The h Bar

ACuriousMind

00:30

@KyleKanos: You just beat me by 7 seconds to a comment.

Kyle Kanos

:D

ACuriousMind

22

Q: An interactive graph of Math.SE tags

Some time I created A Graph Map of Math.SE, which met with a warm response from this community. Encouraged by this, I created a new visualization, this time interactive and up-to-date (as long as the SE API lives): TagOverflow. For Math.SE, it is: http://stared.github.io/tagoverflow/?site=math&si...

^pretty pictures of "tag networks"

Works for all communities, ours is here

infinitesimal

Nice

ACuriousMind

00:47

It's interesting that Math.SE is far more fractured than Physics.SE - our tags are more strongly connected to one another. Indicative of bad tags, or of the more fluid nature of the borders of subfields in physics?

infinitesimal

This reminds me of the website called the visual thesaurus.

visualthesaurus.com

ACuriousMind

In completely unrelated news, how is a question like Why are professors' websites so ugly? not obviously primarily opinion-based, but instead happily living in the HNQ?

dmckee

01:07

-2

Q: George Dodwell and Axis Tilting (Obliquity)

Could you research for me the relevant facts about Mr Dodowell's assertion that a second Axis Tilt took place in 2345 B. C. How many degrees of movement were involved? I have a number of 11 degrees but can't remember where I got this from. That is, 23.5 (approx.)today = 12.5 degrees in 2345 BC...

astronomy

"Could you research for me [...]" Uhm ... no?

ACuriousMind

@dmckee Apparently relating to abovetopsecret.com/forum/thread597829/pg1 where already the link itself tells you you don't really want to click it.

dmckee

@ACuriousMind Sadly only one explicitly experimental tag appears, and its bubble isn't even very big.

ACuriousMind

@dmckee How many explicitly experimental tags do we have?

dmckee

Interesting. If I do one requiring the experimental-physics tag I get only a small number of tags.

ACuriousMind

@dmckee Nope, you just set the maximum tags to 16 :P

dmckee

01:15

Experimental-technique, home-experiment, I'd call data-analysis and error-analysis experimental.

@ACuriousMind Ah ... it fooled me. It does a little better with more tags allowed.

ACuriousMind

Well, no matter the tags, the entirety of experimental-physics here is...919 questions.

That's a bit sad even without a sad-looking orphaned tag map

dmckee

@ACuriousMind Always a good deal. I was introduced to that by a math professor last year.

That's one of the nice things about being at a school small enough that you share buildings with other departments: you bump into people with a different view of the world in the hallway.

@ACuriousMind I think that part of that is that most of those question come from people actually doing experiments at some level or another.

ACuriousMind

@dmckee True, there is not much potential for non-experimental-physicists to ask questions tagged with that

Sofia

01:59

@ACuriousMind go to sleep. By the way, how was your exam?

ACuriousMind

@Sofia It was fine, thanks for asking (though it could have been better).

And my sleep cycle is completely out of sync with "normal people time" now that I've got no lectures to attend. It always happens in the holidays :)

Sofia

@ACuriousMind What theme did you choose for your MSc.?

@ACuriousMind Aaaa! You like to stay by nights? So do I, unfortunately I have obligations in the morning.

ACuriousMind

@Sofia Well, as you might have guessed, my focus is Theoretical Physics. I don't have to formally specialize any further till next year when choosing which topic to write my thesis on.

@Sofia I definitely am a night owl. If I have no obligations, my "natural" sleep cycle is something like waking up around 2 pm and going to sleep around 6 am.

Sofia

@ACuriousMind how goes there, you will be put to teach something in order to get a salary?

@ACuriousMind exactly as I.

ACuriousMind

@Sofia Master students are generally encouraged to lead tutorials in their focus areas, but it is not obligatory (though I like giving tutorials).

But yes, if I do not teach something, I don't get paid by anyone ;)

Which is not exactly a problem because I've got a scholarship, anyway.

Sofia

02:08

@ACuriousMind what is a tutorial. I don't know the terminology in your country.

