The h Bar

Q: Are Germans a different kind of human?

5:20 AM

@peterh Yeah, see this for example:

20

My title is facetious, but my question is serious: I'm being told by a client's business-analyst team that Germans WANT to read every detail on a website and WANT to read every word in a contract—more so than people from other cultures. Research done in North America shows that there people sca...

But that's OK...

I think humanity needs that kind of humans too, to advance physics, math, philosophy and to build better machines...

Dawood ibn Kareem

Haha, I'm 3/16 German at last count. It would certainly explain a thing or two.

interesting question haha]

peterh

5:38 AM

@Mostafa Also I think the same. Btw, US people are in fact a large part German, and they are similar also in this aspect, but not so strongly.

peterh

5:50 AM

@ACuriousMind The idea is not so young, there were a Second Space Odyssey, written in 1982 and the idea may root from here. I think it would be a more nice idea to peel its athmosphere somehow, and then a big, big, Earthlike planet could remain after a little terraforming.

6:08 AM

German ancestry in the US is the largest, right?

peterh

6:37 AM

@Avantgarde As I know, yes. I've just got a half hour ban, for not watching my steps enough carefully.

Dawood ibn Kareem

Is there a name for the rule that says that the period of a swinging pendulum doesn't depend on the angle that it's perturbed?

@DawoodibnKareem not that I know of. In any case this is an approximation using $\sin\theta \approx \theta$ and isn't true for large $\theta$. The period does depend on the amplitude.

Dawood ibn Kareem

True. OK, thanks for that @JohnRennie

9:01 AM

@peterh Yeah...for example Trump is German on his father's side ;)

no racism pls

@Kenshin pls = please?

yeah

We're talking about *facts*.
Not personal opinions.

A "fact" can be racist

9:13 AM

But that's still a fact.

all I said was no racism

9:48 AM

Nobody here?

Qmechanic

@bolbteppa : Why the long face?

Slereah

I wrote "left as an exercize" in an answer

Hopefully that will be good enough

Couldn't be arsed to write down a full proof

John Doe

11:51 AM

@Mithrandir24601 Hi, if you have a chance please see the following query: In the following uploaded picture, the von Neumann entropy is introduced, can you maybe see why a complete measurement (defined as each measurement operator projects the system onto a pure state) implies (2.17)?

Also, do you know what is meant by the last statement "The value of the lower bound is achieved by a von Neumann measurement in the eigenbasis of the density matrix". As I understand, the lower bound $S(\rho) := -Tr[\rho ln \rho]$ refers to $\rho$ before measurement?

@Mithrandir24601 I think I understand the last statement, is the last statement stating that if we diagonalize the density operator $\rho$, then the measurement operators which correspond to projections onto the pure states (eigenstates of $\rho$) are the von Neumann projections of the eigenstates with probability given by the eigenvalues. Hence the entropy of this is $S(\rho)$?

bolbteppa

2:03 PM

@Qmechanic good proof, good references, but don't fully get it yet, apparently the original proof is here archive.org/stream/TheTheoryOfSpinors/… according to physicsforums.com/threads/… which seems less metaplectic but still trying to get them :(

user228700

3:42 PM

@JohnR: Hi! :-)

@Kaumudi.H Afternoon ...

That was good timing, I've only just got back from doing the shopping :-)

user228700

@JohnRennie Ah, I see :-) Nothing at home after having lived at ur mum's for two weeks huh?

@Kaumudi.H I did the emergency shopping, e.g. milk and bread, when I got back yesterday. This was just routine shopping.

user228700

Ah, OK...

Though since I am 5kg heavier than when I arrived at my Mum's, food shopping is not a priority right now :-)

user228700

3:49 PM

Ah, right, right :-)

user228700

Went out with friends today. We went to this place called the Writers' Cafe for lunch and it was so. good.

user228700

I can't even pronounce the names of the food we had but they were all great!

user228700

(Italian, I think but I can't be sure).

Writers' cafe? Is it a hangout for local authors?

user228700

@JohnRennie I dunno...

user228700

3:52 PM

It looked like this on the inside:

user228700

It certainly has a literary theme ...

user228700

Certainly, yes. And there was a reading room upstairs as well.

