The h Bar

12:17 AM

@ZeroTheHero I asked 'cause the Windows laptop was disagreeing with the linux desktop

but then the linux desktop started disagreeing itself

so I imagine it's more of a local issue

@M.N.Raia I'm afraid not

In Mexico, my solution to that problem was to go to second-hand bookshops. They congregate at a specific street in downtown Mexico City, and several of them have reasonably sizeable science sections.

(I haven't been back there for several years, partly through living abroad and partly because the selection at those stores, while great for the beginning of my university degree, started showing its limitations in later courses. But they're still there, and it's a great solution unless you're starting to scratch at postgraduate-level material.)

I don't know what it's like in Brazil, or where you are based there. But I suspect that the two cultures are similar enough that there will hopefully be an equivalent.

dm__

1:41 AM

hello

anyone home?

Anonymous

3:03 AM

@M.N.Raia As for the expensive textbooks, I simply print them after getting hold of a PDF copy from Libgen.

tarit goswami

6:30 AM

In the algebraic method of solving the Schrodinger equation for Harmonic oscillator, while factoring $$-\frac{1}{2m}\big({\hbar^2\frac{d^2\psi}{dx^2}+(m\omega x)^2\psi\big)=E\psi$$, in Griffiths book, it is considered as $-\frac{1}{2m}\big(\frac{\hbar}{i}\frac{d}{dx})^2+(m\omega x)^2\big)\psi=E\psi$.. Firstly, how we can consider an operator like that?

In the algebraic method of solving the Schrodinger equation for Harmonic oscillator, while factoring $$-\frac{1}{2m}\big(\hbar^2\frac{d^2\psi}{dx^2}+(m\omega x)^2\psi\big)=E\psi$$, in Griffiths book, it is considered as $-\frac{1}{2m}\big( (\frac{\hbar}{i}\frac{d}{dx})^2+(m\omega x)^2\big)\psi=E\psi$.. Firstly, how we can consider an operator like that?

it may be very intuitive, but not getting at this moment :(

John Rennie

@taritgoswami $(d/dx)^2$ just means apply the $d/dx$ operator twice ...

Loong

6:46 AM

(ux.stackexchange.com/q/123560/59508)

tarit goswami

@JohnRennie Ok, then why it is treated like a simple variable while factoring it into $$\frac{1}{\sqrt{2m}\big(\frac{\hbar}{i}\frac{d}{dx}\pm im\omega x\big)$$

$$\frac{1}{\sqrt{2m}}\big(\frac{\hbar}{i}\frac{d}{dx}\pm im\omega x\big)$$

John Rennie

You have a rogue {

tarit goswami

Edited :)

John Rennie

$$\frac{1}{\sqrt{2m}}\left(\frac{\hbar}{i}\frac{d}{dx} - im\omega x\right) \left(\frac{\hbar}{i}\frac{d}{dx}+ im\omega x\right) $$

@taritgoswami is that what you meant?

tarit goswami

No

There are two parts, one with + and another -

I have written it as $\pm$

@JohnRennie Yes

John Rennie

6:55 AM

That's a perfectly valid way to rewrite the equation

tarit goswami

How? I am first time having trouble to treat $d/dx$ in this way :(

John Rennie

Just remember that for operators mutiplication is defined as $\hat a \hat b \psi = a(b(\psi))$

tarit goswami

Ok, but when I multiply them there is an extra term $\hbar \omega$

John Rennie

And $\frac{d}{dx^2} = \frac{d}{dx}\left( \frac{d}{dx} \left (\psi \right)\right)$ so it all works.

@taritgoswami I can't see a term in $\hbar\omega$ ...

tarit goswami

@JohnRennie Ok, please wait I will upload the calculation from Griffiths

doesn't that mean $a_{-},a_{+}$ are not the factors of $$\frac{1}{2m}\big( (\frac{\hbar}{i}\frac{d}{dx})^2+(m\omega x)^2\big)$$?

