The h Bar

2:33 AM

$=\frac{1}{2}(\lvert 0L\rangle + \lvert 0R\rangle + \lvert 1L\rangle - \lvert 1R\rangle)$

ok that's clever, so the double slit apparatus will get two different interference patterns at 50:50 which adds up to no interference

thus in agreement with no communication theorem, the interference pattern at the double slit will not be changed when the qubit is measured

Your marble experiment does not violate Bell's Theorem (or any other theorem of classical probability) and is therefore quite entirely irrelevant to the issue here. The wave function does not count as a hidden variable because it cannot *determinstically predict the outcomes of all measurements. In your marble experiment, we can easily explain the result by invoking some determinstic (though mysterious) force. — WillO Apr 29 '17 at 15:47

hmmm... how can that be explained by hidden variables?

> Now compare the above with the following qualitative "watered down" analogy

We prepared two marbles A and B, both colorless. Each carry an instruction of probability which reads as:

When touched, turn into (R)ed rA amount of the time or (Y)ellow yA amount of the time

similarly for B. Should we decide to touch either of them, they will change color, and we found there is no correlation between the colors R and Y.

We brought the marbles close together, leave that for some known amount of time t. The two marbles are still colorless.

2:55 AM

I sometimes don't understand how to visualise bell's inequality...

I mean, the things can be observed for any entangled state are the following:

1. Before measurement, the outcomes don't exists in some form in the system

2. After measurement, when viewed in the perspective of the subsystems in isolation, they will get a statistical mixture of outcomes as governed by the reduced density matrices

3. Now when the outcomes are put together and compared, the correlation is visible

so how is that differ from:

1. The marbles don't have any color before you touch them

2. Viewed the outcomes in isolation, a collection of outcomes of touching many marbles A will give reds and yellows according to some probability distribution

3. When the outcomes of the two marbles are compared together, there is a clear correlation of reds and yellows observed

BAYMAX

.

Hi chat!

I had a query on flux?

where $q$ is the velocity vector(of the fluid)

$c_{p}$ is the specific heat at constant pressure

$K$ is the thermal conductivity of the fluid

How can I get the relations $1,2,3$?

3:16 AM

Flux is defined to be the amount of outflow of something through a surface. You have the $\rho$ as the stuff to be flowing out, and the surface defined by the normal vectors, you then dot the normal vector with the vector field that is the flow to find the portion that is flowing out

which is why you have $\rho (\hat{q} \cdot \hat{n})dS$ for each surface element $S$

BAYMAX

3:31 AM

Sorry for typo, it's $u$, the amount of heat.

hmmm, I think I am missing something, isn't $Q = mc_p \Delta T$?

so your integral has a mass, a specific heat and heat flow (where it should be temperature)?

skullpatrol

3:55 AM

@dmckee congrats!

dmckee

Thanks. I've had the vote count for a long time, but today I got the number of answers up to spec.

"There is, however, no defensible reason to suppose that satisfaction of the preferences of the rich is more valuable than satisfaction of the preferences of the poor."

dmckee

I've been delayed because I don't like to right "So-n-so is right but there is a little bit I can add [...]" and anna v. and a couple of other people routinely beat me to the punch with perfevctly good answers.

My philosophy textbook underestimates my love of the free market

how free is the free market, it seems to be quite poor at regulating its own dynamics?

and one thing I never understood, why in stock markets we based the indexes on the future performance of companies instead of their present performance. Isn't it kinda gambling to base on the future which has not happened yet and hence highly uncertain?

in Economics, Jan 21 at 7:35, by Secret

Something about financial systems similar to the stock market I don't understand. Often the dividend investors will received and the value of a company will depend on how well it is expect to perform in the future. Why is value based on something that has yet to happen, it seems very risky to me?

4:15 AM

@Secret My philosophical thoughts always end up in nuclear war as the optimal solution

I'm kind of a pessimist

I am kinda too, we humans are simply too bad at solving big problems. It often give me a feeling that I want a total and clean genocide of all of us, wiping out every single human being and then Earth will be able to solve itself

I mean, just look at cherbonyl, it is literally an animal and plant haven now after that many years deserted by human beings

It really put us into perspective on how we are even worse than nuclear fallouts

I just think that ethical human interactions are impossible, hence we are a contradiction and shouldn't exist

feels bad man

skullpatrol

:(

And for me, killing all humans including myself is just a revenge against those two humans who hurt me in the past

you cannot kill a god without unravelling the universe

similarly, you cannot kill a concept without eliminating all its sources

I wish science one day will be so advanced that I can finally land that punch on that concept that made me suffer to this day silently

> karma houdini

It is really broken about this world that some bad can get away and died peacefully after they have wrecked the lifes of millions and destroys huge swaft of the environment

But I guess I don't need to worry, sociologists have already predicted that 2020 a social collapse will happen, and long before that, we are already in the 2nd dark ages

4:33 AM

wot

ramblings...

