The h Bar

12:38 AM

← 2 free margs fri, 3 mojitos sat. lol ok ok admit 2 were for ladyfriends. but whos counting? are we having fun yet? cheers :o o_O :P coloradopubco.com/highlands-ranch-lansdowne larumbadenver.com

Anonymous

2:17 AM

@JakeRose The real question is: Is it well-taught and self-contained? Students come from all kinds of backgrounds and tend to forget things which were taught to them in dry/soulless manner. You're already making a fallacy when you're assuming some prior knowledge of experimental methods (that too at an undergraduate level).

Anonymous

And no, I never agreed with the notion that students should spend their limited 3 hours time during the lab in "figuring out" well known things from scratch. It helps a lot to have a theory class immediately before the experimental class, on the same topic.

Anonymous

I could take one step further and say that first year students should have the number of lab classes cut by half. The other half should be filled with theory classes discussing the fundamentals of the experiments.

Anonymous

2:40 AM

> we have an 8 lecture course on exactly that

Anonymous

BTW if it's consecutive 8 lectures on the theory it's not gonna be that helpful. I'd prefer having alternate theory and experiment classes. That way you get to immediately apply what you learn in the theory class, in the next experiment class.

Anonymous

I'd be quite surprised if students still make statements like "this point is an outlier", after having a well-taught class on the methods and philosophy of curve fitting. The point here is that such classes should be well-sparsed and intertwined with the theory classes.

Avnish Kabaj

3:49 AM

@JakeRose Cool

Hans

6:59 AM

I have never seen a website so hostile to new users as PSE.

Akash. B

elementary physics is now boring these days

John Rennie

@Hans some of the site users can be a little unkind in their comments, but I don't think we are hostile though we are demanding. That is we expect a certain minimum standard from posts. Did you have a specific post in mind?

@Hans you're referring to the closure of this question?

2

Q: Force needed to pull an end of a bended carpet with constant speed. Mistake in Gnadig et.al. problem book?

Question. Which of the analysis is correct, in this post or in the book? (details below) The question is about specific physical concepts: conservation of energy and momentum. I want to understand how this happens in this specific system. This problem is taken from the well known problem bo...

Hans

@JohnRennie yes. Have you even read it before voting to close?

John Rennie

@Hans yes I read it

Hans

So how doesn't it fit?

Akash. B

7:09 AM

@JohnRennie hi

@Hans It smells like truth

@Hans don't care about it

John Rennie

@Hans you're asking how to answer a question. That's off topic.

Hans

@JohnRennie I'm asking a question how to answer a question? Where did you see this?

Question. Which of the analysis is correct, in this post or in the book?
The question is about specific physical concepts: conservation of energy and momentum. I want to understand how this happens in this specific system.

I'm asking about conservation of energy and momentum in a specific system.

Avnish Kabaj

You just gave your solution and the books solution

Akash. B

@Hans try to find the answer yourself

that's what makes physics interesting

Anonymous

@Hans I think you've put in quite some effort into writing up the question, which is commendable. But we mean something else when we say "ask about a specific concept". There's a whole chat room dedicated to exercises like those:

Anonymous

7:19 AM

Problem Solving Strategies

General chat for high school physics. For MathJax see [here](m...

1

Anonymous

Firstly, I'd advice stripping off all the numerical values from the question. Secondly, don't use screenshots. Type out all the text yourself.

Anonymous

Next, break it up into small chunks. Perhaps you could say which part of the textbook's solution you find confusing. We can help with that.

Hans

What about this physics.stackexchange.com/questions/461467/… . Looks like should be closed, right?

Anonymous

@Akash.B That's not helping. :)

Anonymous

@Hans Yes.

Akash. B

7:23 AM

@Blue but it helps me a lot

Hans

@Blue my question is not an exercise. I believe the authors of this book made a crucial mistake. Why? because they don't understand the concept conservation of energy and momentum enough. So my question about the concept of conservation of energy and momentum. It's not about problem solving strategy.

Anonymous

@Hans You need to pin-point the specific concept in that case. If you ask us for suggestions to improve your question, we're happy to help. But if you come complaining about the unfairness of the closure of your question, lesser people would be interested in helping.

