The h Bar

ACuriousMind

16:01

Anyway, welcome to the chat session, everyone!

AccidentalFourierTransform

I guess we can call it a day

ACuriousMind

We don't have much of an agenda today - if anyone is new to the site or chat and has some questions, this is the ideal point to get them off your chest. Otherwise, just talk about whatever you want. Any interesting developments in physics lately?

vzn

Feb 8 at 17:40, by vzn

Experiment Reaffirms Quantum Weirdness / wolchover, quanta mag

ACuriousMind

"world still quantum" is not a strictly new development, but I guess we can't be too picky :P

vzn

@ACuriousMind agreed. its trying to look at a "different loophole" called "selection" which has not been considered/ studied as much.

NowIGetToLearnWhatAHeadIs

16:07

One of my answers was in the hot network questions sidebar. Can we make that happen again? I liked that.

ACuriousMind

@NowIGetToLearnWhatAHeadIs Heh. For better or worse, we have no actual influence on the HNQ algorithm (unless you propose changes at Meta Stack Exchange)

NowIGetToLearnWhatAHeadIs

Just wishful thinking

vzn

see a JEE tester in here. would like to say "thx for opening separate room for that" & think it works better/ well. encourage others to experiment with opening rooms.

Yashas Samaga

actually it did help

Problem Solving Strategies

General chat for high school physics. For MathJax see meta.sta...

we were discussing problems few minutes ago

vzn

@NowIGetToLearnWhatAHeadIs youre ~½ joking right? you know how seemingly random that algorithm is right? (not to mention controversial etc)

0celo7

16:11

Chat session?

Yashas Samaga

r.i.p chat session

0celo7

@YashasSamaga hmm?

NowIGetToLearnWhatAHeadIs

@vzn Ya I was joking.

0celo7

@ACuriousMind I'm new to the site

Yashas Samaga

there isn't anything to talk about lol

John Rennie

16:12

It's not very chatty today

0celo7

can I pls have an introduction

vzn

@0celo7 youll be fine if you follow the rules/ be nice :P

0celo7

wow @JohnRennie sure looks like a handsom chap

John Rennie

0celo7, chat session. Chat session, 0celo7.

0celo7

@vzn that sounds like a stupid idea

vzn

16:12

@0celo7 that sounds like troublemaking :P

Slereah

I have a chat idea

NowIGetToLearnWhatAHeadIs

It's just funny that you write a simple explanation of a relatively well-known thing and then it gets featured and all the sudden you get tons of upvotes with very little work.

Yashas Samaga

lol

Slereah

Why isn't there a button on the PSE chat to launch mathjax

vzn

@NowIGetToLearnWhatAHeadIs welcome to the randomness of ~~user generated content/ votes/ ratings/ likes~~ democracy

Slereah

16:13

Currently as it is I have to keep a mathjax button on my bar

0celo7

@NowIGetToLearnWhatAHeadIs muons experience time dilation got someone 1500 points

AccidentalFourierTransform

you can use ctrl+w for that

Slereah

It could be perfectly used as a simple button on the site itself

Yashas Samaga

why hasn't mathjax been integrated into the chat? there are plugins but what's preventing the devs from introducing mathjax in the chat by default?

Slereah

I mean it's not too complicated

ACuriousMind

16:14

@Slereah Simply because chat is not a priority for the SE designers/coders, I think

Slereah

just make a button that launch the script

vzn

@YashasSamaga SE software is relatively mature, there are many (good!) proposed chgs but rarely is much new implemented

Slereah

It doesn't even have to be a design thing

Just put a link to the script

David Z

oops, I'm here

Something on my phone is silencing my reminders :-/

AccidentalFourierTransform

welcome :-)

0celo7

16:15

@ACuriousMind I demand an introduction >;(

Yashas Samaga

@0celo7 Are you aging backwards? :P

0celo7

goo goo ga ga

@ACuriousMind I never got a chat session introduction, pls

this is discrimination

vzn

@0celo7 wow that explains a lot :P

0celo7

what?

vzn

@DavidZ so hows china these days? thinking of staying/ moving?

ACuriousMind

16:17

@NowIGetToLearnWhatAHeadIs Well, sometimes a well-written explanation of a simple thing is worth the upvotes. How much effort it cost you does not always correlate with how good it is. Sometimes it's really just an unexceptional post that got lucky, though

David Z

I'm not in China anymore

vzn

@DavidZ no kidding wasnt aware (did you mention?) where are you at now? new work?

Yashas Samaga

Why aren't completely wrong answers deleted?

