@IceLord people in my nuclear physics class were confused by the strange symbol max{a,b}.

@0celo7 you're wrong

in.news.yahoo.com/…

@JohnRennie It's an opinion, I cannot be wrong.

Classic physics student ^^

@Danu : I was going to say the same :)

@Qmechanic I'm debating whether it's worth it to put in the effort to help explain WillieWong what's going on :P

I understand his issue.

Physicists often define a spacetime by its metric, this is true.

A time waster game

@KaumudiHarikumar : they're thought of as being somewhat arrogant / smug / elitist. See articles like this.

@Danu I left some comments.

who is Valter?

Martin says he is open to it but hasnt picked a date yet. he had scheduling conflicts (attend conference/ vac). havent nailed down anyone yet

@MAFIA36790 havent nailed down anyone yet ... it would help if JR would show up in chat 1st... DS said he wont tell him to do that :|

@MAFIA36790 ok, do you know him? any connection to him?

who is he?

am somewhat )( annoyed nobody is helping out my meta thread for guests, plz consider going out on that huge limb & upvoting/ answering it, really appreciate your enthusiasm/ suggestions in here but it needs to carry elsewhere too :| meta.physics.stackexchange.com/questions/9068/…

@MAFIA36790 it doesnt matter to begin with, feel ppl are overthinking this (annoyed at Danus comment wrt that...) the meta thread is just to show interest/ desire/ enthusiasm & think guests will follow after finding the strong support in meta eg lots of reaction/ votes etc

@MAFIA36790 This guy will be cool cause I would like to have some serious LQG stuff going on in the chat given I often just heard string theory stuff here

@MAFIA36790 so far nobody outside of chat regulars have done it, so that would be a big milestone to go beyond that, thought it wouldnt be such a hurdle starting out, but that now seems to be the case. need less "hands off/ passive" attitude by everyone interested :|

@MAFIA36790 tbh alas eveyrone elses meta posts on subj have high to huge votes but even after huge time/ effort on the prj over months mine struggles to get any... leading to wavering self esteem at best & some bitterness at worst :(

?

@KaumudiHarikumar strongly agreed! also a huge fan of TED talks. they have some of the most elite scientists/ speakers in the world. the topics are outstanding/ cutting edge. its bringing science to the masses. who else can say that? experts routinely sniff at "pop science" and then complain about scientific illiteracy in almost the same breath... anyone who cant find something redeemable/ to like about TED is just a curmudgeonly sourpuss... big accomplishments always have "anklebiters"/ shadow side :(

@KaumudiHarikumar exactly yeah one of my nonscientific friend said she liked videos there & was very pleased about that... sometimes its exceedingly hard to communicate the excitement/ passion of subj to "outsiders", has that geek quality etc

lol at JD quoting/ citing the onion (indirectly via new yorker). find it quite hilarious myself.... have a few silly onion links re physics have been meaning to write up sometime...

@KaumudiHarikumar anyway there are some controversial speakers and its not all totally 100% solid but they probably have 100s of talks at this pt across vast subjs... perfection is not attainable...

← secretly aspires to do TED talk someday that goes viral :P

@KaumudiHarikumar think even curmudgeonly JD could probably find some on his fave subjs he likes if he looked around...

@KaumudiHarikumar dont skip on sleep! helps learning! bye! :)

Proof?

I dunno, give a proof

that's not a proof

that's a JD "proof"

don't be so mean

hint: to attempt proof, use the metric

@IceLord "silent" indices can be renamed, indeed

The canonical name is "dummy index", I believe. Technically, one should call them bound indices.

hey

@ACuriousMind stille Indizes :p

@IceLord I am convinced of that

@Sanya Never heard anyone call them that

@ACuriousMind my professors :|

@IceLord That statement is so vague as to be meaningless. What is true is that Maxwell's equations can be derived from Coulomb's law + special relativity

@Sanya Yeah, mine called them "dummy indices". I don't think there's a "right" or "wrong" name, people will get what you mean either way

Or Gauß' law. Doesn't matter, since you can derive one from the other.

@ACuriousMind Dummy index is perfectly acceptable for PhD level index pushing.

@IceLord no

They don't matter, but that's not the reason.

The usual proof for that doesn't work here. (It does actually, but you have to explain it.)

@Sanya What?

@ACuriousMind Maxwell's equations follow from having a Lorentz invariant vector potential field theory.

(massless)

So it turns out myblender can't blend apples

Gonna have to improvise something to crush them

Baseball bat.

@slereah I still cannot find that Spivak topology book

Or ask a neighbor for a bomb

Might not exist

I dunno

@Secret There is no Spivak topology book.

