The h Bar

0celo7

12:01 AM

@bolbteppa because you're not a genius

@ChrisWhite Wow, 1000C furnace is powerful

totally destroyed the rhenium

I think I'll melt some copper in it sometime just to see what happens

when dust blows in it explodes in a little flash

user54412

12:40 AM

Etendue

Etendue or étendue (/ˌeɪtɒnˈduː/; French pronunciation: [etɑ̃dy]) is a property of light in an optical system, which characterizes how "spread out" the light is in area and angle. From the source point of view, it is the product of the area of the source and the solid angle that the system's entrance pupil subtends as seen from the source. Equivalently, from the system point of view, the etendue equals the area of the entrance pupil times the solid angle the source subtends as seen from the pupil. These definitions must be applied for infinitesimally small "elements" of area and solid angle, which...

user54412

^ One of the most misunderstood, misquoted, and misapplied wiki articles

knzhou

...what's wrong with it?

user54412

I don't know that there's anything wrong with it (tbh I can't be bothered to read it). What's wrong is half the people who cite it.

knzhou

Well, I've cited it, so maybe I'm part of the problem. :P

How exactly is it misapplied?

user54412

Correctly applied: one cannot use a passive optical system to heat something to hotter than the Sun's surface using only sunlight.

user54412

12:44 AM

Incorrectly applied: saying this holds for the Moon too.

knzhou

oh, right. because the moon's spectrum isn't blackbody, right? it's almost the same color temperature as the sun.

user54412

exactly

user54412

even the Sun has some significant non-blackbody components

user54412

someone should make a passive optical system do something cool with the million degree coronal emission -- that would give people something to think about

NeuroFuzzy

2:10 AM

No one's giving me upvotes on my super single mag netic field line

user218912

you made that?

NeuroFuzzy

yis

user218912

coool

user218912

+1

user218912

lol I forgot that definition of divergence

NeuroFuzzy

2:17 AM

I know right, it all comes streaming back

like war flashbacks from vector calc/electrodynamics 101

Hell is rederiving the frenet seret formulas over and over and over again

0celo7

@NeuroFuzzy why would you do that

NeuroFuzzy

@0celo7 I did it once over the summer indep studying vector calculus, once in the actual vector calculus class, once in an introductory diff geo class, and... I did it in electrodynamics if it's in griffiths

user218912

@NeuroFuzzy oh well I haven't even taken an electrodynamics course and I read tong's notes so I can't relate.

NeuroFuzzy

maybe it isn't. But that's at least three times :(

user218912

I don't care about physics anymore, I'm gonna be like 0celo7.

user218912

2:20 AM

8)

NeuroFuzzy

@3750 :^)

0celo7

@3750 there is still hope for you

unlike that other kid

user218912

is this book even legit? amazon.com/Quantum-Computation-Intelligent-Systems-Automation/…

user218912

I can't find any info on the author or other similar books.

user218912

"This monograph describes a crossroad between quantum field theory, brain science and computational intelligence."

user218912

2:29 AM

dafuq

0celo7

929 pages jesus

> Geometrically, (1.1) defines a smooth autonomous vector-field X(t) in ND
neurodynamical phase-space manifold M, and its (numerical) solution for the
given initial potentials vj (0) defines the autonomous neurodynamical phase-
flow Φ(t) : vj (0) → vj (t) on M.

Gotta say, that sounds ridiculous

user218912

in a bad way?

user218912

like it's bs?

0celo7

I have no idea

user218912

same

user218912

2:37 AM

ahhh... why am i so drawn to neuroscience

0celo7

haha, motor control is a functor?

> Author Affiliations
ID1. Technology Organisation (DSTO), Defence Science &, Edinburgh, 5111, Australia
ID2. School of Electrical &, University of South Australia, Adelaide, 5095, Australia

only 2 citations

user218912

gg

0celo7

It might be crazy enough to be true

but maybe 5 people in the world understand that book

it's even more obscure than nlab stuff, probably

user218912

the field is in its infancy I guess.

user218912

mb in 15 years from now that book will be the main resource to learn from.

user218912

2:43 AM

but it's probably bs.

user218912

anyway I shouldn't be distracted by this stuff

Physics Meta

0

Q: Publications Citing Physics SE?

