The h Bar

Stan Shunpike

05:54

Can every quantum state property be expressed as a vector? I find this point confusing. How can something like "spin" be put in linear algebra terms? There are only two positions: up and down.

Or is this part of why the idea of superposition allows an entire range of values that we call "up AND down" and describe using complex numbers....

glance

07:05

@StanShunpike if there are two eigenstates $|0\rangle$ and $|1\rangle$ of a given observable (like spin in your example), the general quantum state is a superposition of these two states. You can take any combination (up to normalization constraints) $c_0 |0\rangle + c_1 | 1\rangle$ of these states and obtain a feasible quantum state. This is why we can talk of a "vector", i.e. an element of a vector space. The superposition principle is what allows us to do so

user54412

@0celo7 Most astrophysicists don't. I think it's a shame, since GR is so beautiful. But I'm basically the only person in my department (20-30 each of faculty, post docs, and grad students) who does anything with GR.

user54412

And most cosmology is pretty trivial on the GR side -- the hardest thing you do is integrate some radial null rays in FRW

user54412

@0celo7 Come back when you've memorized a Kerr metric (any one) :P

user54412

@StanShunpike There are only two basis vectors (which can be taken to be up and down, or any other linearly independent pair). The space of states is a 2D vector space over the complex numbers.

user54412

It's only when you make a measurement and "collapse" the state that you force it to be one of the eigenstates of your operator. There are (up to scaling) only 2 eigenvectors of the spin operator, but there are uncountably many 2D vectors over the complex numbers, even when you account for some of them being just rescalings of the others.

Eka

07:15

@alarge sorry for this late reply but i find some o the nature letters interesting (mostly novel) comparing to its articles eg: nature.com/nature/journal/v455/n7216/abs/nature07378.html

Danu

10:27

@vzn There is no IMHO about this at all: He was from a physics background. In fact, most famous philosophers of science were (ex-)physicists

@innisfree I totally agree with what you're saying. @vzn You are making a lot of statements about philosophy, Bell's theorem, 'a new quantum mechanics' etc while it appears that you have not really looked at the details of what already exists, or of philosophy of science

@ApprenticeHacker I think 3.85 is pretty good: Of course 3.9+ is slightly better but it will not ruin your chances at all. It's more important to get an amazing GRE score try to publish (I know this is hard)

...I personally got rejected at the schools I wanted to go to despite a 3.96 GPA, but my PGRE was not amazing

@vzn No, it's just that you think it's much easier to define that it really is.

Sufficient thought on these issues will reveal to you how amazingly difficult it is to get a consistent notion of even e.g. progress in science

(of course, it's most efficient to read a book on philosophy of science instead)

glance

ehi, what do you think of the following idea for SE: allow the possibility to add "subtitles" to the questions, which would be brief descriptions of the content of a question to appear as alt text when hovering with the pointer over questions' titles. This would allow a better understanding of the content of a question while looking at them in the related section, without actually having to browse every single question.

this would be useful for questions with a content not easily described as concisely as a title requires. Moreover, one can make this "subtitle" feature optional, while displaying by default the beginning of the question as alt-text.

infinitesimal

10:47

pinterest.com/pin/A9pFagAQQIYCXOyaqB8AAAA

Danu

@glance such suggestions should go to Meta Stack Exchange

glance

11:15

@Danu yea I know, I was just wondering what people would think of such a suggestion before actually making it a post (like: "it's totally stupid, don't go for it" and such)

Danu

11:32

It's a nice idea and I would think it's an improvement

However, I think there is a very small chance (at best) that it will actually be implemented

...as it doesn't really do anything vitally new. One can just make a two-part title right now

glance

@Danu what do you mean by a "two-part title"? The whole point of my proposal is to allow people to understand what the questions on related/linked questions are actually about without actually having to browse all of them. It comes from wondering in math.SE which of the ten related "entire function question" questions are actually about something related to a question

Danu

<Main Title>: <Subtitle> can already be done

I think that the main thing is to teach people how to write proper titles, and to improve titles if you see bad ones.

glance

@Danu we don't have much this problem here, but on math.SE it's a hell. The vast majority of questions have titles like "integral question" or "an entire function" or things like that

