The h Bar

obe

00:26

I thought you were Qmechanic for a sec.

skill patrol

Nice avatar @obe

obe

00:41

thanks it's from an anime.

TanMath

@StanShunpike you really do look like @Qmechanic

obe

I am happy my problem set is due the friday after this one.

Rescheduled.

Stan Shunpike

00:59

@TanMath i am the chameleon. My profile pic changes spontaneously for no known reason.

Pies

01:55

Howdy

user54412

02:37

Anyone familiar with accessories for overhead projectors and transparencies?

Pies

Nope...

obe

How familiar?

Pies

Say obe, wanna hear a joke?

user54412

I need the following device: a transparent screen that can display a changing image in semi-transparent color at a reasonable refresh rate. Basically, something I can put on a projector in place of a transparency to play movies.

Pies

What did the electron do when he saw an atomic nucleus? He lepton (leapt-on).

obe

02:39

wow.

Pies

What did one physicist say when he wanted to fight the other? "Let me atom!"

Where does bad light end up? In a prism.

obe

I didn't hear the last one before.

Pies

Never trust a particle. They make up everything.

obe

Your jokes are bad, also self study calculus.

Pies

.-.

Calc is hella difficult. It's gotta be structured or I'll get confused later on

Well how about you? When'd you start calc?

obe

02:52

I did calc in my sophomore year.

Pies

Junior ;-;

Plus, I skipped Precalc. So I gotta catch up on that too...

obe

Hurry.

Rigor

03:07

How did you skip precalc?

Pies

@Rigor I did really well in trig

:P

Though I got held back in 4th grade math...so I'm finally back in a normal schedule. Except they just cancelled calc...

So..

Did you hear oxygen and magnesium got together? OMg

Secret

03:39

Agreed, people just have an impression that physics = theoretical + abstract. Everyday physics usually involve a lot of process that those interested can actually learn a lot more than reading textbooks

PS I have never casted a close vote

An analogy stretched too far...
:24569037 One of the examples where it is easy to draw, but hard to calculate. I like nonlinear equations because their vector fields are pretty, but I am bad at solving them

@Rigor It might seemed nonintuitive to have a hyperbolic surface formed from something basically straight and pointy, but hyperbloids are ruled surfaces thus the animation is completely valid.

So that curved shape is the envelope traced out by the rotating cube

Rigor

04:07

@Secret yes, the animation is completely valid; but there is a visible flaw in the animation that I am asking you to look for pal :-)

DanielSank

05:16

> Everyday physics usually involve a lot of process that those interested can actually learn a lot more than reading textbooks

@Secret Could say that about anything discussed on this site though.

Danu

@skillpatrol Thanks

Hi @DanielSank

skill patrol

np pal @Danu

Danu

@yuggib Err how else do you want it to arise?

Basically you need to non-simultaneously-diagonalizable matrices in your Lagrangian, and you have only the mass matrix and the weak-interaction-couplings matrices to deal with for neutrinos

@DanielSank Just link the question you're disgruntled about :P

@HaykoKoryun It's just a factor 1/2 on the momentum imparted (when the "wind" is straight into the sails, at least)

DanielSank

05:44

@Danu Hello.

I served a friend a dish I've been working on for more than a year.

Danu

That sounds exciting

DanielSank

It's vegetarian, and she's Hindu, so I figured I was up against high expectations.

Danu

Also high pressure on the friend :P

DanielSank

She asked for the recipe!

I was ridiculously proud of myself.

Danu

Do you know she "knows about" food, or is this a case of positive discrimination? ;)

DanielSank

05:47

@Danu I have no idea what her tastes are, but she likes to talk about food and that's usually an indication of someone who pays attention to taste.

Danu

Yes, usually it is :)

DanielSank

She said she considered marrying someone from north India for the food.

Danu

right :P

DanielSank

@Danu Want the recipe?

Danu

@DanielSank Sure ;D

DanielSank

05:57

Ok, let's see if Google docs is as cool as I hope it is.