What publications (papers, books, etc.) have cited questions or answers of Physics StackExchange?

0celo7

haven't seen this one in years

Usher - Yeah! ft. Lil Jon, Ludacris

►

user218912

lol I remember that.

user116211

3:18 AM

@3750 You are not in Physics course?

user218912

I am doing math/physics.

user218912

but focus is on math now.

skill patrol

4:12 AM

you gotta learn to take it easy with the swear words @0celo7

0celo7

@skillpatrol I don't swear often.

vzn

4:54 AM

@yuggib hi my computer crashed this morning, having some troubles, may not be able to attend mtg, plz feel free to start without me, hope it goes smooth, thx again :)

skill patrol

5:20 AM

I know that and you know that @0celo7 but how are strangers suppose to know that?

;)

Anyway, that room is different.

user116211

@vzn C'mon you are the manager ;))

skill patrol

So why would you want to leave flaggable evidence around when you can use "#!@*" @0celo7

Slereah

8:19 AM

So how do you write an electron and an antielectron in the Majorana representation

user116211

8:53 AM

@Slereah, did you get answer to your question at HSM?

Slereah

No

FrancescoS

9:53 AM

Hi guys.What is the physical meaning of the clifford vacuum state in supersymmetry?

ACuriousMind

10:33 AM

@FrancescoS It's the state from which you can get all other states in the supermultiplet by acting with the supercharges on it.

There's no further physical meaning.

FrancescoS

@ACuriousMind Ok, thanks. How it is defined the spin operator? I mean, If I have the vacuum $|\Omega_s>$, how do you know what it is the third spin component of the state $Q_1^\dagger |\Omega_s>$ ?

ACuriousMind

@FrancescoS You have the commutation relations of the supercharges with the ordinary Lorentz group operators - and three of those are the generators of rotations, which are what we call spin.

So you act with the generator of rotation around the z-axis on that state, and use the super-Poincaré commutation relations to evaluate the result

FrancescoS

…in my book there are just commutations relation with the 4-momentum operator.

ACuriousMind

Well, then your book is useless ;P

There are non-trivial commutation relations with both momentum and the Lorentz generators for the supercharges.

FrancescoS

Ahah, it is "Modern Supersymmetry" of John Terning… Probably,these commutations relations are present in the rest of the book…

Balarka Sen

10:45 AM

@ACuriousMind What's the deal with knot theory and physics? I'm curious.

ACuriousMind

@BalarkaSen I don't know many details, but there's a certain three-dimensional gauge theory - Chern-Simons theory - that rather miraculously produces knot invariants as its physical observables - the observables are computed along loops ("Wilson lines") in the 3-fold, and the result is a knot invariant of these loops considered as knots.

Balarka Sen

Interesting.

ACuriousMind

However, the theory is a topological field theory to begin with, so it's perhaps not that miraculous that it produces topological invariants.

It's funny to see the invariants arise from a purely "physical" computation, though

Balarka Sen

So in general these produce knot-invariants inside any 3-manifold?

ACuriousMind

I think so

I'm not sure if it's in general known which ones they produce, though

Or if we even know how to actually compute them

Balarka Sen

10:53 AM

Aha, ok.

@ACuriousMind Can you sketch an idea of how Chern-Simons theory works?

If that's too much work, ignore me.

ACuriousMind

@BalarkaSen That's a combination of being a bit difficult because we'd first have to talk about QFT in general and being difficult because I only have superficial knowledge of CS theory in particular.

Balarka Sen

Ah, fair enough. Nevermind then.

Physics Meta

11:13 AM

0

Q: Should history of physics questions be on topic?

