The h Bar

Sir Cumference

3:13 AM

@NovaliumCompany That's an...interesting pic

Semiclassical

6:01 AM

@JakeRose the obvious starting question is, do you know how to compute operators in the interaction picture?

Slereah

7:14 AM

morning

Physics Meta

9:39 AM

0

Q: Where does this get it's money from?

I was thinking about economics, so maybe I should ask this on the Economics SE site, but nevertheless. It's obvious to prolong this site money is needed. My question therefore is: Where does this subsite of Physics SE, get its money from? From the Physics SE site? Etcetera.

discussion

Secret

12:52 PM

australiandefence.com.au/news/…

World's 3rd Superpower attacking Australia

Knight

1:37 PM

@JohnRennie I heard my first song of the album Animals ( Pink Floyd) : Big man Pig man. Whenever he said “ha ha charade you are” and “you’re a cry” I felt that he is pointing to something, Would you please explain it a little ?

JMac would you want to explain it?

Yuvraj Singh...

1:54 PM

Can anyone help me understanding space elevator?

How it works?

JMac

@YuvrajSingh... As far as I know, it doesn't really work right now on Earth. In theory, there's a big structure in tension going out into space. You could then attach something to the structure and move that up and down. It would mean you wouldn't need the crazy fuel requirements to reach orbit.

The issue is that the tension required to build it on Earth is supposedly greater than any known material can handle

Yuvraj Singh...

Ah, OK but earth rotation doesn, t that effect the elevator?

@JMac

Aaron Stevens

@YuvrajSingh... In what way are you asking about?

Johan Liebert

5

Q: Is this textbook answer incorrect?

In my physics textbook (Tipler et al.), the following equations were given as a solution to a problem. I am slightly in doubt of their equations. I think the answer should be $\frac{m_2}{m_1+m_2+(I/R^2)}g$, with the square inside the parenthesis. Because the units don't seem to work out in their ...

units dimensional-analysis textbook-erratum

Hoe are we supposed to answer this?

JMac

@YuvrajSingh... I'm pretty sure that's how they get the tension in the structure. The Earth's rotation means that the end out in space is actually pulling away from the end connected to Earth. That's how it's in tension; instead of compression like regular standing structures.

Aaron Stevens

2:03 PM

@JohanLiebert IMO it should be closed as a "check my work" problem

Johan Liebert

@AaronStevens yes you are right.

tpg2114

@AaronStevens I'm not so sure (I thought so at first also) -- our eminent tag-wizard opted to put on textbook-erratum but didn't put on homework-and-exercises. There might be scope for our site to answer things like that

Not saying that's always the correct way to evaluate it

But there might be precedent on something like this that I am unaware of

Aaron Stevens

@tpg2114 I suppose so.... although I am always wary of questions that can be answered as "yes, you are right" or "no, you are not right"

Yuvraj Singh...

Sorry I ask reverse question, If you (or e.g. a skater) spin on the spot with your arms outstretched you spin at a given speed, but when you retract your arms you spin much faster, extending your arms again will slow the spin down. Your arms are small in relation to your body but has a big effect in this case. Would a space-elevator have the same effect on earth's rotational speed, and by how much

@JMac

Aaron Stevens

I feel like a better question for that tag would have more detailed answers, and the question would be deeper than just "does this equation have a error"

But I am not familiar with questions like that, so who knows haha

tpg2114

2:06 PM

6

Q: Is it appropriate to ask about possible errors of a specific book?

For example: In the book ABC there is the derivation of SOMETHING as follows: ... I think argument XY is wrong, do you agree? If this kind of question is okay, would you mention the title of the book in the question title?

discussion

Aaron Stevens

@YuvrajSingh... Given how massive the Earth is, I doubt it would have much effect. You could do a quick estimate though

tpg2114

Yeah -- so it looks like it is okay to ask, but it should probably be edited to ask for what the correct equations are rather than "Am I correct?" But since it's about an answer to a question, it's at the intersection of homework and errata.

Which makes it more complicated than I can think about... I haven't had my coffee yet

Aaron Stevens

@tpg2114 Yeah. I'll just put my vote in the ring and see what happens. I won't fight hard for its closure though

tpg2114

@AaronStevens Never a wrong choice to do that :)

JMac

@YuvrajSingh... I'm pretty sure the effect would be next to nothing. The mass of the space elevator compared to the mass of Earth should be quite different than the mass of an arm compared to the mass of a person

tpg2114

2:11 PM

^ Probably closer to a person flinging a speck of dust off them

Or a hair falling out or something

Slereah

2:33 PM

"It was very hard to explain the continuous emission of energy by radioactive substances. One of the several suggested explanations was that radioactive bodies obtain their energy from the gravitational field; therefore their weight should exhibit some kind of anomaly."

