12:01 AM
the obvious starting point is dirac's concept of the dirac sea in QFT
which was circa 1930 (i guess calling it 'qft' at that point is a stretch)
four years later there's a paper by Schubin and Wonsowsky "On the electron theory of metals" which does reference "holes"

12:38 AM
Instead,Dirac's holes have developed into antiparticles...
So,Schubin and Wonsowsky are the ones!

12:59 AM
maybe? i'd need more historical background to be really sure
it's plausible

4 hours later…
4:36 AM
Is anyone here into solid state or condensed matter physics?

5:20 AM

1 hour later…
6:30 AM
Good morning!
I have written 21 answers till now and I am very satisfied with the upvotes I got on them, however the acceptance ratio (accepted answers/total answers) of my answers is quite low than I want it to be. It is 33.33% currently, which is lower than I want it to be. I would like to have somewhere around 66.67% acceptance ratio. What should I do to make my answers get more accepted? Or am I just hoping too high for acceptance ration? Or is there no need to think/worry about low acceptance ratio?

Where do you see the acceptance ratio?

@JohnRennie I manually calculated it :)
That's just a buzz word invented by me
But I am quite sure you can write a SEDE query for it. Let me try...

Ah, OK. I was curious what my acceptance ratio is but I feel disinclined to count manually given that I've written nearly 6000 answers :-)
Anyhow I wouldn't worry about it. I suspect 33% is pretty good. If it was 0% you should be worried, but not otherwise.

@JohnRennie Hmm... That's what I was doubtful about (that is 33% good or low).

@JohnRennie 46 %

6:45 AM
I don't know what I sent does, but it does something similar :P

@FakeMod I think you've calculated the overall average.

@JohnRennie That way, it seems that 33% is a decent acceptance rate, not bad.

Yes

A person with only one answer accepted has an acceptance rate equal to 100%
I don't know who is that however.
In [SpaceExploration.SE](https://space.stackexchange.com/users/32757) I've an acceptance rate = 100% :-)
(I've only one answer there which is accepted)

@Loong thanks. That's higher than I expected.

6:58 AM
Among the top 14 users (by reputation), ACM has the highest acceptance rate (53%). The 15th user, joshphysics breaks this record with his 59% acceptance rate.

@FakeMod That's a better way to do that - order by reputation.

@FakeMod I'm not sure why you're aiming for a particular acceptance ratio. Whether or not an answer is accepted depends a) on the OP (some accept anything that remotely answers their question, some are picky, some never accept anything) b) the timing of your answer - OPs will rarely change the acceptance if you answer days or months after they've already accepted another answer, and some have a tendency to simply accept the first.
c) the amount of other answers - if your answer is the only one, chances of it getting accepted are rather high if it's correct, but if it's one out of five answers to a basic question it's likely that it can be correct and helpful and still not get accepted

@FakeMod joshphysics had the most amazing deep insight into physics and he wrote answers that really go to the heart of the issue. He is sorely missed.

@ACuriousMind Out of 14 unaccepted answers, 10 of those do not have any other related accepted answers. And for those(except two), I don't even know whether the OP has read my answer or not, so I can't even ask them for accepting the answer. But it isn't a problem at all. I was just wondering so I thought I would ask it here. Thank you John Rennie and ACM.

@JohnRennie geez, he's not dead :P

7:12 AM
@ACuriousMind hahaha!

@ACuriousMind :-) Missing in action then!

On his website, he says that he's just too busy to contribute...

@FakeMod answering questions here can soak up time like you wouldn't believe. How people who have a day job can do it I don't know.
I only answered so many questions because I'm retired and have nothing else to do.

@JohnRennie I obviously know :)

joshphysics just found it was soaking up all his time and it was interfering with his work.
8

I am turning to the community to determine a means by which I can limit my incessant desire to participate on this site. Does anyone, especially one of the more active users (you know who you are), have any constructive suggestions?

He had to go cold turkey :-)

7:15 AM
@JohnRennie Like I felt and am feeling right now... But I won't delete the account this time. I might abandon it till the JEE ends.

@FakeMod yes, if the site is helping with preparing for the JEE then obviously use it, but the JEE has to come first. A high rep on this site won't get you a job!

