The h Bar

user228700

6:01 AM

@JohnRennie Ah, yes, I'm glad that the dowry-system is undergoing a radical change now.

user228700

@HsMjstyMstdn I agree that it is certainly more perilous to be a drunk girl than a drunk guy. I speak only of a single glass of wine/beer though. Anyhoo, this is not the hill I want to die on because I don't plan on drinking anytime soon anyway.

John Rennie

I'm not sure I find the idea of dowries attractive at all. It implies sons/daughters are merchandise to be bought and sold.

Balarka Sen

I think everybody should stop drinking, both gender alike, and smoke pot instead

Slereah

please

John Rennie

I might, allegedly, have a friend who used to smoke pot as a student, and I didn't find it anything special. I preferred acohol then and I do now.

Slereah

6:05 AM

the drug of mathematicians is amphetamines

HsMjstyMstdn

A single glass of wine/beer really should be allowed... making me thirsty...

user228700

@JohnRennie Me neither. I don't even understand how this system came to be.

Balarka Sen

@Slereah Paul Erd\"os didn't take it for hippie purposes though, just to produce good work

Slereah

Yes

And so should you

Balarka Sen

I also don't know of any other mathematician who took amphetamines

Slereah

6:07 AM

Take a bunch of it and help me solve that Hausdorff problem

That's why you don't know any famous mathematician

Balarka Sen

No thanks man

get Hausdorff to reincarnate and feed him amphetamines. maybe he'd help

Slereah

I'm pretty sure Hausdorff invented that condition so he wouldn't have to deal with non-Hausdorff manifolds

from the quotes I've read, non-Hausdorff manifolds are the bane of mathematicians

Balarka Sen

That is true. They suck.

Slereah

I mean maybe I should read about foliations

That's about the only field that uses them commonly

Maybe I should ask David Gauld

Balarka Sen

I don't think it's that common. There has been some interesting work thinking about leaf spaces and group action on leaf spaces (Roberts et al) but I don't have to deal with non Hausdorff manifolds yet, and I'm about half the way through the bible of foliations

Slereah

6:11 AM

He seems to be the only modern guy to work on them a bit

He too is in his 70's

Though he's still working I think

Where are the cool young mathematicians

Balarka Sen

The cool young mathematicians are all into deep stuff

4-manifolds etc etc etc

Slereah

Well I am interested in non-Hausdorff 4-manifolds

Perfect

Balarka Sen

"You're such a wonderful person / But you've got problems"

Slereah

though David Gault isn't exactly into non-Hausdorff manifold

His field is the metrization of manifolds

"Foliations on non-metrisable manifolds: absorption by a Cantor black hole"

Not the Cantor black hole D:

Balarka Sen

what the hell is that

Slereah

6:22 AM

"This is derived from a qualitative study of foliations defined on the long tube $S^1 \times L^+$ (product of the circle with the long ray), which is reminiscent of a `black hole', in as much as the leaves of such a foliation are strongly inclined to fall into the hole in a purely vertical way. "

Balarka Sen

Didn't know they used to study foliations on nonstandard things like that

Slereah

I wonder how many manifolds you can make with the long line

The long torus

the long Klein bottle

Balarka Sen

You can literally just puncture out n holes and glue those long tubes back in

From any surface

Slereah

One of Hicks' reference is "Variationsrechnung im Grossen"

It's in German and apparently not on the internet

From the index the proof he talks about seems to be in DIE RIEMANNSCHE MANNIGFALTIKEIT $\mathbb{R}^n$

Slereah

7:10 AM

[1] M. Baillif. Oh Mamy Blue. (Unpublished fanzine by Ibn al Rabin). Musée Rath (2006).

Why is this in a math bibliography

Secret

Distinguishing between black holes and naked singularities via change in precession frequencies of rotating objects in its vicinity

Secret

7:31 AM

These are example research outcomes that I hope there are more detailed mechanisms: Stairwalking enhance work motivation for sleep deprived women

user228700

user228700

It's like I said before:

user228700

2 days ago, by Kaumudi. H

Jesus Christ, such a happy kid Calvin is; I am considering inventing an imaginary friend for myself.

