The h Bar

DIRAC1930

12:00 AM

Do non-interacting particles never become entangled?

PM 2Ring

3:48 AM

Ground track

A ground track or ground trace is the path on the surface of a planet directly below an aircraft's or satellite's trajectory. In the case of satellites, it is also known as a suborbital track, and is the vertical projection of the satellite's orbit onto the surface of the Earth (or whatever body the satellite is orbiting).A satellite ground track may be thought of as a path along the Earth's surface that traces the movement of an imaginary line between the satellite and the center of the Earth. In other words, the ground track is the set of points at which the satellite will pass directly overhead...

JingleBells

1:19 PM

Is there any reason to buy cryptocurrency other than to sell it higher for a profit?

I mean I don't think exchanging cryptocurrency for a pizza for example is very widespread

I like the technology behind cryptocurrency and it's an interesting idea and stuff but I don't find it very useful or practical (besides the profit part) to own a cryptocurrency

I mean the whole purpose of a currency is to be able to exchange it for stuff you actually want, and cryptocurrency can't do that yet?

@ACuriousMind Sup, whatchu think about cryptocurrency?

Slereah

@JingleBells Buying drugs

Loong

You mean "What do you think about Ponzi schemes?"

JingleBells

@Slereah Is that actually legit? I can see why drug dealers would prefer this way of payment

Slereah

That is certainly a common usage of bitcoins

JingleBells

1:35 PM

Is there any way the government can track the drug dealers thru the blockchain technology?

Slereah

They have before, yes

JingleBells

@Slereah Nice

user 726941

1:52 PM

Have you ever heard of money laundering?

PM 2Ring

@JingleBells Here's some modern jazz funk for you. OK, it's a bit removed from the James Brown style, but I hope you can appreciate it. Lalah Hathaway Something.

user 726941

Ponzi schemes are a great way to take a lot of dirty money through the scheme and come out with clean funds; although, the losers far out number the winners...@loong

PM 2Ring

A fundamental ingedient of funk is soul. Here are the amazing Doley brothers from Australia on keyboards, with Karen Lee Andrews (who's also a great guitarist) on vocals, doing an old Soul classic, Get It While You Can

user 726941

Take the money and run.

PM 2Ring

Steve Miller Band Live From Chicago Take The Money And Run

►

user 726941

2:02 PM

Exactly what happens in ponzi schemes.

ACuriousMind

@JingleBells most are scams; the ones that are not are still bad because the decentralization they promise does not happen in practice. This is an excellent overview.

JingleBells

@PM2Ring Sounds good but her singing not very good :P

@ACuriousMind Damn that's long

user 726941

2 hours and 18 minutes could save you your life savings.

JingleBells

@ACuriousMind Yeah it's a bit too comprehensive but generally what bugs me about crypto is that I can't trade it for a pizza, like why is it even a currency then XDD

@user726941 What life savings? ;(

Feynman_00

Oh I see you're talking about astrology

user 726941

2:11 PM

Ok, your future life savings

JingleBells

@user726941 :D

user 726941

:D

JingleBells

@PM2Ring YESS!!!!

holy it's so good

user 726941

Classic

JingleBells

@PM2Ring I got goosebumps bet ong fr fax

user 726941

2:15 PM

@JingleBells go through this diagram and calculate how much the money grows at each level.

Set up a chart.

PM 2Ring

@JingleBells Her dad was a famous soul singer. Her voice isn't as strong as his, but you can hear the family style.

@JingleBells Yeah, it's pretty amazing. :) Listen on headphones, if you can.

JingleBells

@PM2Ring I'm listening on headphones, I was just going to check out the video but ended up listening to the whole thing

you can feel the blues, jazz, and soul so much

PM 2Ring

Oh good. :)

Lachy has a crazy clavinet with a "whammy" (tremolo) bar that sounds like a guitar. Stevie Wonder used the clav a fair bit, eg Superstition, but not with a whammy. Let me get you an example...

JingleBells

What I'm thinking is, during a recession or a depression, what exactly has gone wrong when all the resources, people, and organization are there, the same as it was before the recession/depression?

Like if money is what causes the recession/depression and not an inability to produce, why can't everything be "reset" somehow so everyone is back to producing and stuff?

PM 2Ring

It's a bit intense... Voodoo Chile

JingleBells

2:26 PM

@PM2Ring that's one big pitch bender XD

user 726941

They say the economic strain that the pandemic put on the world's medical system may trigger a global recession...

JingleBells

@user726941 My point is, if all the resources, people, and organization is there ready to function like it did before, surely it can all be "reset" somehow, no?

user 726941

Not to mention the so called reverse Robinhood effects

"resetting" takes time

Politics has changed, a war has started, etc etc

Slereah

2:42 PM

PM 2Ring

Speaking of war, these ladies had to leave Ukraine. Fortunately, they're all safe, but the drummer's house got smashed. The Sixsters (Ukrainian All-Girl-Band) Психоделіка

@Slereah I guess he wouldn't be very happy with $2^{100}!$, then.

