The h Bar

Secret

08:02

Axion models were now further constrained by new laboratory experiments

Hmm... It appears we can now trap electrons with sound waves

John Rennie

@Secret: happy now?

Secret

yup, he failed to answer the questions, thus the discussion ended as expected

(It's not really that long...?)

Anyway, I am suspecting a bot net:

15 mins ago, by internet-entity

damn bot

nature.com/articles/nature24465

There's is really nothing much going on in physics recently...

Mithrandir24601

08:33

@Secret Erm... IBM now have "an operational prototype 50 qubit processor"... Does that count?

Secret

Well, I don't know, various news items in the quantum computing and condensed matter sector also have results of similar (insert suitable word for perceived significance). The news in recent weeks felt more like "research as usual" rather than really cutting edge stuff.

But perhaps that's a good trend, you would rather want the science community to be more evenly spread than to focus mainly on high impact things

Mithrandir24601

Does anyone care that the number of qubits in a working processor has (roughly) tripled in the space of a few months? and is now much closer to the point where it could actually beat a classical computer at something?

Secret

It's good progress, but for it to really matter to us computational chemists, it has to reach at least 1000 qubits

It is also encouraging to see as the number of qubits increases, quantum simulators are also becoming better at simulating many body quantum systems

Mithrandir24601

... If anything, that's probably an optimistic boundary. Put it this way: If things were going at the rate they had been, you maybe would have seen that in about a decade or so, while if it continues at the rate it's been at for the past year, it'll happen in about 2-3 years. Granted, it'll probably be somewhere between those two numbers, but it was just so unexpected - IBM kept talking about things like '50 qubits in a few years', not by November

Although, it's important to note that the performance of the individual qubits is claimed to be the same as the smaller chips, which is good :)

And it's not just about the number of qubits either - it seems to be a necessity, but their graph is quite sparsely connected, so there's the usual question of "how many (logical) qubits would you actually have if you used your processor to get a fully connected graph?"

John Rennie

08:53

@Mithrandir24601 I think there is an element of quantum computing fatigue. It's been hyped for so long we all tend to be a bit sceptical. When the IBM and Google quantum computers start doing useful calculations I'm sure the excitement will build again.

Mithrandir24601

@JohnRennie Especially considering that IBM have also recently said that they found a better way of simulating it classically, so quantum advantage is that bit further away (as opposed to the 50 qubit mark, which was the magic number a month or two ago)

Secret

I wonder where are we in the graph, there's definitely stuff happening steadily in the background

Mithrandir24601

09:10

I'm hoping we're in the productivity section, but I doubt it :P

John Rennie

09:27

We are gradually being enlightened though :-)

Emilio Pisanty

10:13

@peterh Thanks again for voting to reopen poor questions that harm the site.

Shing

hey guys, I am interested in quantum thermodynamics, would anyone be kind enough to recommend me some papers as a good starting point?

Emilio Pisanty

@Shing top three papers here scholar.google.co.uk/… are a good place to start

Shing

@EmilioPisanty thanks, I will check them out :)

skullpatrol

there are lots of references here also :-)

CooperCape

So in $LaTeX$ you can use \hline in tables to create a horizontal line but is there a vertical version and where do I put it?

Emilio Pisanty

10:25

@CooperCape \begin{tabular}{|c|c|c|}

but

the LaTeX typography purists will tell you not to add lines, either vertical or horizontal, to tables, unless they're absolutely necessary

and for the bulk of cases, they're right

CooperCape

Ahh okay...

It's not for a question though it's for my practical write up and I think it looks neater like that

idk though

Emilio Pisanty

how does it look like now?

and what's in the table?

data?

something else?

CooperCape

Yeah data

haven't managed to stick this tabular in yet

does it go under \begin{array} or replace?

Currently it says "Unknown environment 'tabular'"

but that's just me doing it on SE sight so might not be on here

Emilio Pisanty

@CooperCape then you only need one horizontal line below the heading and one vertical line to the right of the index (if there is one)

everything else will just add clutter and make the table harder to read in the long term

it sounds like a good idea at first

but it rarely is

CooperCape

Yeah that's what I wanted

I didn't wanted spacing inbetween just outsides

Emilio Pisanty

10:30

@CooperCape you're putting tables with array?