ACuriousMind

Ah, right, these things are probably different everywhere

Sofia

@ACuriousMind the scholarship is money that the state pays to students?

ACuriousMind

To every lecture, there are exercise sets, and the tutorials are weekly sessions with about 20 students where their solutions are discussed

@Sofia Yes, either the state (as in my case) or another group of some kind - there are also scholarships from most political parties and from most major religious organizations.

Sofia

@ACuriousMind :what you say? Religious organizations pay students? But in that case one has to belong to that organization.

ACuriousMind

@Sofia Yes, of course. The politically/religiously oriented scholarships are granted for being involved with the organization in some kind.

Sofia

02:13

@ACuriousMind there is not one single religion in your country? How can be there different religious organizations?

ACuriousMind

Which is not a system I personally particularly agree with, I must say

Sofia

@ACuriousMind aren't you all catholic?

ACuriousMind

@Sofia Well, first, although broadly "Christian", there is a marked split between the Catholic and Protestant denominations. Further, I believe there are Jewish and Muslim scholarships as well

Sofia

@ACuriousMind Protestant? In Germany?

ACuriousMind

@Sofia Of course, the followers of Martin Luther are strong here!

I think there are about as many Catholics as Protestants, with specific regions often being dominated by one of the denominations

Also, most people you meet on the street would probably identify as Catholic or Protestant, but not as religious in any strong sense.

Sofia

02:17

@ACuriousMind I don't remember. I am supposed to know who was Martin Luther, but I do not remember. So, please tell me.

Kyle Kanos

He's kinda the leader of the Protestant Revolt

Published the 99 Theses on the door of the Friary that he worked at

ACuriousMind

@Sofia He was the fellow who initiated the schism of the Catholic Church known as the Reformation

Nailed his theses to a door

Translated the bible into German (heresy!)

Thought it was a bad idea to take money for absolutions

And also was a really nasty anti-semite

Kyle Kanos

@ACuriousMind False! The Church forbade particular translations because someone did a bad job translating it.

The German version, as far as I know, was not among the verbotten ones

ACuriousMind

@KyleKanos Well, bad job in this context and time meant translating the bible into German the ordinary people could understand

Sofia

@ACuriousMind Heresy? Why? Was he declared heretic?

Kyle Kanos

02:21

@ACuriousMind Translations that take away the meaning of it are bad because they can introduce heresies

Sofia

@KyleKanos the meaning of what? Of the Bible?

ACuriousMind

@Sofia I'm not sure if we has actually declared heretic. I think not

Kyle Kanos

Which is kinda what Luther wanted :shrug:

@Sofia Yes

Sofia

@KyleKanos what meaning has the Bible? It is stories. All sort of stories.

ACuriousMind

@KyleKanos Yes, but Luther claimed that he preserved the meaning, while the existing German translations were as literal as possible from the Greek Septuagint, and hence very difficult to make sense of.

Sofia

02:24

@ACuriousMind which is this meaning? What he didn't translate correctly?

ACuriousMind

It's essentially just the usual fight about who gets to declare the true meaning of the holy book

Kyle Kanos

@Sofia No, it's not stories. It is The Word of God to believers

Sofia

@ACuriousMind the word of God to believers are the 10 Commandments.

ACuriousMind

@Sofia That's kinda the issue. The Church claimed he distorted the meaning of the original Greek by translating it into ordinary German as it was spoken at the time. Luther claimed he preserved the meaning by translating it into the German that people could actually understand

Kyle Kanos

@ACuriousMind Oddly, though, Latin was spoken and understood by most people throughout Europe, so writing it in vernacular wasn't entirely necessary.

ACuriousMind

02:26

@KyleKanos Of course, those who were literate were mostly also literate in Latin, yes

Kyle Kanos

@Sofia That's partially true. Those are the words of God, but they aren't the only words of God. Christians hold that Jesus is God, so anything Jesus said or did (e.g., the whole New Testament) is the Word of God.

Sofia

@KyleKanos Aaaaaa! Now I understand.