When we last visited the issue of history questions, the dedicated History of Science and Mathematics Stack Exchange was in its early stages. At that time, we decided against closing questions for being historical, but with the implication that it may make sense to revisit that decision someday. ...

discussion scope

Qmechanic

11:32 AM

@EmilioPisanty : Hm. Quite a lukewarm reception on Math meta and Academia meta. I don't understand their hesitation. This is a no-brainer!

0celo7

11:52 AM

Good morning

Slereah

Good morrow

John Doe

Hi Slereah

Given the charge density $\rho$ of a sphere of radius $R$, to get the total charge $Q$ of the sphere you calculate the integral $\int_{\mathcal{V}} \rho d \tau = Q$, why is it not sufficient to just consider $Q = \rho*(\text{volume of sphere}) = \rho (\frac{4}{3}\pi R)$?

0celo7

12:14 PM

Because $\rho$ might be variable.

Slereah

It works for the outside of a sphere.

If $r>R$ you have the electric field just being the Coulomb one

John Doe

12:27 PM

@Slereah Given an electric field $E = kr^3 \hat{r}$ the charge density is then (using Gauss's Law) $$\rho = \epsilon_0(\nabla \cdot E)$$ this gives $\rho = 5k \epsilon_0 r^2$ then $Q = \rho*(\frac{4}{3}\pi R^3) = \frac{20}{3}k \epsilon_0 \pi R^5$ but $\oint E \cdot da = 4 \pi k R^5 = \frac{Q}{\epsilon_0}$ so I get two different answers $\frac{20}{3}k \epsilon_0 \pi R^5$ and $4 \pi \epsilon_0 k R^5$ for $Q$. I know the latter is correct but not sure why I get an incorrect answer for the former?

Emilio Pisanty

12:43 PM

Hey folks

Can anyone make sense of this bounty?

mathoverflow.net/posts/959/revisions

user116211

Worth?

ACuriousMind

@EmilioPisanty It's from 09...could that be before the SE 2.0 upgrade from the times when MO was fully independent? I'd not be surprised if there are some artifacts of the migration into the SE network, like such missing bounty points. That's the only explanation I can think of

Might be a case for mother meta in any case, though

Emilio Pisanty

@ACuriousMind Yeah, that's the only thing I could come up with

0celo7

@ACuriousMind @JohnRennie

skill patrol

what's that suppose to mean?

0celo7

12:58 PM

"Don't make me kill you"

skill patrol

?

John Doe

@ACuriousMind Do you maybe know why in the example I gave you can't simply use $\rho*(\text{volume of sphere})$ for the total charge?

0celo7

@skillpatrol the music in that part of the movie was epic

skill patrol

I see.

ACuriousMind

@JohnDoe @0celo7 already gave the answer: $\rho$ need not be constant.

0celo7

1:02 PM

@ACuriousMind Oh, you do read what I say?

John Doe

Oh I didn't see his answer.

0celo7

thanks

John Doe

@Ocelo7 Is that a sarcastic 'thanks'? I see what you mean, yes in this case it isn't constant, makes sense, thanks.

skill patrol

We need to start using the sarcastic punctuation mark (!) in here :P

Balarka Sen

@0celo7 Bah star wars.

skill patrol

1:12 PM

or ¿

0°

@yuggib o/

Emilio Pisanty

@0celo7 Wait, did I fall asleep at the end of Star Wars? When did Obi-Wan decide to quit and go to the pub instead of going to hunt down Anakin?

FrancescoS

@ACuriousMind If you consider a weyl spinor transforming under a global SU(3) and also under a global shift symmetry, you can write the kinetic term as $\psi^\dagger \sigma^\mu\partial_\mu\psi$ with is invariant up to 4-derivative's term. If I want to gauge the SU(3), how can I build the covariant derivative in order to have a gauge theory with fermion shift symmetry?

0celo7

@EmilioPisanty Nigel did kind of chicken out

@BalarkaSen Seriously?