0celo7

@YashasSamaga reasons

Yashas Samaga

such as "frequency is inversely proportional to amplitude" (I read it somewhere today)

0celo7

16:19

@YashasSamaga period amplitude

AccidentalFourierTransform

who decides whats wrong and whats right?

Yashas Samaga

The answer I receive every time for that question is, "the answer is an attempt to answer and how correct it is does not matter"

0celo7

@AccidentalFourierTransform the pope, the president

John Rennie

@YashasSamaga there is some disagreement about the deleting of wrong answers ...

AccidentalFourierTransform

the popesident

Yashas Samaga

16:19

@AccidentalFourierTransform I was talking about the silly answers which are obviously wrong.

0celo7

but not the current pope, he's a commie

David Z

@vzn back in the US

@YashasSamaga It's not part of the moderators' job to judge correctness

ACuriousMind

@YashasSamaga We have generally decided that "obviously wrong" is a slippery slope we don't want to slide down. Once you allow deletion of "obviously wrong" answers, people will get into fights what constitutes "obviously" wrong answers, and generally it is not moderation but up- and downvoting that is supposed to signal correctness/usefulness on SE

Yashas Samaga

the new users don't get to see the heavily downvoted answers, right?

AccidentalFourierTransform

yes they do

Yashas Samaga

16:22

I thought the light coloured answers were visible to users only e.e

ACuriousMind

@YashasSamaga they are greyed out for everyone, but not hidden from anyone afaik

vzn

@DavidZ (reading your blog, re work life balance etc...) any ideas on next directions?

David Z

@vzn Thoughts, yes, but I'm not sharing them until things happen

vzn

@ACuriousMind what about you hows academic life going

0celo7

Shouldn't we talk about the homework policy?

@JohnRennie Can you please let me tell you about topology?

vzn

16:29

@0celo7 aieee o_O

0celo7

It will take 10 minutes of your time

ACuriousMind

@vzn Still working on my master's thesis, not much new to say

vzn

@ACuriousMind what was the topic? (sorry cant remember)

John Rennie

@0celo7 you're going to have to give me up as a lost cause I'm afraid

0celo7

@JohnRennie whyy

ACuriousMind

16:30

@vzn Singular limits of supersymmetric compactifications of M-theory - string theory model building, in a broad sense

0celo7

@ACuriousMind what's the string theory of a black hole?

vzn

@ACuriousMind dont know a lot about this but arent some saying SUSY is now limited with LHC (non)results?

David Z

@0celo7 That was the plan, though part of that plan was also having a meta post up. @DanielSank kind of "claimed" that task and he's still working on it.

But if you have something specific to bring up about the homework policy, this is a fine time to do it

ACuriousMind

@vzn Yes, we haven't found any SUSY so far, yet the SUSY models are the computationally most accessible models so we still hope to learn something from them as toy models

There are also reasons to believe (at least people I trust claim that there are) that even if SUSY is broken it may be broken below the string scale, so that the compactification should still be supersymmetric even if our low-energy theory isn't

vzn

in theory salon, Feb 18 at 16:15, by vzn

saw this last nite on appletv, awesome flick, recommend it CERN documentary / Geyrhalter

0celo7

16:34

@adults My girlfriend's dog was put down. What do I do?

What can I say?

Only serious answers please.

John Rennie

@0celo7 Nothing. Provide hugs as neeeded.

0celo7

@JohnRennie But what do I say?

She texted me, I guess she just found out. I'm at work, I can't go do anything

John Rennie

@0celo7 Nothing. Just be there with the hugs.

0celo7

I can't be there!

vzn

@0celo7 try sending her flower/ crying (etc?) emoticons, isnt that the thing among youngsters these days?

0celo7

16:39

What?

vzn

@DavidZ maybe consider guest chat session sometime?

0celo7

@ACuriousMind apparently there are still people doing research in general topology

wonder how one gets a grant for that

David Z

@vzn perhaps sometime in the future

0celo7

> Manifolds!! manifolds!! manifolds is all I hear.

Is this the hypersphere guy!?!

vzn

@DavidZ soon seems like good time while your latest adventure is still fresh, up to you :) (did you say "maybe" last summer? hard to remember)

David Z

16:47

@vzn Maybe I should put it this way: I'm not interested, though I don't rule out the possibility of changing my mind in the future

vzn

@DavidZ oh, ok :|

0celo7

@vzn I'll do one.

Yashas Samaga

Why does a crystalline solid have 3 translational degrees of freedom?

vzn

@0celo7 srsly? am not opposed to that. trying to recall if we ever discussed this. thought you popped a trial balloon once

0celo7

@YashasSamaga x,y,z??