Kyle Kanos

@ACuriousMind Given that people went to Mass daily, in Latin, for their whole lives, I cannot imagine someone in the 1500's not knowing Latin

ACuriousMind

I think the idea of German translations was mainly so that they would not need a Latin-versed scholar to read from the bible. I have no idea how many people there were who could read German but not Latin

@KyleKanos I think most people attending mass didn't actually understand the Latin

Sofia

@KyleKanos yes, the Bible is the Old Testament, and the Evangellia is the New Testament.

Kyle Kanos

02:29

@ACuriousMind Cite your source

:D

ACuriousMind

If I had one :D

Kyle Kanos

@Sofia In English, the Bible represents both books.

ACuriousMind

These are all more or less dim memories from my religion lessons at school.

I have not actually spent any time thinking about Luther since 8th grade or so

Sofia

@ACuriousMind : I learnt another explanation, but I am not sure. That Lutheranism wanted a cheep church, not to pay much. But I am not sure.

ACuriousMind

It was also partly about money - the church took money for granting absolutions, and Luther thought that to be wrong

As a consequence, to this day, the Protestant churches are less decorated with gold and other precious things than the Catholic ones

Sofia

02:32

@ACuriousMind absolutions! Indulgences!

Kyle Kanos

I still do not see what the big deal is about selling indulgences.

ACuriousMind

Well, Luther also though burning heretics was wrong. Burning witches was fine, though.

Kyle Kanos

What do we burn witches with? More witches

Sofia

@KyleKanos the church wanted money - that's why indulgences.

Kyle Kanos

@Sofia It needed money to pay people to build churches. It also needed money to pay farmers for wheat and wine

ACuriousMind

02:35

...and it also needed money for all the gold-braided talars

Kyle Kanos

The church gets what it wants, the people get what they want. Win-win all around

@ACuriousMind I don't know what that is

Sofia

@ACuriousMind what is talars?

ACuriousMind

God-damn language barrier! :D

A talar is the robe a priest wears

At least, the German word Talar means that

The church also bought (or occupied, or took as gifts) large amounts of land

Kyle Kanos

The cassock?

Sofia

@ACuriousMind Aaaaa! Not only talars. Property, land!

ACuriousMind

02:37

There are still significant tracts of land in Germany, which are used by the state, which formally are only leased from the church for period of 99 years

Kyle Kanos

@ACuriousMind Again, churches are needed...

ACuriousMind

@KyleKanos that's it!

Though the German word for cassock seems to be Soutane

And a Talar is a class of robes to which the cassock belongs

Interesting

Kyle Kanos

I see

ACuriousMind

but a Talar may also be the robe a judge wears, apparently

Kyle Kanos

I googled Talar just now. It's an archway in Persian architecture

Sofia

02:38

@KyleKanos why are churches needed? Because people are religious?

Kyle Kanos

@Sofia That's a good reason.

0

Q: Quadratic equation in various fields of science

Because other fields of science are branches of physics I think i can ask this question here. I'm looking for some information for question: Where does the quadratic equation has the biggest application in: a)Chemistry b)Nanotechnology c) Economy. I need also the reason: Why do You think so - in ...

physical-chemistry quantum-chemistry nanoscience electrochemistry econo-physics

What?

Sofia

@ACuriousMind in Romania priests weren't rich.

Kyle Kanos

Because other fields of science are branches of physics....

ACuriousMind

@KyleKanos Need I even post the xkcd?

Kyle Kanos

No, it will only confuse

ACuriousMind

02:40

@Sofia Well, I'm not sure how rich the individual priests here were. The bishops and cardinals had (and still have) quite a lot, though.

Sofia

@ACuriousMind my dear, I am going now to sleep. Sweet dreams to you !

ACuriousMind

@Sofia Thanks, to you, too

Okay, now who thought that "The followers of Martin Luther are strong here!" was a good thing to star? :D

Kyle Kanos

Not I

ACuriousMind

That's an even weirder thing to star than that time I just said "Argh!".

