The h Bar

Slereah

21:01

I am quite a dapper fellow

JokelaTurbine

21:12

@HDE226868 Well I don't see any difference in his doings compared to any one who is using the scientific method; en.wikipedia.org/wiki/Scientific_method But I did not came to the chat for this. I just asked if G is measured in space /ISS. Simple YES/NO would have been completely enough. - And I do tried to google it. Instead of that I just learned today that HSM = History of Science and Mathematics. -Well thanks for that.

Slereah

An amusing thing about the history of sciece is that in one of Heron of Alexandria's book, there is a diagram of a machine to pretend to turn water into wine

CAUGHT RED HANDED JESUS

In Πνευματικά

himedo.net/TheHopkinThomasProject/TimeLine/Wales/Steam/…

yuggib

so the apostles drank from wolf-shaped cups?

Slereah

Hard to say

Maybe it was a commonly known party trick

yuggib

maybe

Slereah

Old timey religion had a lot of weird party tricks used for miracles

Back before most people realized such things were possible

0celo7

21:23

@Slereah THAT IS NOT A SWAN

Slereah

Ahahah

Went to the park did you?

0celo7

Yes ;_;

Slereah

it's a tough one

If you have a missile launcher on you I would advise it

0celo7

what do I do

I have a pistol!

Slereah

Then run the fuck away!

yuggib

21:24

shooting yourself in the head is another option

fast and painless

Slereah

"Postal 2" had a suicide button

Danu

@JokelaTurbine Glad you feel so enlightened :3 HSM is the best :D

Slereah

You put a grenade in your mouth and say "I regret nothing"

0celo7

is there a way to avoid him

Slereah

If you don't bother him he stays underwater

Do tachyons violate causality if they are non interacting

I think they're pretty benign

ACuriousMind

21:31

@Slereah Didn't we conclude they don't a while back?

yuggib

what do you need them for if they do not interact

Slereah

@ACuriousMind : Well I am talking about tachyon point particles heree

yuggib

?

Slereah

Not tachyonic fields

@yuggib : Theorems!

ACuriousMind

@Slereah Ah

Slereah

21:32

Tachyonic fields are apparently complicated but point particles move on spacelike curves, no doubt about that

yuggib

@Slereah there are plenty of thing to write theorems about

Slereah

Like what

0celo7

awwww

Slereah

there's two crazy cat lady houses in Fallout 4

yuggib

quantum mechanics with the banach space of bounded operators as coordinate space.

Slereah

21:36

Snore

yuggib

it seems as useful as non-interacting tachyons

Slereah

tachyons are exciting, though

I am wondering how much you can stretch causality into accepting things

yuggib

what do you mean "stretch causality"

?

Slereah

Pretty obviously tachyons interacting with massive particles will violate causality

(Well not obviously, but I suspect it is)

I'm not sure about free tachyons and tachyon-tachyon interaction, though

Tachyon-tachyon I think would also violate causality

Since it has a weird little group

And you could totally have closed spacelike curves for tachyons

(that are interacting)

Which would fuck up causality

But free tachyons, I think those might be okay

yuggib

ok, but causality seems one step ahead of detectability for practical purposes

Slereah

21:42

Who cares about detectability man

Do I look like an experimental physicist :V

yuggib

well, theoretical detectability should be interesting for any physicist

obe

anyone play starcraft 2 here?

yuggib

if else you are doing math, but then it is not so interesting (by mathematical standards)

Slereah

Them's fighting words!

yuggib

why?

user54412

21:46

@AngusTheMan Don't guess. Profile. Just about every optimization question asked on Stackoverflow comes down to someone guessing (and being wrong) about what the code was actually doing under the hood.

2

user54412

Even those of us who write high-performance code for a living almost never get it right on the first try. Just about every piece of software ever written can be made significantly faster with proper use of a profiler.

0celo7

@ACuriousMind Just heard Belethor's voice in Fallout :D

AngusTheMan

22:03

@ChrisWhite Thank you Chris, I will look into this area. This is the first time I have ever coded anything so I am really new to it all. I really appreciate the help! :)

Secret

Wow I thought there are only CTCs, now there's CSCs
Should investigate them later after finishing that exercise

user54412

@AngusTheMan Ah well if this is your first time coding, it's easy to get drowned in suggestions. Having fun and getting the right answer are probably more important than efficiency.

Slereah

Closed spacelike curves are not very interesting though :p

Because massive particles move along timelike paths

Also it is not very strange that some spacelike paths are closed

A circle is a closed spacelike curve

A bicycle wheel is

AngusTheMan

@ChrisWhite Indeed! Well I get the correct answer pretty quickly, and I am definitely having a lot of fun! But thanks to both your and alarge's suggestions I have a lot better idea what to do next :)

Danu

@Slereah A curve is a map, not a physical object. But alright :P

DanielSank

22:17

Ever heard of "factorial moments"?