Is there anything mainstream that you enjoy?

Balarka Sen

1:28 PM

sure.

well, I guess this depends on the definition of mainstream. what kind of things do you have in mind?

0celo7

Things that average joe will do on an average day

Balarka Sen

I have no idea; like what?

0celo7

We established you don't listen to normal music

What kinds of movies do you like

ACuriousMind

@FrancescoS Do you have a reason to believe that should be possible? Clearly, the usual covariant derivative spoils shift (quasi-)symmetry.

0celo7

what the hell is shift symmetry

ACuriousMind

1:35 PM

@0celo7 Exactly what it sounds like: $\psi\mapsto \psi+\epsilon$ for a constant spinor $\epsilon$.

Balarka Sen

@0celo7 most often philosophical garbage. but I also watch semi-normal movies.

name something you like

Marvel

i like those

Marvel isn't a movie

It's a type of movie

1:38 PM

Does it mean movies from Marvel comics or by Marvel studio

Jim

it's more of a type of superhero than a type of movie

Balarka Sen

but my favorite along those lines is nolan's batman, which is a dc movie.

Slereah

Nolan's Batman is pretty boring

Balarka Sen

tastes vary

Slereah

It's the movie that spawned all the gritty boring superhero movies

user116211

1:41 PM

@Slereah You didn't like it o.O

Slereah

It's alright

Overrated, though

user116211

Don't tell me now you liked BvS

Slereah

Didn't see it

Balarka Sen

that'd be hilarious

Jim

nolan's batman sounds like he has laryngitis

Aaron Abraham

1:41 PM

@JohnRennie Thank you yet again! It is ,admittedly, rather frustrating to go through each problem in Irodov's until I can "get them in my sleep", but you've echoed what A LOT of other people have told me.....and yes I'll go "get a life" after I'm done XD

Jim

give me kevin conroy any day

Aaron Abraham

Hiya Ocelo!

Slereah

Conroy is best

Especially in return of the joker

0celo7

@AaronAbraham ...hello

@MAFIA36790 it was shit

user116211

@0celo7 yep ;(

user116211

1:44 PM

I liked this last scene:

user116211

Tribute to Heath Ledger?

0celo7

what's that from

Slereah

"Super" is best superhero movie imo

Balarka Sen

dark knight felt better than dark knight returns

Slereah

1:46 PM

Making the Scarecrow a pretty boy feels wrong

He's not called the scarecrow for nothing

user116211

@0celo7 Dark Knight Rises

Emilio Pisanty

@Danu @dmckee @DavidZ Yet another LaTeX grumble

Balarka Sen

he's a lunatic.

0celo7

@MAFIA36790 I don't remember that

user116211

:(

Emilio Pisanty

1:47 PM

You'd think that $f: A \to B$ and $f \colon A \to B$ would render identically, right?

Instead they give $f: A \to B$ and $f \colon A \to B$ resp.

0celo7

never seen colon used

David Z

@EmilioPisanty naively yes... hmm, I gotta turn on MathJax

I guess it makes some sense, if : is defined as an operator, but sometimes you just want a text-style colon, there could be a command for it. Still the naming is confusing.

Emilio Pisanty

@0celo7 Well, turns out it's the correct choice there

@DavidZ No, I get why it does it

The colon can be a binary operator or this bizarrely spaced one, and the explicit : can only take one meaning

But still

0celo7

@EmilioPisanty are you telling me f:X\to Y is wrong

Emilio Pisanty

@0celo7 Yes

0celo7

1:49 PM

Why?

Emilio Pisanty

Spacing is wrong

0celo7

No it's not

what does "wrong" even mean here

Emilio Pisanty

@0celo7 Go ask on tex.se =P

0celo7

Well screw them

Slereah

Or on Philosophy SE

Balarka Sen

1:50 PM

@0celo7 don't be tedious

0celo7

0.1% of the TeX community does not decide what is right and wrong

Slereah

Only god will judge my Tex files

0celo7

@BalarkaSen I don't think that word means what you think it does

@EmilioPisanty What is so horrible about $f:X\to Y$ according to tex SE

I like the space there

it looks weird without the space

Balarka Sen

it means tiresome, which is precisely what i meant.