X|

CooperCape

I'm a latex scrub soz :c

how would you recommend?

Emilio Pisanty

@CooperCape what documentclass are you using, and what system are you compiling on?

i.e. operating system, TeX distribution, and tex/latex/pdflatex compiler you're using

(for LaTeX newbies: all of this is important information and you should have it available when you're asking for help debugging. If any of those questions is unclear, ask now.)

CooperCape

I bring latex newbie to a whole new level... Was just gonna screenshot it off intepreter into word document tbh

Don't have to do write ups... ever... really currently

Emilio Pisanty

@CooperCape don't fall into an XY problem. What is it you want to do?

CooperCape

Ahh okay sorry :c

Basically I just want to create a table in LaTex cause it looks neat

Emilio Pisanty

10:40

@CooperCape are you making your entire document in LaTeX?

or are you writing a document elsewhere and you're importing your table from LaTeX into somewhere else?

CooperCape

the latter

Emilio Pisanty

so what is that somewhere else, and how are you importing it there?

CooperCape

along with some equations but I can handle those

Preferably a word document and I was just gonna screenshot the output into the word document

Emilio Pisanty

@CooperCape you want to do a table in LaTeX because you think it looks nice, and then you're going to take a screenshot and paste that into a word document, and you think that that's going to look nicer than doing the table natively in word?

=|

=| =|

CooperCape

Had a feeling you might say that

Emilio Pisanty

10:42

=| =| =|

CooperCape

yeah fair

(I feel like I've wasted your time)

Emilio Pisanty

@CooperCape If I've convinced you away from an idea that's that bad, then it wasn't wasted

CooperCape

"that's that bad"... ... ... oops...

Emilio Pisanty

@CooperCape srsly tho, never screenshot stuff unless there's really no other way

you want people to be able to copy-paste your data

it needs to be machine readable

CooperCape

It's not for anything even remotely important(ish). Just a write-up of a pracitcal investigation we did for a school project that isn't going anywhere past being printed off and handed into the exam board.

But I do understand what you're getting at... :p

Emilio Pisanty

10:47

@CooperCape then do it natively in word and it will look just fine for the purpose

CooperCape

Sounds like a shout...

Mithrandir24601

Or you could do the whole thing in Latex

Emilio Pisanty

@CooperCape no animosity intended at all ;-)

@CooperCape The overarching theme is that all the schoolwork you've been given isn't designed to get you to produce that piece of work. It is designed to get you to learn the tools to produce quality work, and to develop your own processes to produce quality work.

CooperCape

Didn't think it was... sorry for the colloquialisms just means good idea

Emilio Pisanty

when they teach you theorems and proofs, it's not so you'll remember those theorems and their proofs for all eternity, it's so you'll understand what it really means for something to be a theorem and what it means for something to be a proof, and how to design and build both of them

when they ask you to write lab reports, it's so you'll be able to write experimental sections in papers and technical reports in industry

& so on

when they ask you to produce nicely-formatted written work, take it as an opportunity to learn to produce nicely-formatted work

CooperCape

10:50

eeek yeah... got a long way to go before I write anything near important :p

Gotta love a nice format though...

Emilio Pisanty

hacks like that are mostly you cheating yourself out of your own learning

;-)

Mockingbird

11:53

@EmilioPisanty What does envariance mean in QM?

ACuriousMind

@Mockingbird Do you mean invariance? If so, that's far too little context to give a useful answer.

Mockingbird

@ACuriousMind No, see this paper cds.cern.ch/record/640029/files/0308163.pdf

ACuriousMind

@Mockingbird What makes you think Emilio can explain the notion of envariance better than that paper, then? Also, I'd caution that neither Quantum Darwinism nor envariance are mainstream quantum-mechanical context, so take that paper as what it is - a proposal, not firmly established science.

That is, in standard QM, the term "envariance" does not actually mean anything.

It is only in Zurek's framework that that term occurs.

skullpatrol

12:08

At the bottom of the abstract he explains...

