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7:00 PM
the only example I know is Minix 3
 
@DanielSank who did the Windows install on your laptop, and from what source?
 
> In a microkernel the kernel is tiny
I could not have guessed that
 
@dmckee Darwin is a microkernel?
 
@JohnRennie I bought it from newegg. Dunno who did the install. Someone at Asus, I guess.
So yeah, I could redo it, but guess what? Then I have to buy Windows again.
 
@dmckee If you run Minix you're a bigger nerd than me :P
 
7:00 PM
I already paid the Windows tax when I bought the damn computer.
 
@DanielSank There you go. Asus loaded it up with crap and you're blaming the OS for it being slow.
 
@BernardoMeurer Well, it's a hybrid. But it has a lot of Mach at the core.
 
@JohnRennie No, I'm blaming the OS for running its own updater all the time.
 
@DanielSank You can extract the license key and reuse it
 
@BernardoMeurer Ran, not run.
 
7:01 PM
To be fair, I can't complain that much about 90's Windows effort to have backward compatibility
 
@BernardoMeurer Reuse it how? Where do I get Windows8 to re-install?
 
@DanielSank Download the Windows 10 installer onto a USB stick, wipe the disk and do a fresh clean from scratch install and it will gibve you no more problems.
 
Will the motherboard let me do that or did Asus do some shit to make sure I can't install my own OS?
 
Without it there would have been a lot of programs I wouldn't have been able to run back in the days
 
I don't know!
 
7:02 PM
@DanielSank Download the ISO somewhere, I think MS has some tool. Never use W8 it's crap
@DanielSank I can help if you want
I will be your third world tech support
 
@BernardoMeurer I don't have a W10 license.
I'd rather install Ubuntu, honestly.
 
No, not ubuntu plz
 
@BernardoMeurer My system crashes perhaps once a year, if that often. Not sure I should care about microkernel as a not-designer.
 
Why not?
 
Canonical is shitty
 
7:02 PM
@BernardoMeurer There's a lot of help online though.
 
Apple built Darwin on mach to make it easier to switch architectures (something they've done three times in the history of the company and twice for "macintosh").
 
"They reported this to the Windows developers, who disassembled SimCity, stepped through it in a debugger, found the bug, and added special code that checked if SimCity was running, and if it did, ran the memory allocator in a special mode in which you could still use memory after freeing it."
 
You want me to use Arch?
 
My sides
 
@ACuriousMind You don't :) It's a thing for kernel-loving people I think
 
7:03 PM
@Slereah yeah
 
@DanielSank Arch, Majaro, Antergos, Gentoo
 
@BernardoMeurer Kernophiles?
 
@ACuriousMind Yes!
 
Windows XP and on were much less backward compatible and trust me it was a right ass to run anything old
 
7:03 PM
@dmckee I have dreams that Hurd will work one day
 
@BernardoMeurer OSX is based on the Mach microkernel, but they rewrote it to make it monolithic.
 
it still is
 
@BernardoMeurer So doe RMS.
 
Most old .exe won't run at all on windows 7
 
@JohnRennie So it's a hybrid kernel? kewl
@dmckee Lol, RMS is a bit of a goof
 
7:04 PM
As far as I know there is no mainstream app using a microkernel because the performance hit is too great.
 
I have to fire up the DosBox to run them
 
@JohnRennie Minix runs okay :(
 
Hm, the proper word would be karyophile, I guess
 
Hey @BernardoMeurer I'll need your help getting into my file server.
 
@ACuriousMind Why?
 
7:05 PM
@BernardoMeurer He's ... dedicated.
 
@BernardoMeurer no, it's monolithic but they stole all the code from Mach.
 
I haven't updated the OS in forever, and it's been powered off. I don't remember the password.
 
@DanielSank That's never a good thing :P
Jesus
 
@BernardoMeurer Because karyon is the Ancient Greek word for "kernel"
 
Nah, it's cool. It's been off.
 
7:05 PM
@dmckee He's crazy, but I love him
 
Sometimes that comes across as fanatical or goofy, but he's right enough often enough that it's a mistake to dismiss him out of hand.
 
I'll turn it on, back up the data, and then deal with it, yeah?
 
@JohnRennie Sweet
 
(no network, obviously)
 
"In fact if you poke around in the AppCompatibility section of your registry you’ll see a whole list of applications that Windows treats specially, emulating various old bugs and quirky behaviors so they’ll continue to work."
 
7:06 PM
@DanielSank Yep :)
 
@BernardoMeurer Windows NT 3.1 was originally designed as a microkernel, and the alpha builds were classic microkernel design.
 
