The h Bar

3:00 PM

@bolbteppa There's nothing on that board

what scam are you trying to pull, Einstein

Notebooks are blank too

'In 1946, Einstein, the Nobel Prize-winning physicist traveled to Lincoln University where he gave a speech in which he called racism “a disease of white people,” and added, “I do not intend to be quiet about it.”'

'While at Lincoln, Einstein also received an honorary degree and gave a lecture on relativity.'

They had cameras back then, imagine a full on course on relativity by him

Emilio Pisanty

@bolbteppa ~~why do people go to Lincoln?~~ nvm

I've never really understood

bolbteppa

'Lincoln was the first school in the United States to grant college degrees to blacks.'

All from here
https://woodmereartmuseum.org/experience/exhibitions/john-mosley-photographs/albert-einstein-and-students-at-lincoln-university

Emilio Pisanty

hmmmm, wait

which Lincoln is this?

pennsylvania?

bolbteppa

'Lincoln University in Pennsylvania, the alma mater of Langston Hughes and Thurgood Marshall and the first school in America to grant college degrees to blacks'

Emilio Pisanty

3:07 PM

ah

"cf. supra", as they say

bolbteppa

He sounds very BLM don't you think @0celo7

Emilio Pisanty

^ definitely.

bolbteppa

He was even in the NAACP apparently, and ignored doctors orders for a surgery...
https://www.huffingtonpost.com/2013/10/17/abert-einstein-facts_n_3987801.html

Slereah

Einstein was in the original NWA lineup

Future Historian

Hmmmmmm. I had an idea: as a physics stack exchange, how possible is a wormhole (for a Kardashev Type 2.X civilisation, that is)?

And how can we create a wormhole (in theory) for either communication or travel?

John Rennie

3:22 PM

@FutureHistorian as far as we know wormholes are impossible full stop.

Future Historian

@JohnRennie? Even for a Kardashev Type 2.X civilisation?

John Rennie

Even for God himself.

Future Historian

If he was a thing.

But that is you, and I do me.

John Rennie

"He"? Very sexist of you :-)

Future Historian

Anyway, @JohnRennie. Mathematically, how do you make a wormhole?

As in: what is the mathematics behind a wormhole?

John Rennie

3:25 PM

Actually all the wormholes we know about are static i.e. we know what their structure is but not how you would actually construct one.

I did ask a question on this subject but with no great success.

Future Historian

Because I last checked that negative energy or negative mass was a necessity, and anywhere from a Jupiter’s worth to 100 BILLION stars’ worth of the stuff.

John Rennie

21

Q: Building a wormhole

We regularly get questions about wormholes on this site. See for example Negative Energy and Wormholes and How would you connect a destination to a wormhole from your starting point to travel through it?. Various wormhole solutions are known, of which my favourite is Matt Visser's wormhole becaus...

Nat

Random question: a bunch of posts on SE seem to have a space before punctuation marks where it makes no sense, e.g. before a period at the end of a sentence. This seems to be a pretty common structure here, but I can't recall having noticed it on any site other than SE. Is there a story behind it?

Future Historian

And we have a thing called “negative energy”, but not negative mass.

John Rennie

@FutureHistorian dark energy isn't negative energy, if that's what you're thinking of.

Future Historian

3:27 PM

I know.

It is not that.

John Rennie

Negative energy doesn't exist either then.

Future Historian

en.m.wikipedia.org/wiki/Negative_energy

I mean this as a concept.

Semiclassical

A pet peeve of mine: Going to a crowded computer/library area and finding people who are sitting at computers with their laptops out

Emilio Pisanty

Burning Oxygen In Propane Atmosphere

►

^ super cool

John Rennie

@FutureHistorian That's not negative energy. Alhough we formally often give potential energy a negative sign, that only means it's less than some reference not that it is actually a negative energy.

Emilio Pisanty

3:30 PM

hiya @dmckee

Semiclassical

Not logged into the computer or anything, they’re just using it as a convenient desk (and thereby preventing anyone else from actually using that computer)

Nat

@Semiclassical Because they're monopolizing a public computer when they have a private one with them?

Semiclassical

Yep.

Nat

Hah, yeah, that does sound inconsiderate.

G. Bergeron

@EmilioPisanty It's almost the same vacuum pump I bought in high school!

Slereah

3:30 PM

Dark energy does violate the NEC

Semiclassical

I mean, it’s true that there’s not much space left in that area

But uh

Future Historian

Look. I mean that there could be some quantum effect we are not aware of that could allow for wormholes.

