The h Bar

2:00 PM

In reality there are some absolutely terrible people out there who commit horrible acts of human indecency, but are emotionally and intellectually very mature. The problem is human understanding and visions are not consistent.

Slereah

arxiv.org/pdf/hep-th/9312211.pdf

Balarka Sen

These are dangerous realms of philosophy and psychology you should not just perceive as black and white or oversimplify. You'll find your ideas in a wild knot if you go deep enough.

Anonymous

@BalarkaSen Yes, a lot depends on the situtation one is under. In difficult situations even emotionally mature people (in normal life) can commit terrible crimes.

Giskard42

@BalarkaSen I mean, we really haven't nailed down what "intelligence" even is properly, afaik, so I'd think that's sort of a precursor to any conversation about such?

Anonymous

I was just pointing out that empathy is a part of intelligence.

Giskard42

2:02 PM

Like, almost everything is a gross oversimplification of human intelligence

(AFAIK of course)

Anonymous

Actually it is very difficult to talk about intelligence in quantitative terms.

Secret

So... I see its philosophy session hour atm

Anonymous

Everything is an oversimplification.

Balarka Sen

Yes, it is difficult and yes, I can't define it. It might not even be a consistent notion.

Giskard42

@blue Exactly.

0celouvskyopoulos

2:05 PM

@BalarkaSen when doing complex analysis, did you see the claim "$\Delta u=0\implies \Delta|\nabla u|\ge 0$"?

Balarka Sen

nope

ACuriousMind

One might argue that physical theories are usually an exercise in simplification while precisely avoiding oversimplification. Therefore, "everything is an oversimplification" is an oversimplification.

Balarka Sen

I like that.

0celouvskyopoulos

welp

it's the mystery claim

Giskard42

I mean, the brain is 1000x more complex than a desktop processor, and as any good overclocker will tell you, we haven't even been able to consistently quantify their performance.

(sorry)

0celouvskyopoulos

2:07 PM

So $\Delta |\nabla f|^2=|\nabla\nabla f|^2$ by Bochner's theorem

And $\Delta |\nabla f|^2=2|\nabla f|\Delta |\nabla f|+2|\nabla |\nabla f||^2$.

So $$\Delta |\nabla f|=\frac{|\nabla\nabla f|^2-2|\nabla|\nabla f||^2}{2|\nabla f|}$$

Anonymous

This is an interesting field actually. When intelligence has to be coded into program(s). That's why Artificial Intelligence one of the hot topics. :)

0celouvskyopoulos

That doesn't necessarily look positive to me...

Balarka Sen

@blue You say it depends on the situation. I am uneasy about this too; does situation mean material situation? I can easily imagine persons who lived in the perfect material world, but their own contradictions of thoughts lead them down paths of insanity and paranoid downward spiral. That's something you can't explain with "situation".

There has been numerous examples of this through human history, psychology, literature. An experiment was done with rats a few years ago.

Anonymous

@BalarkaSen Maybe it was too much perfectness that drove them insane!

Balarka Sen

Indeed.

Anonymous

2:10 PM

There is a term for it(this exact situation) in psychology, which I forget

Balarka Sen

Human mind is a strange, strange thing. It's almost a curse.

0celouvskyopoulos

@ACuriousMind Couldn't Newton have invented a buggy door?

that was later adopted to a car

Balarka Sen

@0celo now you're a french, russian and greek at the same time

0celouvskyopoulos

Missing a two above, it's $$\Delta|\nabla f|=\frac{|\nabla \nabla f|^2-|\nabla|\nabla f||^2}{|\nabla f|}$$

So what is $|\nabla\nabla f|^2-|\nabla|\nabla f||^2$...

loltospoon

Hello all

Could someone help me out? I need to calculate $\vec{E_{rad}}=\frac{\mu_0q}{4\pi r} \left [ (\hat r \cdot \vec{a})\hat r - \vec{a}\right ]$ for a point charge situated at the origin and hit by a plane wave $E_I=E_0\cos(kz-wt)\hat y$. I also need to calculate the radiation field $\vec{B}$ produced by this charge.

