The h Bar

3:16 PM

What's the difference between speed and average speed?

@ffahim Suppose you travel a distance $\delta x$ ina time $\delta t$. Then your average speed is $\delta x/\delta t$. OK so far?

0celo7

proof?

fucking right hand rule

my hand cannot contort for this magnetic field

Jim

@0celo7 use left-hand rule then

0celo7

well the real issue is I don't know the direction of the electron velocity

Jim

-1

A: What's the point of Pauli's Exclusion Principle if time and space are continuous?

if they want people can get really mad for what i'm about to say so i will SHOUT IT LOGIC AND MATH/MATH FRAMEWORKS ARE JUST CONCEPTUAL AND SIMBOLIC LIMITS TO OUR MIND!! THE UNEXPLAINED AND THE CEASE OF OXTILITIES AGAINST UNCOMMON AND "ABNORMAL THINGS" IS THE ONLY WAY FOR EXISTENTIAL FREEDOM!! A ...

7 billion people on Earth and all of them think they're the first to make trivial leaps in logic

0celo7

3:30 PM

> s much as we applaud your devotion to living life in a way that you deem logical and intelligently motivated as well as your clearly copious amounts of confidence,

jesus

> Call me close minded, but I believe that there is a time and place for everything and this is not the place for your post.

> If you are indeed as learned a researcher as you claim, you should be a valuable asset when it comes to presenting the proper physics of many issues

@Jim Too savage :(

Jim

@0celo7 I thought I was being very diplomatic

0celo7

who is Jiminion, anyway?

Jim

a different user. I have no insights into (his?) identity beyond that

John Rennie

@Jim Any form of feeding encourages trolls, even feeding them lemons. There are only two appropriate responses, one is to completely ignore them and the other involves a red hot knitting needle.

Jim

@JohnRennie You, sir are frightening

0celo7

3:36 PM

John's obsession with testicle torture is...

Jim

also, I usually try to respond in a way that is directly opposite of the reaction that a troll is hoping to solicit. Acting calm, polite, welcoming, and argument deflating is contrary to the insulting and angry that was clearly intended. It usually irks people when they try to piss you off and you just never get pissed off. So answering all with diplomacy means a serious user is welcomed and appreciated and a troll ends up angering themselves. Everyone gets what they deserve

John Rennie

(a) as a room owner I can see deleted posts
(b) I'm now a worried man :-)

0celo7

@JohnRennie Listen to Denzel Curry's Imperial

It's so good

John Rennie

@0celo7 listening now ...

0celo7

@JohnRennie Don't worry, you're too old for me.

Gook is the best track imo

If you listen to one song, then that one.

how do I get this in scientific notation @JohnRennie ?

John Rennie

3:48 PM

Select the cells, right click and choose format cells

Then choose scientific from the list of number formats.

0celo7

nice

thanks

ACuriousMind

Do we really need unphysical?

user116211

Just one post.

user116211

The tag is that post specific; don't think it will be required in future.

user116211

@MetaEd?

user116211

3:58 PM

Again flagging?

ACuriousMind

This chat needs to stop jumping to conclusions every time a foreign mod enters the room :P

I'll allow you to freak out when a flock of them appears.

MetaEd

@MAFIA36790 Howdy. Nice morning, ain't it :-)

0celo7

You'll allow us?

What the shit?

Mod abuse!

@MetaEd pls ban ACM

ACuriousMind

Hmmm, what is the proper name for an aggregation of moderators?

user116211

@0celo7 Mods are actually Siths.

ACuriousMind

4:01 PM

English tends to have weird names for that for animals, right?

MetaEd

@ACuriousMind Murder's already taken, so I dunno.

0celo7

WORD

ACuriousMind

@MetaEd A...suspension of moderators?

user116211

MS word sucks.

user116211

Windows is evil.

John Rennie

4:03 PM

An inquisition of moderators?

MetaEd

6

Q: What is the collective noun for a group of moderators?

Let us imagine, for a moment, a system wherein there are numerous individual rooms for socializing and chatting. Rather than being handled on a room-based basis, however, moderation is somehow distributed over the community such that every user with moderator abilities is somehow expected to be ...

moderators

user116211

@MetaEd WoW! Such posts exist!!

John Rennie

An auto-da-fé of moderatos :-)

MetaEd

@MAFIA36790 To a first approximation, every question is a duplicate question.

Best I've seen so far are patrol and posse.

Mike Miller

I was told this was the math chat

MetaEd

4:06 PM

saddles up

$Mathematics$ Mathematics

Associated with Math.SE; for both general discussion & math qu...

9

ACuriousMind

@JohnRennie I like the sound of that

Mike Miller

Unfortunately I was told otherwise. I've got no choice but to talk about 3-manifolds here.

ACuriousMind

I'd prefer you talk about some 7-manifolds ;)

But I'll also take 3-folds

Mike Miller

Oh, are you into g2-manifolds now?

ACuriousMind

@MikeMiller Yes, their singular limits are shaping up to be my masters' thesis' topic

Mike Miller

4:11 PM

Hey, very cool. G2 stuff is pretty lively right now since Donaldson pushed his program for gauge theoretic invariants a bit.

Especially in Europe, I think. Is $T^7/\pm 1$ one of your singular limits?