"Other explanations included violation of the conservation of energy, or absorption of thermal energy of the environment and emission of that energy under a new form, in violation to the second law of thermodynamics."

Jake Rose

@Semiclassical yep $A_I = U^{-1}AU$ ?

@YuvrajSingh... That's quite a cool question. Without doing any rigorous maths.. Your arms make up a significant portion of your mass. Where as a space elevator wouldn't even be 0.001% of the earths mass. So you'd have to make it GINORMOUS. Probably even bigger than the moons orbit to have a tangible effect on the rotation speed.

I may do some numbers on that though because it sounds fun.

Novalium Company

2:49 PM

I just realized everything is hierarchical.

Yuvraj Singh...

@JakeRose OK.

Novalium Company

Jya laik me new pic?

Jeff Goldblum and a gorilla

that's fine art

Slereah

3:05 PM

it's always weird reading about science history

Because you learn about the very prosaic topics some big theory guys worked into

Like De Sitter just worked on the orbit of the moon???

Knight

I feel like reacting to Solomon’s comment in my answer.

JMac

@Knight I think his comment makes sense, because your answer is hard to read and it's not clear from your answer if you are aware of the reversible nature of heat pumps and that cycle. From your answer it wasn't at all clear that you were aware of that.

Semiclassical

3:23 PM

@JakeRose yep. So how far have you gotten along those lines?

tpg2114

@Knight A useful way to approach comments that critique what you write -- assume they are correct and even though what you wrote is perfectly clear and makes sense to you, obviously somebody else didn't see it.

Sometimes, they didn't read carefully enough and missed what you said. But that's an opportunity for you to fix formatting, or the flow of the answer, to make it easier to read

Sometimes they are right and something wasn't clear, so it's a chance to expand and clarify things. Or add definitions or links to ideas/concepts you discuss. Etc.

Happens all the time when publishing scientific articles -- we get a review back from somebody and it makes us really angry, or it seems like they didn't read the paper or don't know what they are talking about. But, once taking some time to think about it, it gives us an opportunity to improve how we write so there is no possible way somebody can misunderstand it or miss the point

It's almost always "reviewer #2" that is the worst... There's entire websites dedicated to the crappy things reviewer #2 says in reports.

Aaron Stevens

@tpg2114 We have even tried to guess the identity of "reviewer #2" haha

Knight

@tpg2114 Sir you always make me clam by your example of publication.

tpg2114

@AaronStevens I just had an article accepted yesterday, and reviewer 2 said "The revised manuscript does not incorporate my previous recommendations, and thus should not be published in this journal."

3

Knight

Btw have you said something to him, because he changed his comment, he made corrections in his comment just now.

Aaron Stevens

3:31 PM

@tpg2114 Geeze.... I hope I never become that self-important

Knight

@AaronStevens I too got a reviewer #2 as soon as posted it here.

tpg2114

But we thought we addressed everything they said. The advice from the editor was "I note that even in the revision, one of the reviewers is quite unhappy. Please see if you can accommodate ANY reasonable change in regard to that reviewer's comment. However I would not recommend any recalculation, rather supply an explanation in the text. Maybe a sentence. The other reviews were fine to excellent. So Please proceed at your discretion"

Knight

You’re just an inspiration for me.

Aaron Stevens

@tpg2114 That is good that everyone else was fine haha

tpg2114

I wish I was exaggerating, but it actually was reviewer 2... Haha

Knight

3:32 PM

I’m so fortunate that I get chance talking to you.

tpg2114

@AaronStevens Yeah, and it looks like the 3rd reviewer for the revision is a new one and not one of the originals -- we got a really long set of recommendations from them. But the editor doesn't seem to care, which is weird.

@Knight Lots of folks around here publish -- feel free to ask in chat about experiences with it. It is always an adventure...

Knight

But you’re kindest of them

tpg2114

That's probably not the case... I'm just not around chat enough to show the surly side ;)

Aaron Stevens

@tpg2114 Well hey, sounds like one of the better publishing experiences overall then

tpg2114

Aside from the year it took to get here, yeah.