Danu

Hope it's not super complicado---my kitchen here isn't that amazing :P

Huy

I just used my mixer I bought before summer again.

It's such an awesome device. I don't know why I stopped using it. Lazyness is a bitch.

Danu

Haha :P

DanielSank

@Danu tell me if this works

docs.google.com/document/d/…

Huy

seriously. I tend to forget about eating fruits. with the mixer I can just cut whatever I have left in the fridge and throw it in and it always tastes good. :D

DanielSank

05:59

@Huy Dude, dump a banana into a mixer full of milk and turn it on.

Instant delicious snack.

Huy

that is my current breakfast

plus a little bit of joghurt and honey

DanielSank

Does that link work?

Huy

does for me @DanielSank

DanielSank

Groovy.

I recommend it.

Huy

I'm a terrible cook

Danu

06:02

@DanielSank It does.

@Huy lol

Huy

that's really not funny. :/

Danu

@DanielSank If only I didn't hate milk :P

Huy

u wat m8

Danu

06:19

@DanielSank I assume it's fine to use different peppers, right. I've got a bunch of different kinds (dried) in my cabinet, but they're not going to be the same stuff that one gets in CA, I assume.

Danu

07:10

Breaking News: Scientists on Antarctica found to be only human after an inspection by the National Science Foundation notes problems with alcohol abuse among those who have to live there to do science:

"NSF officials acknowledged that alcohol consumption in the USAP can create unpredictable behavior that has led to fights, indecent exposure, and employees arriving to work under the influence. However, we noted that breathalyzer tests are rarely administered to determine if employees are intoxicated"

DanielSank

@Danu Wait, what?

What does that mean "found to be only human"?

Oh, you're kidding.

Danu

Right

"We were informed by a subcontractor employee that a researcher was brewing the beer at the station, which is also prohibited by the USAP Alcohol Policy."

DanielSank

@Danu I doubt dry peppers are going to work.

Danu

nsf.gov/oig/_pdf/15-2-009-USAP-Health-and-Safety.pdf

@DanielSank Sigh

DanielSank

You might be able to replace the smoked ones with dried, but you'll be missing the juicy sauce they come in and that will seriously change the flavor.

Danu

07:11

I'm in Munich you know :P

DanielSank

I'm certain you can still make something nice!

Danu

Ain't nobody got adobo sauce

DanielSank

It will probably change a lot in translation.

The pasillas are important too. If you get get some kind of fresh mild chili peppers and bake those it will work.

The key is the baking, I think.

@Danu, do you love me?

Danu

@DanielSank Possibly

DanielSank

@Danu Ok, well I'm going to give your love a reason.

amazon.com/gp/product/…

Bam.

Danu

07:15

lol

also

by Pasilla

do you mean

The dried peppers?

or, as Wikipedia puts it "A fresh poblano pepper, often sold incorrectly under the name 'pasilla' north of Mexico"

DanielSank

@Danu Those would probably work, but I wouldn't bother to roast them if you used dried ones.

@Danu Ok ok, yes, I actually mean poblano peppers, but nobody knows that word :D

Danu

Pasilla

The pasilla chile or chile negro is the dried form of the chilaca chili pepper, a long and narrow member of species Capsicum annuum. Named for its dark, wrinkled skin and pronounced pah-SEE-yah (literally "little raisin"), it is a mild to medium-hot, rich-flavored chile. As dried, it is generally 6 to 8 in (15 to 20 cm) long and 1.0 to 1.5 in (2.5 to 4 cm) in diameter. The fresh narrow chilaca can measure up to 9.0 in (22 cm) long and often has a twisted shape, which is seldom apparent after drying. It turns from dark green to dark brown when fully mature. In the United States, producers and grocers...

@DanielSank Aight

DanielSank

I use fresh poblanos.

Also, "north of Mexico", lol.

"north of Mexico" -> "by gringos".

Danu

:D

DanielSank

@ChrisWhite weren't you going to be in SB soon?

Secret

07:36

@Rigor That part of the horizontal line of the middle gridline is missing?