0celouvskyopoulos

2:20 PM

no

loltospoon

But I'm not sure what to use for $\vec{a}$ and $\hat r$

I know that the charge accelerates in the same direction as the oscillating electric field, so I think $\vec{a}=a\hat y$

And I thought that $\hat r = (\hat x + \hat y + \hat z)$

0celouvskyopoulos

o.o

I can't into calculus

Anonymous

@loltospoon What does the plane wave represent?

loltospoon

@blue not sure what you mean. It is a planar monochromatic EM wave. It is the thing that accelerates the charge.

Anonymous

@loltospoon So it is the electric field, right?

loltospoon

2:28 PM

@blue yep.

Anonymous

So you want to calculate the net electric field at a position $\vec{r}$ ?

Anonymous

Just superpose the two fields

paracetamol

in The Periodic Table, Apr 22 at 16:11, by Loong

0celouvskyopoulos

the sad reality is that most of physics doesn't matter.

unless what you're doing influences GDP or war it's not very good

Anonymous

Chemistry matters more than physics :P

Balarka Sen

2:34 PM

yeah but chemistry is feh

0celouvskyopoulos

I agree

chemistry and biology > math and physics

no doubt

Balarka Sen

i don't think math is really a candidate for comparison

it's not even science in the strictest sense

Anonymous

But the thing is one field cannot survive without the others. They are all interconnected. Like development in QM helped to discover a lot in chemistry.

Anonymous

And for development of QM you needed math

0celouvskyopoulos

Not really

Anonymous

2:36 PM

And so on....

Balarka Sen

we can survive without you for sure

paracetamol

@BalarkaSen Well, it isn't a natural science if that's what you mean :/

0celouvskyopoulos

QM is actually completely disjoint from mathematical reality

Slereah

You can do electronics with physics

Very GDP

And uo

And you need qm for it

0celouvskyopoulos

QM doesn't even make sense

Balarka Sen

2:37 PM

@paracetamol I guess? I generally think of "observation, experiment, explanation" whenever I hear the word "science"

Slereah

True

Balarka Sen

Math does not fit in that context.

loltospoon

@blue not sure what you mean by superpose the two fields. Am I not supposed to be using the equation I've written above?

0celouvskyopoulos

...what is $\nabla [g(\nabla f,\nabla f)]$?

index notation to the rescue

Anonymous

@loltospoon What is $\vec{a}$ in that I can't understand.

Anonymous

2:39 PM

The question is vague

loltospoon

@blue the resultign acceleration of the charge after getting hit by the wave

paracetamol

Speaking of science, I heard this a while back: If it moves, it's Biology. If it stinks, it's Chemistry. If it doesn't work, it's Physics

0celouvskyopoulos

drink some HF

it doesn't stink

loltospoon

@blue the charge gets hit by the wave and there is some radiation fields that get created. I need to find these fields.

0celouvskyopoulos

you'll be fine

paracetamol

2:40 PM

@0celouvskyopoulos It's...toxic

0celouvskyopoulos

nah

paracetamol

Plus the resulting mess'll "stink" ;)

Balarka Sen

you'll melt

Anonymous

The equation is not dimensionally correct. $(r.a) \vec{r}$ doesn't have the same dimension as a

0celouvskyopoulos

I don't trust index notation...

paracetamol

2:41 PM

@0celouvskyopoulos Sure, it isn't an ideal body-dissolving chemical, but...meh

8 secs ago, by paracetamol

Sure, it isn't an ideal body-dissolving chemical, but...meh

Balarka Sen

no need to say the same thing twice

0celouvskyopoulos

you'll be fine

I promise on @ACuriousMind 's honor

paracetamol

^ Ah well...if you put it that way...

Fawad

1 min ago, by 0celouvskyopoulos

you'll be fine

0celouvskyopoulos

fugg

you get a curvature term

I hate geometry

Fawad

2:42 PM

You changed name again @0celouvskyopoulos

0celouvskyopoulos

@Fawad what?

please don't slander my good name

paracetamol

^ It was good?!