"I review key ideas of quantum Darwinism and investigate its connections with the environment – assisted invariance or envariance, a recently identified symmetry exhibited by pairs of entangled quantum systems that is responsible for the emergence of probability (allowing, in particular, a completely quantum derivation of the Born’s rule) within the wholly quantum Universe."

Mockingbird

@ACuriousMind Okay, I got it.

John Rennie

12:57

I've just bought a laptop, a powerful laptop, for £54.78. I don't need another laptop, but, well, it was a bargain! A hell of a bargain actually :-) Now WTF am I going to do with it?

skullpatrol

13:12

resell it for a profit?

or

keep it and sell one of your others...

Semiclassical

Four different words in QM (from most standard to least): Variance, invariance, equivariance, envariance

First two are obvious, third shows up in pilot wave discussions, and I dunno about envariance

Anonymous

@JohnRennie Uh, you could use it as furniture :)

Sid

@JohnRennie Give it away? Charity? :P

Anonymous

Like @0celo7 does with his books

Semiclassical

Lol, Googling the word envariance brings up this hit: books.google.com/…

Anonymous

13:25

@Sid Yeah, that would be best :P

Semiclassical

“The Universs is an enlightenment machine “

skullpatrol

The term "inequality" symbol used to bother me when it included the equals sign :P

Anonymous

@Sid Let us both visit him at his house in UK. We will get a few dozen laptops for free (charity)

Sid

@Blue Deal! :P

Anonymous

@Semiclassical lol

Anonymous

13:27

Even the Buddhism SE site is full of QM questions

ACuriousMind

@Blue what

Anonymous

buddhism.stackexchange.com/search?q=quantum+mechanics

Sid

@Blue we will introduce ourselves as a couple of internet strangers who want the laptops. :P

Anonymous

@ACuriousMind I mean it does have quite a few questions related to QM XD

Anonymous

0

A: What are the similarities between quantum physics and buddism?

Quantum physics deals with things that are a subset of Rupa Vedanä Saññä Sankhara Viññana And it tries to understand what happens to these in a subatomic level. Buddhism deals with the understanding of Four Noble Truths of which the First Noble Truth is, Rupa Vedanä Saññä Sankhara ...

Anonymous

13:29

2

A: What are the similarities between quantum physics and buddism?

The Buddha, in aiming to comprehend suffering, from a psychological point of view, sought to understand experience as it actually is. The scientific method, aims to limit itself to the understanding of experience as it actually is, whilst not focusing solely on the psychological. Whilst the Buddh...

Anonymous

6

A: If the law of Karma is a natural law like Newton's law?

Newton's laws are simple, they model of a simplified universe. They describes the relationship between "force" and the motion of a single object in an otherwise-empty universe. If you consider two objects in the universe then there are a bunch of other laws: the law of gravity, laws of electrost...

skullpatrol

stahp! :P

Semiclassical

Tbf that’s not a new impulse. (Some) people were really into that during the seventies

Anonymous

Atleast a dozen of them

Anonymous

lol

Semiclassical

13:31

Fun fact, there’s a book about that era with the (tongue-in-cheek!) title How The Hippies Saved Physics

ACuriousMind

Well, iirc Schrödinger (or was it Heisenberg) liked Buddhism too, and it was no accident Oppenheimer quoted from the Bhagavad Gita after the detonation of the atomic bomb, though I guess that's more Hindu than Buddhist

So it's not just the seventies

Semiclassical

The author visited our uni for a colloquium talk a few weeks ago, which was neat

fair

ACuriousMind

@Blue It appears there's only one question really asking about quantum mechanics, and all the answers making reference to more or less actual quantum mechanics are from the same user

There are only three questions containing the word "quantum", so I wouldn't say buddhism.SE is "full" of these :P

skullpatrol

Buddha literally means enlightened one, a knower.

Mithrandir24601

@skullpatrol some inequalities are just more unequal than others :P

Semiclassical

13:35

i do think the seventies were a high point for this kind of thing

See eg books like The Dancing Wu Li Masters and The Tao of Physics

I’ll admit, I find such comparisons to be distasteful at this point. They tell you more about the speaker than the subject

Anonymous

@ACuriousMind Yeah, I was just over-exaggerating. :D There are some similar questions in Islam SE, Hinduism SE, etc too

Semiclassical

Is linear algebra Buddhist? :P

ACuriousMind

@Blue Yeah, all around the same amount for all religion sites. Interestingly, Christianity.SE seems to be strictest about closing these questions.

skullpatrol

@Mithrandir24601 yeah, that Harriot was a smart cookie :P

Semiclassical

More broadly, the comparison to Eastern religions is always at the level of concepts not of math

Anonymous

13:40

@Semiclassical That's a strange question

skullpatrol

@Semiclassical what about zero?