Danu

Yes, because there are many, many more 'n00bs' on math.se

...and mathematics is too far gone: The quality has not been maintained at a reasonable level over there for a long time

glance

@Danu I feel like that's my major occupation lately. I don't understand why so much effort is put on retagging questions, while very few go into actually changing the title to make it decent enough to be useful to others. I really think that the title is more important than tags to found a question

Danu

11:40

@glance Good point

glance

@Danu that I didn't know. How does it work? I just tried and it doesn't seem to really add a "subtitle"

Danu

@glance No, I know

But it mimics the format

glance

@Danu oh so you meant as a format to implement my proposal. Yes I was thinking of something like that. It shouldn't be so hard to do... more difficult would be to implement a "preview" feature on hovering, that would require some AJAX calls and such. Not that difficult though.

Danu

Hmm yeah, well see how the meta community likes it

There are probably similar discussions to serve as precedent

glance

well I guess I'll go for it. Maybe they'll never do it but at least I'll be able to say "I told you it was useful" whenever someone complains about difficulty in retrieving bad-indexed questions

Danu

12:03

Also, one major obstacle would be indexing all pre-existing questions

glance

@Danu that's way i thought of an optional feature. On older questions, or questions without an added subtitle, one could implement a simpler (and less useful of course) "preview on hovering" feature

Sofia

12:37

@MarkMitchison I voted for closing the question as too broad. The user asks us to explain about half of the quantum mechanics. I wrote him/her a comment recommending to limit the scope of the question.

tpg2114

13:48

I always find it... confusing... when somebody accepts an answer without upvoting it. I mean, if it answered the question enough to be accepted, surely it was useful and clear enough to be upvoted.

Physics Meta

14:28

0

Q: I asked way too many questions at once, now I must pay the price

Previously, I wrote the following question Has anyone formally tested Josh Pellicer's theory on human sexual behavior?. This was a question I wrote with a lot of material from the work in question. This question contained 6 sub-questions to answer for an overarching one question. Oddly enough, th...

discussion

Kyle Kanos

14:43

@tpg2114 Let me guess, new user?

Sofia

15:09

@KyleKanos Since when phys. SE is about sex? Thus is a clinical topic, there are physicians for that, not physicists? The fellow misspelled the profession. He should be migrated to a doctor.

Kyle Kanos

@Sofia I suppose that your comment is in relation to that above Meta post?

If so, you need to click the link and read it. That guy is using a question he posted on a different SE site as an example of a "well-received too broad question."

Sofia

@KyleKanos yes!

Kyle Kanos

He did the same thing here (asking too broad a question) and it got closed as Too Broad

He's asking what he could do to prevent such a thing in the future

Sofia

@KyleKanos well, so be it.

Jimdalf the Grey

Further evidence that the different SE sites have different policies on what constitutes an acceptable question

Kyle Kanos

15:12

^ That

And though sometimes I wish we could make it more uniform (so people couldn't complain), I don't think that it's actually a bad thing to have different rules about how questions should be asked.

Jimdalf the Grey

I agree. A good example is Math.SE vs Physics.SE. They allow HW problems because they deal in math and the solving of it. We don't, but most of our HW problems are just solving math. Thus, it makes sense for us to not allow most where they do

And, while I'm not sure about this, I'd imagine DIY.SE has a lot more tolerance for primarily-opinion questions than we do.

Sofia

@tpg2114 I join you complaint : I also was mocked as unsung hero because my answers accepted without upvoting. What's my fault that the cub was in hurry and forgot to upvote?

Jimdalf the Grey

@Sofia You'll get no argument from us. Maybe it might make sense to change it so that an accept automatically upvotes the answer (if the OP hadn't done so already)

I'll check if there's an explanation on mother meta

Kyle Kanos

-18

Q: Possible solution for (accidentally) not upvoting accepted answer

I have searched the site and found there is already a question about this: Accepting answer without upvoting? but it is already 4 years old. In my opinion, Auto-upvote should be in place and here is the full solution, does anyone know why this is still not in place? :P Improve even without Au...

feature-request reputation voting accepted-answer up-votes

Upvoting $\neq$ accepting

Jimdalf the Grey

Yeah, found that right away too

Sofia

15:20

@KyleKanos it's dirty thing to upvote myself.