Sir Cumference

4:46 AM

@Secret I've noticed you have a habit of that, no offense

yeah, sometimes the software installation frustrate me a lot and that the h bar's tendency to get caught in conversation streams to the point that other users posts get overlooked makes me kind frustrated

That's the lockdown (or more accurately, phase locking as corrected by semiclassical)

h bar don't get that many phase locking before mid 2017 so I have no idea what is changing

it does give me an impression the chat is erractically ignoring people, without actually put anyone on ignore

also the following is strange:

in Mathematics, yesterday, by skullpatrol

Yesterday, both the math and physics rooms were quiet for 4 hours

it seems that the two chats are becoming more coupled

I am not sure if that is a good thing

While I am happy h bar has more diverse activity than before based on what ACM and others told me, this increase in the frequency of phase locking is really annoying

Sir Cumference

5:03 AM

@Secret I just don't think people want to read 4+ connected messages from a single user

@SirCumference actually, I am talking about the occassional new users who asked questions in the middle of a conversation stream, such as futurehistorican recently

but if you mean connected messages as those that are not necessary physically followed one by one in the chat transcript, then fine, it is a valid point

@BalarkaSen coarse geometry is so strange

those users are the ones who tend to have questions got overlooked

Sir Cumference

Are we talking about the same thing?

I thought you were responding to my comment about your ramblings

To clarify: You said about my habit, and I responded to you about how the rambles came about, which lead me to think about a phenomenon I have been seeing in h bar that is getting more frequent, but not related to me, and you suggest it is because peopel don'want to read 4+ messages from a single user, and I clarified I mean something related, but not me

here's an example:

Jan 24 at 18:13, by Hritik

Anyone on my question please ?

I have seen many newcomers asking questions in the middle of the conversation, and they often get easily overlooked

that is the phase locking phenomenon I am talking about

Why it is true that I might be the sole user who post long messages that follow one after another physically, there are newcomers who want to discuss about questions, but it took them 2 or 3 messages to get a response

and some of these are not help vampires, but they easily get lost in the conversation stream\

and thus... ignored by the chat

chat.stackexchange.com/…

grrr, ok fine, the statistics does not add up, I rest my case

5:17 AM

@Secret the help vampires are a real drag on chat unfortunately

not a frequent one, necessarily, but when they show up a lot it's annoying

@BalarkaSen the coarse category is so fucked that $\Bbb R$ and $\Bbb Z$ are isomorphic

@0celo7 wot

(i'm not disbelieving you, that's just gross)

@Semiclassical You might noticed this phenomenon more commonly in maths chat before 2017, but usually when new users first get on and ask questions, they tend to get overlooked easily. Only when they become frequent visitors so that they are treated like regulars, do their posts have a higher chance to get noticed by the chat

but then, it does not help sometimes there are waves of help vampires, so it is hard to tell them apart

@Semiclassical I have an abstract nonsense proof but I should probably work out an actual proof

kk

5:20 AM

the topology seminar at my school is the highest form of nonsense

I don't know what can be done to increase the exposure of newcomers while filtering the help vampires

on that note, I need to write up these HW solutions

modern point set topology

I got one of their bibles for free and am reading it

it's all kind of insane

solutions for my students HW i mean

@0celo7 my brain is now trying to envision the topology equivalent of a Jevohah's Witness trying to spread the good word of Category

@Semiclassical the insane thing is there's no topology

topology is too strong for these folks

they deal with coarse spaces and coarse maps (all put into a category to make things seem more abstract than they are)

the equivalence in the category is bornotopy, or coarse homotopy

5:24 AM

bornotopy

srsly?

$f:\Bbb R\to\Bbb Z$, $f(x)=\lfloor x\rfloor $ is such an equivalence

@Semiclassical yeah

"coarse equivalence" sounds less silly

bornologous is apparently also a word

@Semiclassical yes

Wikipedia says the name comes from Bourbaki

which just about figures

@Semiclassical coarse equivalence arises from a bornotopy, which is a bornologous map :)

5:26 AM

And people say particle physics has weird names for things.