Aaron Stevens

3:36 PM

@tpg2114 I suppose that is true haha...

tpg2114

I think I will request not to get this editor again though, if I submit to this journal again. He dropped the ball many times and/or people don't like him and refused to review for him

Aaron Stevens

We are getting ready to put a paper together. Hopefully it will go smoothly

Knight

Just for example, see this answer of mine. In that answer I never used the equation $E= mc^2$ for light. But just writing that equation in middle made others to feel that I was using it. However, when two people said the same things I thought of removing that line and hence everything is clear now.

Aaron Stevens

@tpg2114 That's crazy

tpg2114

It took 6 months before it got sent out for review, because "everybody told him no." I had to give him a total of 12 suggested reviewers

But I've had other papers in this journal that are done the first round in 30 days, like their policy states

Aaron Stevens

3:38 PM

@tpg2114 Oh wow... at least they were fine with ignoring reviewer 2 though

Slereah

"Gentlemen! The conceptions of space and time which I would like to develop before you arise from the soil of experimental physics. Therein lies their strength. Their tendency is radical. From this hour on, space by itself and time by itself are to sink fully into shadows and only a kind of union of the two should yet preserve autonomy."

tpg2114

Yeah. I am slightly worried it's just because the editor is tired of dealing with me... heh

But whatever. It's still good news to get it accepted. We did the work in the summer of 2018, so it's nice to get it off my plate

Novalium Company

Is synaptic plasticity and neurons self-organizing random?

Knight

@Slereah Who’s words are that?

Novalium Company

Like, how does a neuron know where to go so to contribute to let's say, the creation of a memory?

John Rennie

3:39 PM

Minkowski

Slereah

That is Minkowski

He had a penchant for the dramatic, apparently

Knight

Aha! Wow

By the way who was he?

Aaron Stevens

@tpg2114 Yeah, I bet. It is always a good validation of the work too

John Rennie

He was the first to formulate special relativity as a metric theory, and that paved the way for the development of GR.

The Minkowski metric is named after him.

Knight

@JohnRennie Again the stigler’s law of epotmy?

tpg2114

3:41 PM

@AaronStevens Indeed -- I just hope reviewer 2 doesn't write some angry letter to the editor calling out our work. But if they do, at least I'll know who they are!

Novalium Company

Bow chica bow bow, that's what my momma said, bow bow bow and the horse starts bumping... chicka chicka chick bow, na nananana, baby I love you... tararaa

John Rennie

@Knight no, Minkowski may have played some role in building the foundations for GR, but it was Einstein who built GR on those foundations.

Novalium Company

Gitchee Gitchee Goo with lyrics

►

Knight

@JohnRennie Would you mind explaining me Pigs (three different ones) ?

PM 2Ring

@Knight One of Einstein's mathematics professors.

Aaron Stevens

3:43 PM

@tpg2114 Was their critiques about how your work is invalid? Or just how you presented your work?

John Rennie

2 hours ago, by Knight

@JohnRennie I heard my first song of the album Animals ( Pink Floyd) : Big man Pig man. Whenever he said “ha ha charade you are” and “you’re a cry” I felt that he is pointing to something, Would you please explain it a little ?

tpg2114

@AaronStevens Invalid. We did a forward propagation of uncertainty and they argued we didn't do it correctly. Not enough data points, improperly treated the uncertain variables as independent, and something else

John Rennie

@Knight The song was written back in the 1970s, and in the UK back then there were a lot of rich but corrupt men around. Men who would use their money to pay bribes etc.

tpg2114

Which some of it is valid, some of it isn't -- the independent variable thing had a point, but we had a rationale for why we did it. And we also said we were just looking for relative changes in uncertainty, rather than exact measures.

Knight

@PM2Ring I have read that all those people who are credited with something are the ones who has just completed it by doing merely a step. For example, Newton just completed the half proof of Isaac Barrow’s Fundamental Theorem of Calculus? Is it true in other cases too?

Aaron Stevens

3:46 PM

@tpg2114 I suppose that is the best you can do then

John Rennie

@Knight Waters portrays them as greedy like swine, hence the lyric "Big man, pig man". That is he is likening them to swine.

Knight

@JohnRennie Can you please name some of them?

tpg2114

But it took 130 simulations and 10M CPU hours, so it was basically the best we could afford

John Rennie

@Knight no, because I don't want to get sued :-)

Robert Maxwell was an example I suppose.