Every night, I feel guilty for the time on spent on Physics SE when instead I should be solving JEE integrals, studying JEE chemistry, etc. And the next morning, I again start coming back to the site :P
@JohnRennie definitely!
@JohnRennie and to be fair, I would be learning more JEE stuff if I use the time spent on this site to use for JEE purposes...

If you aren't enjoying something, and no-one sane enjoys preparing for the JEE, then it's entirely natural to seize on every opportunity to do something else.
I think it's good to have some distractions because if you try to do nothing but JEE work I suspect you work less efficiently, but you need to keep the distractions under control.

@JohnRennie In fact I love doing JEE math and physics, but for 2.25 years, NO! It's like, you would like this site for a month and you'd spend your whole day on this site, but doing it for 2 years will bore you out of your wits.
It's the time duration which has made me less enthusiastic about JEE, not the exam or the toughness...
12

I think there are some unnecessarily cynical views in Nikolaj's answer and the comments to it. It's human nature to like approval from your peers, and upvotes are a proxy for approval - a virtual pat on the back if you will. Of course the flip side is that downvotes are really quite wounding - I ...

I see, so it was you who gave Josh the suggestion to leave :P

:-)

7:44 AM
Hmmm... I think I should leave.

1 hour later…
9:06 AM
@ACuriousMind see, now the same question arises for

What "same question"?
(your ping doesn't link to any particular message so I don't know what you're referring to)

9:23 AM
Guys, which political philosophy do you favor most? (e.g socialism, communism, liberalism...)

Pragmatism works for me.

"Consider the practical effects of the objects of your conception. Then, your conception of those effects is the whole of your conception of the object." that's what I mean by overcomplicating simple stuff
i'm a fan of antiovercomplicism
nvm the word is too complicated
I'll call it antiunnecessarioovercomplicaticism
My teacher is forcing me to watch some video about socialism
Since I favor entrepreneurship, I'mma go with liberalism because I don't want to build a big company and then the government comes and says: "I made this."

Ah, the "I choose this because the alternative is a strawman" approach.

@NovaliumCompany When anyone says I am a <insert philosophy here>alist it means they are limiting their mental horizons to their chosen world view. This is a dangerous thing to do because the world is a complicated place and no ism covers all aspects of it.

Ah, I hate when my brother touches My personal things

9:37 AM
@JohnRennie All am I saying is that if my entrepreneurial stuff will be touched by the government, then no thx

That isn't the basis of a philosophy. That's an entirely reasonable perspective on being rewarded for the work you have put into your project.

Also, isn't it a bit unfair if I'm smart, hardworking, inspired, motivated, persistent and then I'm getting the same as the dumbs around me?
I mean, communism and socialism sounds to me like: Hmm, let's treat everyone like equals even tho they are not

People have a tendency to define terms like communism to mean whatever is convenient for their argument. I think you should read Max and the communist manifesto before you start criticising communism.
If you want to criticise a particular country's implementation of communism then of course you can do that.

Isn't this what communism does? It gives everyone equal?

@JohnRennie Not so sure about that. I think it is perfectly possible to describe oneself as an adherent of a particular philosophy while being willing to compromise and recognizing (at least some) other viewpoints as admissible. Not all X-ists are fanatics :P

9:48 AM
It's true I have no in-depth idea of what communism, socialism, liberalism, capitalism, democracy... are. I'm just criticizing the ideas I thought they represented :D

@NovaliumCompany so you were commenting based on what you think communism is, presumably based on what you have heard other people say? That isn't a good place to start.

@ACuriousMind I am generalising of course but over the years I have heard so many people say (and I paraphrase) I am proud to be a xxxxalist. To my ears this sounds like I am proud to be a bigot, and I am instantly suspicious of their attitude.

@NovaliumCompany "Communism" - just like "liberalism" or "conservatism" - is an umbrella term that includes somewhat related but distinct viewpoints. For instance, a famous slogan from Marx is "From each according to his ability, to each according to his needs", which is rather different from some naive attempt to make everyone "equal".

This is entirely different to having sympathies with a world view, which I suspect is how many of us really see the world.

9:52 AM
"From each according to his ability, to each according to his needs" I interpret this as not making people insanely rich. There's two options: you can be lazy and get just enough to survive, or you can be hard-working and get everything you NEED.