Anonymous

lol

Semiclassical

I’m being a bit silly

skullpatrol

me too :P

Semiclassical

But, there’s a reason why Heisenberg is understood to have invented matrix mexhanics

Lagranian

13:42

I wonder how this gamma decay works

can someone explain it?

ACuriousMind

Linear algebra Buddhist exam: 1. Meditate on this matrix and its determinant for five hours. 2. Realize all math is suffering. 3. Reach nirvana.

2

Semiclassical

lol

Sid

@ACuriousMind I wonder if someone would keep a timer to time exactly 5 hours for their meditation. :P

skullpatrol

@Semiclassical that's where the infamous von neumann quote came from

Semiclassical

I can sorta understand pointing to Eastern religions as ‘case studies’ for non-classical concepts, but QM is not just “spooky concepts wooo” but an actual computational formalism

ACuriousMind

13:45

@Sid Usually, someone else will keep the timer and ring some impressive gong when the time's up :P

Semiclassical

@skullpatrol which?

skullpatrol

in math we don't understand anything

Anonymous

Most quotes by famous mathematicians are silly anyway

Anonymous

Neumann's quote doesn't make much sense but sounds good :P

Semiclassical

I thought the Neumann quote was in the context of someone asking about the method of characteristics in PDEs

skullpatrol

13:48

yes. it was

ACuriousMind

@Blue Oh, I think it makes a lot of sense - to me it makes the point that "understanding" often simply comes with time and practice rather than sudden leaps of insight, but that we somehow tend to only value the latter as "understanding".

skullpatrol

@Semiclassical the reference came from that book

Semiclassical

ahhh

skullpatrol

I did some digging, and emailed the "source." :P

Semiclassical

But mostly I don’t like the leap from quantum weirdness to quantum mysticism

At least insofar as the lay person tends to infer that somehow quantum physics = telekinesis is real

(Though tbf nonlocal correlations are pretty d*** weird)

Anonymous

13:53

@ACuriousMind Yeah. But that is your interpretation. If we read it literally it just says in math we never understand things but just get used to them. The meaning of such quotes are almost always open to debate. And only a few particular interpretations of such quotes makes sense (which not everybody can deduce). Someone who doesn't like mathematics would take it in it's literal sense, and hearing great mathematicians making such claims, lose further interest in mathematics.

skullpatrol

44

Q: What are some interpretations of Von Neumann's quote?

John Von Neumann once said to Felix Smith, "Young man, in mathematics you don't understand things. You just get used to them." This was a response to Smith's fear about the method of characteristics. Did he mean that with experience and practice, one obtains understanding?

soft-question

Anonymous

For example, a few months back someone quoted Feynman saying we don't understand QM or something like that

skullpatrol

"solf" indeed :P

ACuriousMind

@Blue So? I don't think someone who hears a quote that's non-sensical on the surface and takes it literally to then condemn the entire field based on that quote is a great loss for mathematics :P

Semiclassical

@Blue to turn my earlier point around a bit, how the quote is read often tells you more about the reader than about von Neumann

ACuriousMind

13:56

^that

skullpatrol

we ALL agree it is a soft-question, yes?

Anonymous

@Semiclassical I agree. But I'm still not very comfortable with people continuously using quotes like "We don't understand X" and all that.

Anonymous

Feynman, not one to beat around the bush, comes right out in his lectures and states "We really don't know what energy is"

Anonymous

4

A: What is all energy made of?

For the longest time, even as a well seasoned engineer, I believed I understood what energy is, but seemed to think of it as a 'thing' not much different than matter. Of course I realized it was very different - not something I could hold in my hand. I realize now it was not all my fault having t...