Kyle Kanos

Well played ocelot:

@KyleKanos: BS. Economics obviously depends on the condensed matter physics of coins. And we all know chemistry is just electron shell physics. — 0celo7 1 min ago

ACuriousMind

02:45

And I'm just sitting here, processing the epiphany that 0celo7 is an ocelot.

Kyle Kanos

ACuriousMind

@KyleKanos Yes, thanks :D

I seriously wondered about that name when I first saw it

Thanks for enlightening me

Kyle Kanos

I'm rather fluent in |337, given that was the language of choice for CS:S players

ACuriousMind

I prefer playing on a LAN, so you can shout at the others instead of typing ;)

My leet skillz are abysmal, I fear

Kyle Kanos

I enjoyed the LAN, but it got boring when it was just the 4 of us

I dropped my wedding ring off at the jewelers today to get resized

Turns out that losing ~40 lbs (18 kg) since the wedding drops your hand down a ring size or so

Danu

08:08

this made me laugh

@KyleKanos Hey, congrats on that though!

@KyleKanos one 't' ;)

@KyleKanos Have you ever lived in a different country? :P I think you'd get the idea rather quickly when living in a country that speaks a very different language.

@KyleKanos gotta love leetspeak

damn, all my replies are to you!

With things like this, the correct procedure is not voting to close but rather 'looks OK', is it not?

Of course, it's not 'OK', but it IS a (bad) answer

JamalS

08:49

@ChrisWhite He's brilliant pirsa.org/index.php?p=speaker&name=Mark_Wise

I hope I have him one day as a professor

David Z

@Danu what choices does it offer you?

Danu

Looks OK, Recommend deletion and Skip @DavidZ

(oh, I see I said 'voting to close' earlier: that's not a thing for answers)

user54412

@JamalS Once in a lecture he was finding some propagator on the board. After writing down the integral he asked, "Class, what's wrong with this Greens function?" expecting something like "We're integrating over a singularity."

user54412

Instead, some guy called out "It's not green!" So Mark Wise dutifully pulled out a piece of green chalk and slowly, carefully, rewrote the entire thing in green, saying something like "There, are you happy now?" I think that guy got a quarter.

infinitesimal

09:05

:D

user54412

Pretty much every lecture was filled with moments like that, and at the same time we somehow breezed through the whole QM curriculum far faster than he expected.

JamalS

09:23

Oh, I'm so envious!

I hope I have a prof like that.

@ChrisWhite Did he ever take the class out to eat/drink?

Here caltech.typepad.com/caltech_as_it_happens/2011/02/… if you scroll down, you'll see he took some students out

David Z

09:41

@Danu yeah, in that case unless you think it should be deleted (e.g. if it's not an answer), "Looks OK" is the right choice

Danu

@DavidZ but it's not OK :P

It's just not explicitly violating policy

David Z

10:00

Yeah, you're not the first to complain about the wording

"Looks OK" should be interpreted as a "none of the above" (or maybe "none of the below" or such) in this context

Sofia

10:19

@DavidZ why is allowed a complete solution to a home-work ?

David Z

@Sofia what makes you think it's allowed?

Sofia

@DavidZ because I see that it is allowed. According to the fact that when I gave a complete solution to a home-work, my post was deleted, this post should be deleted too.

@DavidZ : However, something better should be done.

David Z

@Sofia you say that you see that it is allowed. Where does it say this is allowed?

ManishEarth

@Sofia Existence of a non-deleted answer doesn't mean that it is allowed

It just means that it wasn't noticed

Mods don't look at everything; and if it's not flagged usually we won't see it. You flagged this a few minutes ago, give it time :)

Sofia

@DavidZ I flagged it, but in fact I am not pleased with this method.

@DavidZ something else should be done.

David Z

10:27

What else should be done?

ManishEarth

@Sofia what method?

Do you expect us to look at every answer that comes in? O.o

Sofia

@DavidZ users should be strongly warned not to give complete solutions, only ingredients.

ManishEarth

They are

@Sofia in fact, such posts usually are closed

Sofia

@ManishEarth how they are? A good solution is useful for this site. But not a complete solution.