Hans

@Blue so if I strip it off of all numerical values it will fit or not?

Anonymous

@Hans That would be good start, but wouldn't be sufficient. I'd also suggest discussing only one solution at a time, and typing out the text in the screenshots.

Hans

So why this question physics.stackexchange.com/questions/461467/… hasn't been closed yet? It is older than mine and not closed.

Anonymous

7:33 AM

@Hans Probably just a statistical aberration. It should be closed soon.

Anonymous

We don't have sufficient active reviewers these days, and it keeps getting harder to deal with spam and low quality questions.

Hans

Also "Homework-like questions should ask about a specific physics concept and show some effort to work through the problem. We want our questions to be useful to the broader community, and to future users. " so homework like questions are allowed. and if my question is answered then it will be definitely useful to broder community, because it corrects a mistake in a popular book. if someone else has a similar question while reading the book can google it.

Anonymous

@Hans Trust me, the homework policy has been debated ad nauseam. You don't want to take up that fight. If we allow such questions, we will very soon get drowned with discussions of solutions in textbook exercises questions that would drive away the expert users who're interested in research level physics.

Anonymous

Anyway, I'm not interested in that debate at the moment. You may raise it on Meta instead.

Hans

Seems like quite research level to me, if 3 physics professors who write books couldn't make it right?

Anonymous

7:40 AM

Not to me.

Hans

@Blue you mean you know the answer to my question? it's obvious to you?

Anonymous

@Hans No. I didn't even read your question completely. I was just giving some general advice.

Anonymous

That question looks like a 15 minute read anyway, and I'm not willing to invest that much time.

Novalium Company

7:59 AM

How did they made it so that the input ignores html.

John Rennie

@NovaliumCompany I would guess the server intercepts and escapes the angle brackets i.e. replaces < by < and > by >

Novalium Company

@JohnRennie Yep, makes sense, thx.

Sha Vuklia

8:25 AM

does anyone know why they use curly r in the formula for V?

they refer to eq. 3.99, which is the dipole term of the multipole expansion

and as fas as I know, the whole point of the multipole expansion is to expand the potential as a power series in r, instead of in curly r

here is the equation they're referring to:

here they explain how they go from curly r to r

oh wait, maybe the point of reference doesn't matter in the case of a dipole?

because they seem to have chosen the origin to be $p$, and then indeed curly r = r

Hans

can anybody here clarify the confusion about 2 different answers in this question physics.stackexchange.com/questions/461524/… ? thanks.

Sha Vuklia

Hans

I have never seen a website that purports itself as helping people to understand something and be hostile to people whom ask interesting questions.

Sha Vuklia

i found my answer here; the point of reference doesn't matter for the dipole moment if the total charge is zero

Anonymous

8:40 AM

@Hans Well, it's a place where people voluntarily devote their time. No one is obliged to help anyone here.

Anonymous

And what might appear interesting to you, might not be interesting to most others here.

Anonymous

Your complaint would have been valid if you paid to get answers here. But that's not the case.

Physics Meta

0

Q: What's about all this hostility?

I see a lot of low quality questions on PSE. But for some reason not these low quality questions but my question is targeted by mods: Force needed to pull an end of a bended carpet lying on a floor with constant speed Is there any specific reason for this?

discussion scope specific-question close-reasons policy

Anonymous

I guess there are plenty of other places on the internet like Chegg where you can hire tutors (some of the tutors there are pretty knowledgeable too!) for a short-term. Those websites might be better suited for you.

Anonymous

As for hostility, I didn't really see anything much on that thread apart from a couple people asking you to improve the title. The question closure doesn't really count as "hostility". There may be some deleted comments there which I didn't notice, though.

Anonymous

8:50 AM

In case there really were some hostile/unfriendly comments, you should have flagged them.

Captain Bohemian

here a lot of university students make money by being a tutor for elementary, junior and senior high school students.

Anonymous

@CaptainBohemian Indeed. Several of my classmates tutor grade 9-10 students. Good for making some pocket money. :)

Slereah

Morgen

Avnish Kabaj

@Blue They must be giving up their evenings then

Anonymous

@AvnishKabaj Well, yes.