0celo7

oh you find everything tiresome

stop being tiresome

ACuriousMind

1:52 PM

It's binary operator spacing although the : is not an operator there. I can understand why one would perceive it as wong.

0celo7

maybe walk a bit and you won't be tired out by every conversation

David Z

It probably makes more sense to put it in the same class as relations like = and ~, or such is my guess - and those also have some spacing around them

0celo7

@ACuriousMind o.O

How can anyone find $f\colon X\to Y$ more aesthetically pleasing

Balarka Sen

I'll read some Dostoyevsky.

or watch Tarkovsky, dunno.

0celo7

@ACuriousMind Do you know why the Euler char is invariant under orientation-reversing diffs?

Balarka Sen

1:56 PM

@0celo7 I told you that though.

0celo7

@BalarkaSen Yes, and i agree

maybe ACM has a neat way of seeing it, you never know

ACuriousMind

@0celo7 The fact that you are asking that question tells me you're probably using some ugly smooth definition of it. Can't help you with that

0celo7

who is Betti, anyway

Balarka Sen

he'll just use the homological defn of Euler char - Euler char is invariant under homeomorphisms in particular.

0celo7

you never hear about him anyway

Balarka Sen

1:58 PM

@0celo7 Enrico Betti, I think

0celo7

@ACuriousMind the self-intersection number of the diagonal of the manifold

ACuriousMind

Oh man.

Yeah, can't help you with that

Balarka Sen

it's essentially the thing in Lefschetz fixed point theorem

0celo7

yeah?

what do you mean

I'm sure you have some homological definition of the Lefschetz number too

Balarka Sen

yep

0celo7

2:01 PM

sigh...what is it

Balarka Sen

take some map $f : M \to M$, then it's just alternating sum of traces of $H_i(f)$, iirc.

0celo7

fuck me

what is $H_i(f)$

Balarka Sen

$H_i(f)$ means the map $H_i(M) \to H_i(M)$ induced on rational homology

0celo7

rational homology?

Balarka Sen

homology with rational coefficients

0celo7

2:02 PM

good lord

Balarka Sen

:P

0celo7

how is that less ugly than the smooth definition

Balarka Sen

who said it is?

0celo7

this is why I stick to geometry

Balarka Sen

it just applies to way more spaces than just manifolds, is the point

$M$ can be any simplicial complex here

0celo7

2:03 PM

I only care about manifolds tho

checking hatcher

hmm, I know about induced maps on cohomology

is this $H_i(f)$ similar

I really need to read Lee

Balarka Sen

yeah, you can literally take them to be the same

0celo7

Will do that in a week

@BalarkaSen ah, ok then

Balarka Sen

it doesn't matter for orientable closed compact manifolds ('cause Poincare duality)

Emilio Pisanty

@0celo7 Up to you. But if you're in text mode and TeX needs to space things out to keep a paragraph justified, then the space between the f and the : can stretch loads.

bolbteppa

It's amazing you guys are voting to close questions you can't even answer

0celo7

2:09 PM

@bolbteppa personally, I VTC based on whether the person has a good username or not

bolbteppa

Authoritarian mindset ruins everything, too much free time on ones hands

@ACuriousMind Absolutely stunning you posted a comment asking why one should even expect a qualitative interpretation of a derivation of something, I mean why even do physics if you don't want to understand what you're doing

0celo7

@EmilioPisanty Interesting.

Emilio Pisanty

@0celo7 Anyways, it's an aesthetic choice, so in the end it's not worth arguing.

bolbteppa

I have made this comment to most of you that you don't think enough about what you do, now you're all voting to close a fascinating question, there is a reason good people left this site

Emilio Pisanty

It's just interesting that there's an actual \colon command that's distinct from the simple :.