ManishEarth

Whenever someone posts such an answer, they're warned in the comments and the post is deleted

Sofia

10:29

@ManishEarth I am not convinced of the worth of the deletion.

@ManishEarth maybe the user who provided a complete solution, has to be instructed to erase parts of his post, leave only ingredients.

ManishEarth

They are

what makes you think they aren't?

SOmetimes the answerer edits it and it gets undeleted

however this process mostly happens when the post is deleted so regular users can't see it happening

David Z

@ManishEarth no, actually that never happens - we don't undelete complete answers because the original version is still accessible through the revision history

ManishEarth

@DavidZ right

I might have done that a couple of times >_<

David Z

Ah, well I don't undelete complete answers before the scheduled time

or, I should say, we shouldn't

ManishEarth

yeah, will keep in mind

David Z

10:35

Speaking of flags, @Sofia, I'd suggest you take a look at your flag history for some feedback on which kinds of flags are valid and which ones aren't

Sofia

10:46

@ManishEarth Bottom line, what are you going to do with this answer? I respect work, deleting work done by somebody, in fact, is not the most honorable thing.

ManishEarth

@Sofia temporary deletion, basically

> I'm temporarily deleting this in accordance with our homework policy. Please don't post complete answers to homework-like questions.

David handled it already

Sofia

@ManishEarth I suggest temporary deletion with a comment like "complete answers to homework are forbidden - for reopening your post, reformulate it and leave a comment for us to know.

ManishEarth

That's almost exactly what we do :|

Sofia

@ManishEarth very well.

ManishEarth

(At least, the "temporary" bit signifies that)

Sofia

10:50

@DavidZ how shall I see what you say? Whatever I see is the number of accepted flags. I don't see comments to flags, or something like this.

@DavidZ I don't see feedbacks to flags. Where are they?

David Z

If you click on the number of flags, you should be taken to a page where you'll see the outcomes

this page: physics.stackexchange.com/users/flag-summary/63535

Sofia

@DavidZ I'll try.

David Z

I also thought there was something that would notify you next time you try to cast a flag, when there is a feedback message for you to read. But maybe I was wrong about that.

Sofia

@DavidZ I have right now a technician in my house, fixing some tap. I'll return to you some later.

David Z

No rush. The flag feedback stays there permanently so you can look at it whenever you want to.

God

10:56

hey david.

David Z

Just, it's generally a good idea to be aware of feedback on previous flags before you go on to flag more posts.

@God hey

God

David, are you a physicist?

David Z

I suppose so; why?

God

what is your opinion on the universe, david?

David Z

you'll have to be more specific

God

11:02

david; let's suppose that I bought a new house and decorated it finely, if I asked you about your opinion on my house, would you give it to me or say "you'll have to be more specific"?

ManishEarth

@DavidZ only for declined ones

David Z

@ManishEarth ah okay makes sense

ManishEarth

@God He's a physicist, so he probably would

:p

David Z

11:13

yeah, sounds about right

Sofia

11:30

@God David is a postdoc.

@DavidZ I apologize, once I saw in my profile site, the number of useful flags. But now I don't see. Can you guide me? Where does appear the number of flags?

@DavidZ I found!

@DavidZ with this occasion maybe you'll explain me a bit. Why this text (in the flagging) is not O.K. This question is too broad. – Sofia 14 hours ago declined - flags should only be used to make moderators aware of content that requires their intervention If a question is too broad it shouldn't be closed?

David Z

11:46

@Sofia yes, but that flag was probably declined because you don't need to use a custom moderator flag to indicate that the question is too broad. You can use the standard flag.

Sofia

@DavidZ aha! And something more: what means please use the standard close reason ? Where is the standard close reason?What's standard close reason?

David Z

Any of the other options besides a custom flag for moderator attention.

Sofia

@@DavidZ now, when I suggest closing, shouldn't I explain my motivation? Please see : This is a too broad question. To get an answer the question should me more specific. It is hard to cover all the cases connected to this question. – Sofia Jan 21 at 14:22 *declined - flags should only be used to make moderators aware of content that requires their intervention*

David Z

No, you shouldn't

If you believe a question is too broad, you should choose the "too broad" flag reason

The "other" flag is only for cases where none of the other flag options apply

Sofia

@DavidZ Aaaaa! Then, no additional wording?!