@ACuriousMind karyophile, cool
@JohnRennie I think one day we will have computers fast enough to use microkernels and not care
 
"For example, a lot of developers used to try to make their Macintosh applications run faster by copying pointers out of the jump table and calling them directly instead of using the interrupt feature of the processor like they were supposed to.
Even though somewhere in Inside Macintosh, Apple’s official Bible of Macintosh programming, there was a tech note saying “you can’t do this,” they did it, and it worked, and their programs ran faster… until the next version of the OS came out and they didn’t run at all. "
This article is always a fun read
"a veritable panoply of external dependencies each one of which is going to be a huge headache when you ship your application to a paying customer and it doesn’t work right. The technical name for this is DLL Hell."
 
Inside Machintosh was full of warnings not to take the current implementation as a license to do things. It sometime took years for an update to kick cheaters in the butt, but it happened many times.
 
The no. 1 problem with Windows is that MS have to let OEMs do their own installs and piss about with the install as they do it. Even the big names like Dell overload the Windows install with crap, and the box shifters do installs that should earn them a long spell in jail.
 
7:09 PM
In fact, every time I tried to take a shortcut I was eventually caught by an update.
 
Crime doesn't pay @dmckee!
 
@JohnRennie Android does that crap too. Grrrr...
 
This doesn't affect Apple because they have complete control over the hardware and OS, and it doesn't affect Linux because everyone does their own install;s.
 
you know what else has a crazy amount of backward compatibility?
 
@dmckee Buy a Nexus!
 
7:10 PM
x86 processors
 
x86_64 was a mistake
 
They start in 16 bits mode, just in case you want to install a program from the 1970's on it
 
^ Those (x86 processors) are just full of cruft.
 
At least it's not that Itanium BS
IA-64 GRRRRRRR
 
I mean backward compatibility is fine but maybe we don't need 16 bits mode anymore
 
7:10 PM
Makes me angry just to think
 
@dmckee Eh?
 
It's BS
 
I don't think anyone has seriously used it in 20 years
 
To think we still use BIOS!
 
@JohnRennie They didn't fit in the right spot in features-price-performance space last time we were shopping for phones.
 
7:12 PM
Then a OnePlus, or any of the brands that do a minimal install. Motorola are pretty good for this.
 
Ended up with moto-gs which are nice, except for the stuff I can't de-install and keep gone.
I've considered jailbreaking them just for that reason.
And the G doesn't have an SD card slot, so the on-board memory is it and when it gets full...
 
Is it faster to run a sieve of erasthotenes or to apply miller rabin to all odd numbers to find primes?
OnePlus is cool
I'm stuck with Apple and iMessage though
 
You know what the web needs? An architecture for web-authors to justify their use of external scripts to people trying to load a page.
I'm looking at a page that doesn't actually display anything unless I enable at least 7 separate thrid-party scripts.
 
Scripts are cancer
 
And I don't know what they do or why I should trust them.
Ghaw!
 
7:18 PM
well, I'll be, OP has gone and deleted their account not one hour after asking
0
Q: Do quantum linked rings of quantum knots have energy?

user149451There has been an experiment where infinite quantum linked rings were created to make a quantum knot.The structure is topologically stable and the knot can't be untied without breaking the rings. If these rings have energy and allow the structure to be stable, wouldn't there be infinite energy ...

 
Come to that, I wish more android app authors would explain all the permissions they are asking for.
 
This is really interesting:
Microsoft grew up during the 1980s and 1990s, when the growth in personal computers was so dramatic that every year there were more new computers sold than the entire installed base. That meant that if you made a product that only worked on new computers, within a year or two it could take over the world even if nobody switched to your product.
 
@dmckee load Privacy Badger and if it doesn't display it's its own fault
 
I'm using noscript right now. What advantage does the badger offer?
 
7:21 PM
@dmckee it only blocks stuff that looks like it's tracking you
 
Though I do simple kill the tab for sites that won't come up during casual browsing.
 
specifically by attempting to measure the entropy of any IDs in whatever they're sending
 
I need to be able to see enough to decide I want to see more before I'll even consider what scripts I might be willing to temporarily enable.
 
Here, I'll link to it
 
Hmmm ... cool.
 
7:24 PM
it does break some pages on occasion, but it's overall pretty good
btw @dmckee can mods see whether the OP in that one above deleted their account voluntarily, or what went on there?
 
@EmilioPisanty We can, but I think that's not information we should disclose unless there is demonstrable need for it.
 