Slereah

@PM2Ring He may take a little while to answer

RewCie

2:58 PM

GRUUUUUUUUUUU

PM 2Ring

Some funky Southern Rock from TTB, Gravity

JingleBells

3:18 PM

Gold standard good or bad, I read so much and still don't know

user 726941

Good.

Mad

Good day dear friends, how did he derive the relationship 3.144?say what initial equation he took to reach this result

This from Griffiths,intro to quantum mechanics, chapter 3.

ACuriousMind

@Mad the quote explicitly refers to eq.(3.28), where presumably you'll find the definition of $\lvert f\rangle$ and $\lvert g\rangle$ he then plugged $x$ and $p$ into

presumably they are the same as here; there isn't really a lot else going on there

Mad

3:35 PM

No

He derived the equation 3.143 using the inequality of shcwarz and the inequality for the value of a complex number.

ACuriousMind

yes, and then he plugged the definitions of $\lvert f\rangle$ and $\lvert g\rangle$ in to get 3.144

Mad

I am thinking, the position momentum uncertainity principle is in this case minimal so $ \sigma_p \sigma_x = \hbar/2$

Yes, he plugged them into what? the equation i wrote?

ACuriousMind

in to 3.143

Mad

Oh

God bless

but he chose g to be the impuls one, and f the place one

Does it matter if i switch?

so f is then = $(\OperatorX-<x>) \Psi$

ACuriousMind

well, you get an equation that looks very similar to 3.144 - they essentially differ by something like $a\mapsto -a^{-1}$

Mad

3:41 PM

i am not sure how to write in Latex the operator sign.

ACuriousMind

\hat{X} is $\hat{X}$

Mad

Oh, cute hat.

Okay, so its just a factor difference, no biggy

Also, deriving the eigenfunctions of the position operator, we had somehting in the lines of xg(x) = y g(x) and he concluded this must be diracs delta, since everywhere it must be zero, and at y it is okay, if y is a scalar.

But to me, any function wtih any value at g(y) = something is also valid, i was wondering why he chose diracs delta?

Here

ACuriousMind

@Mad Any normal function $f$ that is just non-zero at $y$ and zero everywhere else has $\int f = 0$

Mad

you mean = 1

ACuriousMind

and in particular also $\int f^\ast x f = 0$, so the expectation value of $x$ in that state would always be zero

@Mad no, I don't

A function that's only non-zero on a set of measure zero, i.e. a point in this case, has zero integral, that's how integrals work

Mad

3:48 PM

Okay.

And then how do you conclude diracs delta?

ACuriousMind

well, the $\delta$ isn't really a function, but to a physicist it has $\int \delta =1$, so it's fine

Mad

Sorry what is a normal function? i thought normalizabl functions have integrals equal to one.

ACuriousMind

@Mad I mean that $\delta$ isn't a function

it's a distribution

Mad

Yes i reliaze, and ?

ACuriousMind

so by "normal function" I mean any $f(x)$ that's actually a function!

Mad

3:50 PM

Alright i am following so far...

ACuriousMind

the "normal" there isn't a technical term, I used it in contrast to "abnormal" "functions" like $\delta$

Mad

Oh

So.. regular functions, i get your drift.

Yea i know that.

So if it is not Diracs delta, expectation will be zero

bummer. right?

Thus it must by necissicty be diracs delta, since the particle is somewhere? am i getting this correctly

ACuriousMind

well, there's a problem where you can't actually compute $\int x \delta^2$ either because the square of distributions doesn't really exist, but physics texts usually carefully avoid talking about that :P

Mad

Yes , but he avoids the problem, by introducing two values to delta, then he can multiply them.

ACuriousMind

you shouldn't think too hard about this because it's not rigorous anyway: The $\delta$ is a "good eigenfunction" because it has $\int \delta = 1$ and $x\delta(x-x_0) = x_0\delta(x - x_0)$ (at least inside of integrals), there isn't anything more going on

Mad

3:59 PM

Alright thanks

RewCie

Average Gigachad

user 726941

who, me?

nothing wrong with being average, pal

RewCie

4:41 PM

@user726941 That's what normal gigachads say

Slereah

Lately I am experiencing a lot of people telling me that there is basically nothing left to research in classical GR and then when I tell them what I am reading about they have no idea what it is

More Anonymous

@Slereah who are these people?

Slereah

Various people

More Anonymous

@Slereah academics or chatroom bumpkins :P?

Slereah

Who can say

More Anonymous

4:50 PM

@Slereah you?

I just wrote a nice PSE question and by the time I was done I had the answer facepalm

user 726941

GR has come a long way since 1919

Muhammed Çağlar TUFAN

Hey everybody, I hope you all having a nice weekend. I'm here to have some recommendations about book or blog, but I prefer a good blog at the moment.