David Z

11:54

in particular, "other" (also known as the custom moderator attention flag) is not for off-topic questions

@Sofia correct, no additional wording. It's not useful.

Or rather, you can explain your motivation, but if you are going to do so, you should do it in a comment on the question, not in the flag.

Sofia

@DavidZ O.K. Now, please see! Some users apply to us as if we are their servants, e.g. he! He! And I want also.... I saw such a thing.

@DavidZ What I wanted to answer was - he! he! I also want you say to your mom!

David Z

um... what?

I mean, if someone on this site tells you they want something, there's no reason you need to listen to them

Sofia

@DavidZ but I just flagged as impolite.

@DavidZ yes, but he should be warned that this is not a way to apply to us.

David Z

@Sofia Ah, I suppose you can do that too. Although that is only mildly impolite.

@Sofia sure, you can just post a comment saying so, if you want to

(BTW "apply" is not the right word to use here... just letting you know, since it might confuse some people if you say that)

Sofia

@DavidZ well. I understand. Thank you for calling my attention and for guidance. Aaaa what is the right word, please?

@DavidZ can you correct me? What is the right word?

David Z

12:02

for example, you can say "this is not a polite way to talk to us"

Sofia

@DavidZ I apologize for my improper English: when someone asks us a question, doesn't it mean that he/she "applies" to us?

David Z

No, it does not

The word "apply" is not used for that meaning

Sofia

@DavidZ I apologize a lot for bothering you. Just one more question. I found in the dictionary the words "appealing to". But the phrase has a double meaning. Can this phrase though be used? (I won't ask you more questions of English, and I apologize) Can we say "if you appeal to us, then proceed so and so"?

David Z

oh, don't worry, you're not bothering me

"appeal to" cannot be used in this way

Sofia

@DavidZ then how to say?

@DavidZ maybe "if you address us, then ..." Is this O.K. ?

David Z

12:13

That might be okay

What would be the rest of that phrase?

Sofia

@DavidZ e.g. *if you address us, then please give complete information (or, please explain your symbols, etc.)

David Z

I guess that is fine. Though it would be a little unusual.

In that example I'd probably just say something like "Please explain your symbols"

Or better yet, "What do X and Y mean?"

By the way, do you know about English Language Learners? That's a good place to ask these kinds of questions

Sofia

@DavidZ Aaaa thank you. Now, there are cases when I need to say "for addressing this site, you have first to improve your knowledge in physics".

David Z

In that case, I'd suggest "To post on this site, you first need to improve your knowledge of physics"

The phrase you wrote would be understood. But it would sound odd to a native English speaker, mostly because "addressing" is a very unusual choice of word for this situation

Sofia

@DavidZ well, English is not mother-tongue for me. Do you mean that "addressing" may be too "stiff", too official?

David Z

12:23

"addressing" is used when you want to emphasize who is being spoken or written to

but when someone posts on this site, it's not really important who they are writing to

Sofia

@DavidZ Aha! Well, a lot of thanks! And have a nice day!

David Z

you too

Danu

14:16

anyone have a good recommendation for a latex shorthand for $\frac{d #1}{d #2}$ aka a derivative, given the fact that I have reserved \d for differentials?

ACuriousMind

@Danu \del ?

Also, I hope those d aren't italic ;)

Danu

of course not

$\mathrm{d}$

Actually, I'm still looking for a good way to distinguish differentials vs forms

I was thinking of maybe using normal d for differentials, and \mathrm{d} for forms

ACuriousMind

@Danu I would not use different d for that, because the differential $\frac{\mathrm{d}f(x,y)}{\mathrm{d}x}$ is mnemonically obtained from the forms equation $\mathrm{d}f = f_x\mathrm{d}x + f_y\mathrm{d}y$ by just dividing by $\mathrm{d}x$

Danu

yeah, but it's a personal thing: I got really confused about this during the first few weeks of diffgeo

It just didn't make any sense to me that $df$ is the jacobian (for functions between Euclidean spaces)

ACuriousMind

$\mathrm{d}f$ was the first time I really thought of the Jacobian as something other than the matrix with $\partial_i f_j$ entries.

