The h Bar

rob

16:00

(point of clarification: I don't think the existence of a mods-only chatroom is, or should be, a secret.)

DanielSank

I just got a bacon hat on Worldbuilding.

@rob It's not a secret. The one thing that made me consider running for mod was access to that chatroom.

(That's a joke)

(If it's the future and I'm running for mod, and you're reading this, know that I take moderation on this site with a solemn attitude. No humor whatsoever. Really.)

rob

@DanielSank The temptation for me to abuse my privileges and edit the word "butts" onto the end of this message is … very strong.

DanielSank

-_-

heather

@rob nope, it's not, I was referring to you saying "where we all discuss our ignorance"

@rob lol

DanielSank

@Rob I'm afraid I can't take you seriously, as you are an abstract green pattern and a burning log. This is too ridiculous and abstract for me.

heather

16:04

though, to get a bit serious @rob - how do you handle it when, as moderator, the site you moderate goes a different direction from what you'd like but you'd still like to help it and perhaps steer it in the right direction?

rob

In fact, now that I think about it, providing a channel for mods to communicate with each other privately and in real time is probably 95% of the reason that chat.SE exists.

heather

@rob, no, we all know its so we can make sarcastic jokes in real time

DanielSank

@heather I'm not sure mods are supposed to steer based on their opinions. I think they're supposed to steer to making sure everyone adheres to community defined rules.

heather

@DanielSank but it seems the rules are changing under my feet. I thought they had been defined, but they now seem to be changing.

DanielSank

I think of the SE sites like the US government.

rob

16:05

@heather That's a good question, which hasn't really arisen in the couple of months that I've been on the mod team.

DanielSank

You need checks and balances.

Mods are supposed to be the executive branch, I think.

No no. That's wrong.

Mods are a mix of executive and courts.

But, importantly, all users have executive powers granted in stages as their rep increases.

And all users have some court abilities in the same way.

Mods just have more of both.

The meta is the legislature, I think.

@heather I think if you find the rules changing there are two things to do:

1) Check that the rules actually are well established. Are they actually written somewhere? If so, enforce them as appropriate in your capacity as mod.

2) If you think the rules should change, do what any user should do and take it to the meta.

@rob right?

heather

i think currently there's not enough active mods or high-rep users to handle situations, and so users keep asking poor questions faster than I can close them or edit them or what have you (for the record, the rules are written, and i don't think they should change).

i don't think kenshin is really on the site enough.

the only user really answering questions is sammy gerbil

DanielSank

Get more mods?

rob

@DanielSank This is good advice, I think.

DanielSank

Hmmm, perhaps I'll make an account.

heather

16:09

@DanielSank for which i need to talk to kenshin, and that's where things get even messier

because, well, i don't think kenshin and i work very well as a team at all (and some of this is my fault)

and ever since a moderator acted against general rules and we removed said moderator from the team and that said moderator started spamming the site...well, it all went downhill.

DanielSank

Teamwork can be hard.

@heather eeesh. Block their IP address?

heather

the whole situation just makes me wince and look away, to be honest.

DanielSank

Makes you appreciate the SE team, eh?

Running a (popular) website is not easy.

heather

@DanielSank did so, but not until they created multiple accounts and kenshin and i had to go through some...unsavory spam, and kenshin had to code some spam blocking tools.

@DanielSank which is scary because our site isn't even really popular yet.

correction: it isn't.

DanielSank

Yeah, so you guys are doing the work of a webmaster while trying to do your "day jobs" too. Fun.

Um, heather... not sure how to say this... but your space shuttle has breakfast stuck to it.

heather

16:12

yup.

@DanielSank yeah...that's on purpose

the astronauts got hungry

the other problem with the site is, well, there's no review queues. The only method for users to get moderator attention is flagging.

and so even having high-rep users wouldn't help.

John Rennie

I think there's something seriously creepy about the bacon hat ...

It's the fried eggs for eyes.

heather

yeah, true

i think i'm going to change it

DanielSank

@JohnRennie I like it.

Looks good on you.

heather

switched to waffle hat

DanielSank

WAFFLES?!

heather

16:16

waffles

DanielSank

how?!?!?

heather

for having 11 hats

=D

DanielSank

zomg

heather

"must...get...more...hats"

waffles!!!

DanielSank

I have nine.