Can I ping you later? (I have to go for lunch.. it will be not available after 20min :p )

John Rennie

7:16 AM

Yes, I'll be around for a few hours

Slereah

8:38 AM

morning

PM 2Ring

Another day, another OP misled by rubber sheet gravity. physics.stackexchange.com/questions/459344/…

Slereah

8:54 AM

Can't we just delete any question that's just "How does GR work???"

I think the answers have been given so far

John Rennie

Breezy in Chester this morning

Physics Meta

11:06 AM

0

Q: Contradictory answers in the duplicate and the main

In this question Can I determine the potential term in the Schrödinger equation based on the eigenvalues? , the duplicate has the opposite answer. I had answered in the linked duplicate In quantum mechanics, given certain energy spectrum can one generate the corresponding potential? saying it w...

discussion

Avnish Kabaj

1:39 PM

'Hercules' vigilante kills suspected rapists in Bangladesh Rights groups fear extrajudicial killings after at least three rape suspects found murdered in the past two weeks.

Anonymous

1:53 PM

@AvnishKabaj ...what's that for?

Avnish Kabaj

3:29 PM

Nothing, just that times are changing.

If you feel that it is inappropriate for this chat feel free to trash it @Blue

Anonymous

@AvnishKabaj I don't think it's inappropriate; just a bit heavy. :)

Avnish Kabaj

That i agree too

Anonymous

Also, I'm not sure from that alone we can conclude "times are changing". Crimes and murders have been rampant in the past too.

Avnish Kabaj

I haven't heard of anything of this sort before.

I'm hardly eighteen though

PM 2Ring

Generally, it's a Good Idea in chat rooms to avoid topics connected with religion, politics, or sex. Unless those things are on-topic on the main site.

vzn

4:15 PM

← always looking out for diverse/ lively chat rooms/ topics/ discussions on SE, increasingly failing

John Rennie

4:32 PM

From the play A Man for All Seasons:
Roper: So now you'd give the Devil benefit of law!
More: Yes. What would you do? Cut a great road through the law to get after the Devil?
Roper: I'd cut down every law in England to do that!
More: Oh? And when the last law was down, and the Devil turned round on you — where would you hide, Roper, the laws all being flat? This country's planted thick with laws from coast to coast — man's laws, not God's — and if you cut them down — and you're just the man to do it — d'you really think you could stand upright in the winds that would blow then? Yes, I'd giv…

2

user351417

@vzn If there's a dearth of diverse or lively discussions topics after excluding religion, politics, and sex, we have bigger problems than still SE chat rooms.

vzn

@Chair sometimes feel theres too many mods + assistants + restrictions for freeform discussion and that it works against the engagement/ cohesiveness of SE chat rooms.

user351417

I had no idea that punctuation in displayed formulas (QMechanic's edit) was a thing, but mathoverflow.net/q/6675 (more specifically mathoverflow.net/a/6684) was interesting and fun.

Anonymous

@Chair Yeah, it's a thing. A lot of papers written in TeX do that. For example: arXiv:1710.03599.

Anonymous

(I use it on QCSE too.)

user351417

4:39 PM

@vzn That's not exactly the point I was trying to make... SE chat rooms should, to a great extent, be able to cover the topics one would casually talk about with a person in real life, right? And surely we should have other topics to cover. I find it reasonable for mods/SE to say that when we talk here, we should stay away from potentially problematic subjects, particularly since they're the ones who'll look particularly bad if things blow up.

user351417

@Blue I keep forgetting to make something of those two sentences I have in the draft of the duplicates answer on meta.

Anonymous

> Whichever rule you follow, the journal you send it to will want the opposite.

Anonymous

LOLOL

user351417

My apologies, there's a decent bit of work at school presently.

vzn

@Chair there are fairly strong differences in philosophy what "SE chat rooms [topics] should to a great extent be able to cover" and some of it along mod vs nonmod lines. official guidelines are puposely vague. wonder why there is so much attn to "things blowing up" etc ... think it can become too vanilla to the point that its not engaging.