Gerold Broser

8:01 AM

I solemnly swear...no, not to become the next president of the US & A...but even if physics hates me, I'm going to go my way!

Slereah

8:19 AM

gulfnews.com/opinion/thinkers/…

Ben Niehoff

I wanna learn to make rotis, rotis are delicious!

Balarka Sen

@Secret Gives a little context to Marcel Duchamp's "Nude Descending a Staircase" [to those unfamiliar with the painting - it's not what you think it is, folks!]

I like the Rude Descending a Staircase parody better anyway.

Slereah

8:43 AM

help

Aaah

It looks like a @Secret diagram

"A $T_1$ space is non-Archimedeanly quasi-metrizable if and only if it has a $\sigma$-interior-preserving base"

that paper isn't useful at all

Gerold Broser

9:02 AM

@Slereah Is this Escher, Giger or Warhol? ;)

Secret

That, is a readable, but very VERY cluttered venn diagram. I have to focus one local region at a time to not felt strained

@Kaumudi.H Will tell more about it later, back in my P.4 I had an imaginary friend, and the story itself gets a bit more interesting due to something happened in 23/6/2016 about it

Gerold Broser

@Secret How do you master to focus one local region at a time and writing in the chat at the same time?

Secret

@GeroldBroser Because I only skim-read it briefly. I don't see much relevance of it to my current focus (currently chemistry and growth functions) and more importantly, my GR still suck thus most of the stuff is incomprehensible to me in that diagram even though it is not obstructed

Slereah

that guy loves long manifolds

Secret

I want non-hausedoff manifolds, because they are the ones important to time travel

AccidentalFourierTransform

9:14 AM

Secret

Terminology makes things precise. Abuse of them to make your article look high-class is not

AccidentalFourierTransform

a Möbius strip walks into a bar, and the bartender asks, why the long face?

Secret

and this is one of the problems we scientist have in communicating science

O wait, nvm, misread

AccidentalFourierTransform

lol

Secret

@Jim The joke summarise well when I talked to physicists and engineers who have ZERO chemistry background: I often cannot answer their question on what is my PhD is without completely doing away the terminology metal complex (or, spend a short paragraph explaining what a metal compelx is without using too much terms like ligands, electron withdrawing etc.)

talk about being a very efficient but inaccurate science communicator

The situation is slightly better for physicists who does computer simulations, because they knew what DFT is

NB when I talk in paragraphs, it usually took a maximum of 5 minutes

This is why despite all my typically LONG messages here, you will not notice they are long when said chat happens face to face

Mar 27 at 22:27, by ACuriousMind

I am beginning to believe @BernardoMeurer is stuck in some kind of bizarre time loop that involves Chris White and free software.

23 hours ago, by ACuriousMind

I'm pretty sure BalarkaSen is an old Soviet philosopher trapped in our time by some freak accident

23 hours ago, by ACuriousMind

I'm sure @Slereah will want to investigate this temporal accident

Why the temporal anormalies. Are there more :P ?

AccidentalFourierTransform

9:31 AM

yeah, talk about temporal loops!

Secret

Slereah is expert on temporal mechanics

Predestination (film)

Predestination is a 2014 Australian science fiction thriller film written and directed by The Spierig Brothers, based on the 1959 short story "'—All You Zombies—'" by Robert A. Heinlein. The film stars Ethan Hawke, Sarah Snook and Noah Taylor. == Plot == The film begins in medias res as a time travelling agent is trying to disarm a bomb that explodes and burns his face. Someone approaches and helps him to grasp his time travelling device, then brings him to a hospital in the future. While the agent is recovering from facial reconstruction, we learn that he has been trying to prevent the "Fizzle...