Robert Maxwell

Ian Robert Maxwell (10 June 1923 – 5 November 1991), born Ján Ludvík Hyman Binyamin Hoch, was a British media proprietor, and Member of Parliament (MP) and fraudster. Originally from Czechoslovakia, Maxwell rose from poverty to build an extensive publishing empire. After his death, huge discrepancies in his companies' finances were revealed, including his fraudulent misappropriation of the Mirror Group pension fund.Early in his life, Maxwell escaped from Nazi occupation, joined the Czechoslovak Army in exile in World War II and was decorated after active service in the British Army. In subsequent...

Knight

@JohnRennie Hahahaha. I meant were politicians or Mafia?

tpg2114

3:47 PM

And prior to us, the only other group to try something similar only did 25 simulations and only varied one input at a time because of the cost. We were able to do more, and look at interactions between pairs of uncertain inputs and it changed the picture quite a bit.

John Rennie

> were politicians or Mafia

is there a difference? :-)

tpg2114

So it's still interesting, and I thought we added enough caveats to it to appease them. But apparently not

Knight

@JohnRennie Ah! I never thought it that way round!

Aaron Stevens

@tpg2114 Yeah. It does sound like progress on something at least. Which is what science is about haha

Knight

@JohnRennie What does it mean “You’re really a cry” ?

tpg2114

3:49 PM

Progress is for amateurs. Unify all physical laws, or don't publish!

Aaron Stevens

@tpg2114 Ah yes, I forgot about that. A famous scientist said that once I think

tpg2114

Reviewer 2

John Rennie

@Knight Anyway, these are people who present themselves as respectable public figures when they are really corrupt fraudsters, so their public face is a charade. Hence "charade you are".

And Waters is saying maybe we should laugh at you, but really we should be crying because you exist.

Knight

@JohnRennie Oh wow!

John Rennie

Waters really goes for it with the lyrics in Pigs. He doesn't pull any punches.

Knight

3:52 PM

@JohnRennie What does that smoke emitting picture in the song represents ?

PM 2Ring

@Slereah Just? Lunar theory is insane!

John Rennie

@Knight which picture?

Slereah

@PM2Ring it's not quite as noble

PM 2Ring

"The number of [trigonometric] terms needed to express the Moon's position with the accuracy sought at the beginning of the twentieth century was over 1400; and the number of terms needed to emulate the accuracy of modern numerical integrations based on laser-ranging observations is in the tens of thousands: there is no limit to the increase in number of terms needed as requirements of accuracy increase."

Aaron Stevens

7

Q: Cause of weightlessness

I'm a first year engineering student who is new to physics, so I apologize if my question is stupid. But in our statics course we are using the book "Engineering mechanics: statics" by R.C. Hibbeler and it contains the following image: Now this conflicts with my previous understanding of weigh...

newtonian-mechanics

What is going on with all of the short answers here? haha

tpg2114

3:53 PM

@PM2Ring Sounds like a Fourier basis is just the wrong choice then! Maybe there's a Lunar basis that only has like 2 terms

Slereah

@PM2Ring I mean that's true of every orbit, really?

bc Fourier

Knight

@JohnRennie This

John Rennie

It doesn't mean anything. It's just a picture of Battersea power station. It was the picture on the album cover.

PM 2Ring

@Slereah I beg to differ. The difficulty of accurately predicting lunar motion has been an important influence on the development of science. If it were simple, we might still be using the Ptolemaic cosmology. ;)

John Rennie

@Knight I'm afraid it has no deep meaning, the band just liked the picture.

Slereah

3:57 PM

@PM2Ring apparently they tried to use GR to explain some moon anomalies!

But this was apparently not necessary

Because the real reason was stupid

Knight

@JohnRennie Okay.

Slereah

(they didn't use the difference between a sidereal day and a real day)

John Rennie

@Knight the cover was designed by a company called Hipgnosis who did arty farty covers for albums in the 1970s and 1980s.

Knight

@JohnRennie Okay.

John Rennie

You might say I know far too much about the prog rock scene of the 1970s. I couldn't possibly comment :-)

PM 2Ring

4:02 PM

@Slereah Sort of. But the Moon's orbit is nasty for several reasons, primarily because its mass is so large relative to Earth's. Also, it orbits in roughly the ecliptic plane, rather than Earth's equatorial plane (most satellites orbit in their primary's equatorial plane). And that plane precesses quite quickly. And we're in a prime position to observe that orbit, so we can easily see relatively small deviations between the observed orbit & the predicted one.