@0celo7 Sure, but that's because we explicitly constructed those theories to yield Maxwell's equations.

I was thinking more mortar and pestle, maybe

Why the hell are you looking for one?

A pestle is just a tiny baseball bat

@Slereah How many apples do you need to crush?

I bought all the apples

About 20 or so

Using mortar and pestle strikes me as...labor-intensive for the amount you need to produce cider

oh he's making alcohol.

Well it's hard finding a press at the supermarket

Sad. He's a criminal.

Brewing is all legal baby

This isn't the US

Morally criminal

Because previously slereah said there is one

@Slereah Ok noted

Alcohol is evil...I don't know why anyone would go near the stuff.

I think that someone producing alcohol is a moral hero

@MAFIA36790 Kids these days

They don't know the pleasure of making something with one own's hands!

@0celo7 Yes, it is evil, which is why we destroy it by imbibing it

and then getting drunk

Bull. You're letting the devil into your lives.

The devil's hooch

I haven't tried alcohol. And I never will.

Yeah I was like that when I was a teen, too

a DORK

Wtf

@ACuriousMind knows your sins

@0celo7 Explain that one!

Explain what

Hm, what could I use as a press

@MAFIA36790 No, it's still model number 7

The closest I can think of available at the supermarket are those little garlic press

@Slereah Put a board on top of the apples, then sit on it :P

But then how do I collect it

Sounds complicated

I'm no engineer

Yeah, I dunno

Drive over them.

I have a vague recollection of seeing it done by wrapping the pulp ina tea towel then twisting it. Might be worth a Google ...

The problem of the blender is that since it's basically solid, it only blends the apples immediatly around itself and then stops

Yeah I've seen that too

maybe I should invest in one

I dunno

I'll go visit the supermarket tomorrow

see if I can rig up something

lol, why did you delete that?

@0celo7 is ashamed of himself

What would be best is some kind of screw press, I think

For the second batch of cider I think I need to invest in some better equipment

I'll just delete my account.

@ACuriousMind do it.

How does one write a hyperreal number, anyway

@0celo7 do what?

I know it's a sequence of rationals

Is there a standard way to write it

@ACuriousMind delete my account

You've publicly shamed me. Might as well finish me off.

Uh, I can't delete your account

^ Can someone explain this to me?

It's not an answer to the questionnaire, but I still don't get what the guy's trying to say. Is he arguing collusion?

Who's making Nobel prizes here?

Or is that supposed to be "mock"?

My stomach is dissolving itself

@ACuriousMind Well, 't Hooft, but I don't think he's the target.

And SE wasn't around 17 years ago.

@HDE226868 Judging by the following comment on tpg's nomination, the user appears indeed to think there's some sort of collusion:

this community became small because a small group monopolized it, perhaps hoping to help their career. Election has a chance to be less unfair if all the users are contacted by email to tell them that the time to change has come – igael yesterday

"the time to change has come" sounds like it heralds a robot uprising.

I'm somewhat surprised how many strange conspiracy theories this election is bringing to light

@HDE226868 Potatos.

@ACuriousMind Can you explain WKB to me later? The lecture is making 0 sense

The F T row of the truth table is also weird for the if..then.. logical structure

@KaumudiHarikumar : please give me an example of a physics-related TED talk that you found to be inspiring.

@0celo7 Hmmm...maybe? I once had to give a talk on it. Just ask about what confuses you and we'll see

@IceLord Unlike you I don't have a perfect memory. I need help sometimes, unlike you.

@vzn : it's not just me who has such an opinion. See for example this: "With all due respect to Lizzie Velasquez, the vast majority of TED and TEDx talks are complete bullshit, and it's high time someone called them out on it". If you'd like to point me towards a physics-related TED talk I'll comment further.

Can it be that the Universe is expanding to lower the entropy? Last MP animation was great to display that. In the Big Bang, you had almost absolute entropy with only local very small entropy variations (microwave background says 1 in 100 000 degrees of celsius different, but that is at random, I believe, since you cannot fix all atoms at exact distance of space if you have at least a little of entorpy). That is why you have got places which are only a little more dense than the others.

With the help of expansion, the surrounding matter was able to collapse upon those places forming the galaxies. It is my illiterate hypothesis. How do you like it?

@ACuriousMind I'll read the book first so I can make sure there were no mistakes in the lecture.

I pointed out at least one thing he said was a mistake

It seems that non-zero entropy was necessary to trigger the galaxy collapse as well as the expanding Universe.

@ACuriousMind In other news, the last homework was really hard and since then the annoying grad students have started taking notes in class...