Whoa...

loltospoon

@blue that's the equation in my book. I just double checked it

Fawad

@0celouvskyopoulos you changed name at some 12 am I guess chat.stackexchange.com/search?q=0celouvskyopoulos&room=71

Anonymous

@loltospoon That's just not dimensionally correct...

Anonymous

2:44 PM

Ask on the main site maybe

paracetamol

@Fawad This is scary...

0celouvskyopoulos

@Fawad idk man

ACuriousMind

@0celouvskyopoulos I admit that would be both possible and hilarious.

0celouvskyopoulos

@ACuriousMind I mean, Euler gets credit for a cohomology class so I think Newton can get a car door ;)

Slereah

How does entanglement even work in QFT

What's a simple example of entanglement in QFT

0celouvskyopoulos

2:46 PM

stop asking these questions

there is no hope

Slereah

why not

0celouvskyopoulos

So I have $2g_{ab}(\nabla_i\nabla^af)(\nabla^bf)$

ACuriousMind

@Slereah $\lvert p_1,p_2\rangle + \lvert p_3,p_4\rangle$ for any set of four distinct momenta.

Slereah

A lot of the measurement business revolves around the notion of being able to have tensor products of two states, but is that even possible in an interating QFT

0celouvskyopoulos

stop it acm

oh god I have to take the square of this

Slereah

2:48 PM

Can you decompose the Hilbert space into sub-Hilbert spaces like that

ACuriousMind

@Slereah Show me the state space of an interacting QFT and I'll show you the answer :P

Slereah

@ACuriousMind First difficulty!

0celouvskyopoulos

$$\nabla_i |\nabla f|=\frac{g_{ab}\nabla_i\nabla^a f\nabla^bf}{|\nabla f|}$$

I'm willing to trust that result

Secret

[Random GR question]

Suppose I have the following metric $\eta_{\alpha\beta}+h_{\alpha\beta}$ where $h_{\alpha\beta}=diag(a,0,0,0)$. Therefore the full metric will be $diag(a-1,1,1,1)$. Are there solutions which can make $1>a-1>0$, or is it impossible to bent spacetime so much so that the signature of the metric becomes 1,1,1,1?

0celouvskyopoulos

that's just a scaling of Minkowski space

there's an isometry to diag(-1,1,1,1).

Slereah

2:50 PM

Also generally, if you have some particles becoming entangled, can you always describe this as one system observing the other

0celouvskyopoulos

oh wait, $a-1>0$

Slereah

@Secret If the signature is like that, it's not GR

0celouvskyopoulos

@Secret that's just Euclidean space.

Secret

Yeah I know, I am just wondering whether GR allows the introduction of a very large distortion so that it causes minkowski space to become euclidien (given we already have a similar(?) case where in black holes the time and space directions get flipped)

Slereah

It doesn't.

Otherwise you're dealing with another theory entirely

0celouvskyopoulos

2:52 PM

$$g^{ij}g_{ab}g_{cd}\nabla_i\nabla^a f\nabla^bf\nabla_j\nabla^cf\nabla^df$$

hmm I see

hmm

hmmm 🤔

hmmmmm

what even is that

2:55 PM

why so many gradients (or is that the covariant derivative)

0celouvskyopoulos

covariant derivatives

@Secret I think that if $\mathrm{Ric}\ge 0$, then $\Delta f=0\implies \Delta |\nabla f|\ge 0$.

The computation is lengthy

I know that $\Delta|\nabla f|^2\ge 0$.

And I have $\Delta|\nabla f|^2=2|\nabla \nabla f|^2+\mathrm{Ric}(\nabla f,\nabla f)$.

Slereah

11

Q: Is quantum entanglement functionally equivalent to a measurement?

I saw the following talk the other day: http://www.youtube.com/watch?v=dEaecUuEqfc&feature=share In it, Dr. Ron Garret posits that entanglement isn't really that "special" of a property. He argues (and shows) that the mathematics behind it is analogous to the math behind measurement. Is this tr...

