Russian~~ Portuguese intuition

Danu

@ACuriousMind Also.. GDi? Have you fallen to "censorship"? :P

ACuriousMind

@Danu Nah, just gotta be a fucking example. ;)

Danu

@ACuriousMind :3

Examplary indeed.

0celo7

@ACuriousMind Language!

There are children in here

Danu

@ACuriousMind Thanks for that central extensions blablabla story (I've bountied it now)---I haven't been able to find any good reference so it's very nice that I can find this stuff on SE :-)

6

Q: Why exactly do sometimes universal covers, and sometimes central extensions feature in the application of a symmetry group to quantum physics?

There seem to be two different things one must consider when representing a symmetry group in quantum mechanics: The universal cover: For instance, when representing the rotation group $\mathrm{SO}(3)$, it turns out that one must allow also $\mathrm{SU}(2)$ representations, since the negative s...

quantum-mechanics symmetry group-representations lie-algebra representation-theory

ACuriousMind

21:04

@0celo7 Yes, and they are far more profane than I :P

@Danu Well, thanks!

Danu

@ACuriousMind Perhaps you'd be interested in this mathematically oriented reference on CFT that Blumenhagen recommended (the first book on that page).

(the others also seem fascinating...)

ACuriousMind

@Danu Why yes, I would. (Sigh, I need to clean up my download folder again soon. And actually read some of the stuff I intend to)

Danu

@ACuriousMind It's in my textbooks folder ;D

The guy seems so awesome... Got me thinking about possible master thesis under his supervision...

ACuriousMind

@Danu The chapter on central extensions there includes what I do in my post :D

Danu

@ACuriousMind I just discovered it too :D

ACuriousMind

21:15

In particular, it concludes with classifying equivalence classes of central extensions by $H^2(G,\mathrm{U}(1))$.

Danu

Totally worth it though :D

(the bounty)

"Another motivation was to discuss the sometimes confusing use of language by physicists"

ACuriousMind

@Danu <3

@Danu: Skimming further through this book, I might have found where my CFT lecturer drew his inspiration from. This is the first CFT text I see that's even remotely similar to what we did.

Danu

21:33

@ACuriousMind hahahaha

Danu

22:03

Also @ACuriousMind in what sense exactly should I view the equality in $S^2=\mathbb{C}\cup \{\infty\}$

Is there more than a bijection?

Some algebraic isomorphism perhaps?

ACuriousMind

@Danu If you understand $\mathbb{C}\cup\{\infty\}$ as the one-point compactification of $\mathbb{C}$, then there is a homeomorphism.

Danu

As it stands, I dont understand anything by the one-point compactification

What does it mean, separately from the Riemann sphere?

ACuriousMind

@Danu Well, it means you add one point to the space and define its neighbourhoods such that the space becomes compact ;)

0celo7

@ACuriousMind I don't see any profane children around

ACuriousMind

Formally, the open sets containing $\infty$ are precisely those whose complements are closed and compact (in the original topology).

Danu

22:11

@ACuriousMind Okay.

ACuriousMind

@0celo7 No mirror? :P

@Danu Is that an "Okay, I understood it" or an "Okay, that didn't help at all"? ;)

Danu

@ACuriousMind I understood it.

While chatting here, I'm playing 2-minute chess games (without increment, mind you), so sometimes my responses are curt ;)

(done now, though)

I should go---class at 8:30 in the morning.

0celo7

22:39

@ACuriousMind :(

Too poor for mirror

Danu

22:53

Does anyone know a good, free djvu-to-pdf converter (one that does not increase the file size by an order of magnitude or more)?

Actually, perhaps there would be a more suitable SE site for questions like that---any ideas?

ACuriousMind

4

Q: Conversion of djvu file into pdf file without increasing file size

Why does converting a djvu file to pdf increase the size of the file? How can we convert a djvu to a pdf without increasing the size?

pdf djvu

Since DVJU is optimized for storing the scans, it is improbable that you can consistently create PDFs of the same size since PDF is not optimized for that.

So, I think you can't get much better converters than just printing to pdf.

Slereah

So whatever happened to the EM drive thing

Did people finally drop it

DanielSank

23:33

@Danu egads.

0celo7

@Slereah the government took over the project and is silencing folks

ACuriousMind

23:51

Hmmmm

A few hours ago I flagged a bunch of answers to a res. rec. question as "not an answer" because they do not conform to our policy on answers.

Now, some of these reviews have been completed, e.g. this one with an unanimous "recommend deletion" vote.

However, the answer has not been deleted, but the flag has been marked as helpful.

Anyone know what's going on here?

Perhaps the Community user is unable to deleted positively scored answers just from a LQ review vote?

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