Slereah

08:05

mornin

yuggib

@Danu And if you have an additional interaction term (maybe mediated by something else) that gives rise to non-vanishing probability of mixing flavors? As I said, to assert that oscillations prove that neutrinos have mass, you need to find a contradiction otherwise, i.e. find a contradiction in assuming flavor change and all the masses equal to zero

Slereah

Ah, the miracle of physics Christmas

We get a mainstream news about physics and 2 months of questions on it :p

yuggib

Without a more convincing reasoning (that may exist, simply I do not know it), it's like saying: I observed two quantities that do not commute, and I know that position and momentum do not commute. Then those two quantities are position and momentum.

@Slereah I am not asking a question, just criticizing the nobel committee press release :-P

Slereah

that is not very convincing

yuggib

@Slereah Which part?

Slereah

08:18

the fallacy :p

that's a pretty old one too

Like ancient greece old

yuggib

yes, probably...

for neutrinos, I feel that they are incurring in that fallacy

but maybe it's just my lack of knowledge

(as a recall, the sentence that is fallacious is the one that can be found here)

Slereah

"the discovery of neutrino oscillations, which shows that neutrinos have mass"

This one?

yuggib

yep

Slereah

It is accurate enough

yuggib

read above^^

Slereah

08:21

Massless neutrinos would not experience proper time and hence would not change during transit

yuggib

and what if they behave like photons (also massless), and interacting they are destroyed and then created with a different flavor (like photons are annihilated and then created with a different energy for example)?

I know that is not allowed by the standard model

but that does not mean there could not be a model where this is possible

I recall you that in present relativistic QFT knowledge, no one knows exactly what happens in the "interaction" :P

we have only asymptotic perturbative knowledge T_T

Slereah

Not quite

It's just that mathematically it is easier to do

there are some exactly solved QFTs

even interacting

yuggib

not in 3+1

and I know very well there are

Slereah

Actually yes in 3+1!

Supersymmetric QFTs

yuggib

not fully relativistic

Slereah

08:26

Still yes!

yuggib

explain "exactly solved"

Slereah

Supersymmetry is nice and symmetric, helps out a bit to solve

yuggib

Is there a self-adjoint generator of time translations, i.e. the Hamiltonian

in a precise Hilbert space realization?

if there is, I am very interested in seeing it, for no one in the mathematical community seem to know about it

Danu

@yuggib With only SM interactions I think this is the only way.

Slereah

I don't know too much about exactly solved SUSY models

Danu

08:28

I don't think it makes a whole lot of sense to assume extra interactions when it's unnecessary.

Slereah

Lemme see if I can dig up a paper

Danu

So within the SM I think it's "proven"

yuggib

@Danu I know, but that does not mean that this assertion is justified. Also, it is crystal clear that neutrino oscillations already go beyond the SM

Slereah

@yuggib : arxiv.org/pdf/hep-th/0306133v1.pdf

a bunch of solved QFTs

Danu

Moshe Moshe

what a name

Slereah

08:30

Let my people gooo

yuggib

@Slereah interesting, but not at the level of rigor I was thinking of

Slereah

Well it's a review

Reviews are not for rigor

Reviews are for you to look at the bibliography

And look up the papers

yuggib

but I am sure, even if I don't want to read it, that I would see an Hamiltonian operator in there

or even a Hilbert space :-D

@Danu Within the SM there are no neutrino oscillations; so since you have to change it, it is not clear which the best way would be. And again, that does not constitute a proof in any reasonable sense of the word

Slereah

@yuggib : Within QFT as it is currently understood, only one type of term valid under the assumption produces neutrino oscillations

>cobordism lecture

Noooo

yuggib

Which assumption? Which term? My point simply is that is not clear; and I do like things when they are clear.

Slereah

08:37

@yuggib Renormalizability, causality, gauge invariance

that kind of things

It constrains the expression of it a lot

Even the Gauge groups are basically constrained to O and SU and E IIRC

Danu

@yuggib Ah, fair enough... It's a sticky issue.