The issue is..........

Semiclassical

Too f***ing bad

Emilio Pisanty

@Slereah ah, but did you use it to burn air in a propane atmosphere?

Semiclassical

If you’re not going to use the PC then don’t monopolize that space

dmckee

3:31 PM

@knzhou We do, but the basic filter accepts a relatively small number of upvotes as evidence that the content is not beyond redemption.

John Rennie

@FutureHistorian There could be wormhole fairies that we aren't aware of who can create wormholes by waving their wormhole wands. Doesn't seem terribly likely though ...

Emilio Pisanty

makes me wonder what would be a good material for a match on Titan

Semiclassical

Speculation gets boring when there’s no empirical constraints

Slereah

The likeliest bound on wormhole radius is $\approx 1.5 l_p$

Emilio Pisanty

@dmckee is that upvotes on those same answers, or upvotes in general taken as an indication that the user does post content that is beyond redemption

Nat

3:34 PM

@JohnRennie Somewhere out there, a super-intelligent alien species who regards us like ants in an ant farm has just decided to create worm hole fairies with magic wands just to screw with us later.

Slereah

That's what you get for self-sustaining wormholes

Future Historian

@JohnRennie. Look. It is dubious as best, but it could be possible that we could see some means of negative energy being a thing (which I hope so, but I am dubious about), and depending on its properties, it could be possible to make some kind of wormhole, either for communication or travel, depending on the process, properties and implications for other fields of physics.

And possible =/= likely.

dmckee

@EmilioPisanty That is a detail that I don't know. Indeed, I'm only conjecturing about the statement in the first place, but as a mod I am in a better place than most to make such guesses.

Future Historian

So, in theory, could a Kardashev Type 2.X civilisation create wormholes?

Semiclassical

If you enjoy such speculations, feel free. I find them untethered from reality and not very interesting

John Rennie

3:37 PM

@FutureHistorian I suppose Clarke's first law applies, but luckily I'm neither elderly nor distinguished so I feel confident in saying wormholes are physically impossible.

dmckee

@FutureHistorian It's not primarily about energy supply it is about what you know.

Nat

@FutureHistorian In theory, it's not meaningful to predict that far ahead. It'd be like cavemen trying to predict whether cell phones would be possible. We're simply not qualified to guess.

G. Bergeron

@FutureHistorian Best bet is with something akin to rails laid in advance that would move as your ship passed across the elements of the rails.

dmckee

With our theory the answer would still be "No. Forget it."

Semiclassical

It’s the futurist equivalent of asking how many angels could dance on the head of a pin

John Rennie

3:38 PM

@FutureHistorian Why do you come and ask physicists about physics if you're then going to ignore what they tell you?

5

Emilio Pisanty

@dmckee have you seen my second link?

Future Historian

I am not.

Emilio Pisanty

it's quite remarkable

dmckee

Yes. Looks promising.

Future Historian

If anything, I am asking......what if wormholes were possible?

Semiclassical

3:39 PM

Must I invoke the obligatory XKCD?

Future Historian

As in: if we found some theory to make a wormhole work, then what would that change for our models of physics?

Nat

@Semiclassical The answer to that question is almost always "yes".

Semiclassical

lol

G. Bergeron

@JohnRennie Why do you say that? As far as I know, anything we know on the topic is just conjectures upon conjectures. That could go both way. Not that I am hopeful or anything, but I don't see what makes you say that.

Future Historian

Besides, it is not easy to remain with current physics and have some Clarketech.

G. Bergeron

3:41 PM

The strongest heuristic I know against wormhole is what happens when you try to put quantum systems being measured in a closed timelike curve, you get really weird conclusions.

Semiclassical

Slereah

@G.Bergeron not much of an issue

A wormhole collapses before CTC formation

G. Bergeron

@Slereah Well, I haven't spelled it out, but this, for me is the strongest argument against the existence of CTCs.

@Slereah Any refs?

Semiclassical

Well, that’s more an argument about not being able to sustain such a wormhole

Though that’s enough in my book

John Rennie

@G.Bergeron wormholes don't necessarily imply CTCs. The wormhole geometries we know about just connect two otherwise disconnected universes.

Emilio Pisanty

3:44 PM

@dmckee I've tried looking at other sites and there's nothing even remotely similar

it does fail for maths.se, though - the site's just too big and the query is too slow

Nat

Predictions about fundamentally possible/impossible phenomena rub me the wrong way; we're wayy too primitive to possibly guess stuff like that. The right questions would seem to be if current scientific models predict a manner in which hypothetical phenomena might be realized.