@ChrisWhite This is good advice.

user54412

Factorial moments?

user54412

Those don't sound good.

Slereah

@Danu Have you ever seen a curve in the sky

^Does anyone know what latex symbol I could use for this symbol

0celo7

$Y$

Slereah

$\curlyvee$ seems the closest one

ACuriousMind

22:24

@Slereah Do you know DeTeXify?

Slereah

It's not quite a Y

user54412

"I thought it would take just a few moments, but it took a whole 6! moments."

Slereah

No

ACuriousMind

@Slereah detexify.kirelabs.org/classify.html

0celo7

@ACuriousMind doesn't work

ACuriousMind

22:26

Yeah, seems it doesn't know that one

0celo7

Slereah

Guess I'll go with curly vee

user54412

I couldn't even get it to give me upsilon. Just lots of psi's.

ACuriousMind

@ChrisWhite Well, upsilon isn't a special symbol, it's just Y, so it doesn't give you that.

user54412

Upsilon

ACuriousMind

22:28

Inconsistently, the standard symbols do not provide things like \Alpha, you have to use A or define it yourself.

0celo7

I think ACM and CW should fight.

user54412

Definitely a palm tree, not just a Y

user54412

@0celo7 Against each other? Or against Witten?

user54412

@Slereah \Ydown from the stmaryrd package

user54412

(from table 52 in this pdf)

0celo7

22:35

@ChrisWhite Nah, throwing a smart person in would complicate things.

user54412

or the boisik package

0celo7

@ChrisWhite how did you find this

you are the TeX god

user54412

that is one of the most useful documents on the internet

user54412

speaking of which, are these German abbreviations?

0celo7

That's pretty bad.

user54412

22:39

ACuriousMind

@ChrisWhite Yes, that's German: Fourth (note) - Viertel(note); Eighth - Achtel; Sixteenth - Sechzehntel

0celo7

> However, mathematical constants such as π = 3.14 . . . are sometimes required
to be typeset in roman (i.e., upright) style

Seriously??

People upright Greek??

ACuriousMind

@0celo7 Well, technically, if you upright the $e$ you should upright the $\pi$, too.

user54412

^ that sentence disturbs me for some reason

ACuriousMind

@0celo7 Sometimes it's good, sometimes it's horrible, but it's worth a try before one goes scrolling through the symbols list

Slereah

22:43

@ChrisWhite Thanks!

0celo7

@ACuriousMind Upright Greek is almost as bad as calling someone 5 years your senior by their first name...

makes me ill

user54412

ACuriousMind

-1

Q: Oxygen IN SPAAAACE!

Now, this may be a...odd question but.. Lets say theres 100,000 ...Oxygen Generators (a machine that pumps out tons of Oxygen) floating around in the vacuum of space pumping out Oxygen. and let's say 50,000 to a million or so years go by with these gens doing there thing. would the Oxygen just d...

soft-question

wat

HDE 226868

I think he's asking about whether or not there would be enough dissipation to make the oxygen density negligible.

user54412

@HDE226868 That's a pretty charitable interpretation...

HDE 226868

22:48

@ChrisWhite Well, after that he kinda wanders off somewhere to the land of incoherence. . .

0celo7

Makes sense to me

user54412

The land of incoherence. Sounds like a place in quantum computer folks' nightmares.

Slereah

Well obviously it would still be bound gravitationally :p

ACuriousMind

@ChrisWhite lol

Slereah

23:03

"It is shown that there are upper bounds on the first and second betti number of compact spacetimes or spacetimes with Cauchy surfaces whose fundamental groups are abelian"

Oh boy

somethingawful.com/flash/shmorky/zeldacdi-remixb.swf

Slereah

23:26

what

ACuriousMind

@Slereah WTF is microcompact and why are there some bosonic interactions in there?

Slereah

you're the math guy

Surely you should know

ACuriousMind

I've never heard of "microcompact"

Where is that from?

Slereah

"Let X be a locally compact space. Then for each x ∈ X and each neighborhood V ∋ x there is a compact neighborhood U ⊂ V of x (X is then said to be microcompact)"

0celo7

Locally compact?

ACuriousMind

23:31

Ah, it's one of these annoying notions that's equivalent to local compactness in Hausdorff spaces, but not in general

Slereah

Locally compact space

In topology and related branches of mathematics, a topological space is called locally compact if, roughly speaking, each small portion of the space looks like a small portion of a compact space. == Formal definition == Let X be a topological space. Most commonly X is called locally compact, if every point of X has a compact neighbourhood. There are other common definitions: They are all equivalent if X is a Hausdorff space (or preregular). But they are not equivalent in general: 1. every point of X has a compact neighbourhood. 2. every point of X has a closed compact neighbourhood. 2′. every point...