0celo7

2:11 PM

@EmilioPisanty According to Tex SE there is an objective, rational, and correct choice for everything related to TeX

ACuriousMind

I think this is the first time I have been called "absolutely stunning" :)

Emilio Pisanty

@0celo7 I don't really have time to discuss the vagaries of objective truth w.r.t. tex.

Balarka Sen

lol

0celo7

@EmilioPisanty That was a joke

(somewhat)

bolbteppa

I have even tested asking experts in real life stuff that's been shunned on this site just for a mental sanity check from an expert after being appalled and at least serious people are at odds with that kind of thinking

Emilio Pisanty

2:12 PM

@0celo7 That was an indication that I'm out of this conversation.

0celo7

Why are people so weird lately?

ACuriousMind

@0celo7 People have been weird since the dawn of humankind :P

Balarka Sen

@0celo7 see what happens when you time travel?

0celo7

@ACuriousMind I just feel like people have been ending conversations weirdly lately

Like @BalarkaSen saying "I'll stop interacting now"

No human says that!

what is going on

Balarka Sen

No, that was Mike. But I said something like that once too, yes.

0celo7

2:14 PM

Well, he's a weird one too

ACuriousMind

@0celo7 Well...the hbar has no "humans only" policy as far as I know... ;)

bolbteppa

@ACuriousMind Do you appreciate how it's the perspective of an amateur not to try to understand things you've blindly derived, something that good books like Zee or Landau or Feynman provide?

0celo7

@ACuriousMind But at least your programming makes you seem somewhat human

@BalarkaSen doesn't like STAR WARS

@bolbteppa you also insist that without memorizing pages of calculations to recall them while at the beach, you do not understand the theory

ACuriousMind

@bolbteppa I appreciate motivation, but I feel it is not an objectively answerable question to ask for motivation since motivation necessarily is not a derivation in itself.

bolbteppa

@0celo7 I said you should understand the calculation well enough so that it's not memorization, not just tell yourself you understand the jist and could do it if pressed

0celo7

2:19 PM

There is no understanding to be gained from symbol pushing.

Especially the stuff you're talking about.

bolbteppa

@ACuriousMind That's why I asked "How would you interpret" so that hopefully a bunch of experts could provide differing motivations assuming they had them, you know, like you find on MathOverflow where experts will give 5 posts with 5 different illuminating answers. I like how your approach excludes that, should be worrying.

You look at, say, Zee's GR book, when deriving flat cosmology, first he wings it, then he justifies it, what any good physicist does, amazing that is shunned on this site now

Balarka Sen

In my opinion, if you do not like this site, don't be here. That's what I would do, at least.

0celo7

@bolbteppa I do have to agree with you on this point.

bolbteppa

@BalarkaSen The hope is someone not of the authoritarian mindset who actually understands the depth of a simple question will answer, but some people just want to vote to close questions they can't even understand let alone answer

0celo7

Waiting for Danu to chime in...

ACuriousMind

2:28 PM

@bolbteppa I do not exclude questions with more than one possible answer - many objectively answerable questions can be answered in more than one way. But for each of those ways, you can tell whether it is correct or not, while whether a motivation is "correct" or just handwaving nonsense comes down to as much personal opinion as expertise.

bolbteppa

@ACuriousMind All these awesome questions mathoverflow.net/q/68339/38721 mathoverflow.net/q/383/38721 mathoverflow.net/q/43681/38721 mathoverflow.net/q/6172/38721 mathoverflow.net/q/364/38721 mathoverflow.net/q/10574/38721 mathoverflow.net/q/8204/38721 just thrown in the bin from your perspective, again should be extremely worrying

Why is it that fields medalists aren't voting those down, indeed answer them in the most illuminating fashion possible, hmm...

0celo7

MO is not PSE?