@ACuriousMind ok, fair enough
I'm annoyed that I put up with that paper's ridiculous intro only for OP to scamper, but ultimately whatevs
I asked in case e.g. they were having trouble getting their account to work correctly or something
particularly since the very next user has the same username
but then again google has a hit for a much older deleted user of the same name
 
what's going on?
@ACuriousMind I like how this result is attributed to Goldstine
That name makes no sense
 
7:44 PM
whats this event about ladies?
 
@EmilioPisanty Aptly observed, Sherlock ;) It's good that you're looking out for new users, we're aware of the situation and handling it.
@Skyler ...what?
There's no event here, and certainly none about ladies.
 
i just saw a message about some kind of event on the h bar
 
@ACuriousMind good to know
 
it was showing in other chat rooms i had open
 
Bajoran, can you be less cryptic
 
7:46 PM
@Skyler Uh, that was the chat session a few hours ago
@0celo7 No, I can't I'm afraid.
 
@ACuriousMind oh ok well that makes sense, grandpa here was in nappy poo land until recently
 
@ACuriousMind Thanks, now I can finally see :)
 
"When they tried to “End Of Life” Windows 98, it turned out there were still so many people using it they had to promise to support that old creaking grandma for a few more years."
heh
 
The coffee machine in the office doesn't seem to work anymore
I am taking suggestions on how to fix it
 
@0celo7 Install Linux on it
2
 
8:01 PM
@EmilioPisanty I hope I'm not muscling into your conversation but I did notice a number of new users trying to vandalize the site by posting garbage questions, answers or comments.
 
@ZeroTheHero possibly, but from what I see it's not the case here
 
@E
oups...
 
that person asked a terrible question, had it closed and deleted, and then came back and asked a much better version
 
there's always a steady stream of garbage posts. I haven't seen an increase in the rate lately but it's entirely possible.
 
8:03 PM
@EmilioPisanty thanks for the clarification. The accounts and posts have been deleted so t'was difficult for me to fully assess the context.
 
"Third, the code may be doggone ugly. One project I worked on actually had a data type called a FuckedString."
 
> As if source code rusted.
is pretty good
@ZeroTheHero no worries. Even I can't see deleted users (presumably mods can? who knows), and I could only find the old question because I voted to close it.
 
I took it apart
 
"Have you ever heard of SEMA? It’s a fairly esoteric system for measuring how good a software team is. No, wait! Don’t follow that link! It will take you about six years just to understand that stuff."
 
it seems to be working now
 
8:12 PM
when a light ray falls perpendicularly on a transparent object from vaccum, then does it bend?
like if the angel of incidence is 0
 
One of the article on that blog is from 2000 and it has a link to a software company, except it doesn't exist anymore and now the link is to a tree removal company
 
by symmetry, which way would it bend?
 
@BenNiehoff All ways at once
 
there you go!
 
and don't even try that symmetry crap
what direction does the ball on that dome fall
and at what time
Norton's dome
 
8:14 PM
arccos 2/3
or something like that
 
to the right
 
@BenNiehoff what?
 
the azimuthal angle at which the ball, rolling down the dome, experiences zero normal force (and thus flies off the surface)
 
do you know what I'm actually taking about :P
 
no
but I see it's time for another episode of Will It Bend?
 
8:16 PM
try solving $x''=\sqrt x$
 
fine, be like that
 
I will
I won't attempt random-ass nonlinear ODEs unless they are first-order
it's a rule I have
 
when a light ray falls perpendicularly on a transparent object from vaccum, then does it bend?
like if the angel of incidence is 0
 
7 mins ago, by Ben Niehoff
by symmetry, which way would it bend?
 
8:20 PM
oh sorry didnt see that
 
Also, it's the angle of incidence, I doubt there's a divine creature responsible for incidence.
 
by symmetry nothing would bend
but it moves nearer to normal
 
@0celo7 not a very good retort
 
$\mathfrak{Proof}$?
 
what?
 
8:21 PM
most people will solve it but fail to see the multiple solutions
 
wait wait wait
lemme refo the question
when a light ray falls perpendicularly on *vaccum from a transparent object*, then does it bend?
like if the angel of incidence is 0
 
same answer
or you can just use Snell's law...is it confusing?
 
@BenNiehoff Sorry, I meant $x''=x^{3/2}$
There are two families of solutions
Clearly $x\equiv 0$
 
Use Snell's law, yes
 
But then there are solutions that start moving after an arbitrary amount of time
 
8:30 PM
hint : $\sin(\pi/2) = 1$
 
and there's no reason why it should move in an particular direction either
so it's perfectly valid for the ball to wait for a while and then just roll in a random direction
Someone should make a perfectly non-Lipschitz dome and try the experiment
 
Hint : you can't
Because reaction forces aren't real in the real world
 
reaction forces?
 