Anonymous

9:02 AM

But not everyone in my class comes from well-to-families. They need to sustain themselves.

Avnish Kabaj

@PhysicsMeta oh god

@Blue I never said it's bad

Anonymous

@AvnishKabaj And I never claimed that you said so. ;)

Avnish Kabaj

Heh :P

Captain Bohemian

@Blue actually nobody has obligation to be hired by you, either. And nobody has the obligation to hire you, either, but you just need someone to pay you.

John Rennie

I occasionally did paid tutoring as a student but I never really enjoyed it. The thing about charging is that it places you under an obligation to deliver. When you're not charging then if you feel tired (or just grumpy) you can just walk away and no-one demands their money back :-)

Captain Bohemian

9:08 AM

@Blue I don't know what is pocket money, but being a tutor has an income which is sufficient for meal fee or housing rent. And that income will not be levied tax.

I think students needing tutors mostly need special attention or guidance. if they don't need that, they can just go to cram schools, which are everywhere here.

Anonymous

@JohnRennie Yeah, that's there. Also, you have the burden of making sure that your students are actually benefiting from your lessons and doing well in class. Otherwise you'd have some uncomfortable moments with their parents. It's an absolute pleasure to teach enthusiastic students though. :)

John Rennie

@Blue that's what makes the problem solving room fun. Everyone there is enthusiastic and highly motivated.

Captain Bohemian

usually teachers in cram school teach very well, far better than formal school teachers.

Hans

@Blue "I guess there are plenty of other places on the internet like Chegg where you can hire tutors" Do I seem like I need a tutor. it is Gnadig, Honyek and \riley who wrote that book apparently need one, not me!

John Rennie

@CaptainBohemian do teachers in cram schools get paid more?

Captain Bohemian

9:19 AM

@JohnRennie I don't know, but the way of teaching in cram schools is just like that in formal schools--a teacher teaches a class which may consist around 10 to over 100 students. But teachers in cram schools are usually very good at teaching, like having got special training in teaching, while teachers in formal schools don't always teach well--some of them teach in a way very difficult to follow.

I also found professors in public universities are generally poor at teaching than professors in private universities here.

but profesors in public universities usually have more research publications than professors in private universities do.

I think in public university nobody cares very much about how professors teach. In my graduate school, a professor teaching my course classical electrodynamics and statistical mechancs teaches in a way most students can't follow or understand, but he still keeps teaching in that way.

Avnish Kabaj

@Hans wow

You sure it's just not that you're wrong

Captain Bohemian

9:39 AM

and in universities I have attended, most professors didn't care if you go to their lecturing classes or submit homework. They will let you pass the course as long as you get high enough scores in mid and final term exams.

Anonymous

@Hans Good luck with that.

Captain Bohemian

actually I often wonder how people need to ask homework questions on web; they can easily ask their classmates or teaching assistants in school; I always did that. I consider websites are for people who are outside school and have nobody to ask.

Slereah

Help

That wormhole article I've been writing for my site is running out of control

there's so many fucking wormholes

I opened up a can of worms, so to speak

Anonymous

10:03 AM

@CaptainBohemian Well, not all schools and universities have teaching assistants. And the professors are usually too busy to clarify individual doubts.

Anonymous

Also, consulting classmates is risky. :P

Anonymous

You never know what misconceptions they might be harboring.

Avnish Kabaj

Out of curiosity @Blue was that message deleted voluntarily or mod magic

Anonymous

@AvnishKabaj It was flag deleted by me.

Avnish Kabaj

I see

Well I was gonna write and try to explain the homework policy and whatnot

But one of my homework questions has been auto deleted I think

And it's too much effort

John Rennie

10:08 AM

@AvnishKabaj I doubt it would have been worth your effort. Hans came in with the mindset that we're all b******s and nothing was going to change that.

Avnish Kabaj

He seemed to be a potentially good user but

@JohnRennie oh lol

Anonymous

Assume good faith holds in chat as well. Calling a whole group of people "rep whores" is not OK, especially after we've been collectively trying to provide them feedback to improve their question. Perhaps our feedback was not good enough, but still that's no reason to be rude.