Semiclassical

Which isn’t really different than my earlier statement, insofar as we’re not really concerned with how people understand von Neumann but with how they use it rhetorically

Anonymous

14:00

For example that answer. It might be so misleading.

Semiclassical

Well

Anonymous

"So Feynman changed my world view of energy from a 'thing' to more of a concept on the same level as 'time'. Don't feel bad if you don't know what energy is. No one else has answered that question yet!"

Anonymous

Cringes

Anonymous

:P

Semiclassical

I think it’s fair to make the point that, as useful as the energy concept is, it’s nit something we ultimately measure directly

We measure stuff like position, or wavelength, or velocity

ACuriousMind

14:03

@Semiclassical Sure, but we know what it is - an abstract concept instead of a measurable entity. The Feynman quote is indeed simply wrong in that it implies there's some sort of "truth" to energy that we don't know.

In the end, it's just Feynman saying something to get people's attention :P

Semiclassical

Sure. It’s an abstract principle that constrains measurements

Though ‘constrains’ is perhaps too strict a word. Regulates?

skullpatrol

like "length" constrains the "ruler"?

ACuriousMind

I wouldn't stress the phrasing. It's a conserved quantity that we can compute from measurements and conserved quantities are useful no matter their ontological status.

Semiclassical

Well, constrains makes sense in the classical context insofar as, if you know the total energy and instantaneous position of a particle undergoing SHM, then you know its instantaneous speed as well

Slereah

Henneaux isn't a very fun read

It's no bike rides and balloons

Semiclassical

14:11

By contrast you can’t say that in QM. But we still expect to have certain statistical relations between the such measurements

ACuriousMind

@Slereah You reading QoGS or something else?

Slereah

No I'm reading his romance novel

The Gauge System's Wife

skullpatrol

lol

ACuriousMind

@Slereah :P He's written enough papers you could've been reading one of these

Slereah

he's not very big on examples

At least in the first chapter

ACuriousMind

14:19

@Slereah The examples are in the exercises

Slereah

even worse!

ACuriousMind

That is, Hennaux and Teitelboim let you do the work :P

Slereah

Hey I'm the one paying for the book!

Let them do the work!

ACuriousMind

Many of these exercises are really interesting and I wished they had included more of them into the actual text

0celo7

Exercises in monographs are truly like f****** EA and their crap

Slereah

14:46

What's a proof that there's no homeomorphism between $\mathbb{R}^n$ and $\mathbb{R}^m$, anyway

for $n \neq m$

or open sets of them (that aren't the empty set)

0celo7

invariance of domain

or homology

Slereah

Invariance of domain

Invariance of domain is a theorem in topology about homeomorphic subsets of Euclidean space Rn. It states: If U is an open subset of Rn and f : U → Rn is an injective continuous map, then V = f(U) is open and f is a homeomorphism between U and V. The theorem and its proof are due to L. E. J. Brouwer, published in 1912. The proof uses tools of algebraic topology, notably the Brouwer fixed point theorem. == Notes == The conclusion of the theorem can equivalently be formulated as: "f is an open map". Normally, to check that f is a homeomorphism, one would have to verify that both f and its inverse...

indeed

Why does wikipedia write $\boldsymbol{R}^n$

91

Q: Elementary proof that $\mathbb{R}^n$ is not homeomorphic to $\mathbb{R}^m$

It is very elementary to show that $\mathbb{R}$ isn't homeomorphic to $\mathbb{R}^m$ for $m>1$: subtract a point and use the fact that connectedness is a homeomorphism invariant. Along similar lines, you can show that $\mathbb{R^2}$ isn't homeomorphic to $\mathbb{R}^m$ for $m>2$ by subtracting a...

general-topology

2

Q: Homeomorphic manifolds have the same dimension

So I want to prove: If two manifolds $M$ and $N$ are homeomorphic then $dim(M) = m = n = dim(N)$. My idea was to use the property of the manifolds that they are locally homeomorphic to the $\mathbb{R}^m$ and $\mathbb{R}^n$ respectively. So I want to take an open subset $U \subset M$ which is hom...