Emilio Pisanty

and no chance of a cross-site query as currently structured

G. Bergeron

@JohnRennie Indeed, but presumably, one could set them up using wormholes.

@Nat Well isn't that a bit defeatist? Also, way too primitive, really?

John Rennie

@G.Bergeron you're assuming we can create wormholes that cause our spacetime to be multiply connected. As far as I know there is no evidence that we can do that, even if we had access to the required exotic matter.

Semiclassical

@G.Bergeron for our descendants, maaaaaybe

For us? It strikes me as simply realistic

Nat

3:46 PM

@G.Bergeron Not at all! I'm super-positive about the future and the possibilities. Just, it's silly for us to presume to have any sort of complete knowledge about the universe. Each answer brings new questions, and that trend'll likely continue for ages.

Semiclassical

I’d prefer to have experimental evidence first

G. Bergeron

@JohnRennie But I am curious, why do you say you think wormhole cannot exist?

John Rennie

@G.Bergeron they require exotic matter

G. Bergeron

@JohnRennie Ah, ok

Semiclassical

Right now the issues are not so much that we don’t have theory which describes nature so much as we don’t know how to combine our well-validated theories into a whole

Eric Silva

3:49 PM

wut is exotic matter and what's so exotic about it

Semiclassical

If you’re in a scenario where you know what the Standard Model will give as empirical predictions, then I think we pretty much have no evidence against it

G. Bergeron

@Semiclassical Yes. And my point was that throwing QM in the mix with GR, in my opinion, only makes the possibility of wormholes even less likely.

John Rennie

@EricSilva Think of an exotic dancer, then ... erm ... just keep thinking about the exotic dancer :-)

Eric Silva

o i c

G. Bergeron

@Semiclassical Except that clearly, the cross sections ought to be wrong at the energy scale where one would expect blackhole creation

Nat

3:51 PM

@EricSilva There's normal matter, which is what we normally think of and discuss. And then there's other kinds of matter, which are exotic by contrast. Then there are exotic dancers, which @JohnRennie thinks about and then gets others to think about. Then there's the hypothetical possibility that there may be a form of exotic matter composed of exotic dancers.

dmckee

@EmilioPisanty Uhg. If it is just us then we might have a harder time making the case, Unless it is so striking that it makes the case all by itself.

G. Bergeron

@EricSilva negative energy density, among other exotic properties.

Eric Silva

why is that exotic though, as in, why doesnt that happen normally

G. Bergeron

MMhhh exotic and dangerous dancers!

@EricSilva Never observed and not predicted by any experimentally confirmed theories.

Emilio Pisanty

Eric Silva

3:53 PM

ok cool

Emilio Pisanty

you can argue either way about whether it makes the case all by itself

pretty much no other site I've tested has any negatives

and when they do they are typically folks with a few (one to maybe three or four) moderately downvoted answers, and they get their rep from either a couple of HNQs or from of a big bunch of questions

G. Bergeron

What's this event ''Physics chat session''? Anything special? Free cookies/coffee?

Emilio Pisanty

@G.Bergeron yes, but you need to buy the cookies yourself and brew the coffee locally from your own supplies

Nat

@G.Bergeron Never any shortage of cookies! If you want some more, Amazon.com should load ya up.

As much as I enjoy Google Chrome for casual browsing, it really seems to track the heck out of ya.

G. Bergeron

@EmilioPisanty It's ok I'm drinking some now and have a brewing machine in my office! :p But really, is it a focused time to chat here?

John Rennie

3:59 PM

@G.Bergeron the chat room used to be a very quiet place, so we organised fortnightly chat sessions to try and bring people in. These days we could talk the hind legs off a donkey so the fortnightly chat sessions have largely fallen out of use.

dmckee

@EmilioPisanty ::chuckles::* You've put to of my other favorite problem posters in the "just us category".

Emilio Pisanty

@dmckee indeed

G. Bergeron

I see

Emilio Pisanty

I have seen no. 4 lurking about on blogs and the like

John Rennie

@G.Bergeron Ever since we created that black hole the chat room has been really busy :-)

Emilio Pisanty

4:01 PM

very often rambling off-topic in the comments sections

Nat

@EmilioPisanty Where do ya get that table from?

G. Bergeron

@JohnRennie :P

I should try and answer a few questions, it's been a long time since my last...

Emilio Pisanty

@Nat data.stackexchange.com/physics/query/840733/…

Nat

@G.Bergeron If you're up to it. SE.QuantumComputing could use the boost. I hope that it succeeds, though I dunno how wide a demographic it might reach given the topic.