Someone gimme two hats!

heather

16:18

post ten comments and get someone to upvote them

AccidentalFourierTransform

"someone"

heather

right

okay, thoughts on this question:

1

Q: Can electrons be non-fundamental in higher dimensions?

I am sorry if this is a stupid question; I do not know much about particle physics or string theory. I'm just a beginner who started studying these topics just a few months back. I was wondering, is it necessary that all elementary particles remain elementary in higher dimensions too, or can't th...

it seems a poor question

but i don't know if it's too broad

i did try to edit it for more clarity

AccidentalFourierTransform

idk, the question doesn't make much sense to me :-/

John Rennie

@DanielSank It looks sufficiently surreal to be entertaining :-)

DanielSank

@heather I think I have that one. Is that the blue feet one?

heather

16:22

@DanielSank yep

@AccidentalFourierTransform well basically it's asking whether or not which dimension a particle is in changes whether or not the particle can be decomposed into smaller particles.

AccidentalFourierTransform

fun fact: there is a certain post from one month ago that, if gets upvoted, will get me a hat

heather

@AccidentalFourierTransform, what's the post?

John Rennie

@AccidentalFourierTransform go on then, post the link :-)

heather

oh, yay, waffle hat is showing up! =D

AccidentalFourierTransform

well, its not a post of mine

its someone's else

heather

16:23

what might the post be...

AccidentalFourierTransform

that makes it fun ;-)

or someone else's?

grammer is hard

John Rennie

POST THE LINK!
I'm curious now

heather

someone else's, i believe

DanielSank

@heather there's still breakfast on your shuttle.

Hi @SurazBasnet.

heather

@DanielSank, yay!

breakfast + rockets = many good things

AccidentalFourierTransform

16:26

@JohnRennie nope lol it would be unethical

heather

did you edit it?

::tries to find in profile::

John Rennie

AFT has done lots of edits so that's a bit of a dead end ...

heather

yup i know

why do you have so many actions @AccidentalFourierTransform!?!

i give up

no hat for you

AccidentalFourierTransform

haha

heather

=P

DanielSank

16:29

Mads Mikkelsen serves himself vodka during Rogue One interview

John Rennie

@heather BTW I think that question you posted could be usefully answered, though the OP is so badly confused that I'm not sure what they will get out of it.

I was toying with writing an answer when the question was closed.

heather

see that's what i mean, i think it's a legitimate question.

i'm voting to reopen.

i think it's a worthwhile question.

John Rennie

Here's a question for the panel:

DanielSank

Goodness @AccidentalFourierTransform has a lot of hats.

John Rennie

If light falls into a gravitational well it is blue shifted so its momentum changes. Does that mean that the planet/star/black hole has to accelerate in the direction of the photon to conserve momentum?

heather

16:32

you know, i think i just saw a question related to that...

AccidentalFourierTransform

@DanielSank meh, he doesn't even sip it

poser

John Rennie

i.e. does the blue shift imply a gravitational; attraction between the light and object?

heather

0

Q: Impossible dilemma about Shapiro delay and momentum conservation

I'm having an impossible dilemma, with no right answer. Starting with the Shapiro delay from the General Relativity theory, I can't understand how the conservation of momentum applies to it. The problem is like this: If I launch a photon from point $A$ to point $B$, the photon goes with light ...

general-relativity photons conservation-laws

DanielSank

@AccidentalFourierTransform hahahahahaha

AccidentalFourierTransform

@DanielSank well, Im literally "Just Here for the Hat(s)"

John Rennie

16:33

@heather that's what made me mention it. I've just posted an answer, but not discussed the question I just mentioned above.

heather

ah, i see.

-1

Q: What sources can you point to me?

I want to start watching and reading about science as a hobby in my free time to gain more knowledge of the universe. I am taking my first steps and dont know what I should read/watch and where. Youtube would be a nice place. I am 21 and already familiar with science so I can skip the basic thing...

homework-and-exercises

^vtc as duplicate of book recommendations?

John Rennie

@DanielSank doesn't everyone have 18 hats? :-)

heather

::sighs:: sadly, no

i only have 14

John Rennie

16:49

@heather one of the few occasions that having a gold badge in the homework tag is useful :-)

Sir Cumference

@Kaumudi.H Nope...

One hour or so. And it sucks that it's always overcast here, makes waking up even harder

heather

@JohnRennie nice

Secret

math chat is so busy, I cannot even ask a question

AccidentalFourierTransform

let us all go there and start talking about... idk, feet with six toes?

come join me and lets get disruptive :D

man Im bored

heather

17:06

@AccidentalFourierTransform, why are you so bored?