general-topology algebraic-topology manifolds homology-cohomology

there we go

0celo7

@Slereah Homology is easier

Slereah

I still don't know what a homology is

to my shame

0celo7

15:03

it's a functor

Slereah

Isn't everything a functor

or a category

is there a category of functors

0celo7

that's what a 2-category is

Slereah

Category theory is basically like the old set theory of Russell

With hierarchies of sets

skullpatrol

15:20

Young man, with von Neumann you don't interpret quotes, you just get used to them. — Meni Rosenfeld Nov 22 '16 at 12:13

Slereah

heyooo

skullpatrol

:-D

0celo7

15:37

@Blue @Phase I propose we do a reading group on amazon.com/Multiple-Integrals-Calculus-Variations-Mathematics/…

I want to learn distributional regularity theory

Slereah

Man Lee has a lot of topology in it

Which makes sense for a book on topological manifolds, I suppose

But also a lot of point set topology

Slereah

15:53

"Finally, consider the doughnut surface $D$"

Is "torus" too advanced for this book

Slereah

16:19

"The torus $\mathbb{T}^2$ is homeomorphic to the doughnut surface $D$"

Oh I guess they are different things!

0celo7

they probably mean $\Bbb R^2/\Bbb Z^2$ vs. the usual donut

Slereah

The doughnut is the solid of revolution made via a circle

Torus is $S \times S$

ACuriousMind

16:43

@Lagranian Since I just squished another sock of yours, it appears your "apology" was not at all sincere. You are no longer welcome in this chat room.

@Slereah But what is the solid of revolution of a surface $X$ if not $X\times S^1$?

Slereah

you'll have to ask Lee

ACuriousMind

I mean, how would you actually define it other than that?

Slereah

Well it's the topology of the graph of a function versus the product topology, I think

0celo7

@ACuriousMind Is that an official stance?

@ACuriousMind If "is" means "homeomorphic to" then that's exactly what Sam said.

ACuriousMind

@0celo7 "is" means "is defined as" there

skullpatrol

16:54

or "exists"

:-)

0celo7

@ACuriousMind Well, it's that as a set, but the topology is inherited from the ambient space.

ACuriousMind

@0celo7 In what sense "official"? If this user shows up again, I'll kick them out. They're abusing our good will and show not the slightest remorse about it.

@0celo7 Ah, I see

skullpatrol

Good Will hunting?

:P

Slereah

you can tell it's an old fashioned book

Because he uses doughnut

instead of donut

0celo7

@ACuriousMind And actually you might have some weirdness near cusps where it’s no longer that.

S^2 is a surface of revolution but not a product.

Emilio Pisanty

17:12

@ACuriousMind is that related to any posts I might've seen lately?

John Rennie

Is there a closed form solution for the metric of a thin ring of matter?

A thin ring that isn't a black hole I mean, so not the Kerr metric.

Emilio Pisanty

@JohnRennie what's wrong with the Kerr metric but putting a tarpaulin over the singular bits?

Phase

@0celo7 Im not going down without a fight

I've asked for maths syllabuses, and having seen them there's barely anything there I havent already done aside from some of the analysis

Slereah

Do you mean like

a torus?

of matter

Emilio Pisanty

@0celo7 there's several commercial suppliers

it's definitely a product

=P

0celo7

17:15

Lmao

Phase

the algebra has only gotten as far as Equivalence relations n shieet, and I'm gonna pester them all for assessment materials to prove I can do it + my course leader is gonna talk to the maths course leader

wish me luck innit

John Rennie

@Slereah yes

Slereah

I can't really think of one, although it will have like the...

Papapetrou metric?

I think

Since that's the generic axisymmetric metric

skullpatrol

@Phase good luck

Phase

@skullpatrol thanks bby

skullpatrol

17:18

cya

Slereah

I don't think people tried to do a lot of torus metrics because there isn't really any astrophysical object with that shape

John Rennie

@Slereah thanks, yes, though simplifying the general metric to a torus is going to be a challenge :-)

Slereah

well, if that helps

the outside of the torus will have the tomimatsu metric

I think so, anyway?

not sure if the shell theorem works for non-spherical symmetries

probably not

John Rennie

@Slereah have you seen this book?

I stumbled over it while Googling for the Tomimatsu metric. Amongst other things it has a compilation of dozens of metrics.