John Rennie

I've just managed to recompile the Windows NT4 File manager to work on Windows 7, so it has been a great day? For some rather esoteric meanings of the word great :-)

Emilio Pisanty

4:04 PM

@JohnRennie rather

John Rennie

:-)

It gives me something to do ...

G. Bergeron

@Nat Oh, I've got a lot of friends working specifically in that area, I'll try and point it out to them!

Nat

@EmilioPisanty Ohh very nice tool, thanks!

Secret

@JohnRennie I wonder where is the date where that "black hole" is first created. It might help to renergise other main chat rooms :P

Emilio Pisanty

@Nat no worries

I do seem to be the resident SEDEician

John Rennie

4:06 PM

@Secret I don't know why the chat room suddenly took off.

Secret

lol I see

G. Bergeron

So they parse SQL for you, damn!

Emilio Pisanty

@G.Bergeron indeed

as they put it "we teach people SQL using the very questions we use to teach as an example database"

which does have a good deal of caché to it

G. Bergeron

@EmilioPisanty As a web admin, I'd be afraid of opening that up to the public... and especially afraid of somebody JOINing tables until my servers died!

Emilio Pisanty

@G.Bergeron time-limited

try running it on MSE, for example

data.stackexchange.com/math/query/840733/…

John Rennie

4:08 PM

Why do any useful work when you could be doing this? !!

G. Bergeron

loading Hold tight while we fetch your results

So it's capped to 1 ms?

Nat

@JohnRennie Hah wow, blast from the past! They got rid of File Manager after Windows 3.x, didn't they? I think it became File Explorer in Windows 4.x (Windows 95).

Emilio Pisanty

@JohnRennie why do that when you could be doing ANYTHING ELSE?

@G.Bergeron dunno what the cap is

longer than a second

John Rennie

@EmilioPisanty I still find File Manager the fastest way to manage files.

G. Bergeron

@JohnRennie I've never really used windows. I'm always clicking everywhere trying to find what I want when it does happen.

@JohnRennie My file management is akin to: '' Oh my cluttered desktop is getting too cluttered. Let's make a a new Stuff folder, drag and drop everything in it and.... tadaaaa! A brand new computer!''

John Rennie

4:12 PM

@G.Bergeron I was on the Windows for Workgroups beta programme back in, erm, 1992 ish I think. I've used Windows continually since.

Jesus, 26 years.

Nat

Hah that's about as old as some of us.

G. Bergeron

@JohnRennie I was like 1 or 2 at the time, no computer for me...

John Rennie

We had to hand crack our computers back when I was a lad

It was a huge advance when the first steam powered computer was built.

That fellow Babbage was a genius!

G. Bergeron

@JohnRennie LOL, but seriously, you worked with those punch-card computers? My mother used to tell me it was hell when you dropped your pile of cards and hadn't numbered them...

Nat

Hah I went to a conference in celebration of the founder of a CAD company. One of the opening speakers talked about how they used to have cathode ray tubes (or something) in the early days of their company. About half-an-hour later, I realized that they were being serious.

John Rennie

4:15 PM

Yes, I used punch cards but I never dropped them. Friends did and much swearing ensued.

G. Bergeron

@Nat HIGH cathode ray tubes ??? I mean I used CRTs too.

Ah ok

Nat

@G.Bergeron =P

Nehal Samee

Sorry to interrupt ... But , can anyone give me some link or PDF including mathematical problem regarding all tensile-bulk-shear stress or any of the two ?

Nat

I did go through some old pics lately and my girlfriend was commenting on how weird it was that I used to have a computer with such a weirdly large monitor, before they became all flat.

G. Bergeron

@Nat You never used CRTs? They're so much fun taking appart. Those flyback transformers and deflection coils core have so many uses!

Nat

4:17 PM

@G.Bergeron The who and the what now? I'm pretty sure that you're making up words.

G. Bergeron

@Nat CRT - cathode ray tubes (those big screens), flyback transformers - a kind of transformer used in the flyback switching mode power supply topology en.wikipedia.org/wiki/Flyback_transformer

Nat

@G.Bergeron Nope, don't believe it. You just forged that Wikipedia page.

G. Bergeron

@Nat I collect them for their cores. Its a good quality big chunk of ferrite, nice to design your own high-frequency transformers around.

Nat

Weird how fast stuff changes. Microsoft's recently announced that they're putting in neural-network models as a basic Windows feature in an upcoming update, so developers can use neural nets as a basic part of making apps.