@KyleKanos I have many such cases.

Jimdalf the Grey

what do you mean "upvote myself"? You can't upvote your own posts

Kyle Kanos

@Sofia: Out of curiosity, are you aware of the "link answer to this comment" feature here in Chat?

Sofia

@JimdalftheGrey of course not, s.t. what it means auto-upvote? Who is auto?

Kyle Kanos

Auto is short for automatic

(at least in this case, it can also mean "car" as in automobile)

As a complete aside, why don't the network sites have a profile page like the ones on Mother Meta? Those Meta.SE ones are so nice looking

Sofia

@KyleKanos why do you mock me? Which car? My car doesn't know do vote.

Kyle Kanos

15:24

@Sofia Why do you think I'm mocking you?

You asked about the "auto" in "auto-upvote." I said it was short for automatic and that, sometimes, cars are called "autos" because that is short for "automobile."

Sofia

@KyleKanos because you say that auto also means car in this case. --- This case, is the case of the voting.

Jiminion

@Sofia I'm sure Kyle is not mocking you.

Kyle Kanos

That aside was for the automatic. In this case, auto means automatic.

Sofia

@Jiminion I didn't learn to read minds, only texts.

Kyle Kanos

@Jimdalf: Did you flag that "feeding the bears" answer?

27

Q: Help us test the shiny new "User Activity" page! (Plus a bunch of new features.)

Today, we're shipping the new "Activity Page" of the Profile here on Meta SE, so you can test it out and hopefully share some feedback and suggestions before we ship it network wide. Hate words? Assuming you're signed in, just click your face up in the top bar, and you can see it right now. Or,...

discussion featured design profile-page feedback

Jimdalf the Grey

15:28

@KyleKanos Saw it in the LQ queue, so I couldn't flag without clicking through to the post. I just left that comment and recommended deletion

Kyle Kanos

I agree with it being deleted because it's a blatant answer to a HW problem. But I'm conflicted about actually doing so because none of the criteria actually fit it, IMO.

ACuriousMind

@0celo7 I once had a lab where we let cylinders roll down an inclined plane and measured their velocity at the end. They had about 50% more kinetic &rotational energy at the end of the incline than they had potential energy at the top. We never found our error.

@KyleKanos I think they're testing it on meta.SO before rolling it out to everyone else

Jiminion

@Sofia I can't read minds either, just context. Whenever I try to read Kyle's mind, I see the kwisatz haderach staring back at me. Get out of my mind!!!!

ACuriousMind

Argh

You posted that right there, sorry :D

Jimdalf the Grey

@KyleKanos I've flagged enough of these to know a mod would delete it if I flagged it for them. I used the "no comment needed" option because me recommending deletion is the same thing and saves the mods th trouble

Kyle Kanos

15:32

@ACuriousMind It seems that way.

Jimdalf the Grey

Yeah, the new profile page is nice, but it'll take some time to get used to it

Kyle Kanos

@Jiminion I assure you, I am not Paul Atreides (if that's what you're trying to imply)

Jimdalf the Grey

I want to see my impact score for Physics.SE now

and what constitutes highly ranked for an answer?

Kyle Kanos

Isn't impact based on # of views?

Sofia

@Jiminion what is kwisatz haderach?

Kyle Kanos

15:36

@Sofia It's from the book series Dune by Frank Herbert

Frank Herbert's Dune

Frank Herbert's Dune is a three-part miniseries written and directed by John Harrison and based on Frank Herbert's 1965 novel Dune. The series was produced by New Amsterdam Entertainment, Blixa Film Produktion and Hallmark Entertainment Distribution. It was first broadcast in the United States on December 3, 2000, on the Sci Fi Channel. It was later released on DVD in 2001, with a director's cut appearing in 2002. A 2003 sequel miniseries called Frank Herbert's Children of Dune continued the story, adapting the second and third novels in the series (1969's Dune Messiah and its 1976 sequel Children...

Jimdalf the Grey

Yeah, # of views on your questions and questions where you posted a highly ranked answer

Kyle Kanos

(NB: I grabbed the link without realizing it was the Sci-Fi Channel movie version and not the book version. Sorry to those offended)

Sofia

@Jiminion I almost read it in Romanian, and I got something that you for sure didn't intend.