Knight

@JohnRennie I was just about to say that you should devote some years to old music. General Relativity shouldn't be the only life partner of yours.

Aaron Stevens

I sometimes have a hard "change of gears" between doing reviews on this site and tutoring. I start to tutor and think "this question is not on topic", but then I have to remember I am tutoring and not on Physics SE haha

John Rennie

@Knight I've devoted far too many years of my life to dubious prog rock bands. If I hadn't wasted all that time I'd have developed a unified field theory by now and won a Nobel prize.

2

Jake Rose

@Semiclassical I end up with something like $e^{-i(AA +1/2)\omega t}fA e^{i(A*A + 1/2) \omega t}$

JMac

@JohnRennie Do you listen to Rush at all? I can't remember if I asked you about that, or just like 20 other people here.

Knight

4:06 PM

@JohnRennie This means that I should sue Roger Waters. He conspired to keep you from getting the Nobel Prize. It's a personal loss to me. I would have been talking to Nobel Laureate

John Rennie

@JMac I love early Rush. Up to and including Hemispheres.

Jake Rose

Mhmm

my latex plugin isn’t working

strange

John Rennie

They lost me a bit when they went more metal in the 1980s.

Jake Rose

But, I know I can separate the N from the time dependent omega factor, but then beyond that I’m not quite sure how to proceed.

Semiclassical

@JakeRose should have unitaries on both sides

oh, you do

your latex isn't loading for me, not sure why

JMac

4:09 PM

@JohnRennie I'm assuming you've heard that Neil Peart passed away a few weeks ago?

John Rennie

@JMac yes.

Aaron Stevens

-1

Q: Differential equation as a function of dependent variable in the equation

Here 't' stands for time and 'beta' for opening angle of structure similar to cantilever beam. A & B are constants, approximate values of which are mentioned in the image, but you can take them as any simple value for solving. I was trying to solve a differential equation(in the image), but the...

differential-equations

John Rennie

That's the problem with being 58. So many of your childhood heroes are now dead.

Aaron Stevens

The title makes it seem like it is not normal to have the dependent variable in the differential equation?

PM 2Ring

@JohnRennie I'll have to find some Aussie prog rock for you. Here's a brief example: Golden Miles. It's not exactly prog, more like a cut-down radio-friendly version. And the audio of that video clip's slightly wonky at the start. But I still love that song. :) (I have a nice clear version of it on CD).

Semiclassical

4:11 PM

$e^{-i(A^\dagger A +1/2)\omega t} f(t) A^\dagger e^{i(A^\dagger A + 1/2) \omega t}$ @JakeRose

John Rennie

@PM2Ring I can't think of any Australian prog rock bands. Lots of rock bands, but no prog.

Semiclassical

is what you should have (for the unitary transformation on $A^\dagger$)

Jake Rose

Yep that’s right

yeah mine wasn’t loading either?

Semiclassical

probably the use of *'s was making headaches

since * is also used for bolding/italicizing

Jake Rose

ahhh I see

Semiclassical

4:12 PM

e.g. italic bold

Jake Rose

hit yeah I got that

Semiclassical

anyways. first thing to notice is that f(t) doesn't matter here

Jake Rose

Yep

Semiclassical

What I'd note next is that computing $A^\dagger$ in this interaction picture amounts to computing $A^\dagger(t)$ in the Heisenberg picture

So you've esssentially got $A^\dagger(t)=e^{-i (A^\dagger A+1/2)\omega t}A^\dagger e^{i (A^\dagger A+1/2)\omega t}$

Jake Rose

yeah sure

Isn’t A the same as in the interaction picture though?

Semiclassical

4:16 PM

yeah

Jake Rose

because you can commute through the time operator since $[H,A]=0$?

Knight

@JohnRennie I wanna sue all those writers who quote something like this

Semiclassical

no

because it's $H_0$ in the interaction picture

Jake Rose

OH

Knight

Jake Rose

4:16 PM

be sure it

because it doesn’t commute with N

Semiclassical

and $[H_0,A]\neq 0$

right

Jake Rose

Yeah, I forgot A wasn’t hermitIan

ahh

Knight

These types of quotes has caused so much turmoil in my life. I wouldn't leave those writers ever.