Avnish Kabaj

19 secs ago, by John Rennie

@AvnishKabaj I doubt it would have been worth your effort. Hans came in with the mindset that we're all b******s and nothing was going to change that.

Yes

That's what I was about to type in

@Blue Ah my ping preview didn't show the rep whoring part

John Rennie

Calling people rep whores is just childish and petulant. Anyone with that attitude is beyond reasoned argument.

Slereah

I am one

vote for me plz

I am not a crook

Slereah

10:25 AM

"New examples of sandwich gravitational waves and their impulsive limit"

the most delicious waves

Slereah

10:46 AM

It's kind of weird that the whole theory of discontinuous ODEs was made for robotics

researchgate.net/publication/…

anyone got access to this?

Anonymous

11:13 AM

@Slereah I sent a request for the full text. You'll probably be able to get access to it before that though. :P

Avnish Kabaj

11:29 AM

cough

Sci-hub.tw

cough

Lib-gen

cough

Slereah

tried libgen

It's a thesis

Not on libgen

Anonymous

Yeah, it's not on Scihub...

Slereah

Also doesn't seem to work on sci hub

Also that would be ILLEGAL

You scoundrel

Anonymous

@Slereah Not at my place!

Anonymous

And I don't care about morality. :P

user351417

11:47 AM

@Blue Is that a mod superpower?

Anonymous

Yessshhh...mods are unimpeachable. LIES! :)

user351417

Captain Bohemian

@Blue really? When I was in junior years of undergraduate school, I just dare not ask professors because I was given the impression that professors are solemn people who may be accidentally agitated, so I usually asked teaching assistants or classmates. But in my senior years of undergraduate and graduate schools, I tried to ask professors, finding most of them are so glad to solve my scientific problems; they mostly even talk more than I ask like hoping to enlight me more as possible.

Anonymous

12:09 PM

Help, I set my white balance wrong and suddenly everyone is screaming at each other about whether they've been to Colorado.

Anonymous

Loved this one. :P

Anonymous

@CaptainBohemian That's my impression too. Just that we don't have the concept of "teaching assistants" here.

Captain Bohemian

@Blue your teaching assistants are called assistant professors, right?

Anonymous

@CaptainBohemian No, not really...

Anonymous

Assistant professors are like full professors, just without tenure. But one class is usually taught by one professor alone.

Captain Bohemian

12:14 PM

I just heard several Indians on web saying they are assistant professors. I consider they have completed PhD because only PhD holders can be professors, but it turns out they are just MSc holders doing teaching job like our teaching assistants.

Anonymous

At our university all assistant professors have PhDs. It's not a strict necessity, but it's difficult to get that position without a PhD.

Captain Bohemian

@Blue in my country, that position is called instructor, which is a very rare position, particularly in research universities.

Anonymous

We did have a professor last year who had joined with a masters degree, but he was extraordinarily well learned for his age (I think he was just 25). He left this year to get a PhD. I guess the one year of teaching experience was a plus point in his CV, for grad school application.

Captain Bohemian

some universities, whose main function is not research but some kiind of professional education or others whose main function I don't know, may have more positions of instructors, but I am not quite sure.

that depends, I have seen a PhD program saying that the applicant should not emphasize their teaching experience because we are research institute, not teaching institute.

Anonymous

12:31 PM

::shrugs::

Captain Bohemian

actually not only instructors are rare positions, but also full-time teaching assistants become rarer and rarer positions here. Most universities prefer to hire graduate students as part-time teaching assistants than full-time teaching assistants.

Slereah

2:10 PM

who are the war criminals who call cylindrical coordinates $(x_1, x_2, x_3)$

Answer : it's Curzon

Slereah

2:53 PM

Secret

3:27 PM

Optical flow

Optical flow or optic flow is the pattern of apparent motion of objects, surfaces, and edges in a visual scene caused by the relative motion between an observer and a scene. Optical flow can also be defined as the distribution of apparent velocities of movement of brightness pattern in an image. The concept of optical flow was introduced by the American psychologist James J. Gibson in the 1940s to describe the visual stimulus provided to animals moving through the world. Gibson stressed the importance of optic flow for affordance perception, the ability to discern possibilities for action within...