And e.g. ideas like workers owning the means of production are not about material equality but removing the exploitation of labor, i.e. not letting people ("capitalists" in the original Marxist sense) profit off the labor of others simply by virtue of owning something.

I've something to ask - there are numerous selection rules regarding the total, orbital, spin, magnetic, quantum nos. for electric dipole transitions, however there is sometimes written that there is no bound on 'n'. Does this means that transitions within same 'n' are allowed?

@ACuriousMind Hmm, sounds interesting. When you say it like that, it makes capitalism look bad.
I feel like knowing that you can't own A LOT demotivates you to even try to be inovative.
donno
I've never looked at it that way, something to think about. Thx curious mind
@ACuriousMind If that's so, then why a lot of people prefer capitalism over communism? Why the citizens of East Germany jumped over the Berlin wall to go to the "heavenish" west side?

@Vivek good question. I think the answer is that yes transitions with $\Delta n = 0$ are allowed.
I'm fairly certain we see these transitions in some atomic spectra.

Personally, I see entrepreneurship as a tool to acquire the power I need to create wondrous things, to improve lives and to explore the unknown. Or better said, to target resources to places that push humanity forward and to uncover the beyond. I don't give a damn about politics and money. It's just an illusion and a mess.

10:06 AM
@NovaliumCompany As I said, "communism" is an umbrella term. The authoritarian and repressive regimes of East Germany or Soviet Russia are not necessary for anything that calls itself "communism". E.g. there are anarcho-communists who don't want a large nation state at all, and aside from hardcore Stalinists you will not even find many "big government" communists who will be willing to defend the actions of these regimes.

@Vivek In fact I've just remembered that the well known sodium D lines are the transition 3s to 3p, so they are an example of $\Delta n = 0$.
Apologies for interrupting the political philosophy with physics :-)

meh, I said what I had to say, I hope it reveals that I'm not a bad person who cares about power and money just for the sake of having

@Vivek The 'n', in the end, is just a number that represents energy, it has no other conserved quantities associated with it, while the other quantum numbers all in one form or another relate to spin or orbital angular momentum, which has to obey conservation laws as well as certain coupling rules (due to the way some spin representations decompose into others). So there are no restrictions on 'n' because it's the 'boring' number of the four ;)

Let's make a government system like capitalism where the instantly rich are forced to invest a part of their capital into something they believe in, something that will benefit the whole, push humanity forward, discover the unknown and generally do something positive. In that way, all the idiots with money who only care about feeding their bellies will be eliminated. I'm not seriously proposing this, just a thought. Does something similar exist already?

@NovaliumCompany You're describing taxes.

10:15 AM
Then taxes are good. Proven.
:D
Yes but the insanely rich are not investing their capital into something they believe in, it's the government transforming their resources into Mexican walls and who knows what else that has nothing to do with pushing humanity forward.

I would say that that is a failure of the specific government and not a problem with the institution as such :P

If I was Trump, I'd invest in science guys, engineer guys and basically people who want to push the world forward. I'd still build the wall if it's necessary tho
I'd invest in physics guys as well

Taxes can - and do, in many countries - pay for things like education, research, healthcare, social security. Looks pretty good on the score of "benefitting the whole" to me.

Then yay, taxes
is math related to science?

It's its second-degree cousin.