ACuriousMind

@bolbteppa Mathoverflow has a very different culture, they also tend to make too broad or opinion-based questions community wiki instead of closing them because they trust their userbase to not abuse that leniency.

bolbteppa

I guess this is a question of what stage you're at in Tao's mathematical education schematic terrytao.wordpress.com/career-advice/… definitely worth reading apparently

You mean to tell me the culture on here is to exclude questions that experts can answer, but students find too frustrating?

ACuriousMind

@bolbteppa That is not at all what I said

bolbteppa

2:38 PM

It is exactly what you said

0celo7

@ACuriousMind The analogy between Lefschetz fixed points and particle physics is interesting, what do you think about it

bolbteppa

Using Tao's schematic: 1: 'The “pre-rigorous” stage', 2: 'The “rigorous” stage', 3: 'The “post-rigorous” stage', in which one has grown comfortable with all the rigorous foundations of one’s chosen field, and is now ready to revisit and refine one’s pre-rigorous intuition on the subject, but this time with the intuition solidly buttressed by rigorous theory.
You are literally arguing this site is for stage 2 people, not stage 3 people, why pretend that's not what you're saying?

ACuriousMind

@bolbteppa If you think that is what I said then talking to you has no point since you seem to hear what you want to hear anyway.

bolbteppa

Ok better to just run away

0celo7

@ACuriousMind To be honest I'm having a hard time understanding what you're saying too.

I know you're not saying what @bolbteppa thinks you're saying, but I don't see your point either.

ACuriousMind

2:42 PM

@0celo7 I said MO has a different culture. Particularly because they trust their userbase not to abuse that leniency. The implication being that we have a sizable fraction of users who would abuse if opinion-based questions are not stringently closed.

0celo7

@ACuriousMind What do you mean by that?

I can read.

Balarka Sen

That a lot of traffic in PSE comes from people who do ask naive questions based on their naive understanding of physics, probably

Think of all the laymen who thinks they "know" physics from reading pop science books or something

bolbteppa

@0celo7 He said the culture here is very different, then invents a reason about trust as if that was even enough if it were true, the implication being this is a site for children and that is for adults, even though all the rules are supposed to keep this site to a higher standard, it's ridiculous

0celo7

@BalarkaSen We do get a lot of cranks.

Balarka Sen

But this is just my interpretation.

@0celo7 That's my point. Not sure if ACM's too.

ACuriousMind

2:45 PM

@0celo7 We get a lot of confused questions asking about what something "really" means or how to "really" understand something, or how to overextend this or that faulty analogy. I cannot justify leaving some of these questions open and others not

bolbteppa

MO gets even more, they just moderate with an authoritarian fist that does not exclude actual learning

0celo7

Er, "otherly educated non-physicist physics aficionados"

Would not want to upset them

Balarka Sen

@bolbteppa MO gets more crank traffic? I do not think so. Do you have any proof of that?

0celo7

@ACuriousMind You don't like drawing arbitrary categories?

bolbteppa

In other words - stage 3 people moderating on there, stage 2 on here, maybe it's time to evaluate if that's the site people want, where tons of good users had to quit over authoritarianism on sites like these

0celo7

2:46 PM

@bolbteppa You're starting to sound like John

bolbteppa

@0celo7 How so?

ACuriousMind

@0celo7 I like categories (arbitrary or not) that are clearly delineated. "Interesting question about how to really understand something" and "Confused question about how to really understand something" are rather the opposite

bolbteppa

@ACuriousMind That's exactly my point, I gave about 6 posts on MO where they were the opposite of what you like, again which should be troubling

@BalarkaSen they delete any question not near research level, but they magically have all these questions asking for intuition, even about things like differential forms, why is that? Answer with reference to Tao's 3 stages

Balarka Sen

Questions not near research level is not the same as crank questions.

bolbteppa

It includes them

Balarka Sen

2:50 PM

Yes, being a subset is not the same as being equal as sets.

bolbteppa

Exactly

Balarka Sen

Crank questions is a very small subset of non-research questions.