Jiminion

@Sofia kwisatz haderach is the superbeing messiah from the novel Dune. And Kyle IS the K.H. (Note: Who PLAYED Paul Atreides in the 1984 Dune movie? I rest my case.)

Kyle Kanos

Uh, does anyone actually count the 1984 movie as being in existence?

Jiminion

15:38

The Dune movie is a disasterpiece.

Kyle Kanos

Uh

Wot?

Really?

I thought it was universally panned as an awful movie

I personally am glad that Lynch screwed up that movie & not Return of the Jedi that he was offered at the same time.

Sofia

@KyleKanos why not! Is someone counting the today movies? All are the same, gangsters, rimes, a lot of fighting. Ehhh! The same stuff.

Kyle Kanos

@Sofia Actually, I'd argue a lot of movies made these days are rotten as well.

Sofia

@KyleKanos Aaaaa! I am not sure I understood you.

Kyle Kanos

And if you want to get to it, there are only 7 basic plots:

The Seven Basic Plots

The Seven Basic Plots: Why We Tell Stories is a 2004 book by Christopher Booker, a Jungian-influenced analysis of stories and their psychological meaning. Booker worked on the book for 34 years. == Summary == === The meta-plot === The meta-plot begins with the anticipation stage, in which the hero is called to the adventure to come. This is followed by a dream stage, in which the adventure begins, the hero has some success, and has an illusion of invincibility. However, this is then followed by a frustration stage, in which the hero has their first confrontation with the enemy, and the ...

@Sofia I think I misread your previous comment as well. The answer to your question is Yes, people do count recent movies in "what is good vs what is bad"

Great reasoning

Jimdalf the Grey

15:46

@KyleKanos I assume you improved the edit because of the "aA"

Sofia

@KyleKanos once there were movies. And there were artists. We loved them. Our beautiful actors. Who didn't see "Ben Hur", and "Qvo Vadis", and many, many beauties? What is left today?

Kyle Kanos

@JimdalftheGrey Oops, didn't catch it

Jimdalf the Grey

I'll get it

Kyle Kanos

@Sofia Lord of the Rings, though often venturing away from the books, is quite a beautiful set of movies.

ACuriousMind

@KyleKanos I never get why people get so hung up about units. Who cares what we define as fundamental and derived, if you can in principle set all the constants to 1 and never care about units at all (except for translating it back into numbers people can actually use)?

Sofia

15:49

@KyleKanos it seems that all these giants of the screen passes away, and left void. Where is a "Ingrid Bergman*, a Beth Davis, a Robert Taylor? I see none who can take those places.

Kyle Kanos

@ACuriousMind Naivete?

ACuriousMind

@Sofia The trend goes away from movies to very carefully planned and executed series.

Which naturally don't have main stars, but an ensemble cast

Sofia

@KyleKanos I speak of grandeur (grateness).

ACuriousMind

@KyleKanos ::nod::

Kyle Kanos

@Sofia I think there are still many good actors acting today. For example, Julia Roberts and Matt Damon

Sofia

15:53

@KyleKanos would you compare Julia Roberts with Elisabeth Taylor?

Kyle Kanos

@Sofia I usually don't compare Actor/Actress A to Actor/Actress B.

Sofia

@KyleKanos give me one name, one single name that would match Charlton Heston.

Kyle Kanos

John Wayne

Though he died a while ago

But he's still, IMO, better than Heston

I guess Clint Eastwood could be a modern-day comparison. But like I said, I don't normally compare person A to person B.

Sofia

@KyleKanos Better than Heston? Whaaaat? Did you see "Ben Hur"? Or, "The 10 commendments"?

Jiminion

Heston was the last actor who could go shirtless without worrying if he'd been to the gym that day.

Kyle Kanos

15:56

Did you see True Grit or The Searchers or The Quiet Man?

Or The Man Who Shot Liberty Valance?

Those are phenomenal movies, not just >3 hour epics that Heston did

Jiminion

Or The Cowboys.

Sofia

@KyleKanos What is person A and person B? I speak of giants of the screen here. Who can compare with them?