Hm

I guess it's possible that measurement and entanglement are mostly the same thing

Then doing measurement of a "single particle" would be doable

in the abstract, that is

Maxwell

Fawad

If $\Delta(PV^{\gamma})=0$ then $P\gamma V^{\gamma -1} \Delta V + V^{\gamma}\Delta P=0$...Why is it similar to product rule? It is differentiating with respect to?

Aryabhatta

Prove $\angle BDE=\angle BAC$.

Secret

3:04 PM

for entanglement in indistinguishable particles, refer to this for details

arxiv version: https://arxiv.org/abs/1511.03445
If I recall, going to QFT does means making particles indistinguishable

Anonymous

@Aryabhatta Are you the user Maxwell?

Aryabhatta

No.. he had asked me this ques. On FB

Anonymous

Sorry, too hard to believe.

Anonymous

One asks the question and other asks the other part of the question :P

Anonymous

At the same time

Aryabhatta

3:06 PM

@blue, that's on you.

I.said him to post it here.

Anonymous

Fine fine. I am not interested in the question anyway. And I don't think anyone will answer it for you until you show your effort in solving it.

Fawad

@JohnRennie

John Rennie

@Fawad Hi

Fawad

@JohnRennie hello,teach me

Aryabhatta

@blue, that's not my part

John Rennie

3:09 PM

@Fawad OK?

Slereah

The amusing thing is that the quantum measurement problem is barely related to QM itself

Fawad

@JohnRennie yes?

Slereah

I can do QM and QFT for months without ever worrying about measurement

John Rennie

@Fawad What do you want me to help with?

Fawad

@Fawad @JohnRennie I don't understand why expansion of Delta is like that. Why is it similar to product rule?

ACuriousMind

3:12 PM

@Slereah That's why I choose to not worry about it, mostly :)

AccidentalFourierTransform

I decided that -+++ is not that bad and I might change into that convention from now on

MWI is the correct interpretation

thats pretty obvious

John Rennie

@Fawad I have only just joined the chat and I have no idea what you are talking about. What expansion of Delta and what do you mean by Delta?

@AccidentalFourierTransform :: John faints in shock ::

Fawad

If $\Delta(PV^{\gamma})=0$ then $P\gamma V^{\gamma -1} \Delta V + V^{\gamma}\Delta P=0$...Why is it similar to product rule? It is differentiating with respect to?

ACuriousMind

@Fawad What is your definition of $\Delta$? What does it mean?

Fawad

@ACuriousMind change

AccidentalFourierTransform

3:14 PM

definition as in formulas, not words

Fawad

$\Delta = \text{final}-\text{initial}$

AccidentalFourierTransform

$\Delta f(x)=f'(x)\Delta x+\text{small}$ typically

ACuriousMind

@Fawad You sure it shouldn't infinitesimal change?

Because then that is basically using a derivative without explicitly saying so

Slereah

@ACuriousMind but then there is the point where I must!

ACuriousMind

I'll never understand why people insist on doing thermodynamics without properly introducing differentials.

AccidentalFourierTransform

3:17 PM

"properly introducing differentials" and "infinitesimal change" are not really related

:-P

Fawad

@ACuriousMind it isn't mentioned ,it is in waves ,while correcting Newton's formula for wave as adiabatic not isothermal.

@AccidentalFourierTransform correct. If + small typically is not taken then it is ≈

ACuriousMind

@AccidentalFourierTransform Oh, they are, because if we would just say "Take the differential" we wouldn't need to wave your hands around talking about change :P

Sir Cumference

Wait, quick question

ACuriousMind

I never really understood what all the $\delta W$ or $\delta Q$ and such are about in thermodynamics before I learned about differential forms.

Sir Cumference

Chandrasekhar is pronounced "Shondo-she-kor", right?

AccidentalFourierTransform

3:20 PM

"Chondo-she-kor"

Sir Cumference

Wait, you sure?

AccidentalFourierTransform

yesterday, by blue

Chondro-Shekhor

0celouvskyopoulos

Chan-drah-see-car

Slereah

@ACuriousMind they don't even introduce the contact manifold of thermogeometrodynamics

Sir Cumference

Grah, I'm confused

ACuriousMind

3:21 PM

@Slereah I know, right?! ;P

Joking aside, you really don't need to be that fancy to be a little better in explaining thermo.