Danu

14:30

What I mean to say is the following

$df: T_pM\to T_pN$ while $\mathrm{d} f: T_pM \to \mathbb{R}$

the notions only coincide in the simplest case, right

so I am not very happy to use the same notation for these two things

...because I got really confused about it

and also, well, they're just not the same thing

ACuriousMind

Wait, what is your latter $\mathrm{d}f$ supposed to be? $\det(\partial_i f_j)$?

Danu

The 1-form associated with $f$

ACuriousMind

But a one-form also takes values in $T_p N$, no?

It's rather $\mathrm{d}f : M \to T_p^* N$?

Because "a one-form is a section of the cotangent bundle"

Danu

Do you agree that a 1-form can act on $v\in T_pM$?

ACuriousMind

Yes, a 1-form $\omega$ is an object, for which, for every $p\in M$, $\omega_p : T_p M \to \mathbb{R}$, or, equivalently, $\omega_p \in T^*_p M$.

Danu

14:38

okay, cool, I agree

So if $\mathrm{d}f$ is the one-form associated with the smooth function $f$, then $\mathrm{d}f: T_pM\to \mathbb{R}$

oh terrible, actually

I should have said

then $\mathrm{d}f_p: T_pM\to\mathbb{R} $

yes?

ACuriousMind

Ah, now, that is a bit tricky! Is your $f$ a 0-form or a smooth map between manifolds $M \to \mathbb{R}$?

Danu

Right, I meant it to be a smooth map so we need the subscript $p$

for it to be in $T_p^*M$

And the map needn't be $M\to \mathbb{R}$ right? Can it not be $M\to N$?

ACuriousMind

A 0-form lives entirely on $M$, and would induce its exterior derivative $\mathrm{d}f : M \to T_p^*M$. If $f : M \to \mathbb{R}$ is seen as a morphism of manifolds instead, you get the induced morphism of tangent spaces $\mathrm{d}f : T_p M \to T_{f(p)}\mathbb{R} \cong \mathbb{R}$.

And now I think I have understood what confuses you - the first $\mathrm{d}$ is the exterior derivative of forms, while the second one denotes an induced map of tangent spaces

Danu

exactly

ACuriousMind

Okay, now I agree there should be two different d :D

Danu

14:43

The exterior derivative is different

yay!

But I think I want $\mathrm{d}$ for the exterior derivative

so I thought just $d$ for the induced map of tangent spaces

ACuriousMind

Yes, the upright $\mathrm{d}$ should be the one where $\mathrm{d}^2 = 0$ is a sensible thing to write

Danu

right

Was I wrong anywhere in this discussion? :P

ACuriousMind

@Danu No, I was just a bit slow :P

(Though you did write $\mathrm{d}f$ where you should have written $\mathrm{d}f_p$, but, well)

Danu

I can never tell when talking to you, because you appear so sovereign ;)

Yeah, but I corrected that one myself :D

ACuriousMind

@Danu You may safely assume that I make at least as many errors as you do ;)

Danu

14:52

I remain unconvinced

Perhaps the more appropriate measure is the ratio knowledge/errors

Stunning chess game between Anand and Aronian unfolding right now

chess24.com/en/watch/live-tournaments/zurich2015/3/1/3

Go back to around ~29th minute for interesting stuff

ACuriousMind

I fear I find nothing interesting about chess :/ Speaking of which, Phonon hasn't been arond lately, has he?

Danu

No :(

but this game is great!!!

@ACuriousMind What kind of things do you do in your free time? Mostly video and/or role playing games, or other hobbies too?