10:21 AM
Katy Perry has a net worth of $330 million dollars. Now I'm afraid my break for planting the seed of communist revolution in the hearts of the youth is over and I should get back to work :P @ACuriousMind Happy coding (even tho it's probably boring at this point). I can conclude, after our discussion, that I don't give a single damn about politics anymore. It's such a mess and I don't want to be involved. If I had to choose a system, I'd choose a one which allows me to do the things I described above (that seems to be liberalism, capitalism stuff). I know that those systems are not perfect, but suit my needs, motivation and drive. Okay I'm getting back to my retarded geography homework. Sadly there is no political philosophy dedicated to supplying me with free food and as many laptops as I can carry. @JohnRennie If I was president, I'd give you free food and as many laptops as you want only if you use your broad knowledge of seemingly everything (mostly physics I guess) to push the human race forward and to discover the unknown. I believe that's what's important. Why are we here? What's beyond us? What is the substance of intelligence and can it be exploited? Can we create machines more intelligent than us? Those are the questions (and many more) to which I go to sleep and wake up. And of course, those are only the questions my little brain can come up with. 10:38 AM @JohnRennie that's ok, thanks, but recently I solve a problem in which I have to find the number of allowed transactions in the fine structure of$H_\alpha$lines, and the answer was coming out correct only when I was not allowing any transaction within the same$n$The$H_\alpha$transition is specifically the$n=2 \to n=3$transition isn't it? 2 hours later… 12:24 PM @JohnRennie yes, and it has 7 allowed transitions of fine spectra. the result and the only obtained if there is no allow transition in the same n level @Vivek I believe John's point is that "$H_\alpha$" is by definition transitions from 2 to 3. Your problem isn't saying the other transitions are forbidden but that they are not$H_\alpha$transitions. @Vivek as ACM says,$\Delta n = \pm 1$by definition for the$\mathrm{H}_\alpha$line. So it cannot possibly be zero regardless of any selection rules. How did you get 7 lines? Isn't it just a doublet i.e. split due to the spin orbit coupling? I'm beginning to suspect we are talking about different things. It seems like communism and socialism are doomed to fail. They essentially don't motivate productivity and innovation, which are the basis of growth. I guess that's why countries like China and North Korea are not truly communistic and are partially merged with capitalism. 12:41 PM @NovaliumCompany 1. I think I already said why I think the "argument from history" is too narrow to be valid, but nevertheless: 2. That's an exceptionally clueless argument because it invokes historical "evidence" that's simply wrong - even Eastern Germany notoriously had production plans and workers were rewarded (e.g with a "Hero of Labour" award) when their production exceeded expectations. @ACuriousMind You fool, why are you arguing with @NovaliumCompany @Slereah Why not? You will demonstrate why not soon enough If you're interested in communist and socialist thought, you need to read communist and socialist thinkers, not watch 3 minute Youtube videos from their detractors Communism and socialism do not motivate productivity and innovation as much as capitalism, true or false? 12:47 PM @JohnRennie I've calculated the allowed transitions in the 'fine-spectra' of$H_\alpha$lines. Thus, as we know, its from n=3 to n=2. The I took l=0,1,2 for the n=2, and l=0,1 for n=2. For l=0, n=3, and one electron, we can write the spectroscopic term as -$2 2_S_{1/2}\$, and proceeding similarly for all the terms.
Then, we can apply the selection rule, and will get 7 lines when there is no transition within the same n level. I'll provide link to an image i found regarding this.

@Slereah What have I done for you to completely quit on me?

@NovaliumCompany neither

@ACuriousMind so it's in a quantum superposition?

There are certainly schools of communist thought that are actively hostile to "innovation" (see the "agrarian socialism" that found its worst historical expression in the atrocities of Pol Pot's regime), but - to invoke fictional evidence - original Star Trek's post-scarcity utopia is a very technocratic conception of socialism.

I haven't watched Star Trek sorry

1:01 PM
Displacement vector in electrodynamics is also known as Electric Flux vector, is it right?

But the idea that "motivation" for innovation must consist in a capitalist reward structure is itself capitalist, and there is plenty of evidence that humans can be motivated to do great things without that structure. For real historical evidence, many great things have been achieved by non-profits - famously, the polio vaccine was not patented, and its creator publicly rejected the idea that he should profit from it personally.
No one - to my knowledge - has gotten obscenely rich from eradicating small pox, and yet we did it. None of the actual inventors of nuclear technology - for good or evil - worked for profit either, that was all government programs.

I want to do great things and I'm not motivated by profits, fame or anything. My problem is that if I'm under communism, I can't get to the tools I need to make the impact I want.

That's a strange statement because that depends very much on your concrete situation and the specific systems in place, not on some grand dialectic between 'capitalism' or 'communism' :P

@NovaliumCompany ...Why would capitalism solve that problem? If we're going to make broad sweeping assumptions about the systems, shouldn't I be able to say that under capitalism unless you had sufficient funding from something else, you couldn't afford to have the impact you want? Couldn't we say in communism you would be given the resources you need without requiring an investment? It seems weird to assume capitalism would allow that and communism wouldn't. Capitalism should only allow for profit

Political systems are not about you, personally. I'm partial to Rawls' veil of ignorance (a less deontological version of Kant's categorial imperative, if you will) to evaluate social contracts and political systems

1:10 PM

@JMac If I'm under communism, how would I acquire the resources I need to have to make the impact I want?
I can't start a business, nor am I allowed to allocate resources.