0celo7

@BalarkaSen You don't find this conversation tiring?

Balarka Sen

I'm not really participating in this discussion tho

ACuriousMind

@bolbteppa I am not troubled by MO being somewhat less stringent in their moderation. They can afford that because they have a more cohesive community and not as many people trying to use the site for their own ends. In particular, they lack our eternal meta discussions about the on-topicness of homework/opinion-based/non-mainstream questions.

David Z

2:52 PM

btw our chat session is in an hour, right?

0celo7

@BalarkaSen Pages 126 and 127 are highly interesting, imo

Balarka Sen

@DavidZ It started an hour ago.

bolbteppa

My point was basically to tell you all to raise your game and enter stage 3 in terms of questions on this site to make it better, it's just stunning to see downvotes on all these good questions, you can ignore me and treat me like John if you like and swim in stage 2, at least you know what you're doing

Balarka Sen

Today's topic: fight

0celo7

::swims merrily::

ACuriousMind

2:53 PM

Our current policies are already heavily contested for relying too much on individual judgement, making one them rely even more on the individual judgement of hte close voters is bound to invite disaster.

Balarka Sen

Lefschetz stuff, @0celo7?

0celo7

@BalarkaSen yes, the particle physics analogy is very interesting

John Rennie

@bolbteppa The PSE is a community, and like any community it has members with differing perspectives. Some members like to give rigorous answers, that's ACM, some like giving intuitive answers, that's me, and some don't like giving any answers.

ACuriousMind

@DavidZ Yes, it starts in an hour

0celo7

if you have a map with a fixed point, then you can homotope the fixed point region to get a bunch of Lefschetz fixed points

David Z

2:54 PM

cool, just checking ;-)

bolbteppa

@ACuriousMind Dude you are just inventing reasons that make no sense, MO are more stringent than on here, way more - they are a research level site but they allow people to ask questions about non-research level material in intuitive ways because that's part of

"The “post-rigorous” stage, in which one has grown comfortable with all the rigorous foundations of one’s chosen field, and is now ready to revisit and refine one’s pre-rigorous intuition on the subject, but this time with the intuition solidly buttressed by rigorous theory." My point was your approach is at odds with the thinking of the post-rigorous stage and it should be worrying

0celo7

and the sum of resulting Lefschetz numbers is independent of the homotopy

Balarka Sen

@0celo7 Lefschetz fixed pt of a map $f : X \to X$ being a fixed point where the diagonal is transverse to the graph of $f$ in $X \times X$, yep?

0celo7

yes

Balarka Sen

Right, then transversality theorem says that.

What's the analogy with particle physics?

bolbteppa

2:57 PM

@0celo7 there are videos on the Lefschetz number and other stuff from Guillemin here youtube.com/playlist?list=PLTBqohhFNBE_09L0i-lf3fYXF5woAbrzJ in the last lecture he discusses the table of contents of all lectures to find out the syllabus

0celo7

homotopy creating the lefschetz fixed points is turning compound particle into elementary ones

ACuriousMind

@bolbteppa I really don't see what Tao's three stages of a mathematician have to do with deciding what questions are on-topic on physics.SE or not.

0celo7

and the sum of leftschetz numbers is the electrical charge

I thought @ACuriousMind might find it interesting but apparently not

dmckee

@EmilioPisanty MathJax isn't even consistent about spacing. Try rendering isotopes as $^A_Z\mathrm{Sy}$ . Sometimes the sub/super-scripts will be tight to the Element and sometimes floating a thin-space or more back. Argh!

0celo7

$^A_Z\mathrm{Sy}$

ACuriousMind

2:59 PM

Not every good question is on-topic here and not every bad question is off-topic. Being off-topic is not, in itself, a judgement of the value of the question, just a statement that the close voters believe such a question is not a good fit for this site.

0celo7

what the heck is Sy

ACuriousMind

@0celo7 what?

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