Yashas Samaga

16:49

@0celo7 how?

the atoms are fixed into the lattice

they can vibrate in their positions

0celo7

you just edited in that "crystalline"

Yashas Samaga

but can they move in the x, y, z direction?

yea I just added that

so crystalline solids have just 3 vibrational degrees of freedom?

Aluminum exists in the crystalline form?

0celo7

I think the heat capacity is like $3k$ or something

Yashas Samaga

so it shud have 3 degrees of freedom in total?

0celo7

so three degrees makes sense

Yashas Samaga

16:50

0.5 kt for each degree

dU = n1.5R dT

0celo7

well then it would have six

Yashas Samaga

dU = Q

dQ=mcdT

dQ = n1.5R dT

0celo7

11

Q: What are the six degrees of freedom of the atoms in a solid?

A monoatomic ideal gas has heat capacity $C_v=1.5$ which comes from the three translational degrees of freedom. For solids at high temperature, $C_v=3$, implying six degrees of freedom. What are those six degrees of freedom? I do not know much about how solids work, but I suppose translation and...

Yashas Samaga

There are 3 directions of vibration: namely the components x, y and z and each of these directions has 2 degrees of freedom; one of potential energy and one of kinetic energy. So in total there are 3×2=6 degrees of freedom.

wut?

kinetic energy and potential energy are separate?

Danu says there are 3 translational degrees of freedom

Nanite's answer answers my problem.

BLAZE's answer also makes sense now

DanielSank

@DavidZ I wasn't super encouraged by feedback on the draft. If you have time later let's pow-wow?

0celo7

16:57

@YashasSamaga I do believe this is derived in Shankar's QM book for the Einstein model. I can give you a page if you want.

David Z

@DanielSank Sure, though I probably won't have time today.

DanielSank

@DavidZ OK. I was hoping that draft could be asynchronous pow-wow :-)

0celo7

You really like that word

Yashas Samaga

@0celo7 Shankar's Principles of Quantum Mechanics?

0celo7

@YashasSamaga yes

David Z

16:59

@DanielSank Oh, I assumed by "pow-wow" you meant something more synchronous than leaving comments on the draft

Yashas Samaga

I got a PDF of it ty

0celo7

@YashasSamaga check the chapter on the harmonic oscillator

Anonymous

@YashasSamaga A proof is given here vallance.chem.ox.ac.uk/pdfs/EinsteinDebye.pdf

DanielSank

In particular, I would like to know your goals. I'm still not sure whether you support the idea of fixing the immediate objectivity confusing bits, because you sort of said you didn't, but then sort of said you did.

@DavidZ I did, since the draft didn't work.

0celo7

@YashasSamaga page 220

David Z

17:01

I suppose that ends the chat session, then. Two weeks to the next one....

John Rennie

I wonder if we should stop the pre-scheduled chat sessions, and arrange chat sessions as and when they are needed.

vzn

@JohnRennie like idea of recurring mtg to draw in engagement but DZ founder sure doesnt seem into it much at moment :|

DanielSank

This just in from main:

> there is not a relationship cause i have a dog and my fish ate my cookie so i have a dollar and i need a home to go see my carpet

John Rennie

That spares the mods from having to keep the time free when, like now, there just isn't anything to talk about.

@DanielSank link?

David Z

@JohnRennie I dunno, the point of the chat sessions is really to get people in the room, more than to talk about specific things. So I think even if we don't have anything particular to talk about, it's still useful to have them.

0celo7

17:06

yeah, proof?

David Z

@vzn it's not that, it's just that I keep missing them - today because my reminder was silenced, as I said, and I didn't notice when it started.

DanielSank

@JohnRennie I generally support only having meetings as needed, but this one seems like a good idea because we e.g. welcome the n00bz.

David Z

(The chat sessions shouldn't rely on me to run them, anyway. Anyone else could handle the introductory stuff.)

ACuriousMind

@DavidZ I can't recall a single regular that would've showed up first during a chat session - it doesn't really draw people into the room for times other than those sessions themselves.

John Rennie

0

Q: Could AnyOne Tell Me How It works?