This movie taught me an important lesson in time travel:

(and is model independent)

> In terms of knowing the future, a time traveler is actually no better than non time travelers, as they cannot know where they will end up next and why

In other words, past and future becomes relative, and everyone, including time travelers, have full knowledge of their relative past at every point in time they have went through, but no knowledge on their relative future

This probably explains why in many time travel stories, trying to change the past to the target one often face a lot of obstacles (besides plot element restrictions)

Slereah

my french fries are exhaling steam through their membranes

Makes it sound like they're screaming in unison

No god will help you now, french fries

2

This one looks very normal for a time reversed movie

user228700

9:48 AM

@JohnR: Off to the station :-/

John Rennie

@Kaumudi.H Have a good trip and good luck with the exam!

user228700

I'm going to be around for awhile; I have some data on my phone :-)

John Rennie

Read the C&H pdfs on the train - that's guaranteed to make anyone feel good :-)

user228700

:-) I wish I could. Leave it up to me to make it so that I have revision to do even on the damn train!

Slereah

What about the realization that there will never be any more Calvin and Hobbes comics

AccidentalFourierTransform

10:21 AM

hehe, nice

Slereah

Hey @ACuriousMind

ACuriousMind

Mornin'

Slereah

how are things in the fatherland

ACuriousMind

@Slereah You should be glad about it because this way there's no risk of Watterson running out of ideas and the strip becoming bad.

Slereah

Are you being mean to Garfield

America's favorite cat

ACuriousMind

10:26 AM

@Slereah rainy

I was actually thinking of the Simpsons, but I guess Garfield works, too :P

Slereah

Immortality truly is a curse

Can you build a fiber bundle on $\Bbb N$

After all they can be built on any topological space

not sure what it would be useful for, though

@ACuriousMind what does your wizard eye see in this

2 hours ago, by Slereah

ACuriousMind

@Slereah I think fiber bundles on discrete spaces are not interesting, they should just all be trivial since you can refine every open cover to the open cover that consists of the individual points of $\mathbb{N}$ and has no overlap, so no transition functions

@Slereah I see someone who should work on their presentation skills :P

Slereah

he was just so excited about manifolds

ACuriousMind

That diagram contains probably interesting information but it's very hard to read

Slereah

Apparently there are exactly four manifolds of dimension one

Real line, circle, long line and long ray

I guess there's no long circle

Danu

10:39 AM

@ACuriousMind heyo

ACuriousMind

heyhey

Danu

Fiber bundles on discrete spaces can be interested because of the context, though :)

The space of holomorphic line bundles on a complex manifold is a torus bundle over the image of $c_1$

Slereah

I guess he called it a nose to be polite

Danu

@ACuriousMind How's the thesis going? What kind of stuff are you concretely trying to do?

(or is it a secret?)

Slereah

I think I'm going insane

Those foliations look deeply upsetting

Danu

10:48 AM

Nice pictures

Which book is this?

The Reeb foliation is nice though

Slereah

arxiv.org/pdf/0910.1897.pdf

Danu

Wtf is a non-metrizable manifold supposed to be?

ACuriousMind

@Danu I think I'm trying to see if there are interesting topological transitions on Kovalev's TCS construction, that is, the TCS develops a singularity and then that singularity is resolved in a different way, leading to another TCS - this process should physically correspond to different versions of symmetry breaking.

Something like that is buried in the Klemm et al. paper (and there's also an example by Halverson/Morrison), but I'm still working through that paper - I think I have about finished my detour through complex algebraic geometry to understand what's going on here.

Slereah

@Danu non-paracompact manifold

also non-Hausdorff, if you allow them to be manifolds

Danu

@ACuriousMind What's a TCS? :P

Slereah

10:49 AM

but only non-paracompact for this paper

Danu

I'm actually thinking of applying to Klemm... Getting a bit scared doing my math applications

ACuriousMind

@Danu Twisted connected sum, a way to construct $G_2$-manifolds from asymptotically cylindrical Calabi-Yaus

Danu

Oh, right.

ACuriousMind

@Danu How's your own thesis going?

@Danu I think Slereah is in a world where "manifolds" might not be paracompact or Hausdorff, you can't put metrics on some of these pathological things

Oh, Slereah already said that

Danu

Most of the computations (of Chern numbers) are done for me, but there is a lot of underlying theory most of which I am ignorant of, but which needs to be in my thesis. I know something about twistor spaces, but I also need some stuff on homogeneous and symmetric spaces, nearly Kaehler structures...