hmm.. velocity, space and time are all related to motion

I wonder, can we turn this onto its head by creating exotic spaces in VR with specially shaped optical flow

Also:
1. given an object that teleport at fixed distance away per unit time can give an illusion of motion if the separation is small enough

2. Likewise, an object that blink in and out of existence in a fixed position will be moving along a geodesic

3. Thus a row of identical objects can be used to encode time if they changed in a correlated fashion say turning red in the order 23415

4. Likewise, an object that is self correlated in a given time period can encode a notion of space

5. As for optical fields, the rate these correlations in time and space are established can thus encode both distance and time

So in theory one can encode a spacetime structure by having a velocity field plot as seen in all reference frames

@vzn Solitons phys.org/news/…. There isn't much soliton stuff in recent weeks though

Physics Meta

3:50 PM

0

Q: The role of good mechanics problems

Today I saw that this question about pulling a bent carpet was closed for being a homework question. I think this was an incorrect call that illustrates a flaw with the homework policy and the way people vote to close. The linked question is a subtle mechanics question, where the answer depends ...

discussion

PM 2Ring

4:21 PM

@Secret Our visual processing system "cheats" when it detects periodicity in the optical flow. By internally simulating the regularity it reduces the amount of incoming data it needs to process. But when the periodic motion stops it takes the brain a little while to switch off the simulation. There's a demo of this effect in this short video.

An old friend who worked on the railways told me that this illusion can strongly affect train drivers, especially if the train line is mostly straight. After a long journey with lots of periodic optical flow it can take several minutes for their visual field to stablise.

Also see en.wikipedia.org/wiki/Motion_aftereffect

Student404Mus

4:43 PM

Someone could figure out this equality $\mathrm{tr}(|b_1\rangle\langle b_2|) =\langle b_2|b_1\rangle$ ?

Because the cyclic trace property if defined or proven for operators not for vectors?

Student404Mus

4:58 PM

my second question is: what do we mean by unknown state ? how it is related a mixed state?

Secret

5:20 PM

PM 2Ring: Ah I see

Anonymous

9

Q: Trace of an operator matrix (Quantum computation and quantum information)

I'm reading the book Quantum computation and quantum information by Mike & Ike and I'm stuck at 2.60/2.61. There, the author says that, given the operator $A|ψ⟩⟨ψ|$, its trace is: $${\rm tr}(A|\psi\rangle\langle\psi|) = \sum\limits_i\langle i|A|\psi\rangle\langle\psi|i\rangle$$ Why would that b...

quantum-mechanics quantum-information quantum-computer linear-algebra density-operator

enumaris

6:25 PM

sup y'alls

Anonymous

Soup.

Anonymous

How's it goin'?

enumaris

looking into speaker identification atm

looks like Microsoft azure does it

If anyone knows of any open source packages that does that, let me know :D

How about with you? @Blue

Anonymous

@enumaris Cool stuff!

Anonymous

There's some fancy math there.

enumaris

6:29 PM

the other data scientist used open source to build out a speaker recognition system but it's outputs are not quite the correct output to solve the problem we want to solve

ACuriousMind

Meanwhile, OpenAI has trained a high school essay writer :P

2

enumaris

you mean fake news generator?

I think Elon quit over that?

ACuriousMind

It's a "general language" model and the stuff it generates seems right in the uncanny valley - not enough to completely fool a human, but close enough that it's getting eerie

enumaris

generalizable to chat bots?

ACuriousMind

Probably? It's not task specific, and it seems to be acceptable at answering questions about a text it has "read".

It can also generate LotR fan fiction!

enumaris

6:33 PM

hmmm

Anonymous

@enumaris Exam season beginning from next week. The course on finite state machines is quite interesting. Also, learning some differential geometry and trying to read Shor's paper intermittently. :P

Anonymous

The analog electronics courses are meh as usual.

ACuriousMind

In completely unrelated news, does anyone know what data structure I'm looking for with the following: I have a type with two attributes, one of which is a type on which a order relation exists, and the other type is hashable. I want kind of a priority queue - sorting the elements by the attribute with the order relation - that also allows you to delete items from it using the second attribute as a key. I.e. I want a cross between a priority queue and a hash map

But just declaring the type itself to be orderable (just order by the first attribute) and hashable (just hash by the second attribute) is a contract violation, because hashable types are supposed to have equal hashes when they compare as equal.