G. Bergeron

@Nat Well that's just trend following. It's the new catchy tech.

Nat

4:23 PM

@G.Bergeron Crazy useful, too. Back in optimizing engineering systems, we used to have to pick variants of Newton's method and whatnot. Now it's getting to the point that we're having AI perform the search on larger problems.

I mean, screw the Hessian; let a neural network find the search direction and step size and whatnot. But then, neural networks also need to be optimized, so then may as well neural network their training, too. Infinitely regressive, then turns into something weird in the end.

G. Bergeron

@Nat .... Aaannndd you end up with so many parameters that makes an untrainable mess that collapses under its own weights (pun intended!)

Nat

@G.Bergeron Hah which is exactly what the bottom-level optimizer regularizes! I mean, it works great, it's just crazy complex to keep track of.

G. Bergeron

@Nat It was meant as joke on the infinite regress.

anyway gotta commute

Nat

Good chattin' with ya!

0celo7

@JohnRennie went pretty well

John Rennie

4:32 PM

@0celo7 good :-) No dazed expressions?

ACuriousMind

4:52 PM

@0celo7 No, the canonical German name is Tom Vorlost Riddle (the middle name is different and rather absurd in most languages to make the anagram work in the respective language).

Abcd

Hey @Secret. Just wanted to ask why $\ce{C-X \sigma^*}$ is lower in energy than $\ce{C-H \sigma^*}$ (X=halogen).

Secret

The CX bond is more polarised, thus the uneven electron density of the bond pair means it is easy to break away

Abcd

So due to large electronegativity difference shouldndn't CX sigma* be higher in energy?

Secret

CX sigma* will be lower in energy compared to CH sigma* because of the polarisation (which makes the MOs overlap less good and hence the splitting will not be as pronounced as the CH case if I recall...)

Abcd

Okay, thanks.

Emilio Pisanty

5:01 PM

Harry Potter and the translator's nightmare - Vox

►

Secret

likewise, the CX sigma MO will be higher in energy than its CH coutnerpart

Abcd

@Secret Did you learn many reactions as a part of your chemistry study? Do you remember all of them? (Just asking)

Secret

Well, most of these in my 1st-2nd year org chem. Nowadays, I remember some of the main ones, but for some such as aromatics, I sometimes need to refresh my memory by looking them up

Abcd

Are there mechanisms of inorganic chemistry reactions too?

Like mechanisms make organic chem so easy.

Secret

There are mechanisms for inorganics and metal complexes too, but they are not as easy bcause there is no arrow pushing

there are however some simple mechanisms such as dissociative and associative mechanisms

Abcd

5:05 PM

Oh that's sad.

Secret

this is expected because when you have d orbitals available and hence a lot more coordination possibilities, the electronics get very complicated.

Oxidative addition

Oxidative addition and reductive elimination are two important and related classes of reactions in organometallic chemistry. Oxidative addition is a process that increases both the oxidation state and coordination number of a metal centre. Oxidative addition is often a step in catalytic cycles, in conjunction with its reverse reaction, reductive elimination. == Role in transition metal chemistry == For transition metals, oxidative reaction results in the decrease in the dn to a configuration with fewer electrons, often 2e fewer. Oxidative addition is favored for metals that are (i) basic and/or...

Nehal Samee

Hello .. will a ball dropped in a lift accelerating (at a ) upwards and downwards experience only g ?

Secret

For organometallics, we use the kinetic, spectral and thermodynamic data to determine what reactions occur in different steps, and it often involve a lot of transition state modelling

Abcd

@Secret is the mechanism of $\ce{NH4Cl + NaNO2 -> N2 + NaCl + H2O}$ complicated?

John Rennie

@NehalSamee yes, give or take a bit of air resistance

... and until it hits the floor of course.

Abcd

5:10 PM

or is it just basic double displacement then thermal decomposition of $\ce{NH4NO2}$ but I wonder how that thermal decomposition happens

Nehal Samee

@JohnRennie .. what will be the acceleration when it's thrown upwards ?

John Rennie

@NehalSamee as long as the ball isn't touching anything else the only force acting on it is the gravitational force $mg$.

Secret

Well, for main group non coordination chemistry (like the above) some degree of arrow pushing is still possible. I don't remember the mech of that one on top of my head, but I will probably expect the NO2- to attack the N at the NH4+ and thus trigger the formation of N2 and then H2O.

Nehal Samee

@JohnRennie ...Thanks ... My book suggested differently .. so I was confused ...