@Semiclassical completely different context.

bornology is different from bornologous?

a bornologous space in the sense of Bourbaki is related to topological vector spaces

bornology is something in coarse geometry

them both having that obscure of a name in common seems like it can't be a coincidence, though

@Semiclassical born just means bounded in French

5:30 AM

hmm

okay, fair

bornotopy sounds like something out of QM though

that'd be a good fake meaning for it: a transformation which preserves Born's rule :P

@Semiclassical the only thing you need to know is that $C_c^\infty$ with its LF topology is bornologic, and then remember the various things that gives you for free

though if you can remember/care to remember that stuff, you don't need me telling you that

I certainly don't

lol

there is a dark world of non-Banach vector spaces out there

it's a mysterious black box that should be avoided

I'll just sit here and be happy with Hilbert space

@Semiclassical we had a debate in the topology seminar about "large" Hilbert spaces

there's a dark world of nonseparable Hilbert spaces

no one knows why they'd be interesting

5:34 AM

huh

nonseparable states, mmkay

nonseparable Hilbert spaces, no thanks

@Semiclassical basically the only interesting Hilbert spaces are $L^2$ on separable measure spaces (or subspaces thereof)

so in applications everything is separable

inb4 some von Neumann algebra person appears

"a wild algebraist appears!"

@Semiclassical von Neumann people are analysts

hmm

i'll take your word on it

actual analysts, not the kind of analysis geometers pretend to do

@Semiclassical the amazing thing is that these people are still figuring out matrices

skullpatrol

5:40 AM

@Secret careful pal, those kind of messages get flagged a lot by drive by users. In my experience in these chat rooms :-)

Meanwhile, I cannot see flags cause my rep is too low

@0celo7 wait what

@Semiclassical yes, for instance math.utk.edu/~nicoara/twisted.pdf

there's a need in quantum information theory for such things

hmm

Hadamard matrix

In mathematics, a Hadamard matrix, named after the French mathematician Jacques Hadamard, is a square matrix whose entries are either +1 or −1 and whose rows are mutually orthogonal. In geometric terms, this means that each pair of rows in a Hadamard matrix represents two perpendicular vectors, while in combinatorial terms, it means that each pair of rows has matching entries in exactly half of their columns and mismatched entries in the remaining columns. It is a consequence of this definition that the corresponding properties hold for columns as well as rows. The n-dimensional parallelotope spanned...

5:46 AM

yeah, i was about to say

i know those are linked to quantum information theory

so exotic variants of them showing up as well seems plausible

hmm, this is the first XKCD in a while that's elicited a laugh out loud from me:

link

that image was bigger than I expected :/

the hover is good

@Semiclassical well really when you think about it, $\Bbb R$ and $\Bbb Z$ being isomorphic in the coarse category is no different than $\Bbb R$ and $\{0\}$ being isomorphic in $\mathsf{hTop}$

although $\Bbb R$ and $\{0\}$ are not coarsely equivalent

i'm a just smile and nod

@Semiclassical also coarse structures are just the dual of uniform structures

for some value of those words...

@Semiclassical the original motivation was the analysis of manifolds too large to treat classically

so you replace the manifold with a discrete coarsely equivalent bounded geometry metric space and then study its coarse cohomology and K theory

if none of this makes sense, feel free to ignore. Not sure why I go to those seminars

the only phrase in there I recognize is K-theory

and I don't understand K-theory

sooo yeah

@Semiclassical me neither, but it's something I should learn...

not sure where to start though

5:58 AM

yeah

somehow it matters for some condensed matter people

problem is, "K theory" means different things to different people

That I can believe

there's a K theory of C* algebras that's probably not awful

but I bet algebraic K theory is awful

and topological K theory is Grothendieck

I don't know which version of K theory that cond-mat people use

looking at sources, it looks like cond-mat theory is interested in 'K-theory of real and complex vector bundles'

or at least that's the simplest thing they'd be interested in

I don't know how that fits in with C^* vs. algebraic vs. topological though

topological

6:07 AM

kk

@Semiclassical but they're all closely related, hence the names being the same...

sure

"I will lead the fight against the big banks, special interests, the earth's climate, and our children. I..."

I think that's my favorite one

I am anti child

'No Values Voters' Search For Most Evil Candidate

►

@Semiclassical I will end this discussion with a vague hint that the index theorem says that C* K theory and topological K theory are """"the same""""