ACuriousMind

@MikeMiller Yes, but a boring one ;)

Mike Miller

It's the only one I know.

ACuriousMind

Point singularities seem to have been well-understood by others, the interesting physics seem to go down when the singularities have codimension three or four

Mike Miller

Are these supposed to be like associative or coassociative submanifolds as the singular set?

ACuriousMind

@MikeMiller Yes, exactly!

Mike Miller

4:14 PM

Point singularities are reasonably easy, given that one has an ALE Calabi conjecture type thing. Joyce proved something like that to construct the first compact G2 manifolds.

ACuriousMind

Having the singular set as such a calibrated submanifold, one can view "producing" the singular limit simply as a perturbation in the $G_2$-structure 3-form.

Mike Miller

@ACuriousMind If one tries to make Gromov-Witten type invariants for G2-manifolds by counting associative (or coassociative) submanifolds, you don't actually get an invariant - such submanifolds can 'bubble off'. Is that visible somehow in your singular limits? That these are the walls that crossing which changes the count?

walpuski's work is relevant here

ACuriousMind

@MikeMiller The singular limit is essentially "sending the volume of the (co)associvative submanifold to zero", and one can physically argue that for some of the singular limits the third Betti number must change when you "pass over it".

But I just started reading into this subject at some level of detail, so I can't say much definitive yet

Mike Miller

But can you then resolve that singularity in a different direction in which the coassociative submanifold is just gone after that?

I think that's basically what I'm asking.

ACuriousMind

@MikeMiller Yes - there are examples where on one side of the limit you have an associative 3-cycle and on the other side you're left with two 2-cycles instead you can't calibrate.

Mike Miller

4:21 PM

Nice.

Well, it sounds like you're doing really interesting stuff. I'd like to learn a lot more about what people are doing on the G2 side of things at some point. But it's not easy to jump right into it.

We'll have some G2 speakers (well, at least one) at UCLA's gauge theory conference.

ACuriousMind

The one you linked here a few days ago?

Mike Miller

I think weeks, but yes.

Emilio Pisanty

↑ dafuq?

man, youtube does some weird shit sometimes

oh, wow, and the monkey is an svg encoded into the html

weeeeeeeird

ffahim

@JohnRennie yes:-)

John Rennie

@ffahim OK. That distance $\delta x$ can be very large e.g. you might average the speed over 100km, or very small e.g. you might average the speed over 1 micron.

But whatever the size of $\delta x$ it's always an average.

To get the speed at a point we have to reduce $\delta x$, and therefore $\delta t$, all the way to zero.

Obviously if $\delta x = \delta t = 0$ then we get a speed of $v = 0/0$ and that is undefined. So what we do is take the limiting value of $\delta x/\delta t$ as both tend to zero.

And we write this as $v = dx/dt$, where we've changed $\delta$ to $d$ to show we've taken the limit.

This is known as the differential of $x$ with respect to $t$.

Jim

4:43 PM

@ACuriousMind a modicum of moderators?

a parliament of moderators

John Rennie

A superfluity of moderators

Jim

a murder of moderators

a network of moderators

user116211

brotherhood of moderators

Jim

forum of moderators

John Rennie

@Jim parliament and murder are both taken

Jim

4:46 PM

@JohnRennie we can't use descriptors twice?

user116211

no.

John Rennie

an immoderate number of moderators

Secret

@vzn cropped form wikipedia in the interpretation of quantum page

Jim

then I go back to modicum of moderators

user116211

Mods are basically Sith Lords.

John Rennie

4:48 PM

Voldemod

Emilio Pisanty

@MAFIA36790 also an important collection of people without a suitable collective noun

I hope

but then knowing star wars fans...

Jim

@EmilioPisanty A pair of sith lords. "Always 2 there are. No more, no less"

user116211

@Jim There has been exception.

Emilio Pisanty

@Jim ah, indeed. Point taken.

user116211

Have to check SFF.

Emilio Pisanty

4:49 PM

@MAFIA36790 "what do you call three Sith lords?" "a fight"

user116211

3

Q: How many Sith masters obeyed the "Rule of Two"?

We all know that the "Rule of Two" was oft violated and in an audiobook I'm listening to it seems that Even Darth Plagueis' master didn't obey this It says "precious few" Sith Lords did I am wondering if someone who has read more of the books may be able to actually count how many Sith Lords...

star-wars star-wars-legends sith

user116211

3

A: More than two Sith in the prequel trilogy despite the Rule of Two?

In this specific case, they weren't. At the time that Darth Maul was a Sith Apprentice, Count Dooku was still a Jedi, though he was already becoming disillusioned by their order. It was only years later, after Darth Maul was thought dead1 at the end of Episode I, that Palpatine approached Dooku ...

user116211

Too many questions related to energy?

user116211

0

Q: What is the rigorous quantitative definition of the concept of "Energy"?

First of all I acknowledge you that I posted this Question on many other forums and Q&A Websites. So don't be surprised if you found my question somewhere else. I bet when the experts saw the title, many of them said: "...again another dumb guy seeking answers to useless questions...". But belie...

classical-mechanics energy definition

user116211

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Mathematics

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$Mathematics$ Mathematics