Anonymous

4:42 PM

@Blue Reminds me: I received the comments from the reviewers yesterday. It was disheartening...to say the least. :P Apparently, I have to put in another month's worth of work.

Anonymous

@Chair Yeah, no worries. Take your time. :)

user351417

@Blue Honestly though, it's a bit disappointing that certain things need to be said there: for instance, that it's not just about physics SE duplicates: google indexes lots of nice stuff and among the most popular non-deleted comments are "I'm voting to close this for insufficient prior research" and similar stuff. And presumably the people who don't do much duplicate-hunting are the kind who won't open the links to the help center and math SE posts which are there in the question.

user351417

I should totally put a lmgtfy link in the answer

user351417

Must rephrase that yikes

user351417

I should condense the important bits of data.stackexchange.com/physics/query/6348/…, regarding the insufficient-prior-research comments.

user351417

4:58 PM

Yeah, but that deleted message... I want to be clear about the status of questions which are not particularly well-researched (i.e. a few focused attempts to think/search online would take OP very far), but do not have answers on Physics SE yet. But I'm not quite sure what we should be doing with those in general; it's all quite subjective so there's no room for making an actual policy of sorts.

Anonymous

@Chair From what I've seen, on Physics, the insufficient research effort close reason is hardly used. There are some arguments on the other end like: "Yes, but I thought an answer here would be useful. There are plenty of questions on Stack Exchange sites that have already have answers elsewhere on the internet. It doesn't make the question on Stack Exchange less than useful." .

Anonymous

That statement is from a Cryptography mod. FWIW I don't quite agree with their point. ^

user351417

Yes, there is definitely a strong argument that we should be willing to keep such questions around here. Perhaps it could be argued that our quality standards are less... relaxed... than some other websites, so a well received answer here probably does mean something. But with the broken window thing we could get a whole lot of questions which haven't shown up before, but have been covered so much that they're really boring to go over again.

user351417

(just speculating; I don't have any examples at my disposal at the moment)

John Rennie

I used the insufficient effort close reason today. Give me a moment and I'll find the question ...

0

Q: What is the relation between salinity and refractive index?

Salinity is the amount of dissolved salt in the one kilogram of the water. There are many factors affecting salinity, such as density, concentration, refractive index of the medium and many more. I want to know about the exact relation between salinity and refractive index.

electrical-resistance water fiber-optics

user351417

5:13 PM

There are a whole lot of problems with that data explorer thing I was thinking of though... firstly, there's a HUGE survivor bias. Secondly, if I'm adding all the insufficient research-related comments (including "What are your thoughts?, which is also used for homework), I'll need to do the addition for migration and homework-related comments as well, to make a meaningful comparison (e.g. to say that comments regarding the insufficient research close reason are the (3rd?) most popular variety)

Emilio Pisanty

ah, wait

user351417

@EmilioPisanty 10k tools?

Emilio Pisanty

yes

that's the last 90 days' worth of custom close reasons

user351417

Huh, they (10k tools) never sounded very useful/interesting in the privileges help center, but I guess I last looked at it a while back.

John Rennie

Harsh :-)

Emilio Pisanty

5:15 PM

@Chair the documentation of the 10k tools is.... uh, rudimentary, I guess?

@JohnRennie more on the "unwelcome or unkind", I should say

user351417

@JohnRennie But perhaps not incorrect.

user351417

@EmilioPisanty It is certainly extremely condescending, and if 5 voters choose that as the custom reason to put a score of 4 on that comment, we're quite crude.

John Rennie

@EmilioPisanty it's very easy to get annoyed towards the end of the morning's reviewing and say something cutting. I've been guilty of this.

user351417

Hopefully most people chose something a bit more mild like 'homework' or 'insufficient prior research'.

Emilio Pisanty

@JohnRennie sure

but that's the point of Not Holding Grudges while still flagging, no?

user351417

5:18 PM

I found the politeness of my comments increase drastically once I started using those userscripts.