AccidentalFourierTransform

bc I have a lot to do

heather

ah, that makes sense.

you can't do anything fun because that'd make you feel bad about the stuff you have to do and then you don't want to do the stuff you have to do so you have absolutely nothing to do.

what do you need to work on?

AccidentalFourierTransform

@heather I see you've been there too >_<

homework and stuff :-(

heather

I'm so sorry

AccidentalFourierTransform

1

Q: Can electrons be non-fundamental in higher dimensions?

I am sorry if this is a stupid question; I do not know much about particle physics or string theory. I'm just a beginner who started studying these topics just a few months back. I was wondering, is it necessary that all elementary particles remain elementary in higher dimensions too, can't ther...

particle-physics string-theory electrons dimensions

^ its open

heather

17:11

=)

ooh, i got a new hat..."no longer grinchy"

for voting to reopen

AccidentalFourierTransform

meh, I already have that one lol

heather

i'm just very grinchy, apparently

=P

heather

17:41

-4

Q: Am I right about this theory - Time Does Not Exist?

There is no such thing as time. Time, the dimension doesn’t exist. It’s all a matter of perception. An activity performed by someone in Delhi is indirectly connected with another person doing another activity sitting at a casino in Las Vegas. Sounds crazy? It is. Suppose a person got seriously i...

cosmology time big-bang space

^non-mainstream, most certainly

s.harp

18:01

Dumb question: The supertrace does not need to return an even element right?

AccidentalFourierTransform

@s.harp I don't think so

after all, $\text{tr}=\log\det\exp$

and the det over fermion fields need not be even

right?

or does it?

s.harp

I don't know so much about physics, so you have lost me with fermion fields

AccidentalFourierTransform

=odd variables

s.harp

I'm thinking about a morphisms $A^{p\mid q}\to A^{p\mid q}$ of where $A$ is a super-algebar, where the super trace can be defined

AccidentalFourierTransform

something is fermionic iff it is odd

s.harp

18:07

in the book by deligne they write it is an element of $A_0$ where $A$ is the super-algebra, I suspect it is a type

AccidentalFourierTransform

idk, sorry

s.harp

thanks^ if you look at it from a different perspective and you say it can be odd then I am reassured that I am not dumb

heather

-1

Q: Do light also make after image?

As it has been said in many theories and science fiction books that objects moving at a very high speed creates an after image, is it really possible if an object vibrates at a very high frequency (speed) it can make a after image? Is this somehow related to time travel?

visible-light time speed

^vtc as unclear what you're asking/non-mainstream physics?

AccidentalFourierTransform

@s.harp no, wait. I'm the dumb here :-) I might be wrong with what I said above, don't trust me :P

heather

also, thoughts on this question:

-1

Q: Can super membrane spikes grow to infinite length?

I know that supermembranes can grow spikes at no extra cost of energy, but is there a certain length to which they can grow?

string-theory

AccidentalFourierTransform

18:14

@heather why do you need constant confirmation? do whatever you want, you're a high rep user :-P

heather

@AccidentalFourierTransform my apologies

AccidentalFourierTransform

noooo I was joking its fine

what I was trying to say is that you've been around here for a lot of time. If you feel that a question is off-topic, it probably is. VTC with no regret

heather

see i actually haven't been around that long...just since August or so, which is why I'm still a bit tentative in some things, though I did vtc on the first question. I'm completely unsure about the 2nd question; it seems like a poor question, but I don't know if it's actually something to close, which is why i brought it into the general chat.

AccidentalFourierTransform

the second question is about string theory, which I know nothing about. So yeah, it seems like a poor question but I wouldn't vtc

heather

makes sense =)

AccidentalFourierTransform

18:24

(OP might be onto something after all, and we won't be able to realise that bc we don't have the necessary background, right?)

heather

yeah, i certainly don't know much at all about string theory.

DanielSank

@JohnRennie smug.

@heather how are you feeling w.r.t. rotation matrices and the trig identities from yesterday?

heather

@DanielSank, pretty good, I think.

DanielSank

Ooooh, trendsetter is easy to get.

AccidentalFourierTransform

physicists: I just posted a question in math.SE, but the background is QFT, so some of you might have something to say

1

Q: Functional differential equation (from Quantum Field Theory).