Anonymous

@SirCumference Not "S"...whew...where did you get that!

0celouvskyopoulos

I don't know what forms have to do with thermodynamics

AccidentalFourierTransform

but for what?

after all, its thermo

nobody really gives a f

Sir Cumference

@blue Wikipedia's pronunciation sounded like that :P

0celouvskyopoulos

@AccidentalFourierTransform is a really infuriating troll

He's not an idiot, clearly

Sir Cumference

3:23 PM

OK, so is "Chandra" pronounced "Chondro"?

Anonymous

@SirCumference Probably not written by a native :P

AccidentalFourierTransform

Pronounce Names - How to Pronounce Chandrasekhar

►

Anonymous

@SirCumference Yes :)

Anonymous

@AccidentalFourierTransform That sounds weird

Anonymous

kher at the end

0celouvskyopoulos

3:24 PM

Your face sounds weird.

AccidentalFourierTransform

@blue of course it does, it's Hindi

Sir Cumference

@blue Like "kur"?

Anonymous

@AccidentalFourierTransform Man, Hindi is my native language.

Bernardo Meurer

@JohnRennie halp

0celouvskyopoulos

@blue why tho

AccidentalFourierTransform

3:25 PM

@blue I know.

Slereah

De Broglie sounds weird and it's my native language

John Rennie

@BernardoMeurer what have you broken now?:-)

3

Bernardo Meurer

@JohnRennie I have a question on pointers :P

Anonymous

@0celouvskyopoulos That "kher" sound at the end isn't what it sounds like. It is more widely used like "khor"

John Rennie

@BernardoMeurer OK?

Bernardo Meurer

3:26 PM

@JohnRennie Remember how we allocated a matrix like this:

matrix = calloc((size_t) m_size, sizeof(int *));
if (matrix == NULL) catchError("Matrix allocation failed.");
for (int i = 0; i < m_size; ++i) {
    matrix[i] = calloc((size_t) m_size, sizeof(int));
    if(matrix[i] == NULL) catchError("Matrix allocation failed");
}

Anonymous

Chundra-Shekhor or Chondro-Shekhor sounds better and is more widely used

John Rennie

@BernardoMeurer Yes, OK, an array of pointers ...

Sir Cumference

Can anyone else from India confirm?

No offense to @blue, just seeing if it's unanimously pronounced that way

Bernardo Meurer

Yeah, matrix is int **matrix

0celouvskyopoulos

So what happened to 2017?

@ACuriousMind did he delete his account?

Bernardo Meurer

3:28 PM

@JohnRennie So, how do I move this into a function of it's own, that receives **matrix and m_size. I tried this:

HsMjstyMstdn

@SirCumference, are you referring to the video's pronunciation ?

Bernardo Meurer

void allocMatrix(int **matrix, int m_size){
    matrix = calloc((size_t) m_size, sizeof(int *));
    if (matrix == NULL) catchError("Matrix allocation failed.");
    for (int i = 0; i < m_size; ++i) {
        matrix[i] = calloc((size_t) m_size, sizeof(int));
        if(matrix[i] == NULL) catchError("Matrix allocation failed");
    }
}

Anonymous

@SirCumference If you ask Kaumudi you'll get a slightly different answer...because she is from South India

Sir Cumference

@HsMjstyMstdn Just the pronunciation in general

Slereah

which india is best india

Sir Cumference

3:28 PM

Ok :)

Bernardo Meurer

But that explodes

Sir Cumference

@Kaumudi.H, how do you pronounce "Chandrasekhar"?

HsMjstyMstdn

I agree with @blue that the ending is weird

ACuriousMind

@0celouvskyopoulos have you tried using the user search? :P

AccidentalFourierTransform

@Slereah the one in north america

Sir Cumference

3:29 PM

upload.wikimedia.org/wikipedia/commons/a/ab/…

"Shandrashekar"?