Anonymous

@Chair That's true. Anyway, the longer I think about this, the more I come to agree with JR's sentiments here:

Anonymous

19

A: Flagging low quality answers: an experiment

I heartily support Emilio's proposal, but to explain why I support it will require a bit of rambling. So please bear with me and I'll try not to make this too painful. The Physics Stack Exchange has evolved into an educational resource. We hoped it would be a research tool akin to the MathOverfl...

Anonymous

> The Physics Stack Exchange has evolved into an educational resource. We hoped it would be a research tool akin to the MathOverflow but for whatever reason that didn't happen. It appears that the culture amongst research physicists just doesn't lend itself to this goal. The Theoretical Physics SE got canned due to lack of traffic and the Physics Overflow is withering on the vine. So an educational tool is what we have ended up with.

user351417

@EmilioPisanty Looking at that picture, there are some which may or may not be synonymous to "insufficient prior research". For example, the last one is a link to a wikipedia page, which could perhaps be interpreted as an indication that the solution to the question was extremely obvious. But we don't know without seeing the question.

Anonymous

The thing is, it may be boring for us to go over the same topics again and again and again, BUT

Anonymous

5:22 PM

simply linking to older discussions related to that topic often doesn't solve their problems (the new users' or beginning physics students'). Sometimes they need answers tailored to their specific questions. They can't spot the link between their questions and previous duplicates probably due to lack of experience.

Anonymous

Also, there's this thing that most users really don't know how to use Google. Using Google is indeed a "skill" these days.

Anonymous

I really don't know how to solve this problem, tbh.

Anonymous

The best we can do is to train our current "experienced" users to use guide the newcomers well. The flood of duplicates and low-effort questions isn't going to stop anytime soon and attempts at completely blocking them will simply lead to vehement protests.

Anonymous

I mean, c'mon, the homework issue has been debated ad nauseam with no net result. We couldn't manage to stop them altogether. If it were just upto me, I'd not only close them but directly delete them. But well, such a policy needs to be implemented from the beginning of the site (by a rather vocal group like Math Overflow) and not suddenly in the middle.

PM 2Ring

5:50 PM

On a couple of homework questions I've written comments like "Ok, we don't do worked exercises here, or check their solutions. We answer conceptual questions. So do you have a conceptual question that will help you solve this exercise?" But I haven't gotten a positive response, and once the question is put on hold the OP usually abandons it. I get the impression that most OPs that post assignment dumps don't even understand what we mean by a conceptual question.

Anonymous

@PM2Ring That. It takes considerable skill and knowledge to convert a homework question into bite-sized conceptual chunks.

Anonymous

And, EFFORT...which not many are willing to put in.

PM 2Ring

Maybe it's a language barrier, or cultural thing. A big percentage of assignment dumpers seem to come from India, or other countries with a strong emphasis on the object of study being to pass exams, rather than to actually gain knowledge in the topic. So maybe we need to give them more assistance in extracting conceptual questions from their assignment question.

Anonymous

> So maybe we need to give them more assistance in extracting conceptual questions from their assignment question.

Anonymous

Yeah, but what's our incentive for that?

Anonymous

5:55 PM

The experienced users would rather spend their time answering something they find captivating.

Anonymous

And there's also the rudeness thing from newbies. They'd rather spend their time arguing than trying to improve their question.

PM 2Ring

Of course, that does take the OP's cooperation. Otherwise, it just turns into a guessing game, trying to figure out what the OP doesn't know but needs to know.

Anonymous

36

Q: Have we lost the necessary critical mass of professional physicists?

A while back, we had this discussion in which we tried to measure quantitatively whether the site was gaining or losing non-novice users. Since then, I've had the distinct subjective impression that the quality of discussion on the site has gone down markedly. I went through some of my own questi...

discussion content-level users

Anonymous

> Subjectively, I'm finding that I've been spending my time on the site in unenjoyable activities like arguing with angry and belligerent beginners about friction and Newton's third law. I've decided to become inactive on the site.

Anonymous

I can totally empathize with Ben there.

Anonymous

5:58 PM

@PM2Ring Yep, and that's exactly what drives away the experts.