ACuriousMind

10:55 AM

Maybe I'm not quite awake yet :P

Slereah

yeah the paper is mostly about variations on the long line

Including the bagpipe manifold

Danu

Currently I'm trying to rush to write at least one chapter because Bonn's application package has to include a sample of academic writing "of substance", which reflects my mathematical development. My BSc. thesis won't do, for obvious reasons :P

Deadline: 15 May

ACuriousMind

@Danu Ah, I think I might be taking the opposite approach, I'm digging through the theory now and will probably scramble at the end to actually compute stuff in an example or two.

Danu

Right. I just got lucky that my supervisor is interested in this himself.

ACuriousMind

Although I'm of course leaving some black boxes...I'm a physicist, after all :P

Danu

10:58 AM

Therefore, he told me what to calculate :P

I'm blackboxing all kinds of classifications (of nearly Kaehler manifolds, etc)

Slereah

I'm guessing that a good intuition on why the long line is not metrizable is that if you have two points separated by $\omega_1$ intervals, they're too far apart for the metric to spit out a real number

ACuriousMind

@Slereah I think that's it, yes

@Danu Oh boy, you mentioned that already

Danu

I have 3 pages so far...

Mostafa

@Danu Are you a PhD student?

Hi, btw

Danu

Obviously not, by the above conversation :p

Mostafa

11:01 AM

I looked at your profile

...Graduate student of Dutch origin...

Slereah

jstor.org/stable/2037193?seq=1#page_scan_tab_contents

oh boy

Danu

@Mostafa Yup. I have a BSc. already.

Mostafa

So no Master's?

Danu

Graduate school

A graduate school (sometimes shortened as grad school) is a school that awards advanced academic degrees (i.e. master's and doctoral degrees) with the general requirement that students must have earned a previous undergraduate (bachelor's) degree with a high grade point average. A distinction is typically made between graduate schools (where courses of study vary in the degree to which they provide training for a particular profession) and professional schools, which offer specialized advanced degrees in professional fields such as medicine, nursing, business, engineering, or law. The distinction...

ACuriousMind

@Danu The conversation does not bear out whether we're talking about a master's or a PhD thesis

Slereah

11:03 AM

ahah

Danu

@ACuriousMind This does not invalidate my claim.

Slereah

It's one of those one page article

Danu

Wait, lol

It does

But the fact that we are talking about applications

That's what I was referring to :P

ACuriousMind

Uhhh...okay :D

Mostafa

Application for what? PhD or Postdoc or ...?

Danu

11:06 AM

PhD

ACuriousMind

Janitor

Mostafa

Anyways, I had a question about history of science.
Do you know since when (approximately), being a *full time* scientist or researcher (as one's job) became prevalent?

Danu

No idea

Slereah

Define "full time scientist"

Does a professor that does research count as a full time scientist

Mostafa

One whose main job is doing research

and is paid for that

ACuriousMind

11:08 AM

@Mostafa That does sound like a question for History of Science and Mathematics, right @Danu?

Slereah

I'm guessing probably the 19th century

When people realized there were money in doing science

Maybe 18th

but you know, there has been paid science work for quite a while

For various applications

Galileo worked at ballistics calculations for the money

Danu

@ACuriousMind Yeah, though it might be a bit broad.

Slereah

"However, after accidentally attending a lecture on geometry, he talked his reluctant father into letting him study mathematics and natural philosophy instead of medicine."

Poor Galileo dad

He wanted a nice doctor son

Mostafa

Doctors were paid more than others even at Galileo's time....

It's REALLY unfair

@ACuriousMind I'm asking because these days I'm hearing quite a lot that we're going in that direction now: having science developed by people whose main job is not science.

user228700

@ACuriousMind I agree.

John Rennie

11:16 AM

Can a world line start and end at the same timelike singularity?

Slereah

are we

@JohnRennie sure

John Rennie

No such world line can exist for a spacelike singularity, but I'm not sure if that applies to timelike singularities.

Slereah

Take the timelike cylinder

Remove a line

John Rennie

Timelike cylinder?

Slereah

$S_t \times \Bbb R$

Minkowski space with $t= 0$ and $t = T$ identified

John Rennie

11:19 AM

I was thinking about physically realistic spacetimes.