Slereah

In a QFT it is usually restricted to like

- a kinetic term

- an interaction term of power 4 max

beyond that things start to get a bit fucky

You can't have higher derivatives because it fucks with causality

Same with integral terms

You can't have interactions too fancy because they cease to be renormalizable

You can't even have mass terms for bosons because it breaks gauge invariance

(well gauge bosons)

yuggib

@Slereah Yes, but that is just at our present level of knowledge

Slereah

well yes

but that is what the assumptions are

yuggib

per definition, something that is beyond the SM is already beyond our current knowledge XD

Slereah

08:43

if you want to rewrite the standard model from scratch feel free to

I am talking about QFT in general

Not the standard model

yuggib

the one I do not agree with is renormalizability; we know too few about that

Danu

@yuggib Not really, since we know neutrinos have mass :D

yuggib

@Danu we know that they oscillate :D

so who knows which type of theories we are able to study non-perturbatively...at the moment very few of them (at the same level that we can study QM)

Slereah

@yuggib : But then with that logic you can dismiss everything

How do you even know photons exist

All we know is that our instruments say a thing!

yuggib

I can study reasonably well models of quantum electrodynamics

not the most fundamental ones, but reasonable ones

like quantum EM field interacting with extended charges

Slereah

08:47

well yes, but that is just the model we know of :p

yuggib

I agree

Danu

Hmmm

yuggib

it is called making effective theories

Danu

Is this an explicit solution to a homework-type question?

yuggib

;)

Danu

08:47

0

Q: Why are the odd point green functions in free field theory zero?

I don't understand why the $(N=\mathrm{odd})$-point Green functions calculated in free field theory are identically zero. Is it because the Green functions are odd? If so, then how do I prove it? Is there any physical interpretation of the result?

Slereah

well the solution is in Peskin certainly :p

yuggib

maybe yes

Slereah

09:00

0

A: Which will collide first, the moon and Earth, or Sun and Earth?

The Moon and The Son will collide - Answer from The Creator of all, The All Knowing: Allah says in The Holy Quran 75: 6. He asks, "When is the Day of Resurrection?" 75:7. When vision is dazzled. 75:8. And the moon is eclipsed. 75:9. And the sun and the moon are joined together. 75:10. On tha...

Ahahah

yuggib

13:10

without @0celo7 the chat is really quiet

4

almost deserted

ACuriousMind

::tumbleweed rolls by::

Slereah

Only 4 working days left

woo

yuggib

then holidays or unemployment?

Slereah

unemployment

The best holiday

yuggib

T_T

you should return back to the path of $E\wedge E$

Slereah

13:16

I might

Spend some time doing physics during that time

yuggib

you should try to find a PhD grant

not that one of those should serve you well on the job market

but it is fun! :D

Slereah

Ahahah

I tried for 3 years :p

ACuriousMind

34

Q: How can I keep my cat off my keyboard?

This is a common scenario when typing: When the family assembled for Sunday dinner, With their minds made up that they wouldn't get thinner On Argentine joint, potato^DR&FTGYB`kuhadrggoy867rt98wouth4bfgdhjlkhdsfghhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhf This happens beca...

technology pets

Asking the real question

yuggib

@Slereah you should think about leaving loire atlantique

Slereah

I have :p

Leaving France mb I suppose

yuggib

13:20

it's time to see europe :D

Slereah

But that is a whole other can of worm

I'd need to be paid pretty well to be able to

Danu

@ACuriousMind "technology" tag lol

yuggib

PhDs in non-latin europe should be paid well

ACuriousMind

@Danu Not sure if it refers to the fact that a computer is involved or that cat-deterring technology is desired :D

Slereah

The real geek solution would find cat-like patterns in the keyboard input

yuggib

13:23

@ACuriousMind the cardboard box solution is surely not high-techy

ACuriousMind

@Slereah That is one of the answers.