Kyle Kanos

@Jiminion That one too (sad now that I forgot about it)

@Sofia How are you defining "giant of the screen" here?

tpg2114

Everybody is giant when they are on a movie screen. And really tiny when they are on a TV, unless you happen to be really rich and then I guess they could be giant there too...

Sofia

@KyleKanos Ingrid Bergman and Spencer Tracy were names "sacred monsters of the screen" (of course they weren't monsters, but super- adored actors)

Kyle Kanos

16:02

@tpg2114 Especially Tom Cruise. He's like 5'6"

ACuriousMind

@tpg2114 Are dwarves or gnomes or goblins also giants when they are on-screen?

Kyle Kanos

@Sofia Again, what are you using to define as "sacred monster" or "giant" on the screen? Without that, I cannot give you an answer

tpg2114

@ACuriousMind A 15 foot tall dwarf is still pretty giant. Not as tall as the 30 foot tall human, but still pretty giant.

Jiminion

@KyleKanos I think there is a translation issue.

tpg2114

Sorry, that really was the most meaningful thing I could interject into the conversation. I'll go back to lurking.

Jiminion

16:04

Balaur ??

Sofia

@KyleKanos Tom Cruise is excellent. But the movies are not his full measure. Only once I saw him in a movie as he deserves, "interview with the vampire". There, he was at his full measure, as actor, as play.

ACuriousMind

@Jiminion The Rumanian version of dragons, or a dinosaur

Jiminion

I thought TC was good in War Of The Worlds. It's easy to hate on him, but seometimes he does ok.

tpg2114

@Sofia The Tom Cruise reference only came about because I made a play on words and used "giant" to mean physical size when projected on a large screen. Which is not to say that he is or is not a good actor, but his name only came up due to a pun that was unrelated to the discussion

Sofia

@ACuriousMind what's between you and Romanian? Someone in the family? Some relatives? Friends?

@ACuriousMind what an unexpected surprise!

ACuriousMind

16:09

@Sofia No, I just answered Jiminions query about "Balaur"

I have no connection to Romania

I just happened to read about the Balaur a few days ago, rather by chance

Sofia

@@ACuriousMind and how do you pronounce it? Can you write the letters by pronounciation?

ACuriousMind

@Sofia I have no idea how it's pronounced.

I stumbled across the Wikipedia article by chance when searching for mythical creatures

Sofia

@ACuriousMind it's pronounced the same as dinosaurs. But, do you indeed love such movies? I mean, "Lord of rings" and such?

ACuriousMind

@Sofia Well, I'm not that big a fan of Lord of the Rings in particular, but I am a big fan of fantasy and science-fiction in general. (Though most fantasy movies are horrible)

Jiminion

Sounds like it is pronounced bah-loud.

Sofia

16:17

@ACuriousMind what type of movies you like most? May it be history too?

ACuriousMind

@Sofia No, I find most history movies excruciatingly boring, I have to say. I really like series more than movies, but if I have to pick a movie type, I'm afraid my tastes are unrefined enough that I'd just watch action movies, preferably sci-fi.

Sofia

@ACuriousMind what is "unrefined"? Not yet crystalized?

ACuriousMind

@Sofia No, rather "barbaric" or "uncultured" in this case :D

Jiminion

Yes, the Ironman seires is rather not yet crystalized.

0celo7

16:39

@ACuriousMind Would it be too much trouble for you to get ahold of Di Franceso? I have some questions about specific paragraphs and equations.

It's fine if you're too busy.

ACuriousMind

@0celo7 No trouble, I think, I just need to visit the campus. Was going to do that anyway sometime this week, so I could tell you when I've got it.

0celo7

@ACuriousMind (on my phone at school, in class, forgive typos) If I have some infinitesimal coordinate change $f(z)=z+/epsilon(z)$, how do I get ε?

I feel like I've done this a million times before, but I can't put my finger on the exact method

ACuriousMind

17:01

@0celo7 It's very annoying to do this formally, but you get $\epsilon$ by letting $f$ vary smoothly infintesimally as $f_\delta$ and then take $\epsilon(z) = \frac{\partial}{\partial \delta}f_\delta \lvert_{\delta=0}(z)$.

A Googler

How do you calculate potential due to an infinite (this is an approximation) plate carrying a finite charge ?