Slereah

Physically realistic spacetimes don't have singularities :p

John Rennie

Does Minkowski space with $t= 0$ and $t = T$ identified have a singularity?

Slereah

What is a "physically realistic spacetim"

user228700

Ugh, this sucks a bit more than I'd originally anticipated:

Slereah

It does if you remove a segment from the manifold

John Rennie

11:20 AM

@Slereah A Reissner Nordstrom black hole for example

Slereah

I think what you're asking will always involve spacetimes that aren't strongly causal

John Rennie

It has a timelike singularity, but I don't think worldlines can begin and end on it.

Slereah

Also by "the same singularity", do you mean a single point, or possibly different point of an extended singularity

user228700

Gah. Never mind.

John Rennie

What's an extended singularity?

@Kaumudi.H train woes?

user228700

11:22 AM

@JohnRennie Yes :'-(

Slereah

@JohnRennie A singularity of more than one point

John Rennie

@Slereah such as?

Slereah

Well

Minkowski space with a segment removed

If you mean a single point, I think any such spacetime won't be strongly causal, so not "realistic"

John Rennie

Oh, OK. Again I was thinking of singularities that could reasonably exist given that we're relaxed about the strong energy condition.

Slereah

Because it would be one point away from being a closed timelike curve, basically

John Rennie

11:26 AM

@Slereah Ah, you mean one point in space not one point in spacetime?

user228700

Stupid image won't upload.

Slereah

If you mean "one point in space", then yes, it's not too hard to have a geodesic from a singularity at $t = a$ rejoining it at $t = b$

Just take a naked singularity (pick your favorite Kerr black hole with naked singularities), have a geodesic come out of it, and rejoin it later

John Rennie

@Slereah ah, good point. Yes, OK, I'm convinced.

Slereah

$\Bbb R_ t \times (\Bbb R^3 \setminus \{0\})$ is the easiest example

Mostafa

Damn I'm turning 25 in 4 months.

John Rennie

11:29 AM

Young git! :-)

Mostafa

:(

Slereah

I think all the non-Kerr Perjès spacetimes have naked singularities

That's why they are seen with scorn and Wald won't even mention them

The 60's and 70's really had a whole bunch of weird GR stuff

Everyone was trying to solve the mystery of GR without any clear idea of what made sense

ACuriousMind

11:46 AM

Do we have a clear idea of what makes sense, now?:P

Secret

Wait until 2018, when the event horizon telescope images have done analysing

Slereah

Well, to give you an idea, people played with the idea that maybe the Schwarzschild solution was not time orientable or causal

it was a weird time

Mostafa

@Slereah What do you mean by mystery of GR?

(I know almost no GR)

Slereah

The big thing at the time was the singularity theorem

It was proven that singularities were a generic feature of general relativity

So people were trying to make sense of it

Mostafa

you mean the issues that led them to quantum theories of gravity?

Slereah

11:53 AM

nah

People have been trying to make quantum gravity since the 30's or so

Mostafa

Ah I think you mean this (from Wikipedia):
*The first modern solution of general relativity that would characterize a black hole was found by Karl Schwarzschild in 1916, although its interpretation as a region of space from which nothing can escape was first published by David Finkelstein in 1958. Black holes were long considered a mathematical curiosity; it was during the 1960s that theoretical work showed they were a generic prediction of general relativity. The discovery of neutron stars sparked interest in gravitationally collapsed compact objects as a possible astrophysical reality.*

God! Maxwell is here

@ACuriousMind a boring question:
Do you prefer (like) loop quantum gravity or string theory as a quantum gravity theory?

ACuriousMind

@Mostafa I don't know enough about loop quantum gravity to like or dislike it but I do like string theory/M-theory for its interesting mathematics and intriguing uniqueness results (e.g. all possible 10d and 11d QFTs w/ supergravity arise as the low-energy effective QFT of a string theory)

In contrast, I haven't found anything that would intrigue me to delve into LQG, so far

Slereah

well they are different types of theories

LQG is just a quantum gravity theory

While string theory is a whole bunch of things

Mostafa

Yeah I knew that one.
wanted to tell ACM make up his mind about this if he ever wanted to marry a HEP-theory student, so that this won't happen to him:

TBBT S02E02. Loop Quantum Gravity Vs String Theory

►

ACuriousMind

12:08 PM

@Slereah Is it? I've heard some of its adherents make strange and wild claims about emergence of spacetime or whatnot. What does "just" a quantum gravity theory even mean?