Semiclassical

the main reason I bring up the Heisenberg picture, though, is because of how time-dependance works

PM 2Ring

@JohnRennie Yeah. They didn't get a lot of radio airtime here, so it's not surprising that they're unknown elsewhere. But some of the prog bands released rock & pop singles to earn a bit of money. So fans of those singles were in for a surprise when they turned up to gigs, or bought albums. :)

Semiclassical

4:17 PM

namely, what is $\frac{d}{dt}A^\dagger (t)$?

(in other words, what's the Heisenberg equations of motion for an operator?)

John Rennie

@Knight I think you might be taking this a bit more seriously than it deserves :-)

Semiclassical

alternatively, just carry out $d/dt$ on the $A^\dagger (t)$ I defined above

Knight

@JohnRennie But they should be charged with some section of law book which says "Crime of spreading something which always gonna cause hatred"

Jake Rose

Commutator wirh Hamiltonian?

Semiclassical

yep

John Rennie

4:21 PM

@Knight Hatred?

JMac

@Knight ... how do vague sentimental quotes "always cause hatred"

Semiclassical

and $[H_0,A]$ is easy to compute here

Jake Rose

Yeah, why do we need the derivative though?

Knight

@JohnRennie Yes. If you were to do it in practical they always cause hatred between those who seemingly had love.

I mean following that quote results in doomsday.

JMac

... How does telling people you love them before you lose the chance cause doomsday?

Semiclassical

4:24 PM

@JakeRose same reason we compute time-derivatives in the Schrodinger picture: to get a differential equation which we can solve

John Rennie

It just means that if you love someone you should tell them so before they:
a) leave
b) die
c) start studying interpretations of quantum mechanics

6

Jake Rose

Okay @Semiclassical

Semiclassical

and the ODE you get for $A^\dagger(t)$ in the present case is delightfully simple

because of how simple $[H_0,A^\dagger]$ is

Knight

@JohnRennie It should be like this:

John Rennie

I guess you should be careful about telling people you love them unless you're fairly confident they love you back.

Semiclassical

4:28 PM

I mean, if the statement is "don't tell people you love them if you're not already in a relationship", then sure

But uh

PM 2Ring

Here's something a little more prog: Extraterrestrial Boogie by Mackenzie Theory, featuring the amazing Cleis Pierce on electric viola. Last I heard she was living up north, teaching viola & violin.

Semiclassical

I'd rather hope that's not what the writer intended.

Aaron Stevens

@Knight Why not try it anywhere?

Knight

@JohnRennie I hope that next generation would remember that Caution.

JMac

Plus there's the whole catch-22 of it all. If you don't tell them, may never know if they feel the same. Then you might be left with regret and uncertainty not knowing if they did feel the same way. It depends quite a bit on the relationship between you and the person you're telling.

Knight

4:30 PM

@AaronStevens Anywhere = beach, hotel, shops, etc.

Aaron Stevens

@Knight I know what "anywhere" means. I am asking why can you not do it anywhere

Knight

@AaronStevens You can do it but you shouldn't do it.

Aaron Stevens

@Knight .... why not

Semiclassical

Vague platitudinous statements are generally not intended as commandments.

Jake Rose

@Semiclassical sorry, still a bit confused on how this gets the thing out from above. Why can we commute through f?

Knight

4:34 PM

@AaronStevens Well you have passed your examination (marriage) that's why you cannot understand it.

Semiclassical

because $f(t)$ is just a scalar

it's not an operator

Aaron Stevens

@Knight Love exists outside of marriage as well

Knight

@AaronStevens Please amplify your answer a little bit.

Semiclassical

Telling a family member that you love them? Seems reasonable enough. Telling someone you're in a relationship with, that you love them? Again, seems reasonable enough.

John Rennie

s/amplify/clarify/ ?

Aaron Stevens

4:36 PM

Love does not have to be romantic.

Semiclassical

Telling someone you're infatuated with, that you're in love with them? ...yeah, maybe tread carefully on that.

Again, though, vague platitudes are generally not meant as daily commandments.

Knight

Amplify = clarify and elaborate

My statistics can prove all of you wrong (well this is the ony thing where I can be more experienced than you all :) )

Semiclassical

riiiiight

John Rennie

@Knight I'm never wrong - reality is occasionally wrong though.