I have heard that the way that bats bite people, is by their razor sharp fangs yet i caught a bat with a team of experts and no fangs were seen. I have been confused ever since and i need to know how they get their food and blood and manage to eat it. I understand this question is illogical, yet ...

classical-mechanics quantum-information non-perturbative

vzn

17:08

@JohnRennie think biweekly is not that frequent & sustainable even with low engagement/ agenda etc

ACuriousMind

And it's often a bit awkward right now - one week we have an empty agenda, like today, and other times we're rushing through topics because it's full of hotly contested/interesting stuff

Terry Bollinger

Hmm, missed it today.

vzn

@ACuriousMind see that as more a PR problem than an issue with the mtgs per se

DanielSank

2

Q: Relationship between amplitude and frequency of a wave

What is the relationship between amplitude and frequency of a wave? Some say there isn't any relationship, some say that there is, but from their answers the relationship is still unclear.

homework-and-exercises forces waves

David Z

@ACuriousMind That could be, but having seen the effect chat sessions had on this room in the old days, I wouldn't be so sure. This room used to be dead. We'd go for days without anyone posting at all. Chat sessions changed that.

DanielSank

17:09

@JohnRennie

Yashas Samaga

@DanielSank I was talking about that Q earlier! "Frequency is inversely proportional to amplitude."

those are very bad answers

DanielSank

Yep

David Z

It could be that the chat sessions are not so useful now that the room is self-sustaining, but I personally think there is still enough value in them that it's worth keeping the regular schedule for the times when we do have something to talk about.

Yashas Samaga

and I am too emotionally sensitive, to an extent that I feel bad to downvote a new user's answer

DanielSank

@DavidZ FWIW I rarely show because of the time. It would be nice to modulate the time.

vzn

17:11

@DavidZ agreed but it kind of needs a (consistent? rotating?) leader

0celo7

I volunteer.

David Z

@DanielSank We could do that. Maybe have a meta poll for a new time slot.

@vzn I didn't think so, but if that's the case, we can plan accordingly

vzn

@DavidZ predict there will be no ideal time (too much variance in user time zone/ commitments etc) but a meta exercise to try to determine one seems worthwhile

ACuriousMind

@DavidZ Hm, maybe we could shift it periodically instead of fixing it so that people in other timezones/with different schedules might show up, that might encourage some new faces

David Z

@ACuriousMind Yeah, that's a promising idea IMO

vzn

17:14

@0celo7 really hard to tell if you are serious about anything you say :(

David Z

@vzn even the current time isn't ideal, and never was, it was just the best compromise

5

Q: When should we have regular chat sessions?

I'd like to set up a regular series of chat sessions, to allow us to discuss events on the site or in the world of physics, and to boost our community spirit. Or something like that. Anyway, what time works for people? Please upvote any times that work for you, downvote any that don't, and if not...

discussion chat

@DanielSank well, the TL;DR of my view is this: we're looking at two possible ways to change the homework policy, yours and mine. Yours is a relatively small change in wording, mine is a major change in content. I don't believe your change fixes all the big problems with the current policy, but I do believe it represents a net improvement. I support your proposal as long as it's understood that I still believe there are significant problems that your proposal doesn't address.

vzn

@DavidZ nice, but notice there was no response other than yours :| (2012!) o_O

David Z

I was kind of confused about where your draft fits in, though - it seemed to be more in line with my plan (fix the big problems) than with yours (make a single specific change)

0celo7

@vzn Why?

David Z

@vzn Yes, I believe that was based on some earlier feedback from a few people who would be most likely to attend. The "floor" was open for someone to suggest an alternate time, if they preferred.

0celo7

17:17

I'm not a nihilist

vzn

@0celo7 try reading boy who cried wolf

0celo7

my mom used to tell me about that

I thought it was pretty stupid and nothing like me

ACuriousMind

@DavidZ Is anyone who voted on that post even still around? ;P

David Z

@ACuriousMind Well of course I have no idea who voted on it

Yashas Samaga

0

Q: Reviews of laser-laser interactions

I'm looking for reviews or introduction to nonlinear laser-laser interactions. My interest ranges from CW lasers to pulsed lasers, coherent combining in nonlinear regimes, solitons interaction or any of their specific applications. Thanks

optics resource-recommendations laser non-linear-optics laser-interaction

off-topic?

John Rennie

17:18

@DanielSank aha, thanks. I remember that one.

0celo7

6

A: Additional chat room owners?

Our first appointments as additional room owners are Chris White and John Rennie. Welcome to your new role! We'll continue to add additional room owners in the future as needed, and as qualified candidates become available.

RIP

vzn

← dusts cobwebs

John Rennie

It's OK, I'm only brain dead

David Z

@YashasSamaga hm, maybe... I think it's certainly not a good resource-recommendations question, but not sure if it's actually off topic

vzn

@0celo7 maybe she had some reason for sharing it with you... maybe sometime think on the words self awareness/ denial...