Slereah

It's not supposed to solve like unification

at least as far as I know

Hey @0celouvsky

0celouvsky

Hello

Secret

LQG made no attempt to unify the other 3 fundemental forces with gravity. This is one of the key difference of it compared to string theory.

It only tries to quantise gravity by quantising spacetime

The unification ambition of string theory is one reason it receive a lot more media coverage than LQG

LQG, if I recall, is also background independent, in that spacetime emerges from some more fundemental building blocks

That, however is what I knew about LQG so far. I planned to read up more about it and string theory in the future once I tackle QFT and GR

0celouvsky

12:25 PM

8 hours ago, by 0celouvsky

there's an ode $$\frac{\partial}{\partial\psi}(\sin^2(\psi)\frac{\partial}{\partial\psi}\xi)=-3‌\sin^2(\psi)\xi$$

@ACuriousMind halp

Slereah

@0celouvsky do you want me to check

The Book

0celouvsky

I doubt it's in there

But sure

Slereah

I think it's that one

solution 3

wait no

It should be arctangent, not tangent

well, not arctangent

Just $\tan^{-1}$

cotangent, that's the one

that should help

0celouvsky

12:51 PM

Is that the same one?

Slereah

Seems to be

up to some minor variable change

0celouvsky

So what's the solution for 47?

Slereah

The solution for 29, with some changes

Slereah

1:10 PM

Hm

This introductio says that the infinite rotini is the fiber bundle $\exp : \Bbb R \to S$ with fiber $\Bbb Z$

0celouvsky

all covering maps are fiber bundles with discrete fiber

fiber bundles generalize covering maps

Slereah

Neat

0celouvsky

"If $G$ acts properly discontinuously on the arcwise connected locally arcwise connected Hausdorff space $X$ then $p:X\to X/G$ is a regular covering map with deck transformation group $G$"

I guess one just has to show that Spin(n) is a manifold

Slereah

Seems to be a nice intro

Slereah

1:43 PM

What's the structure group for a covering map, the deck transformation?

Are they principal bundles? :o

ACuriousMind

@Slereah Yes, regular covers (where the deck transformation acts transitively on the fibers) are principal bundles

0celouvsky

@ACuriousMind I don't understand Spin

why should it be a manifold?

what's the topology supposed to be?

ACuriousMind

What? It's the universal cover of SO, and covers of manifolds are manifolds

Slereah

He means from the clifford algebra

ACuriousMind

Then he needs to be more precise :P

0celouvsky

1:49 PM

@ACuriousMind No, it's $\mathrm{Pin}(n)\cap \mathrm C\ell^\mathrm{ev}(\Bbb R^n)$

I'm guessing it should be the subspace topology from $\Bbb R^{2^n}$

ACuriousMind

Yeah, so that one doesn't have a topology until you biject it to the universal cover of SO and get the topology from there :P

0celouvsky

wtf

ACuriousMind

At least, that's how I'd solve the problem :P

0celouvsky

does that make it into a topological group?

are universal covers of groups groups?

I think this is an exercise in some book I read

maybe

ACuriousMind

Make what into a topological group? The universal cover of a Lie group is a Lie group by Lie theory, you don't need any general things about topological groups here

So you take your definition of Spin(n) and a group isomorphism to the universal cover of SO, and there's your Spin(n)-as-a-manifold

0celouvsky

1:53 PM

How the hell do you expect me to remember things about Lie groups

ACuriousMind

I'm not sure I expect you to, I'm just saying that that's one way to see it's a manifold :P

0celouvsky

I'm not sure I know why that's true

I can't find it in Lee

I mean, this has to be somewhere

@ACuriousMind Actually it is true for topological groups

Transcript for