ACuriousMind

I take it your definition of locally compact is merely "Every point has a compact neighbourhood"?

Slereah

yes

user54412

@Slereah and which one is paracompact? or is the diagram incomplete?

ACuriousMind

Wait a moment...what's the difference between compact and quasi-compact here? Usually, the quasi- means "not necessarily Hausdorff", but if stuff is Hausdorff, locally compact and microcompact are the same

Slereah

23:34

arxiv.org/pdf/math/0609098.pdf

ACuriousMind

Or are the two arrows supposed to tell me that?

Slereah

It is from here

"We call a space quasi-compact if from any open cover one may extract a finite subcover, and compact if moreover it is Hausdorff"

Wait what

That is an odd definition

ACuriousMind

No, that's the usual one

Slereah

Isn't that the definition of compact usually?

ACuriousMind

@Slereah Well...it depends on who you talk to ;)

Slereah

23:37

What if I talked to a sane person

ACuriousMind

For algebraists and general topologists, it's common to say quasi-compact for the cover property and compact for "quasi-compact and Hausdorff"

Slereah

Odd

ACuriousMind

People working with metric spaces and the like won't need this distinction because everything is always Hausdorff

So they'll just define compact to mean the covering property and never mention that others call this only quasi-compact.

Slereah

Well good to know

ACuriousMind

Using manifolds without the Hausdorff axiom is really a rather unusual thing to do

Why are you looking at this?

Slereah

23:40

Book on CTCs

There's a spacetime model where they use non-Hausdorff manifolds to deal with CTCs

ACuriousMind

I get the CTC thing. I don't see why you would allow spacetime to be non-Hausdorff, though.

Slereah

Called branching spacetime

ACuriousMind

Non-Hausdorff spaces just aren't reasonable models for anything that's supposed to be physical spacetime, imo

Slereah

it has been proposed to deal with quantum mechanics

every branching corresponding to a different measurement of the wavefunction

Basically many world with a topology

It hasn't been investigated a lot, though

Basically the spacetime branch at every point around the light cone

0celo7

@ACuriousMind You have no imagination

ACuriousMind

23:43

@Slereah You introduce this entire apparatus just to accomodate a silly interpretation?

0celo7

Give me one good reason why spacetime should be Hausdorff

Slereah

Like thus

I'd like to be thorough :p

ACuriousMind

@0celo7 You can't separate points, that wrecks a lot of the usual goemetrical structure. Stokes' theorem fails. You can't take limits towards a point. Etc.

Slereah

Hell yes you can take limits on points

Sequences can converge to TWO POINTS

That's like twice the limits on points

0celo7

I don't see why Stokes theorem should fail. Partitions of unity are woo.

ACuriousMind

23:46

24

A: Stokes' theorem etc., for non-Hausdorff manifolds

The existence of flows in the direction of a vector field seems to require Hausdorff; indeed, consider the vector field $\frac{\partial}{\partial x}$ on the line-with-two-origins. We have no global existence of a flow for any positive t, even if we make our space compact (that is, considering the...

Slereah

But as said

Some work has been done on non-Hausdorff manifolds in GR

But none in QM

People propose it a lot but nobody actually put forward a model that isn't vague

I guess because that sounds like a hornet's nest of math

ACuriousMind

@Slereah Well, you can say that, but the notion of limit then becomes rather useless if you never know how many of them you get

Slereah

Well as many as you want, depending on the manifold :p

ACuriousMind

@Slereah I'd rather guess because no one really see what the benefit would be.

Slereah

that has never stopped anyone from making a QM interpretation

0celo7

23:51

All that is not forbidden must be allowed.

Slereah

I mean really no QM interpretation will ever increase the GDP

0celo7

The EEP does not mention Hausdorff.

Slereah

EEP?

0celo7

Einstein Equiv Principle.

ACuriousMind

I'm not even fully convinced that you can do GR on a non-Hausdorff manifold. You have to reprove every single theorem from analysis and differential geometry without using Hausdorff-ness, partitions of unity, or whatever.

0celo7

23:52

Bah.

You just don't want to think for yourself.

Slereah

@ACuriousMind There's some work done on non-Hausdorff manifolds

Not a lot though

ACuriousMind

@Slereah By people who are careful or by people who just think it's fancy and deduce some things without laying the fundamentals?

@0celo7 Stop trolling. :P

Slereah

@ACuriousMind a little of both!

0celo7

@ACuriousMind Bah.

The original thinkers get call "cranks" and "trolls."

ACuriousMind

As the MO post shows, it's not even clear that you are allowed to switch between the velocity vector and the derivation description of a vector field.

Slereah

23:54

The big non-hausdorff manifolds used are like

Splitting real line and the complete feather

0celo7

@ACuriousMind That's...an issue.

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