@MAFIA36790 Vacuous truth is a lie.

One has to impose "vacuous hypothesis" $\implies $ "vacuous truth" as a logical axiom.

one cannot prove it

@Secret Why don't you just get a book on topology and read it

I don't know what you're doing, but it's not working

@0celo7 I am currently reading Boubaki on Chapter 1

Read Munkres like a normal person

yes, and a MSE link told me that is because assign that to true makes the proving stuff easier

Don't you mean false always?

@MAFIA36790 What's the name of that book, I only got his diff geom in the google hits?

@0celo7 nope

The implication is only false when P is true and Q is false

I don't know what implication means.

Oh well, PhD logic isn't interesting anyway.

NB The reason of this logic tangent while everybody think I am reading topology is because a statement in Ch. 1 requires the notion of the intersection of the empty set which is the universal set. This weird me out and I thus google it. I then read the proof, convinced, by it, but that does not mean I do't felt weird about it : )

@IceLord I believe that was sarcasm :P

Vacuous truth is something that convince me yet I still find it very alien, it's almost like as if someone who first touch upon the concept of infinity

(well, emotional things don't really contirbute to the knowledge, thus I tend to dimiss my own emotions as irrelevent)

@JohnDuffield am aware of some criticism of some speakers & the format. but you can find a lot of laudatory editorials too. why did you not look? geez dude thought you liked/ can use search engines. you cant find anything in these 71 to like? if says maybe more about you than anything else ted.com/talks?topics%5B%5D=physics

@ACuriousMind Do you have access to Sakurai 2nd ed?

@ACuriousMind Would you mind to give me a theoretical explanation of this question. I think it would be better if I have both the experiment and theory to study togethe (experiment already given by the answerer))r?

@0celo7 "Modern Quantum Mechanics", 2nd ed? Yes.

@vzn : tell me about a physics-related TED talk you liked, and I'll give you some comment on it.

@ACuriousMind Yah.

@JohnDuffield must concede that this is an example of "controversial/ questionable" content/ research/ science ran across/ for example, presumably there is other stuff slate.com/articles/health_and_science/science/2016/01/…

Eq. 2.5.45 on page 112.

Why does the sign in front of the second term become a $+$?

@JohnDuffield ok, admit havent gotten into very many talks myself incl physics, just generally find them very high quality. this just jumped out on fast skim, have this guys book, hes very qualified, have been tracking "qm biology" paradigm shift myself lately on my blog (am sure theres other tons of way cool stuff... browsing further) ted.com/talks/…

@vzn : you betcha.

Uhnnn. Quantum biology. FFS.

@Secret I don't know what you mean by "theoretical explanation". The answer you got is the correct one: The Einstein-de Haas effect demonstrates that for the purposes of the magnetic moment, both angular momentum and spin behave essentially in the same way.

have been tracking simons career... huge CS theory benefactor... try an interview if you are against talks :P ted.com/talks/…

@ACuriousMind Are you saying JD is right?

nephente's comment is also spot on: Depending on your definition of the magnetic moment in quantum mechanics, asking why spin and magnetic moment are collinear is a non-sensical question.

this machine/ deep learning talk is under the physics section. not sure why yet, havent looked. the field has been shown to have deep connections to energy optimization problems. ted.com/talks/…

@ACuriousMind Something like a theoretical or mathematical model to explain the Einstein de haas effect and calculate the observed experimental result. That is, what is the model that will explain the observation that spin and magnetic moment are parallel?

@0celo7 Because for the upper choice of signs it's $+\cdot +$ and for the lower choice of signs it's $-\cdot -$.

@ACuriousMind Think again. The signs are not the same.

the $\pm$ on the right is not the same $\pm$ as on the left.

Bad notation, yes.

@vzn : that looks reasonable. Unlike Jim Al Khalili's talk: "This is the quantum skier. He seems to be intact, he seems to be perfectly healthy, and yet, he seems to have gone around both sides of that tree at the same time. Well, if you saw tracks like that you'd guess it was some sort of stunt, of course. But in the quantum world, this happens all the time". Sigh.

@JohnDuffield whats your take on LHC/CERN? try this, might even like its msg about lately-so-called "desert," have questioned Big Science™ myself at times ted.com/talks/harry_cliff_have_we_reached_the_end_of_physics

@0celo7 It may be bad notation, but it is the case that you can't choose the signs such that you get a minus there

@ACuriousMind Why not? Pick the first one to be a minus and the second one to be a plus

Then you get $$-\hbar\int\cdots-\frac{i}{2}\cdots$$