ACuriousMind

@NehalSamee What did your book suggest?

John Rennie

5:14 PM

@NehalSamee is your book talking about the acceleration relative to the elevator maybe?

Nehal Samee

They gave acceleration of lift , height of ball from floor , and value of g ... Then they told to find time required to touch the floor ...

@JohnRennie

@ACuriousMind

ACuriousMind

That does not suggest the ball experiences any acceleration but g.

That you cannot ignore the acceleration of the lift doesn't mean the ball has to experience it!

John Rennie

Well the ball accelerates down at $g$ but the lift floor accelerates up at $a$, so the acceleration of the ball relative to the lift floor is $g+a$.

Nehal Samee

@JohnRennie ... Then I have to use the lift frame I guess ...

So , while throwing up , ball experiences $g-a$ for upward and $g+a$ for downward motion ...?

John Rennie

@NehalSamee Working in non-inertial frames can be tricky. Can't you just write the height of the ball relative to ground as a function of time, and the height of the lift floor relative to the ground as a function of time, then set them equal?

Nehal Samee

5:20 PM

@JohnRennie ...

@ACuriousMind

?

ACuriousMind

@NehalSamee Yes?

Nehal Samee

@JohnRennie ... They didn't give any hint about ground ...

What say about the next case ?

@JohnRennie

John Rennie

Suppose the lift floor starts at ground level at time 0, then the height of the lift floor is just $\tfrac{1}{2}at^2$. If the ball starts at height $h$ above ground level with an initial velocity $v$ then the height of the ball is $h + vt -\tfrac{1}{2}gt^2$. Set the two heights equal and solve for $t$.

eulB

@ACuriousMind can you help me with something please

ACuriousMind

@eulB Depends on the something :P

eulB

5:25 PM

was just wondering what the main areas of mathematical physics are.

Nehal Samee

@JohnRennie ... why it isn't $a-g$ for lift ...

eulB

can you just name several of them please with an example maybe?

Nehal Samee

You wrote only $at^2$ ...

ACuriousMind

@eulB That depends on how broadly or narrowly you define mathematical physics :P

John Rennie

@NehalSamee the lift has a motor controlling its movement so it has a fixed acceleration upwards of $a$ due to the motor.

eulB

5:26 PM

@ACuriousMind narrow

it doesn't really matter so you can just keep it in your domain of what you did/ are familiar with

Nehal Samee

@JohnRennie ... Another thing ...

John Rennie

Yes?

Nehal Samee

@ACuriousMind ... you see too...

John Rennie

I think you might be annoying ACuriousMind by continually pinging him ...

Sir Cumference

@NehalSamee You can reply to a chat post by clicking the arrow on the right of it

eulB

5:29 PM

@NehalSamee acm is mine right now and i'm pretty sure literally anyone in this room knows enough to help you so you don't need to ping everyone for multiple opinions.

Nehal Samee

@JohnRennie ...Air temperature is 30°C and wet bulb temperature is 28°C ... If air temperature decreases 1°C suddenly , then what will be Change in Dew point ...? I have all the Glaishier factors ... I want a mathematical approach ...

eulB

that's 50% a joke btw don't kick me please (at this point i'd have to write a disclaimer on most things i say i think)

John Rennie

@NehalSamee I have no idea, sorry. If it can wait until tomorrow morning I'm willing to Google it - at the moment I don't even know what a Glaishier factor is.

0celo7

@bolbteppa we already know Einstein was insane (just see what Duffield references)

Nehal Samee

@JohnRennie ... No problem ... But please make sure you find one ...😄 .. I searched a lot but I'm not getting any satisfactory answer ....

Slereah

5:33 PM

@JohnRennie Exotic matter isn't too hard

It's the ANEC that's hard

0celo7

@bolbteppa but denying there was racism in the 50s...that’s low even for you

bolbteppa

@0celo7 Excuse me?

John Rennie

When did bolbteppa deny there was racism in the 50s?

Nehal Samee

@eulB by the way ... He was discussing my topic ...Earlier ...😏

eulB

@NehalSamee wow nice dude

ACuriousMind

5:35 PM

@eulB Well, there's a lot of mathematical angles in QFT. There's rigorous perturbation theory ("causal perturbation theory", Epstein-Glaser), there's mathematical gauge theory (instantons, Donaldson), there's TQFTs (Lurie's work), there's mathematical string theory (there's a 2-part book on St for mathematicians whose authors' names I continually forget), there's constructive field theory (Glimm/Jaffe), Ask @0celo7 for a completely different list of mathematical physics topics ;)

Slereah

How many math fields aren't used in physics

bolbteppa

@0celo7 are you sure mathematical GR isn't just a slippery slope to BLM?