Slereah

heheh

skill patrol

13:48

Interesting...JD has come and left without a word?

user54412

@DanielSank November 1-3.

skill patrol

14:07

Back in the bebop jazz era, a good trumpeter or sax player would be said to "blow a good horn" (and variants). It got shortened to "he blows." Then when people wanted to say he blows a bad horn, that got shortened to "he doesn't blow, he sucks."

So goes the evolution of phraseology :-)

Danu

14:39

That blows... :P

skill patrol

:P

I was wondering @Danu is one mod allowed to cancel the suspension given by another?

Is that even in the rule book?

I think I've seen it done...

perhaps a meta question :-)

skill patrol

15:18

0

Q: Can one moderator cancel or reduce the suspension given out by another?

I was wondering if this is even discussed anywhere in the policies of this network?

discussion

Asking the real question :P

Danu

@skillpatrol Why would you ask that on the Physics Meta? Ask it on Mother Meta!

@skillpatrol ...without checking out what's out there :P

9

A: How can a temporary account suspension be lifted?

Moderator here: Yes, suspensions can be cancelled. Speaking in general, there is not a strict rule. For example, a suspension can be lifted if say, it's a first offence, it wasn't something that bad, and you know the user just had a bad moment... etc. But note: this is not always true. While ...

skill patrol

I keep forgetting about the meta of the meta :( @Danu

Thanks btw.

obe

15:38

It's lonely here without 0celo7.

Physics Meta

0

Q: Can one moderator cancel or reduce the suspension given out by another?

I was wondering if this is even discussed anywhere in the policies of this network?

discussion

Secret

DIVIDE AND CONQUER!

skill patrol

@Secret did you find it?

Secret

find what?

skill patrol

12 hours ago, by Rigor

@Secret yes, the animation is completely valid; but there is a visible flaw in the animation that I am asking you to look for pal :-)

Secret

15:49

Yup, I am guessing its the missing line, I already replied on rigor on that

skill patrol

Oops, sorry I missed that.

Good job :-)

Hi @DavidZ

David Z

hi

skill patrol

how's it going?

David Z

Busy, as always

skill patrol

16:15

Busy keeps the business going :-)

John Duffield

@skillpatrol : I was going to say something but I was pushed for time and had to log off.

The animation shouldn't have concave sides.

skill patrol

Why not?

John Duffield

Because the sides of the cube are straight.

skill patrol

What would you suggest Sir?

John Duffield

The sides shouldn't be concave, they should be vertical.

skill patrol

16:21

Like a cylinder? @JohnDuffield

John Duffield

Like a cone on top of a cylinder on top of an inverted cone.

ACuriousMind

The concavity of the sides is correct, since the corners of the cube are indeed farther out from the rotation axis than the middle points of the edges.

John Duffield

But hey, I could be wrong.

skill patrol

What evidence do you have?

:-)

John Duffield

I haven't. You wanted me to say something. I did. And I've just seen what ACM said. Oops, my bad.

Secret

16:24

https://en.wikipedia.org/wiki/Ruled_surface
This is why they are curved

John Duffield

Humble apologies for getting it wrong.

2

skill patrol

Did you notice the missing line along the equator?

obe

equator

John Duffield

Missing line? Nope. I didn't notice it.

skill patrol

Look at the left side going right, the line stops.

It should rap around like the rest :-)

obe

16:30

What is the point though?

John Duffield

I saw it after you mentioned it. I was a bit surprised I hadn't noticed it before, because I'm usually pretty good with stuff like the man in the gorilla suit.

Have you see the big Spanish castle illusion? I think it's brilliant.

skill patrol

@obe developing powers of observation.

Attention to detail etc.

John Duffield

IMHO the PacMan illusion is brilliant too. You can't always trust your own senses.

You can't always trust what you think you know either.

ACuriousMind

abstrusegoose.com/276

bolbteppa

That pacman thing is awesome, what causes it?

Secret

16:38

@ACuriousMind well, to be fair, we won't ever develop models if we don't have senses

bolbteppa

I like how that went from classical to quantum

Or at least, pre-Einstein to Einstein

lol

skill patrol

All^^^ very good questions/comments.