ACuriousMind

@Danu I also read a lot, mostly Sci-Fi and fantasy, and I play card or board games with friends regularly, when we're not tormenting our livers in some bar ;)

Danu

15:13

Alright, sound solid :)

Danu

15:56

Man, this game is epic though!!! Anand is totally crushing, totally outprepared Aronian

with a very interesting piece sacrifice

Hey guys (e.g. @DavidZ, @DanielSank, @ACuriousMind, @KyleKanos, @alarge and anyone else who's interested), what do you think about doing something like this: meta.math.stackexchange.com/questions/13422/…

ACuriousMind

12

Q: What's the possibility of a Physics.SE community blog?

It's possible for a Stack Exchange site to get a community powered blog, as done so by many sites seen on SE, e.g. Math.SE. To get our own, what we first need is community support, since the blog will be run only by this site's users. The purpose of this post is to answer the following question:...

discussion

Physics Meta

0

Q: TagOverflow - an interactive graph of Physics.SE tags

I created a graph of tags from Stack Exchange sites (including Physics.SE), TagOverflow. I made an interactive version of Map of 64 Tags from Physics.SE, with always up-to-date data. Nodes represent the most popular tags, with their area being proportional to the number of questions with them....

discussion tags

2

ACuriousMind

@Danu I personally would very much like a physics.SE blog, but it seems the last meta discussion about this did not gain much traction

Perhaps it is time to ask again

dmckee

@0celo7 To avoid answering outright where the OP can see it: I'd use a block and tackle if sufficient length of cord were available.

Danu

16:19

@ACuriousMind Yeah, I had your personal blog in mind too

what do you think, @dmckee

@ACuriousMind Right, it's been 2.5 years

dmckee

@Danu We have many more active users now than we had the last time it was brought up. If our top 50 users could average 2 decent article a year, we'd have almost two a week.

Not sure what would constitute a "decent article", though.

Summaries of breaking news.

Danu

I think the math.se blog sets a good example

dmckee

Expositions on interesting corners from subject experts (or better from people nearing expertese but still learning).

Danu

Breaking news is one aspect, another is in-depth exposition in a style that the main site is not adapted to

dmckee

@Danu Don't follow it. I suppose I could go look.

Danu

16:23

We're on the same page :)

dmckee

@Danu I'd personally be interested in articles on pedagogy, but that may reflect where I am in my career.

Danu

Full disclosure: The reason I mentioned this is because it came up on a discussion on the meta of History of Science and Mathematics, so I think that historical articles could also be interesting here

ACuriousMind

@Danu If you don't do a hsm blog, then I think history articles would be a very good addition to a physics.SE blog

If you do a hsm blog, we should probably not mix the two too much

Danu

@ACuriousMind I'm pretty sure hsm is much too small at this point to have its own blog.

ACuriousMind

Yes, I think so, too

Danu

16:27

In fact, someone brought this up as an idea of how we could increase our numbers over there ;)

0celo7

@dmckee @dmckee I don't think a block and tackle is allowed.

dmckee

@0celo7 Double the line and twist then. Failing that the scheme you describe is it.

0celo7

@dmckee I had this this question on a quiz. Doubling the rope was not allowed.

dmckee

@0celo7 Personally I try to avoid questions like that, but I supposed I'd say "the rope is just a little longer than the height of the [whatever]".

But setting up that kind of scheme in real life is very hard, and I don't like questions phrased in real world terms that use a physicsland solution.

vzn

17:52

AC has a blog?

ACuriousMind

@vzn Ah, I removed the link from my profile because I found some errors in what I had written there. It will return when I have fixed them.

Basically, I am still searching for the best explanation why the tensor product and not the Cartesian product is the natural product of QM.

0celo7

@ACuriousMind: Interesting question. You get any (somewhat) satisfactory answers?

vzn

ppl are sometimes perfectionists when it comes to blogs. seems many on SE have blogs that they dont put into their profiles, dont understand that at all.

maybe it has to do with se's site policy wrt personal blogs, which is not really very clearcut.

re a physics blog, like the idea. participated in the math.se blog discussion heavily that opened last may in a chat room. however it is quite tricky at times. it requires committed volunteers which surprisingly are quite rare. there is a pattern of initial enthusiasm & then lack of longterm commitment.

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