ACuriousMind

@Slereah Number theory :P

Slereah

@ACuriousMind what about zeta regularization

ACuriousMind

Unless you subscribe to the Journal of p-adic Physics (which exists, sooo...)

bolbteppa

5:37 PM

You call that complex analysis not number theory

ACuriousMind

@Slereah How is that number theory?

0celo7

@JohnRennie he was indicating Einstein was BLM for opposing racism in the 50s

Sir Cumference

@ACuriousMind Someday I will find a way to make number theory useful

0celo7

IMO opposing the systematic racism of the 50s was reasonable and good

John Rennie

@0celo7 Black Lives Matter?

ACuriousMind

5:38 PM

@SirCumference Well, there is one, it's called cryptography.

Slereah

Isn't the Zeta function related to prime distributions?

Sir Cumference

@ACuriousMind Yeah but, actually useful

bolbteppa

That's like an application

ACuriousMind

@Slereah I'm sure the $\zeta$-function has been related to almost everything

Slereah

@SirCumference Tell that to the criminals who haven't stolen your credit card number online

bolbteppa

5:39 PM

But you need to do analytic continuations of it so it's like complex analysis

ACuriousMind

See Connes and his attempt to find a physical Hamiltonian whose eigenvalues are the zeros or something

Captain Bohemian

@eulB You don't know what mathematical physics is? Have you read the 32-page booklet published by IOP regarding the introduction of mathematical physics?

eulB

link

bolbteppa

Mathematical physics

Mathematical physics refers to the development of mathematical methods for application to problems in physics. The Journal of Mathematical Physics defines the field as "the application of mathematics to problems in physics and the development of mathematical methods suitable for such applications and for the formulation of physical theories". It is a branch of applied mathematics, but deals with physical problems. == Scope == There are several distinct branches of mathematical physics, and these roughly correspond to particular historical periods. === Classical mechanics === The rigoro...

eulB

gee thanks dude

i can't wait until i learn how to use the internet one day

Captain Bohemian

5:41 PM

@eulB I don't know the link, but I have downloaded that file. I don't know if PDF can be uploaded here.

0celo7

@ACuriousMind not GR

It does show up in geometric analysis, which is aggravating.

eulB

@CaptainBohemian oh

i just skimmed through it

that's not what i wanted it just says stuff i already know about and not in any detail

@ACuriousMind thanks just what i wanted.

@CaptainBohemian i take that back there are some things in there that i want to read actually.

thanks

Captain Bohemian

@eulB The first time I touched the term mathematical physics is when I told my research advisor what I am interested in, and he said my interest is mathematical physics; that time I hesitated to admit because I think what I am really interested in is physics, not mathematics.

But gradually I perceive the subjects of physics I am greatly interested in all contain a lot of mathematics. Then I think probably those themes are the so-called mathematical physics.

Nehal Samee

@ACuriousMind sorry .. I didn't understand if you got my point ... Will acceleration be $g-a$ when lift moves up and $g+a$ when lift moves down , while ball is thrown up in both ...?

rob

5:59 PM

6

A: Somebody scraped our answers and sold them as a book

I'm the creator of these books. Firstly I should say it was not my intention to break any copyright or cause any ill feeling among contributors. When initially evaluating submitting the books to Amazon/Google/iTunes I checked the terms of the license and checked with Stack Overflow and believe I ...

Hmm, interesting.

Emilio Pisanty

@rob disingenuous at parts, though

> When initially evaluating [...] I checked the terms of the license

maybe he read the summary and missed the part where it said "This is a human-readable summary of (and not a substitute for) the license" and neglected to actually read the license?

But yes, definitely a positive development

0celo7

@ACuriousMind So I saw a post on r/de that said Tom Ratsel

but that sub is 99% ironic so it's hard to tell

s. patroller

@EmilioPisanty how is that supposed to be "positive"?

Emilio Pisanty

@s.patroller well, he responded, for one

he realized that there are copies with hyperlinks stripped and he realized that that's not OK and he's attempting to fix that

(or claims to, at the very least)

s. patroller

6:18 PM

sorry tl;dr

bolbteppa

That's hilarious

Someone made these questions into a terribly-formatted book

rob

@EmilioPisanty If his first paragraph had ended in "believed" rather than "believe," that would have been a pretty good mea culpa. We'll have to see what happens, though.