Norton's dome is based on the concept of reaction forces
 
what?
 
8:32 PM
by "start moving after an arbitrary amount of time", what do you mean? x is some non-analytic function?
 
@BenNiehoff Almost all functions are not analytic
 
The surface on which the ball is exerts a force perpendicular to the surface
 
of course
 
The soltutions of $x''=x^{3/2}$ are not unique
 
but what do these solutions look like? literally flat until they transition to a nonzero function?
 
8:33 PM
There are solutions that are $x(t)=0$ for arbitrarily large $t$
 
or with some sort of small tail?
 
@BenNiehoff Yeah
 
The solution is like $\approx t^4$
 
$x''=x^{3/2}$ corresponds to a ball sitting on a dome of some particular shape
then apply Newton's law
 
The exact class of solution is $$x(t) = \Theta(t - T) \frac{1}{144} (t - T)^4$$
 
8:34 PM
so x would have to have things in it like e^{-1/t}...is that what you're saying?
 
For every value of $T$
 
what @Slereah said looks right
 
@BernardoMeurer around?
 
you obtain a solution for any value of $T$, it's quite amazing
 
oh, right, because x only needs to be C^2, not C^\infty
 
8:35 PM
Is that there actually not smooth?
I'd have to plot it
 
and the problem is basically because x=0 is some kind of singular point
 
It's not smooth, no
 
I think it's fine...all the derivatives are equal to zero at $t=T$
@Slereah why not?
 
But the problem isn't that it's $C^2$
 
no, it's obviously not smooth, its 4th derivative is discontinuous
 
8:36 PM
The problem is that the problem isn't Lipschitz continuous
 
I don't see how that's obvious, but ok
The third derivative gives a kink, ok
In any case, there's no physical reason for things to be Lipschitz or smooth
 
Do you think you can have a non-Lipschitz continuous metric
 
Yes.
$g=x^2\mathrm dx^2$
$x\mapsto x^2$ is not Lipschitz
 
Hm
Does it give rise to issues though?
 
No, why would it?
 
8:44 PM
Is $x'' = x^2$ ill defined
 
@Slereah Oh, for ODE you only need locally Lipschitz
 
Well can you have a metric that isn't locally Lipschitz
 
$x^{3/2}$ fails to be Lipschitz on any neighborhood of $0$
 
$\sqrt x$ isn't gonna work
Would fuck up the signature
Maybe a root on one of the off-diagonal terms?
Can you have a $C^2$ function that fails to be locally LC though
 
No, all $C^1$ functions are LL.
 
8:47 PM
yeah I guess it would be a pretty fucked up metric anyway
although some metrics are just $C^0$
 
You can define metrics with values in Sobolev spaces
If you do it correctly you can get Sobolev-valued Christoffels and curvature
 
gross
 
Indeed
You need something called the Sobolev multiplication theorem
It says that certain Sobolev spaces can be paired via a generalized multiplication operator
 
9:01 PM
@BenNiehoff doesnt snell's ;aw break when angel of incidence is zero?
 
no?
 
it does
or thats what my notes say anyway
sin of angel of incidence / sin of angel of refraction is no longer constant so..
 
@MartianCactus Not when you write it in a form without fractions
I.e. $n_1\sin(\theta_1) = n_2\sin(\theta_2)$
Also, it's still angle, not angel.
 
I can be your angle or your devil
 
Don't you mean devli? :P
 
9:06 PM
devle
 
Send me an angel ohohohohohhhhhh
Send me an angeeeel
 
@0celo7 I did a GR problem once where the curvatures ended up with second derivatives of Dirac delta :P
 
propagating gravitational shock wave, basically
 
Shock waves are pretty shit
 
9:20 PM
@BenNiehoff you're a terrible person
 
"The story goes that one programmer, who had to write the code to calculate the height of a line of text, simply wrote “return 12;” and waited for the bug report to come in about how his function is not always correct. "
Help, i have died of laughter
(this was code for Microsoft Words)
 
@Slereah Word or Works?
 