3

Semiclassical

If saying "I love you" comes off as being a creepy stalker, then that's indeed a bad idea. But telling that to your SO/family members? I fail to see what makes emotional honesty so dangerous.

Knight

4:41 PM

@Semiclassical Do you agree with me in my knowledge of this matter? @JohnRennie Sir my survey can prove you wrong.

Semiclassical

Given that we have no idea what your knowledge in this matter is, and given that it's limited to your own experience

no

not at all

Aaron Stevens

@Knight This isn't something you can prove, it is completely subjective

Knight

Come on! No one has got any respect for me.

Semiclassical

considering how little respect you're having for everyone else's experience in this room?

get used to it.

John Rennie

@Knight you haven't given us any idea of what your claims are yet.

How can we judge?

Knight

4:44 PM

What claims?

Novalium Company

1917 - Official Trailer [HD]

►

yes.

Aaron Stevens

So anyway...

Knight

@Semiclassical Are you serious here? Have I disrespected you in anyway? If yes then I apologize but please do let me know.

Aaron Stevens

@NovaliumCompany I saw that movie last week

Novalium Company

@AaronStevens we don't have it released yet :(

Semiclassical

4:46 PM

@JakeRose the other approach for this is the Baker-Campbell-Hausdorff formula:

Baker–Campbell–Hausdorff formula

In mathematics, the Baker–Campbell–Hausdorff formula is the solution for Z {\displaystyle Z} to the equation e X e Y = e Z {\displaystyle e^{X}e^{Y}=e^{Z}} for possibly noncommutative X and Y in the Lie algebra of a Lie group. There are various ways of writing the formula, but all ultimately yield an expression for...

But that's rather overkill here. Finding a differential equation for $A^\dagger(t)$ is much more direct.

Aaron Stevens

@NovaliumCompany I am not sure if this was supposed to be known to be before watching it, but I did pick up on something really cool. Aside from one very obvious cut, the whole movie is supposed to run as if the entire movie is one continuous scene

Novalium Company

Damn

Aaron Stevens

Essentially during the entire movie the camera does not cut (or gives the appearance of not cutting at least)

Novalium Company

srsly?

Knight

@AaronStevens "So anyway.." Will you please complete it?

Novalium Company

4:47 PM

Does that mean the actors had to take 1000000 takes before nailing the whole movie... in one take?

Aaron Stevens

There are some spots where I thought "they could have done a cut there"

Well they obviously had places where they could stop

But the appearance is as if it was all done at once

Novalium Company

DAAAMNN

Aaron Stevens

except for one obvious place

Novalium Company

u got me hyped now

Knight

@Semiclassical Will you let me know?

Aaron Stevens

4:48 PM

I greatly enjoyed the film

Novalium Company

i'm pretty sure people's opinion about the film is biased. Bcs it has high rating and everyone is says to themselves - "if others like it, then I should because it's my evolutionary desire to fit it for the sake of increasing my chances of reproduction" ... yea.... I should just eat my fries and watch jumanji

Aaron Stevens

@NovaliumCompany Like there were spots where the camera pans across a wall, or they go through a dark tunnel. So those are places where they could have easily stopped and then edited the movie so that it still looks continuous

@NovaliumCompany Yeah I didn't hear much about the movie before seeing it. We mainly chose to go watch it because my wife loves war movies

So I would say I was not really biased into my opinion

Novalium Company

@AaronStevens That's good. I wish I didn't see the ratings.

Aaron Stevens

I did know it had been nominated/won certain awards, but I have seen movies like that and I didn't like them. So I don't think that is a factor in my opinion here as well

So I think I "unbiasedly" enjoyed it :)

Novalium Company

Cool. I really want to see it now but it's not even in the upcoming section here in Bulgaria

Knight

4:53 PM

Not for best film

It is out of list for best film

Novalium Company

guess it's time to load the ship... cuz I'm going pirating.

Aaron Stevens

It might partially be because I was not expecting the cool "continuous camera" effect though haha

Novalium Company

don't spoil it for others tho

ok I'mma go now, dinner time

Knight

I want the Irishman too win Oscar for this year.

John Rennie

@AaronStevens didn't Hitchcock do a film like that? Filmed as if it was a single take?

Knight

4:55 PM

variety.com/2020/film/news/…

@JohnRennie Yes.