John Duffield

@bolbteppa : I think it's an after-image thing. There will be a detailed explanation somewhere. Edit : see Wikipedia

bolbteppa

At least I know it's not the self-induced computer-vision-syndrome I've given myself

ACuriousMind

@Secret The comic is not disputing that.

John Duffield

16:45

@Secret : funnily enough most of your senses are motion detectors in some guise or another. Your ears detect sound, which is moving air. Your eyes detect light, which is moving electromagnetic waves. You feel the wind on the skin of your face, or somebody moves their hand and touches you. There's even a Vibration theory of olfaction.

skill patrol

Optical illusion

An optical illusion (also called a visual illusion) is characterized by visually perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a perception that does not tally with a physical measurement of the stimulus source. There are three main types: literal optical illusions that create images that are different from the objects that make them, physiological illusions that are the effects of excessive stimulation of a specific type (brightness, colour, size, position, tilt, movement), and cognitive illusions, the result of unconscious...

obe

@skillpatrol When I cover the cylinder the shadow remains.

John Duffield

@skill patrol : I used Edward Adelson's CheckerShadow illusion in something I wrote back in 2008 about conviction.

Danu

Okay, that wasn't nice. Sorry

ACuriousMind

@obe I never thought to try that, but...yes

obe

16:51

Weird, A and B still look different.

Danu

@obe Yeah, even when I blind out the other squares

Funny, how that works

John Duffield

With practice you learn to see what's there. The checkershadow illusion just doesn't work for me any more.

obe

I demand a refund.

skill patrol

@JohnDuffield The point here is that "practice" trains the brain.

ACuriousMind

@obe Even after you remove the cylinder, the issue is still that the squares surrounding B are darker than B while the square surrounding A are lighter than A

John Duffield

16:55

@skill patrol : agreed. It's the same for R Beau Lotto's illusions, such as this. He told me that certain people in the colour-printing business and clothing business aren't fooled by these colour-context illusions.

skill patrol

@JohnDuffield just like the spinning cube :-)

Danu

@JohnDuffield Inb4 reference to that ridiculous shirt nonsense that happened a few months (maybe more?!) back...

ACuriousMind

@Danu 'Twas a dress :P

John Duffield

Yep. Look at the checkershadow illusion at an angle and the context disappears. You see the colours as they are.

skill patrol

That was a great meme :-D

John Duffield

16:57

@Danu : shirt? Dress? Maybe that was before my time.

Danu

@JohnDuffield It was

John Duffield

And what wasn't nice?

Danu

@JohnDuffield Never mind it.

John Duffield

Huh. OK, time for tea. Back later.

skill patrol

Memes are intended to entertain

Like optical illusions.

Danu

16:59

Who starred that message of mine? Seems rather useless

8

skill patrol

obe

What is the illusion here?

skill patrol

From the math room

No illusion

Real beauty imo

ACuriousMind

@Danu You should know by now that meta-comments about starring usually achieve the opposite of what they're intended to ;)

skill patrol

in Mathematics, 1 hour ago, by J. M. is back.

@anon Thanks, it's an old elliptic function plot I had lying around. :)

Danu

17:46

@ACuriousMind Who told you that wasn't exactly my plan?

skill patrol

Are you a reverse psychologist? ;P

obe

He's a reverse astronomer.

skill patrol

Reverse engineer :-)

NeuroFuzzy

18:38

@skillpatrol pretty! what function is it?

@skillpatrol oh. nm.

Huy

where's 0celo7

NeuroFuzzy

0celo7, USA

1 6 26

general-relativity homework-and-exercises quantum-mechanics differential-geometry lagrangian-formalism quantum-field-theory electromagnetism

Huy

wat he do

NeuroFuzzy

My guess is that it was constant teasing comments about JD. Either that or there was some really offensive chat message that got totally removed.

But dmckee is here and i wouldn't gossip. ::whistles to self::

:)

skill patrol

:)

dmckee

18:53

@NeuroFuzzy I don't get to gossip. I signed something about that at some point.

skill patrol

NDA?

Transcript for