PM 2Ring

@Blue For sure! Yet we still have Ben, thank goodness.

.I guess in some cases, if we see a homework question on a topic we like, we can ignore the OP, extract a relevant conceptual question, and answer it (or close it as a dupe if it's already been adequately covered). That way, they can't claim that we're refusing to help them, and we can say we're giving them the help they really need.

Larry Harson

@Blue ironically, Ben who posted that question left for a while, then came back: so he must like the site :)

ZeroTheHero

@Blue IMO the proportion (and maybe the absolute number) of good questions has gone done, but the quality of the answers to these good questions has not.

Anonymous

@LarryHarson That doesn't change the fact that he truly had those bad experiences. Also, Ben was perhaps only one (out of a handful) who expressed those feelings so publicly. You will never know how many users silently left the site for good.

Anonymous

@ZeroTheHero That maybe true...

ZeroTheHero

6:09 PM

@PM2Ring I agree with this: if the OP doesn't get an answer to his/her specific question in a short time he/she will abandon. If the question of downvoted the time to abandon is even faster.

PM 2Ring

When I see those assignment dumpers, I'm often reminded of Feynman's experience in Brazil just after WWII. The academic culture there was highly focused on passing exams. What hope do the kids have when the professors themselves believe that science expertise means the ability to answer exam questions, and who cannot really apply the scientific method?

Larry Harson

@blue in particular I can think of Matt Reece at Harvard who no longer posts here; and Lubos Motl visits perhaps once or twice a week, as opposed to every day in the past. On the other hand Prof Andrew Steane is a relatively new user; so I'd say people are moving on to new things and being replaced

PM 2Ring

You can read about Feynman's sxperience here: v.cx/2010/04/feynman-brazil-education

Larry Harson

I'd say the problem is that the good questions have already been posted, so it's very difficult nowadays to post a good original question; it's likely to be a duplicate

ZeroTheHero

@LarryHarson there are plenty of good questions to be posted. It's ** hard ** to post good questions so they are few and far between.

Anonymous

6:20 PM

@ZeroTheHero A more interesting query would be: "Has the number of quality answers to those good questions gone down?".

Physics Meta

0

Q: Why directly voting to close a question does not add to your number of reviews in the queue

If you go into the "close votes" review queue and either selecting "Leave Open" or "Close" adds a count to the number of reviews you have done in the "close votes" queue. However, if you are viewing a question outside of the queue and vote to close it, this does not add a number to your number of...

discussion vote-to-close

ZeroTheHero

@Blue It's hard to get a grip on this because a single good answer will often be enough to attract consensus.

PM 2Ring

6:45 PM

I get a bit frustrated by questions from OPs who've been mislead by some pop science, or at least misunderstood it, and have then gone on to develop their off-track ideas in some bizarre direction. Eg, this question I linked earlier chat.stackexchange.com/transcript/message/48914427#48914427

It can be really hard to educate these people because they cling so fiercely to their misconceptions. And invariably they don't know any calculus, which is why they got so misled in the first place.

Anonymous

> It can be really hard to educate these people because they cling so fiercely to their misconceptions.

Anonymous

Uff, that brings back some bad memories. :P

PM 2Ring

I used to live near a really good public library. Over the years, I read almost all of their pop science books. Some were really good, because they were written by actual scientists, although most of those were rather old, like popular works by Gamow. The modern trend is for pop science to be written by people with arts degrees with an interest in science. Or they're written by scientists like Hawking who get told that each equation will halve the sales.

Anonymous

> get told that each equation will halve the sales.

Anonymous

Well, that isn't false...

Anonymous

6:59 PM

Say, hardly any non-scientist would try to work through Penrose's Road to Reality on their own.