ACuriousMind

Heuristically, $\epsilon$ is the vector field induced by a diffeomorphism $f$.

0celo7

What is f_delta? How does one perturb exactly?

ACuriousMind

@0celo7 That's why I said it's very annoying to do this - you never do it explicitly, it suffices to know that it is formally possible. Very formally, you take $f : (-d,d) \times M \to M$ such that $f_\delta(p) = f(\delta,p)$ is a diffeomorphism for every $\delta$ and define the action of $\epsilon$ on a function $g$ by $\epsilon(g)(p) = \partial_\delta (f_\delta^* g)(0,p)$, where $f^*$ is the pullback.

But you don't need to know how you arrive at the infinitesimal transformation to use it. It's often the case with these constructions that they would be absolutely horrible if you needed to actually calculate them, but fortunately, you very rarely have to.

(If you have an explicit $f(z)$, you choose $f_0 = f$, or course)

Glen The Udderboat

17:37

If I'm on the Moon and shoot up a rod at an angle (with the acceleration directed through the rod), one which end will the rod fall back down?

A Googler

depends i think

you'd have to calculate the torque on it due to gravity

Jimdalf the Grey

@GlenTheUdderboat Gravity on the moon behaves the same as gravity on Earth, it's just weaker

ACuriousMind

@GlenTheUdderboat Why does it matter that you're on the moon - i.e., why should the answer differ from earth?

Jimdalf the Grey

@ACuriousMind First!

Glen The Udderboat

@ACuriousMind Because of air.

ACuriousMind

17:38

Damn

Kyle Kanos

Ugh, I've run out of close votes and it's only noon-forty local time

tpg2114

@KyleKanos Noon-39 here. The Clemson timezone must be different ;)

Kyle Kanos

@tpg2114 We like to stay ahead of everyone else

A Googler

@GlenTheUdderboat it depends on how fast and at which angle you throw it and also its ength

*length

tpg2114

@KyleKanos Have you tried playing Bloons Monkey City yet?

Kyle Kanos

17:40

@tpg2114 I tried it when it first came out, but not since.

Glen The Udderboat

10 m/s, 45 degrees, 1 m

Or something similar to a javelin.

tpg2114

@KyleKanos I played it on the PC when it came out awhile ago, but actually like playing TD5 on my phone more. Now that it's out on the phone, I'm trying to figure out if I like it or not. It's repetitive in a different, possibly more boring, way.

A Googler

first find the time it takes for it to fall down and then find how many rotation it makes in that time then you can figure out which end it'll fall down

tpg2114

But also way harder cause the progression in each map is different and you have to pick and choose towers by building the buildings beforehand. So mixed feelings about it.

Kyle Kanos

@tpg2114 I enjoy BTD5 on my Kindle Fire because of the extra features

(e.g., the bonuses, the permanent unlocking of things)

Glen The Udderboat

17:43

If I throw two balls in quick succession, the pair or them will "rotate" (half). So, how's a javelin different? Does the fact that the balls are not connected (fixed length rod) make a difference?

tpg2114

Yeah, although there are bonuses in MC too, they just work differently (and in some ways better). I do like having as many of whatever tower I want in TD5 though.

I got tired of playing regular maps and just stick to the daily challenges

Kyle Kanos

I still haven't beaten all the maps at all levels yet

On either system

Jimdalf the Grey

@GlenTheUdderboat Try throwing two balls at the same time (one ahead of the other along direction of throwing) see what happens. When you throw 2 balls in quick succession, you release at same point. When you throw a rod, you release at same time, but not at same point

tpg2114

17:57

@KyleKanos I know your financial industry job requires it, but how good is your C++ at the moment?

Kyle Kanos

Probably as good as my Python

tpg2114

I don't know how to take that :)

A Googler

@KyleKanos I want to learn python , any good resources?

tpg2114

I may have kinda figured out how to do what I want to do... I really shot myself in the foot by making everything templates

Kyle Kanos

@tpg2114 I can manage it for the most part, but require the aid of my Google-fu every now & then

tpg2114

17:59

@AGoogler The best resource I used is just trying to do stuff with it. Do you have a problem domain in mind (physics, graphics, data analysis, games, etc)?

Kyle Kanos

@AGoogler Trial + Error + Google when necessary.

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