This must have been invented over and over again because this is how e.g. initiative queues in turn-based games should work, but I can't find anyone actually describing this structure in the wild

Avnish Kabaj

This is a ping for @Hans

If you do come back I just wanted to say that what's set the stackexchange network apart from quora is it's self moderation and quality checks. The by product of this was the adoption of homework policies on chem,math and physics

Physics has the strictest one

Try to be a bit receptive

4

Q: The role of good mechanics problems

Today I saw that this question about pulling a bent carpet was closed for being a homework question. I think this was an incorrect call that illustrates a flaw with the homework policy and the way people vote to close. The linked question is a subtle mechanics question, where the answer depends ...

discussion

Anonymous

7:06 PM

@ACuriousMind If I'm not misinterpreting, you want something like priority queue dictionaries?

ACuriousMind

@Blue Yes, but that doesn't seem to be a standard name, all hits point solely to things related to that pqdict

At least you found one instance of this being talked about, I guess

Anonymous

I guess the proper name is "indexed" priority queue. Gotta check...

Anonymous

Indexed Priority Queue | Data Structure

►

ACuriousMind

Yes, that seems to be it. Thanks!

Anonymous

Yay. This is new for me too. :)

ACuriousMind

7:12 PM

I mean, it was clear to me that this structure must have been described already, I just couldn't hit the right combination of search words to not get flooded with descriptions of any of the other queue-like structures :P

Anonymous

Same here. Apparently it's there in Sedgewick's textbook (dunno how I missed it earlier...gotta revise these data structures stuff). :P

Anonymous

The concept is quite simple though, yes.

Jacob P.J

Hello

I had a question on transistors

Anonymous

Hollo.

Anonymous

Damn. ::flees::

Jacob P.J

7:21 PM

No other chat rooms seems to be active

Anonymous

It's okay, go ahead. :)

Jacob P.J

😆

Okay so in a common collector circuit like electronics.stackexchange.com/questions/274794/…

See the diagram in the link

For the emitter and collector both are n but are forward and reverse biased simultaneously , i cant understand why

Common collector is not in our syllabus, but the curiosity is 😈

I believe that emitter collector jn must be reverse biased

Anonymous

Well, the necessary biasing will depend on the region of operation.

Anonymous

Note the chart on the right.

Jacob P.J

I am just starting on transister

Yeah on the right is my prob

Its an npn and both n are weirdly connected

Anonymous

7:27 PM

What do you mean by "weirdly"?

Anonymous

It looks fine to me.

Jacob P.J

It is supposed to be reverse biased , but both n are connected to the negative and positive terminal at the same time

Anonymous

What you need to note is the biasing at the CB junction and the biasing at the BE emitter junction. Find out the region of operation from there (i.e. the chart). "It is supposed to be reverse biased here" --- that doesn't make much sense until you define "it". We talk about biasing of "junctions", not of "n" or "p".

Jacob P.J

I dont understand

Anonymous

It's better if you consult a proper textbook. It's difficult to teach whole chapters here. I'd suggest Boylestad. The Neso Academy lectures are nice too, for beginners.

Jacob P.J

7:33 PM

Okay

Neso academy lecture couldnt clear my doubt

Anonymous

You probably didn't watch them in order?

Jacob P.J

There were numerous comments also regarding the same question, i guess ill try boylestad or study common emitter and base first

Thanks for trying 😊

Anonymous

FWIW this is the complete playlist. I suggest starting right from the first lecture.

Anonymous

@JacobP.J Np.

Jacob P.J

Okay

Student404Mus

9:02 PM

i appreciate you answer. In Mike M.Wilde Quantum information book, he stated, "... The evolution of a closed quantum system
is reversible if we do not learn anything about the state of the system (that is,
if we do not measure it). Reversibility implies that we can determine the input
state of an evolution given the output state and knowledge of the evolution". is the same to say, quantum circuits are reversible. how we would know the output without measurement?