PM 2Ring

Anyway, I found so much dodgy or misleading stuff in those books that I decided I had to do something about it. So I started writing corrections in the books. In pencil, because it felt less like vandalism than using pen. ;)

Anonymous

Lol

PM 2Ring

@Blue Probably not. I've never actually seen a copy of Road to Reality, but I do intend to investigate it one day. I've got his Emperor's New Mind, which has lots of great stuff

Anonymous

If you're actually trying to learn the subjects I don't see much value in reading the pop science books anyway. They will of course contain misleading articles because they're meant for getting the public curious about science rather than teaching then rigorous science. Writing non-misleading textbooks for the layman is extremely difficult.

PM 2Ring

It's a shame about the quantum consciousness stuff though.

Anonymous

7:07 PM

Well... :P

Anonymous

It's a business too.

Anonymous

@PM2Ring Ah, yes. Emperor's New Mind is a good book. I had read the first half of it.

Anonymous

IIRC the first chapter is mostly about binary conversions.

tatan

@Blue You study EE at JU right? How did you learn so much Quantum Computing ? It is a part of your course ? ;-)

PM 2Ring

But it's not like Penrose only got interested in consciousness in his mature years, it was always an interest. I first learned about him in connection to the Penrose triangle and staircase, which the Dutch artist Escher made famous. Penrose was fascinated that our minds could (sort of) make sense of such counterfactual structures.

Anonymous

7:12 PM

@tatan Eh, I don't know much. Just read some textbooks, papers and watched some videos.

Anonymous

I picked up most of what I know while asking and answering questions on QCSE.

Anonymous

No, it's not a part of my course.

Anonymous

@PM2Ring Yeah, I've heard a lot of stories about him!

Anonymous

Mar 18 '18 at 9:19, by Dawood ibn Kareem

Almost 30 years ago, I attended a lecture by Roger Penrose where he presented the idea that since a classical universe is entirely deterministic, free will must be a quantum phenomenon. Somehow from there, he jumped to the idea that consciousness must also be a quantum phenomenon. I happened to be sitting next to a leading expert in AI, who spent the entire lecture with his head in his hands muttering "you can't say that" over and over.

PM 2Ring

> Writing non-misleading textbooks for the layman is extremely difficult.
Definitely! Physics without maths is like pornography without pictures. ;)

Anonymous

7:18 PM

4 hours ago, by PM 2Ring

Generally, it's a Good Idea in chat rooms to avoid topics connected with religion, politics, or sex. Unless those things are on-topic on the main site.

Anonymous

:P

PM 2Ring

@Blue Very smart people aren't immune to really dumb ideas.

@Blue Ok, I deserved that. :)

Anonymous

I mean, I do agree with your general sentiment there. It's impossible learn physics without the mathematical formalism!

Anonymous

N'way, good chatting. Sleep time now. Cya! :)

PM 2Ring

See ya, Blue!

JMac

8:42 PM

physics.stackexchange.com/a/456465/127931 lol the comments, how silly of me to not assume that OP was talking about gravity due to "macro-entanglements" and "space is not naturally ordered ("3d") and arises due to interactions of consciousness" and instead address actual physics

PM 2Ring

9:00 PM

@JMac Damn. Now I have to recalibrate my crank index calculator. Again.

vzn

9:44 PM

← prefers pictures :P

DanielSank

10:20 PM

Building a quantum computer with superconducting qubits (QuantumCasts)

►

7

:-D

ACuriousMind

You have far less tentacles than I expected from your profile picture.

2

I like the little jester hat to denote "quantum" :D

DanielSank

@ACuriousMind Thanks. The video editor originally converted it to a magic wand and I was like "NO".

@ACuriousMind They're tucked into the shirt.

ACuriousMind

@DanielSank Right. I guess they never show your lower half for a reason ;)

DanielSank

10:37 PM

>.>

ACuriousMind

But, seriously, @DanielSank, nice video. I appreciate that you're actually getting just technical enough to not distort what's happening in the way pop-sci often does.

DanielSank

@ACuriousMind Thanks. That's the goal.

I don't want to hand out easy falsehoods.

...and I think it's important to understand why classical is classical and quantum is quantum.

Not saying the video explains it all (it doesn't) but it might get people to ask some good questions.

Transcript for