Aaron Stevens

Rope (film)

Rope is a 1948 American psychological crime thriller film directed by Alfred Hitchcock, based on the 1929 play of the same name by Patrick Hamilton. The film was adapted by Hume Cronyn with a screenplay by Arthur Laurents.The film was produced by Hitchcock and Sidney Bernstein as the first of their Transatlantic Pictures productions. Starring James Stewart, John Dall and Farley Granger, this is the first of Hitchcock's Technicolor films, and is notable for taking place in real time and being edited so as to appear as a single shot through the use of long takes. It is the second of Hitchcock's...

Looks like it :)

Knight

@JohnRennie Brian De Palma too

Yuvraj Singh...

Is two account from same user are allowed?

Aaron Stevens

@YuvrajSingh... I would think not

John Rennie

@YuvrajSingh... yes, that is allowed as long as the user isn't abusing having two accounts.

e.g. using one account to upvote the other.

Yuvraj Singh...

4:59 PM

@JohnRennie Thanks sir. I am one making for Alesha!

Aaron Stevens

@JohnRennie I would think the potential for abuse would make it not allowed, but I suppose if nothing bad is happening then who would care?

Yuvraj Singh...

@JohnRennie Thanks sir. I am making one for Alesha!

John Rennie

@AaronStevens yes

Yuvraj Singh...

@PM2Ring hi sir, are you still angry with me?

Knight

@JohnRennie Have you watched Dressed to Kill?

John Rennie

5:03 PM

@Knight I'm not a big film fan. I watch very few films - only ones I consider extra special. I haven't seen Dressed to Kill.

Knight

It's extra special.

John Rennie

A neo-noir erotic slasher film according to Wikipedia.

Knight

Yes.

Jake Rose

@Semiclassical how do you know that??

Semiclassical

@JakeRose what?

Knight

5:06 PM

Good Morning ACM

Jake Rose

That f(t) is a scalar?

Semiclassical

Because the problem doesn't work if $f(t)$ is an operator :P

Knight

does noir pronounced as nowar ?

Jake Rose

Of

Semiclassical

also, note that they wrote the perturbation as $f^\star (t)A+f(t) A^\dagger$

Jake Rose

5:09 PM

I was assuming it was an operator... bugger

Semiclassical

which isn't hermitian if $f^\star(t)$ is an operator

also, note that they only were concerned with taking the complex conjugate of $f(t)$

Jake Rose

Ahhh

Semiclassical

not the Hermitian conjugate

Jake Rose

Yeah I should have noticed that

Semiclassical

Problem becomes substantially harder if $f(t)$ is an arbitrary operator function of $t$.

Jake Rose

5:10 PM

Mhmm. Quite so.

John Rennie

@Knight you can find web sites that have recordings of how to pronounce words. I find that very useful with foreign languages.

Knight

@JohnRennie Oh yeah!

Yes it is pronounced as nwar.

John Rennie

@JMac well caught sir! :-)

Semiclassical

@JakeRose it's unfortunately rather easy to come up with time-dependent problems that are really quite hard

a good example is the Landau-Zener formula

where the Hamiltonian is of the form $$H=\begin{pmatrix} \alpha t & V \\ V & -\alpha t\end{pmatrix}$$

that might seem like it shouldn't be hard, but oof

Jake Rose

I’ve noticed ;)

oddly deceiving buggers too

Semiclassical

5:20 PM

yeah

the issue is that $[H(t),H(t')]\neq 0$

the moment you have that, oof

Knight

It’s no good to apologise someone when they just say “You have disrespected me” and walks away. From now on, I may disrespect but wouldn’t apologise for vain. Thank you for making to wait.

Semiclassical

@JakeRose another problem in this vein, which you might find interesting: Let $\hat{D}(\alpha):=\exp(\alpha A^\dagger -\alpha^\star A)$. Compute $\hat{D}(\alpha)a \hat{D}(-\alpha)$.

JMac

5:43 PM

@JohnRennie That was the series I was suggesting here like a month ago. I was pretty excited to see it as an ID question.

Aaron Stevens

@JMac I need to get back into reading books with actual stories. Lately I have been reading biophysics text books :( haha

JMac

@AaronStevens I got pretty into audiobooks last year because I was traveling a lot. I don’t actually read many stories, but I’ve listened to a buttload of audiobooks over the last 2 years

Aaron Stevens

@JMac Yeah I have considered audio books. For some reason I just can't make the switch though

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