Anonymous

@Student404Mus Well, in a quantum circuit you get an "output state" at the end, due to the action of the quantum gates on the input state. You don't necessarily have to measure it. BTW it's not clear what you mean by "output" in the last sentence. Are you referring to the result of measurement or the output state?

Student404Mus

what does it mean output if you didn't perform measurement

Anonymous

The output "state". That is, the final composite quantum state of the qubits.

Anonymous

It seems you're missing some essential background here.

Student404Mus

i think "knowing" output means you measure it first. without measurement we are ignorant about the output. Rather knowing the input .

Anonymous

9:17 PM

I don't see the term "output" independently in your quote from Wilde's textbook, so I can't comment.

Jake Rose

Why in fluid dynamics is $\frac{D(dl)}{Dt} = dl \cdot \nabla v$

as in shouldn’t there be a $\frac{dl}{dt}$ term?

Anonymous

10:15 PM

Cosmas Zachos

Cosmas K. Zachos (Greek: Κοσμάς Ζάχος; born 1951, Athens) is a theoretical physicist. He was educated in physics (undergraduate A.B. 1974) at Princeton University, and did graduate work in theoretical physics at the California Institute of Technology (Ph.D. 1979) under the supervision of John Henry Schwarz. Zachos is a staff member in the theory group of the High Energy Physics Division of Argonne National Laboratory. He is considered an authority on the subject of phase-space quantization. His early research involved, jointly, the introduction of renormalization geometrostasis, and the so...

2

Anonymous

> He is considered an authority on the subject of phase-space quantization.

Anonymous

Whoa, I didn't know this.

Anonymous

> Cosmas K. Zachos, David B. Fairlie, and Thomas L. Curtright, Quantum Mechanics in Phase Space. (World Scientific, Singapore, 2005)

Anonymous

Indeed, eqn (3) describes the celebrated Moyal bracket (MB) and the $\hbar$ multiplying the PB is highly significant. That is, as $\hbar \rightarrow 0$ — Cosmas Zachos Sep 27 '15 at 19:09

Anonymous

Definitely should get a copy of that book. Looks pretty nice.

Mo_

10:20 PM

@Blue $191

Anonymous

@Mo_ Just found a free PDF!

Anonymous

Oh, it's on arXiv too: arxiv.org/abs/1104.5269.

Anonymous

That's not the full book, wait.

Anonymous

The one on ResearchGate probably is the full text.

Anonymous

Indeed. It's a 560 pages textbook.

Mo_

10:28 PM

@ACuriousMind Ah...

you're no longer a curious mind in my book. Just a curious guy with a long hair

why did you do this to us

Anonymous

@Mo_ Nah, he's a shapeshifter AI.

Anonymous

That's just one of his forms.

Mo_

@Blue something like a self-modifying code?

btw it seems he's been high

Emilio Pisanty

10:43 PM

So, you're saying burning the which-way information doesn't change anything? In this video at 5:44 youtube.com/watch?v=xo176uIPmbY it states that it will change the screen data. Or am I getting it wrong? I am new to this... — all is mind 41 mins ago

ugh

boy, that's one awful video

@Blue well, that does scream for a [by whom?] superscript

but I'm not surprised

I suspect the book is the one he mentions here

7

A: Is the Moyal-Liouville equation $\frac{\partial \rho}{\partial t}= \frac{1}{i\hbar} [H\stackrel{\star}{,}\rho]$ used in applications?

"Used in anger" or "killer ap"? To my knowledge, no problem has been solved in the phase-space quantization language that was not solvable in the other two formulations/pictures (Hilbert space or path integrals). This is in contrast to, e.g., path integrals (whose gauge fixing, Faddeev-Popov, and...

actually, come to think of it

that's an excellent place to invest

Anonymous

11:01 PM

@EmilioPisanty Indeed, that's the booklet he's talking about there! I have been curious about the quantization stuff (and phase space formulation of QM) for quite a while and was looking for good references; this looks like a nice review-paper type text.

Anonymous

@EmilioPisanty Heh, yeah. I was wondering too. :P

Anonymous

By the looks of it, he definitely has worked extensively in this area.

Problem Solving Strategies

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