I have a certain differential equation that includes functional derivatives. I know the solution, but I'm having a hard time to show that the equation is indeed solved by the solution. The background for this question is quantum field theory (in particular, scalar $\phi^4$). The equation, called...

differential-equations derivatives pde physics quantum-field-theory

heather

18:34

@DanielSank, yep =)

DanielSank

@heather Explain it back to me?

heather

well, to create a matrix that rotates your basis vectors by an angle $\theta$ you can create a right triangle where the new vector is the hypotenuse, the axis is one leg, and a line perpendicular to the axis is the other leg. Using the trig identities you can then find the rotation matrix to be

yesterday, by DanielSank

Yeah, so your matrix is $$\left[ \begin{array}{cc} \cos(\theta) & - \sin(\theta) \\ \sin(\theta) & \cos(\theta) \end{array} \right] \, . $$

AccidentalFourierTransform

hey new hat :D

DanielSank

@heather Yep. No trig identities needed there. Just definitions of sin and cos.

Trig "identities" are things like the expansions of $\cos(a + b)$.

heather

right, my mistake

DanielSank

18:38

np

So yeah, that's one rotation matrix.

We also noted that if you compose two rotations...

heather

then, the next interesting thing is if you compose two rotation matrices (i.e., matrix multiplication, rotating by an angle $\theta$ and then an angle $\phi$) two matrices are equal:

yesterday, by heather

$\begin{bmatrix}\cos(\phi)\cos(\theta)+\sin(\theta)-\sin(\theta) & -\sin(\phi)\cos(\theta)+-\cos(\phi)\sin(\theta) \\ \cos(\phi)\sin(\theta)+\sin(\phi)\cos(\theta) & -\sin(\phi)\sin(\theta)+\cos(\phi)\cos(\theta)\end{bmatrix}$

and

yesterday, by DanielSank

So, the result must be equal to $$\left[ \begin{array}{cc} \cos(\theta + \phi) & - \sin(\theta + \phi) \\ \sin(\theta + \phi) & \cos(\theta + \phi) \end{array} \right] \, . $$

or, each individual entry must be equal

and so you get the angle addition identities.

tada!

DanielSank

Yep.

heather

=)

DanielSank

Alternatively, you can say that because we know the addition identities, we proved that rotation matrices compose how you'd expect.

Can think of it either way.

Nice, sounds like you got it all.

Lol, got trendsetter.

That was easy.

AccidentalFourierTransform

@DanielSank you could mention something about $\det R(\theta)$

DanielSank

18:41

@AccidentalFourierTransform Ooooooh yeah.

Yo @heather, what's the determinant of $R(\theta)$?

heather

@DanielSank, creative hat placement, by the way.

DanielSank

@heather Which one is showing up for you? Bacon or trendsetter?

heather

@DanielSank determinant...uh...*(::mind goes blank::)* let me find my notes real quick

@DanielSank bacon

DanielSank

Before you compute stuff, what should the determinant be?

Hint: The determinant of a linear transformation is the amount that the transformation scales the volume/area/whatever.

So, for example, if I give you $$\left[ \begin{array}{cc} 3 & 0 \\ 0 & 1 \end{array} \right]$$

heather

oh, wait, now i remember: isn't it $\cos^2(\theta)+-\sin^2(\theta)$

@DanielSank for that I think it'd be 3

if i remember right

DanielSank

18:43

that scales x by 3 and y by 1, which means it increases the area by 3 times.

AccidentalFourierTransform

Dec 14 at 18:14, by AccidentalFourierTransform

determinants suck

DanielSank

^ False.

heather

@AccidentalFourierTransform for 2x2 matrices they aren't bad

AccidentalFourierTransform

lol

DanielSank

They're awesome when you understand them geometrically.

heather

18:44

yeah!

the area of the new transformed "unit square" if i can put it that way.

DanielSank

Yes yes yes yes yes ^^^^^

YES

heather

whoa, you're new hat is...interesting @DanielSank

DanielSank

@heather Thanks. I just earned it.

heather

waffles are better.

just saying.

DanielSank

I'll have waffles shortly.

heather

18:45

@DanielSank i earned a bunch of hats today...that one, this hat, bacon...

DanielSank

So, heather, how much does a rotation scale the area of the unit square?

I'm going to get my phone so I can get the one you get by using the Android app.

heather

@DanielSank would it be $\cos^2(\theta)-\sin^2(\theta)$?