@NovaliumCompany From the community.

@JMac What do you mean?

@NovaliumCompany I mean if resources are shared, why would you assume that you couldn't get access to them?

@JMac Because I'm an average worker. I can't become more and I certainly can't be given the power and money needed for me to do the impact I want. Are you telling me that I should become a politician, a president?
all set guys, I'm becoming a president
@ACuriousMind Seems fair. We have to take into consideration that not all people are motivated to innovate and most just want happiness and safety to reproduce.

1:17 PM
@NovaliumCompany Why do you need power or money? Just pitch your idea to the community, if they agree it's a good idea they'll support and implement it. Maybe there's a grant commitee like the ones we have for science research already, maybe the means of production are collectively owned and you have to win some sort of grass-roots voting against other ideas. Maybe something else, 'communism' is far too vague here, as I've already said and tire of repeating.

I warned you

@NovaliumCompany I don't see how capitalism would help you either. If you're just average, and don't seem to have a reason to get the power and the money for the impact you want... then in capitalism you wouldn't have the money to do what you want... If your idea is good and helpful, you could probably get someone to invest in you in either society; one would be for profit reasons, the other would be for societal reasons. And you said you didn't care about the money...

1:31 PM
In unrelated news, civilisation is collapsing - I had to take a cold shower today because apparently everyone showers at 10am now!

My brain is really tired and it seems to be stuck. No thoughts pass by. I'll be back soon.
Thank you for not giving up on me. Thank you for taking the time to chat with me.

@ACuriousMind Are you in an apartment building?

It's the time of the plague, where my Newton's inventing Calculus at

@JMac yes

1:37 PM
@AbhasKumarSinha No one will understand that.
2

@FakeMod K...

I get it
Where's the Irodov version

Because they don't know about HCV

@bolbteppa XD...
@bolbteppa I completed both Irodov and Krotov when I was preparing for IPhO

@ACuriousMind I'm glad I only have to share a place with 3 other people. The hot water tank can kinda suck; but at least it's rare that there's not enough hot water.

1:38 PM
If you've done Irodov, why aren't you doing a phd

@bolbteppa One does not simply solve an Irodov question in a single attempt

My biggest issue is that my washroom is basically on the opposite side of the pipework as far as I can tell, so it takes like 1 minute for the water to heat up in the morning.

@bolbteppa Irodov -> only JEE required parts, left QM and unnecessary par.
^same for Krotov

To be fair I rodov is not tough, imo, it is moderate...

@JMac It's a pretty modern passive house and usually everything works really well, but the hot water supply is a bottleneck. it's usually between 7 and 8am that it's hard to get hot water, and now it's shifted to later in the day (most people who live here are technology workers or students now working/studying from home)

1:39 PM
@FakeMod easy... specially mechanics

@AbhasKumarSinha Just a few nice questions sprinkled here and there... Everything else is quite straightforward once you get the feel for it.

@FakeMod Questions are also arranged with their similarity, so, solving one gets your couple of others too.

In any one wants something challenging, I would suggest you to do this book. It's questions are really tough.

First 10 questions took me a month, then there was a speed up kinda thing... and after the end of 8th month, the book was completed...
@FakeMod Completed that too.

1:43 PM
^Except few questions
I didn't get...

I don't believe you...

lol
@FakeMod k....
XD
@FakeMod SS Krotov is harder than that book

One of my friends (we are in the same class) got a bronze (or maybe silver) in APhO (Asian Physics Olympiad). And even she hasn't completed this book yet!

@ACuriousMind Does it come from some sort of district heating, or is it just like a hot water tank/boiler in the building? (I'm kinda a nerd for energy management and heat transfer, and these passive houses sound interesting, sorry if this seems oddly prying)

@AbhasKumarSinha Nope! I have done a bit of Krotov and it is just little bit harder than Irodov

1:46 PM
@FakeMod I doubt, getting bronze and not completing such books...
@FakeMod Krotov requires more imagination...
Completed whole mechanics^
in 2 months...