Yashas Samaga

17:20

@DavidZ He/she also said looking for "Reviews". Not sure what he/she meant by that.

0celo7

@YashasSamaga Review is a standard academic term.

Survey works too.

Yashas Samaga

I just learned a new meaning for review lol

A review article is an article that summarizes the current state of understanding on a topic.[1] A review article surveys and summarizes previously published studies, rather than reporting new facts or analysis. Review articles are sometimes also called survey articles or, in news publishing, overview articles. Academic publications that specialize in review articles are known as review journals.

0celo7

@heather 1200 words.

vzn

@Danu lol everyones a critic eh? thought the movie was mostly indistinguishable from the strip. do you not like the strip? agreed movie was not much by (hollywood) movie stds.

0celo7

@vzn He's always a critic.

loltospoon

17:33

Hello everyone :)

vzn

@0celo7 & youre a rap critic. eg eminem :P

0celo7

I'm not constantly in a bad mood.

vzn

@0celo7 never said that. "criticism" is not nec regarded as related to authors mood, its also like "intellectual analysis" etc. eg literary criticism, movie criticism etc. then there are other meanings of "criticism"

0celo7

@yuggib I knew that compact resolvent trick. It's in Evans.

vzn

@DavidZ btw thx for helping accomplish all that, like to see/ encourage/ promote engagement in all different forms :)

Yashas Samaga

18:04

"the molar heat capacity of any substance must go to zero as the temperature goes to absolute zero." why?

textbook says it violates the third law of thermodynamics but how?

ACuriousMind

@YashasSamaga That depends on your exact formulation of the third law

dmckee

@YashasSamaga The thing to take away from this is that serious review articles are a big project and are usually undertaken by up-and-coming stars (partial to announce the breadth of the mastery, but also to place the developing tools in context for the established practitioners) or end-of-career sages (to pass along their large body of knowledge and set the record straight on issues which have developed a questionable folklore).

Yashas Samaga

@ACuriousMind My textbook has the Carnot statement, Kelvin statement and Planck statement.

Kelvin and PLanck statements are the same thing though.

ACuriousMind

@YashasSamaga In any case, Wiki has your answer

dmckee

@YashasSamaga The thing I hate about that caption is that it doesn't admit to the statistical nature of the process. It's not a picture of an atom, it is the overlay of many pictures each of which contains very little information about the overall structure. But the ensemble tells us a lot.

Yashas Samaga

18:11

I am going to guess that it is going to some some QM stuff

ACuriousMind

The entropy simply diverges if you can't suppress the $1/T$ factor by a heat capacity going to zero.

Yashas Samaga

ok now it makes sense

ty

loltospoon

18:25

@AccidentalFourierTransform if you're out there....(cue dramatic music)

ping me

skullpetrol

DUN-DUN-DUUUUN!!! - Sound Effect

►

Sir Cumference

Is it possible to add a vector graphic to an SE answer?

DanielSank

@DavidZ thank you, that is quite clear.

ACuriousMind

@SirCumference No.

dmckee

52

Q: Allow SVG image uploads

I am unable to upload SVG image files to Stack Overflow. So I would like to know why it is blocked while other image formats are allowed. SVG images are useful for diagrams such as tree diagrams for algorithm discussions.

feature-request images imgur

Sir Cumference

18:34

Dang...same time

ACuriousMind

@dmckee Ninja'd :)

dmckee

This much more recent post seems to suggest they are noodling improvements, but doesn't give any hints as to how they prioritize these things.

Here is a work-around (from the original link, none-the-less), but I think that unofficial hosting sites are being officially discouraged these days.

Sir Cumference

Hmm...testing in the chat:

...nope

Anonymous

@SirCumference upload.wikimedia.org/wikipedia/commons/1/1a/…‌ly)‌.svg

Anonymous

Sir Cumference

18:48

@Mystic Huh, neat

Anonymous

Just paste the link

Anonymous

Directly

Sir Cumference

Yep

@Mystic Does that work on pdfs?

Or just svgs?

Anonymous

@SirCumference Don't think so

Anonymous

Just svg

Sir Cumference

18:54

k thx

Yashas Samaga

19:12

http://physics.stackexchange.com/questions/137382/is-momentum-of-a-moving-body-a-vector-or-a-scalar-quantity/317090#317090
-_-

VLQ?

that person even commented "Nice answer very very good " for themselves

Jaime Gallego

Oh god

DanielSank

19:57

What is a-goin' on around here?

Jaime Gallego

Times are not a-changin'

jdbiochem

Hey physicists.

Problem Solving Strategies

Transcript for