Slereah

Ahah

Sir Cumference

That's on the Wikipedia page

Anonymous

@SirCumference Why do you need it anyway ? :P

HsMjstyMstdn

@Sir

oops

Slereah

The PSE post I pasted about entanglement and measurement

One of the answer?

Sir Cumference

3:29 PM

@blue So I can accurately pronounce "Chandrasekhar limit"

HsMjstyMstdn

@SirCumference, that one's even weirder

Slereah

This topic is discussed a bit in somewhat lay terms in chapter 1 of my thesis. – DanielSank Jun 24 '15 at 5:37

John Rennie

void allocMatrix(int ***matrix, int m_size){
    *matrix = calloc((size_t) m_size, sizeof(int *));
    if (*matrix == NULL) catchError("Matrix allocation failed.");
    for (int i = 0; i < m_size; ++i) {
        (*matrix)[i] = calloc((size_t) m_size, sizeof(int));
        if((*matrix)[i] == NULL) catchError("Matrix allocation failed");
    }
}

Slereah

I guess I'll read Sank's thesis

Bernardo Meurer

@JohnRennie Do I really need three levels of indirection :(

I was hoping to get away without that :P

0celouvskyopoulos

3:30 PM

@ACuriousMind how do I do that?

@BernardoMeurer I'm signing for my apartment

Anonymous

@SirCumference Pronounce it anyway you like...doesn't even matter :P Foreigners sound cute when they pronounce Indian names in their own way. :D

0celouvskyopoulos

You can tell Michelle to...something. I don't know why she couldn't be bothered to help me.

Bernardo Meurer

@JohnRennie Could I return the address instead? so then I do int **matrix = allocMatrix(m_size) ?

0celouvskyopoulos

But fuck it

Whatever

Bernardo Meurer

@0celouvskyopoulos Sigh

Sir Cumference

3:31 PM

@blue But...but...I want to sound educated :P

John Rennie

@BernardoMeurer yes, that's a neater way to do it.

0celouvskyopoulos

@BernardoMeurer it's not my fault

She didn't respond to me

HsMjstyMstdn

@SirCumference look here, the lady does a fine job
https://www.youtube.com/watch?v=n-lJjR7pM7k

0celouvskyopoulos

I'm already doing things last minute

Bernardo Meurer

@JohnRennie Sweet, so then I return &matrix ?

ACuriousMind

3:32 PM

@0celouvskyopoulos There's a big "Type to search user" box on the users page

Anonymous

@HsMjstyMstdn Yes, that's better

Anonymous

She doesn't use the "kher" sound at the end

HsMjstyMstdn

@blue (Y)

John Rennie

Just return matrix not the address of matrix. matrix has type **int and your function returns **int. So just return matrix.

Balls, how do I render an asterisk in the chat?

0celouvskyopoulos

Please do not mention the make generalizations.

AccidentalFourierTransform

3:33 PM

` * `

0celouvskyopoulos

*male genitalia

Slereah

I'll make generalizations all I want

Bernardo Meurer

@JohnRennie Got it

@JohnRennie It works!

Sir Cumference

@HsMjstyMstdn "Chandra-sekar"

John Rennie

@BernardoMeurer Naturally :-)

Bernardo Meurer

3:34 PM

@JohnRennie Do I have to free that memory? Only in main right?

Or wherever I called that function from

HsMjstyMstdn

@SirCumference I'm no expert but in general, Indian words are best pronounced when not overthought

Anonymous

@SirCumference That lady's pronunciation is fine. You can use that :)

John Rennie

@BernardoMeurer If you're only ever going to allocate the memory once there's an argument for not bothring to free it as it will be freed anyway when your process terminates.

Sir Cumference

Sigh, I guess I'll just use "Chrondro-shekor"

Bernardo Meurer

@JohnRennie That doesn't sound like good practice :P

John Rennie

3:36 PM

But it's probably better practice to free it. Pointer values are global so you can free the memory anywhere you want.

HsMjstyMstdn

@SirCumference Monstrosity

John Rennie

@BernardoMeurer C or C++?

dmckee

The reason for manually freeing just before (normal) termination is to prevent a surprise if you ever re-use the code in another context.