@AbhasKumarSinha The questions in that book are even harder than you usually expect in APhO

@FakeMod Lengthy... I'd say... Needs a lot of imagination and tricks tho.

If anyone wants an easier challenge, try doing this : amazon.in/…

@FakeMod I fell sick just before IPhO (first round, dun remember) and couldn't go to exam... bad luck...

@JMac yes, it's district heating

1:47 PM
I have done the first few chapters of that book.

The nearest center was in BBSR which is 2 hours from here (with train), so, I couldn't give the exam... :-(

@AbhasKumarSinha That's the worst thing that could ever happen...

Very sad tho, I worked very - very hard....
Only thing, I suck is Chemistry, not for me... Specially organic ones...

@AbhasKumarSinha Organic is still good, but inorganic can be a nightmare!

@FakeMod I'm not very good in memorizing things...
You can understand...
JEE needs balance...

1:51 PM
@AbhasKumarSinha neither am I, but I have learnt to do it by practicing questions. I end up discovering and remembering more facts when I solve questions

@FakeMod Do you go to some coaching?

@FakeMod Are you taking any courses in lockdown?
@FakeMod which?

@FakeMod okay...
I'm taking a course on game theory and Advanced C++

1:53 PM
What is the point of doing all these problem books, is it just to pass those crazy university exams

@ACuriousMind Nice. That seems to be a lot less rare in Europe. I'm reading about these passive houses. Does yours have any type of additional supplied heat, or is it able to maintain temperature with just heat recovery and insulation? (this concept is kinda blowing my mind that they are able to recover/retain enough heat to make this work in some places in Germany)

@AbhasKumarSinha I would be reluctant to disclose that... However they are quite famous and most probably the one you are thinking about right now...
@bolbteppa To get some practice, am I wrong?
@AbhasKumarSinha I would be reluctant to disclose that... However they are quite famous and most probably the one you are thinking about right now...

@bolbteppa That's the fun...

Yeah but what about real problems

@FakeMod I get that.
@bolbteppa We don't study JEE for real life problems... We just do it so that no one can do it... even though it doesn't make any sense... Majority of people are very young and energetic and it's important to channel their energy to make them competitive.

1:55 PM
@bolbteppa We are not qualified yet to account for air resistance. We are solving these problem books just to go somewhere and get qualified foe solving real life problems.

@FakeMod That's a part of explanation.

The Course of Theoretical Physics is a ten-volume series of books covering theoretical physics that was initiated by Lev Landau and written in collaboration with his student Evgeny Lifshitz starting in the late 1930s. It is said that Landau composed much of the series in his head while in an NKVD prison in 1938-1939. However, almost all of the actual writing of the early volumes was done by Lifshitz, giving rise to the witticism, "not a word of Landau and not a thought of Lifshitz". The first eight volumes were finished in the 1950s, written in Russian and translated into English in the late 1950s...

@AbhasKumarSinha No, it definitely isn't the case. Most of the people I have met are just doing because there's no other option which guarantees them a good higher education...

India is a country with very high population and very less opportunity, so, competition is bound to be there....

@bolbteppa That's on my reading list.

1:57 PM
There are 10 huge books of all areas of physics, why spend all this time on a perspective of Mechanics that's barely even addressed in these books

@bolbteppa Statistical mechanics after lockdown....
@FakeMod I can speak for my perspective only.

If you can solve enough of these problems, you could figure out how to solve them all eventually

@AbhasKumarSinha exactly! If you want the best branch/course (the one which I and thousand others want), you'd need to be in 50 among the total 1.3 million test takers...

@JMac The district heating also supplies radiators but I only need to turn it on when it gets to negative Celsius outside - otherwise it stays pretty warm on its own

@FakeMod That's fun for me.... Fight....
@bolbteppa You mean L&L can help us solve all problems?

1:59 PM
@bolbteppa We do have many more things than mechanics. It's just that I know mechanics the best and it is way more interesting than the other topics that we've been taught.

@bolbteppa It depends entirely on what you would want to do... Why read 10 books on theoretical physics if you are going into a field that's only going to use classical mechanics.

@JMac those 10 books are basis....We need even 100x more advanced physics.