Were there any scruffy impoverished young people scribbling furious in notebooks :-)

user228700

3:54 PM

@JohnRennie Hehe :-) I saw one girl just at it on a napkin but nothing else.

user228700

I'll post a few pictures of the food we had once I get hold of them, if u want!

@Kaumudi.H yes, why not. Can you remember the names of any of the dishes?

user228700

Hang on...

user228700

Dang, this might take a while. I'll just show them to u tomorrow, then...

No hurry, I was only idly curious.

@Kaumudi.H: Any news on the college? Have you been formally accepted?

user228700

4:05 PM

@JohnRennie OK...

user228700

@JohnRennie Nope, not yet. The rank list is s'posed to come out in 8 days...

I guess for now you just have to chill and try not to think about it ...

user228700

Yes, yes...

user228700

*Chill*=Eat and sleep, apparently :-P

@Kaumudi.H well eating and sleeping are kind of obligatory. I trust there is more to your life than that :-)

user228700

4:13 PM

:-) Well, yes, but only almost. I'm meeting friends, reading those books I ordered and playing the harmonica from time to time...

user228700

Catching up with friends is taking much more time than I'd anticipated; haven't talked to any of them in over a year, you see...

Anonymous

@Kaumudi.H Where are you joining?

Presumably your friends are all back from college now?

user228700

@blue A govt. engineering college in Kerala. And you?

user228700

@JohnRennie Yep yep! :-)

Anonymous

4:14 PM

@Kaumudi.H Oh nice :) I've not decided yet

user228700

OK...

user228700

Travelled the metro today and it was so good!

Hello

user228700

Hi :-) How's it going?

:(

hey

4:23 PM

There was 5.5 hour long power cut.

:(

user228700

Damn :-(

:( power cuts after lunch till dinner time.

DanielSank

Hi, everybody.

hey Daniel

4:30 PM

Hey Daniel

Shing

5:12 PM

hey what's up

6:34 PM

@JohnDoe Whatever is actually going on here, I'm not too sure at the minute, but to me it looks like the measurement operator is $M = \sum_m \alpha_m |\psi_m\rangle\langle\psi_m |$ as this directly gives $p_m = tr\left(\alpha_m |\psi_m\rangle\langle\psi_m | \rho\right) = \alpha_m \langle\psi_m |\rho|\psi_m\rangle$. But that's what they say is $I$, not $M$... O_o

6:56 PM

@JohnDoe After measurement, the density matrix is $\rho ' = \sum_m |\psi_m\rangle\langle\psi_m |\rho |\psi_m\rangle\langle\psi_m | $, which if $\rho = \sum_n\lambda_n |\psi_n\rangle\langle\psi_n | $ (as the measurement is in the eigenbasis) gives $\rho' = \sum_{n, m} \lambda_n |\psi_m\rangle\langle\psi_m |\psi_n\rangle\langle\psi_n |\psi_m\rangle\langle\psi_m | = \sum_{n, m} \lambda_n |\psi_m\rangle \delta_{n, m}\langle\psi_m | = \sum_n \lambda_n |\psi_n\rangle\langle\psi_n | = \rho$

HDE 226868

7:07 PM

I see Physics passed 100,000 questions, and I see I forgot about it, as I predicted.

This one might be it.

Q: Possible classical roots of quantum entanglement

@JohnDoe Wait - for the first thing I said - I was being a complete idiot - ignore that bit :P

Giskard42

I hope this isn't too OT here, but anyone know of a material (refractory ceramic, anything really) that can handle 2800c, doesn't react with aluminum, is non-conductive, and I can realistically drill a small hole in?

Secret

7:44 PM

0

I read this very recent article that is titled - "Classical synchronization indicates persistent entanglement in isolated quantum systems", is published at https://www.nature.com/articles/ncomms14829 If it is within physics SE norms, may I ask QM folks to comment whether this article is credible...

quantum-mechanics classical-mechanics entanglement

too lazy (sleepy) too read