Word
 
9:40 PM
@ACuriousMind For a Dirac spinor $\psi$, what are $u$ and $v$, if they are defined by $(\gamma^\mu p_\mu - m)u=0$ and $(\gamma^\mu p_\mu+m)v=0$? Are they the Weyl spinors which constitute the Dirac spinor? Or are they the sums and differences of the Weyl spinors like $\psi = (u,v) = (\psi_L + \psi_R, \psi_L - \psi_R)$?
The latter are normally written as $\psi = (\phi, \chi)$, and the former are usually called $\psi_L$ and $\psi_R$, so I believe they are neither.
 
@Bass They are the positive and negative frequency solutions. For any constant Weyl spinor $\xi$, $u = (\sqrt{p\cdot \sigma} \xi,\sqrt{p\cdot \bar{\sigma}}\xi)$ and $v = (\sqrt{p\cdot \sigma}\xi,-\sqrt{p\cdot \bar\sigma}\xi)$ are such solutions.
 
$u$ and $v$ are the particle and antiparticle solution
They are not Weyl spinors
Weyl spinors don't split particles and antiparticles all that well, IIRC
and especially not Majorana spinors
 
Ah, so they are not anything specific from a group theoretic viewpoint?
 
well positive and negative frequency solutions are pretty specific
you don't get that without the $T$ part of the Lorentz group
 
@Bass The terminology is a bit confusing here - one should distinguish between Weyl and Dirac spinors, which are just elements of their specific group representations, and there are the spinor-valued fields. $u$ and $v$ are specific spinor-valued fields, but not special as mere spinors.
 
9:48 PM
Like without time orientability you can't get those I think
 
But in which Lorentz irrep do they transform?
 
@Bass Both $v(\vec p)$ and $u(\vec p)$ are Dirac spinor-valued fields.
 
$(0,1/2) \oplus (1/2, 0)$
 
Ah, I see.
What's the difference between $u,v$ and $\phi,\chi$?
 
9:50 PM
with $\phi = \psi_L+\psi_R$ and $\chi = \psi_L - \psi_R$.
 
Well for a start there's no $u$
It's $u^s$
 
@Slereah OK, go on.
 
@Bass You need to be more explicit whether you're writing down spinors or spinor-valued fields here. First, the $u,v$ depend on the choice of a Weyl spinor $\xi$, so they're Dirac-valued fields $u_\xi(p)$ with a Weyl-spinor parameter $\xi$.
 
I think you have $$\frac{u + v}{2} = \psi_L$$
or at least something proportional to it
 
@ACuriousMind OK, I'm trying: $\phi$ and $\chi$ are just spinors, they are defined by their transformation under the Lorentz group. $u$ and $v$ are spinor fields, i.e. solutions to the Dirac equation.
 
9:54 PM
Now, if you look at my formulae up there, for the choices $\psi_{L,\xi}(p) = \sqrt{p\cdot \sigma}\xi$ and $\psi_{R,\xi}(p) = \sqrt{p\cdot \bar\sigma}\xi$, then you have indeed that $u_\xi(p) = \psi_{L,\xi}(p) + \psi_{R,\xi}(p)$ and $v_\xi(p) = \psi_{L,\xi}(p) - \psi_{R,\xi}(p)$.
 
Yeah that sounds reasonable
 
Oh, of course.
Cool, thx!
 
I am slightly annoyed that the Einstein notation for spinor never stuck
I find it usually more clear
though spinor calculus has weird rules
 
which spinor notation is the "Einstein" one?
and I think you mean Grassmann calculus has weird rules
 
@EmilioPisanty Now I am, what up?
 
10:11 PM
Is grassman calculus anything more than purely formal?
Is the grassmann integral actually an integral in the MT sense?
 
@BenNiehoff $\psi^\dot A \sigma_{\dot A}^A \psi_A$
That kind of stuff
 
@BernardoMeurer on that qsub thing
I write a shell script and hand it off to the queue manager
I suspect the issue is that the shell inside the thing isn't bash
How do I find out what shell is interpreting my .sh file?
 
10:33 PM
@OBE So...is this Astro design idea not happening or...?
 
OBE
10:56 PM
@SirCumference wait im working on a different graphics project right now.
all my free time is on that
 
All right
 
OBE
should be done soon
 
Oh, by the way, should I learn how to make music digitally?
 
OBE
sure
 
I'm thinking of learning a new skill of some sort
 
OBE
10:58 PM
physics is a pretty useful skill
 
I'm already majoring in it
That ain't new
 
0
Q: How to define complex mechanics problems mathematically correct?

doumhamI asked a similar question in the math section but no one answered , hopefully I will find the answer here.I am an engineering student and I often face mechanics problems which involves usings concepts like infinitesimal and limits . I have a clear idea of those concepts ,however applying them on...

Too broad?
 

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