I'm looking for a blog about history and philosophy of science, physics, biology, geography and maybe a little bit about technology and ongoing researches etc.

Is there any blog that you follow regularly and would recommend?

More Anonymous

5:08 PM

@MuhammedÇağlarTUFAN one blog with all of this or many blogs?

Muhammed Çağlar TUFAN

@MoreAnonymous any blog that publishes posts related to any of these subjects would be fine.

More Anonymous

@MuhammedÇağlarTUFAN I'm not sure what level of physics your after but Sabine has youtube channel for the general audience

The Best Science Hoaxes, Spoofs, and Nerd Jokes (500k subs celebration)

►

RewCie

5:28 PM

My uncle got heartattack day before at night.

I guess stents are much better alternatives to surgery.

He's much better now. It just took 15 min afterall.

to the valves.

Stents installed

Much cheaper, safer, permanent and faster than Open Heart Surgery

Silly Goose

6:43 PM

is there a one stop shop resource for understanding the dirac delta distribution?

Nike Dattani

@MoreAnonymous Did you tell the mods here that you flagged that question for migration?

Feynman_00

@SillyGoose What do you mean by "one stop shop"? And most of all, how much detail do you need?

More Anonymous

I flagged the question

Its pending I beleive

Sir Cumference

@SillyGoose You wanna understand it mathematically or just its applications for physics?

Silly Goose

mathematically so that any manipulations done in physics can be followed and understood (like get a good hold of its important mathematical properties, and a sense of how to check properties myself)

Sir Cumference

6:54 PM

'Cause for the latter, there's a simple ad hoc explanation

Nike Dattani

Have you told the mods here, such as @ACuriousMind? An unexplained flag can be hard to approve, I would assume. But maybe you explained it well enough :)

Silly Goose

@Feynman_00 kind of like a single book with all the information. i would like to be able to follow or prove any presented property of the dirac delta function

More Anonymous

@NikeDattani Didn't directly ping him. I did mention when I flagged I wanted to migrate the question

to matter modelling

Silly Goose

not all people are hims @MoreAnonymous

Nike Dattani

@MoreAnonymous I guess the problem might be that mods don't tend to migrate questions away unless they're sure that the destination site will be okay with it.

Feynman_00

6:58 PM

@SillyGoose Well, we're talking about someone we know about, so what's the problem? :P

@SillyGoose You would need a book about distribution theory, I don't have specific suggestion. Well, I'm in the same boat with distributions, I just happen to know some pretty basic stuff. If your aim is just about understanding manipulations in Physics, I don't know if studying distributions is overkill

More Anonymous

@NikeDattani Ah ... Should I just ping AQM?

@SillyGoose is this about the pronoun stuff?

Feynman_00

@MoreAnonymous A quantum mind?

Here we go again with the potara fusion :P

More Anonymous

@Feynman_00 Lol ... sounds like an insult. ACM my bad

Feynman_00

No, that's the canon name for the fusion between ACM and Qmechanic

2

How do I quote old messages?

Nike Dattani

Why do you want to move it to MMSE by the way? It's only been on Physics.SE for 1 day. There's way more users on Physics.SE. Also, no one's really talked about the Maxwell distribution or Stosszahlansatz on MMSE.

Feynman_00

7:04 PM

@MoreAnonymous Here

Nike Dattani

But people have talked about both on Physics.SE a fair bit.

More Anonymous

@Feynman_00 Oh lol I forgot about that one

@NikeDattani I see maybe I should let it be then

Feynman_00

My quote doesn't show the message :/

More Anonymous

@NikeDattani I think MMSE entertains original ideas better whereas PSE is quite cautious (for good reason) of crackpottery

Sir Cumference

7:37 PM

@Feynman_00 You mean like > quote?

Feynman_00

7:51 PM

@SirCumference I don't know. Sometimes ACM quotes old messages and they appear in a box

DIRAC1930

Can someone help me understand a paper in private?

Nike Dattani

8:06 PM

@DIRAC1930 a minute ago, I invited another SE user who wanted to speak to me about a paper in private, to chat with me on Discord. So if you want to do that too, this invite is valid for 7 days: discord.gg/fuuqxpGY (I'm not sure how to increase the default expiry date for invites).

Shiki Ryougi

9:49 PM

@Feynman_00 Are you Italian? (for some reason I think so but cant remember). Is Ricci pronounced like Ritsi or Riki? en.wikipedia.org/wiki/Ricci_curvature

Feynman_00

10:07 PM

@ShikiRyougi I am. A double "c" before "i" is pronounced like "ch" in "cherry"

Or if you prefer, like rich-ee

Shiki Ryougi

Ohh oki. In greek we pronounce ''ch'' as ''ts'' so that's why I wrote it like that xD

Thank you

Feynman_00

Don't ask me about Levi-Civita though :P

Shiki Ryougi

10:32 PM

:D