Bernardo Meurer

@JohnRennie C :P

Sir Cumference

@HsMjstyMstdn ;-;

dmckee

3:37 PM

And to be in the habit and caring about that every single time.

John Rennie

@BernardoMeurer OK, no helpful class destructors to do the freeing then.

Bernardo Meurer

@JohnRennie Hell yeah, greatest language of all

dmckee

@BernardoMeurer The lisp guys would disagree. But it would be a parenthetical comment.

John Rennie

David has a good point. By far the majority of obscure bugs in large C apps are due to mishandling pointers. It's good to develop an obsessive regard for memory management.

Bernardo Meurer

@dmckee Lol

0celouvskyopoulos

3:38 PM

@BernardoMeurer what the hell are you doing

Bernardo Meurer

@JohnRennie I am very obsessive

@0celouvskyopoulos Programming lab

John Rennie

@BernardoMeurer: I am currently about halfway through writing about 20,000 lines of VBScript to do data replication.

It is actually quite good fun, especially since it successfully replicated some data for the first time this morning. But my goodness it makes the brain hurt.

0celouvskyopoulos

Can this chat please talk about something other than programming for once?

John Rennie

When did we last talk about programming?

It was ages ago.

0celouvskyopoulos

Yesterday

Slereah

3:41 PM

Well gee I tried talking about QM but I didn't see you jump on board for that!

John Rennie

@0celouvskyopoulos That's ages ago in the IT world :-)

Fawad

So what you say @JohnRennie on that product rule?

Bernardo Meurer

@JohnRennie I have all the VB stuff :P

John Rennie

@Fawad what you posted isn't well defined. Presumably you lifted it out of some book or article and that will give the context for what exactly $\Delta(PV^\gamma)$ means.

Anonymous

@0celouvskyopoulos Like the thing that starts with a J and ends with an E ? :P

Bernardo Meurer

3:43 PM

The first language I put a lot of time into was VB.NET

Sadly

John Rennie

I'd guess it is a differential in disguise ie it is really $\frac{d}{dx}(PV^\gamma)$ where $x$ is some parameter being varied.

@Fawad in which case it looks like the product rule because it is the product rule.

Fawad

@JohnRennie I too guess same. Then since LHS is 0 ,dx vanishes.

John Rennie

@Fawad differentials aren't fractions so you can't just multiply both sides by $dx$, though to be fair physicists frequently do treat differentials like fractions and it usually works fine.

Fawad

@JohnRennie there is a hot question on math.se

707

Q: Is $\frac{\textrm{d}y}{\textrm{d}x}$ not a ratio?

In the book Thomas's Calculus (11th edition) it is mentioned (Section 3.8 pg 225) that the derivative $\frac{\textrm{d}y}{\textrm{d}x}$ is not a ratio. Couldn't it be interpreted as a ratio, because according to the formula $\textrm{d}y = f'(x)\textrm{d}x$ we are able to plug in values for $\text...

calculus analysis math-history nonstandard-analysis

Slereah

I'm looking at a 3 years old post that has unlatexed math in it

Should I edit it

Fawad

3:53 PM

@Slereah yes,if it also don't have good answers

Slereah

it has an accepted answer

I leave it to Jesus to say if it is good

Fawad

@Slereah good luck then.

Slereah

is it possible to edit a post without bumping it back to the front page, perhaps

ACuriousMind

@Slereah no, but texifying a post is a valid reason to edit, imo

Fawad

@ACuriousMind you not searching on meta.stackexchange? I saw one question like that

ACuriousMind

3:58 PM

Sorry, I don't know what you are trying to say - why would I search meta.SE?

Bernardo Meurer

@JohnRennie If i have a txt file which is a list of words, one in each line. How can I read that into an array in C?

Fawad

-1

Q: Editing without upping?

Is there some way to edit an answer without pushing the question to the top of the list? My use case would be this answer that I just edited because the English was bad enough for two people to add comments about it. But an edit that minor shouldn't have pushed it to the top of the question list.

support

Btw funny English^

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