@bolbteppa (5!)!

Are you sure

6:29 PM

Nowadays are books still sellable? I see more and more bookstores in my surrounding are closed probably because more and more people prefer to find information from web rather than books.

Emilio Pisanty

@rob indeed

dmckee

@rob I saying determinedly optimistic on the matter for now.

rob

@dmckee Agreed. If Mr. Duckett were going to do his best to make things right, it would like that Meta response.

Emilio Pisanty

@dmckee I saying super grammatical for now

=P

dmckee

And on thinking about it for a while I concluded that a careful curation could represent an added value that would justify the sort of price that you usually find on a paperback book.

Emilio Pisanty

6:31 PM

rob too.

dmckee

Alas the curaction that Mr. Duckett has actually done is ... laughable.

Emilio Pisanty

curaction?

OK, I'll stop now.

rob

@EmilioPisanty A contraction of "curation" and "inaction"?

Emilio Pisanty

@rob I hadn't read the first comment and read that as a mistype of "correction"

but

@dmckee yes

@dmckee and yes.

dmckee

@rob ::chuckles::

Very apropos.

But I sure can't type straight today.

Captain Bohemian

6:33 PM

even newspapers become cheaper than before probably because fewer and fewer people read them; most people nowadays read news on web.

Emilio Pisanty

Indeed, a careful curation would be a very good way to get around the oft-bemoaned feature that we have a bunch of incredibly high-value answers sitting in rather undiscoverable corners with criminally low scores.

2

dmckee

@CaptainBohemian Lower readership apply downward pressure on the price, but it would simple result in papers going out of business if they still had the staffing costs that they used to carry.

Automation is what allows them to follow that pressure down.

Emilio Pisanty

@dmckee not the only important viewpoint ;-)

David Simon testifying about the future of Newspapers

►

I'm reasonably certain I've seen other extremely cogent expositions of that viewpoint by Simon but I can't be arsed to find them.

but a half-hour or two listening to David Simon speak is rarely wasted.

Captain Bohemian

I am that kind of person who originally didn't read newspapers much even before the tedency that people started to read more on web than newspapers.

because articles on newspapers are mostly regarding people in politics and in the recreation circle.

Emilio Pisanty

7:20 PM

this is mystifying, though - a five-star review saying "An excellent book" on the Mathematica one

s. patroller

@EmilioPisanty thanks for sharing

Emilio Pisanty

@s.patroller no worries

seriously, watch more David Simon

David Simon on why he created The Wire | Observer Ideas

►

this in particular

also this youtube.com/watch?v=nRt46W3k-qw and this youtube.com/watch?v=DNttT7hDKsk

s. patroller

7:38 PM

interesting...

vzn

8:35 PM

@Slereah joking? theres a lot of cool connections betwen zeta fn and math physics (mostly qm) now, decades worth, active area of research, have collected a bunch of links :)

Emilio Pisanty

1

Q: Why polarization filter do not dim the light completely?

In a circle there's infinite amount of degrees (eg. 0 deg, 0.00000000000...1 deg etc.) In a ground school we are thought that there's 360 degrees in a circle. A landscape behind my window is incoherent light source, so it randomly emits photons with all polarization directions. When I put a pol...

quantum-mechanics electromagnetism electromagnetic-radiation classical-electrodynamics polarization

Somebody competent please answer this asap

Mithrandir24601

@EmilioPisanty does "perfect filters don't exist" count as a long enough answer? :P

Emilio Pisanty

@Mithrandir24601 that's not the core question

Mithrandir24601

@EmilioPisanty Aww, you're no fun :P

dmckee

@EmilioPisanty Can we make that the unofficial motto of the h bar? Please?

ACuriousMind

8:52 PM

@EmilioPisanty On it

dmckee

@EmilioPisanty Finally found time to listen to that and I should clarify. They staffing costs I was talking about were the ones in the bowels of the building, rather than the reporting staff.

The printing costs used to be a very big part of the pie.

You can pool reporting cost in the sense of overseas operations, but the actual reporting is their core value and the cost that can't be cut while staying in business.

Emilio Pisanty

@dmckee sure, why not

I don't normally see time-critical questions on this chat

But why not

Emilio Pisanty

9:32 PM

@ACuriousMind grand

G. Bergeron

9:45 PM

@Mithrandir24601 Even a perfect filter would not work like that...

Mithrandir24601

@G.Bergeron Yeah, it was just a not-overly-serious comment (although it's generally worth repeating that perfect filters just don't exist anyway)