Slereah

I did not

Tomimatsu metric is the generic metric for a vacuum axisymmetric stationary spacetime

of which the Kerr metric is an example

thinking about it, what I said is probably true?

Take the spacetime with the torus

Remove the torus part from the spacetime

you get a vacuum spacetime

John Rennie

17:27

Slereah

which is still axisymmetric

John Rennie

Flippin' 'eck!

Slereah

yeah it's ugly

the difference with the Kerr metric is the multipolar moment, IIRC

ACuriousMind

@EmilioPisanty Yup

CooperCape

17:44

Oh my goodness I'm such a fool!

(language toned down from irl)

Spent an hour wondering why my js code wasn't working... it was because I had a line saying var findplus = inpt.search("+");

And... I forgot to put a slash in front of the plus

I think

Okay so putting a slash there doesn't help smh

John Rennie

@CooperCape is that a regular expression search?

CooperCape

Yeah it is...

John Rennie

Presumable you need \+ then?

CooperCape

I tried that but to no avail?

Currently I have `<script>
function calculate() {
var inpt = document.getElementById("example").value;
document.getElementById("example1").innerHTML = inpt;
var findx = inpt.search("x");
var findeq = inpt.search("\=");
var findplus = inpt.search("\+");
document.getElementById("example2").innerHTML = findeq;
}
</script>`

ACuriousMind

@CooperCape Did you put a slash or a backslash? :P

CooperCape

17:49

backslash...

the equals sign doesn't need one but...

was testing

the document.getElementById("example2").innerHTML = findeq; doesn't output anything if it has the var findplus = inpt.search("\+"); line in it...

ACuriousMind

I don't know js, I have no idea what's happening there in the first place :P

CooperCape

Basically just practicing by making a program that doesn't maths calcs n' stuff

And like the find (insert char here) is finding the position of the chararcter in the string

or should be

I'm a bit of a newbie though so...

Tanner Swett

I'm wondering what liquid-like properties Silly Putty has and which ones it does not have.

CooperCape

Okay so really weird I fixed it by changing var findplus = inpt.search("\+"); to var findplus = inpt.search("\\+");

Phase

Isn't silly putty a form of non newtonian fluid?

CooperCape

17:53

Maybe \+ means something to some code happening somewhere

Tanner Swett

The molecules in a glass of water are mobile: one molecule may, given enough time, move from one side of the glass to the other. The atoms in a chunk of iron, though, are immobile; they just stay in one place.

Phase

Or am I mixing up silly putty with something else

Tanner Swett

How about the molecules in Silly Putty, are they mobile or immobile?

Silly Putty contains multiple different types of molecules; are some of them mobile and some of them not?

John Rennie

@TannerSwett as I recall it is based on a silicone elastomer, usully with some form of filler.

So the molecules in it are high molecular weight silicone polymers

ACuriousMind

@CooperCape Ohhh, I know what's happening :D

CooperCape

17:56

Oh yeah? I haven't come across this before sooooo... ;p

ACuriousMind

Or, at least, I guess I know - the RegEx is supposed to be \+. But `\` is not only a special character in RegEx, but already in JS string - it escapes whateer is after it.

John Rennie

@TannerSwett On the long timescale the polymers will flow, but because they are very large molecules and entangled with each other they flow only very slowly. That's why silly putty flows so slowly. On the short term the polymer molecules can be deformed, just like rubber, which is why it behaves elastically.

Slereah

a bunch of axisymmetric stationary and non-vacuum solutions :

I dunno if any of them are a torus

ACuriousMind

So when you write "\+" that escapes the + on the level of the code, and + is passed to the function

Slereah

I don't think so

ACuriousMind

17:59

When you write "\\+", that escapes the second backslash on the level of the code, leading to \+ being passed to the RegEx.

Tanner Swett

@JohnRennie That makes sense. So the molecules will spontaneously move around just like water molecules do, but only extremely slowly, since the molecules are very large and tangled together?

CooperCape

@ACuriousMind Ahhhh! Now you say that I think I recall something similar with str.replaceAll("\\s",...) having to have \\s so regex doesn't booboo :D Thanks a bunch that's pretty interesting (but annoying gah!)

John Rennie

@TannerSwett Yes

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