@DanielSank oh, you get ones using the app?

didn't know that...*(::reaches for iPad::)*

oh, wait, Android?

darn it, iOS!

making me lose hats.

AccidentalFourierTransform

someone wants to use hyperbolic geometry

DanielSank

IOS works too.

heather

oh, good.

DanielSank

18:47

@heather Forget formulas. What should it be based on geometrical reasoning?

As my freshman year physics prof said:

"Never do a calculation until you already know the answer."

heather

well...actually...wouldn't it be the same?

1

DanielSank

yep

heather

because rotations don't stretch or anything

DanielSank

Now do the calculation.

@heather Correct.

heather

uh, is there some trig identity i'm forgetting that magically makes everything one?

John Rennie

18:49

@AccidentalFourierTransform Right, I've done my bit!

0

A: Can electrons be non-fundamental in higher dimensions?

Particles are not the fundamental objects that many think. Our best current description of particles is quantum field theory, and this describes particles as excitations in the modes described by the (asymptotically free) quantum field. We regard the quantum field as fundamental, and the existenc...

DanielSank

@heather I think you're forgetting the formula for determinant.

Or you got the matrix wrong.

heather

well, okay, the matrix i'm going off of is

13 mins ago, by heather

yesterday, by DanielSank

Yeah, so your matrix is $$\left[ \begin{array}{cc} \cos(\theta) & - \sin(\theta) \\ \sin(\theta) & \cos(\theta) \end{array} \right] \, . $$

so i'm thinking the formula i'm using is wrong

let me grab my notes real quick

John Rennie

@DanielSank Yes :-)

heather

huh, i think i'm using the right formula (at least according to my notes)

AccidentalFourierTransform

@JohnRennie I have the feeling that the question will end up in the "hot this month" queue

heather

18:52

so i must be applying it wrong

AccidentalFourierTransform

remember my words ;-)

heather

$\cos(\theta)\cos(\theta)--\sin(\theta)\sin(\theta)$

AccidentalFourierTransform

man, math.SE sucks

DanielSank

@heather go on...

AccidentalFourierTransform

my question got 8 views and it is already buried

DanielSank

18:53

@AccidentalFourierTransform How so?

@AccidentalFourierTransform link?

heather

$\cos(\theta)\cos(\theta)+\sin(\theta)\sin(\theta)$

DanielSank

@heather which is?

AccidentalFourierTransform

1

Q: Functional differential equation (from Quantum Field Theory).

I have a certain differential equation that includes functional derivatives. I know the solution, but I'm having a hard time to show that the equation is indeed solved by the solution. The background for this question is quantum field theory (in particular, scalar $\phi^4$). The equation, called...

differential-equations derivatives pde physics quantum-field-theory

@DanielSank ^

heather

or $\cos^2(\theta)+\sin^2(\theta)$

DanielSank

@heather which is?

heather

18:54

wait, wait, I remember this!

this is a trig identity!

it's one!

the pythagorean identity or something

AccidentalFourierTransform

@DanielSank thanks ;-)

@heather yes

heather

and it makes sense.

DanielSank

@AccidentalFourierTransform eh?

@AccidentalFourierTransform +1

heather

@AccidentalFourierTransform +1 as well

AccidentalFourierTransform

well, yes, thanks for that

@heather hey thanks to you too :-)

heather

18:57

@AccidentalFourierTransform, no need to thank me, it seems a well thought out and well written question.

definitely deserves the +1.

DanielSank

heather, did you figure out the determinant?

the suspense is killing me.

heather

@DanielSank, yeah =D

DanielSank

ok cool.

heather

$\cos^2(\theta)+\sin^2(\theta)=1$ by the pythagorean identity

AccidentalFourierTransform

@heather @heather well I have standards you know ;-)

DanielSank

18:58

Yep.

AccidentalFourierTransform

(but thanks again)

DanielSank

By the way, just an interesting note, $R(\theta)$ is unitary, i.e. $R(\theta)^{-1} = R(\theta)^\dagger$.

heather

dagger's the hermitian, right?

DanielSank

It's really each to check that.

@heather Yeah, in this case since the matrix is real it's the same as the transpose.

Unitary transformations are all rotations in some sense.

heather

hmm, would this so happen to be the phase shift gate?

or is that different, i can't quite remember

AccidentalFourierTransform

18:59

in this context, orthogonal (and this name has a reason)

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