« first day (2727 days earlier)   

12:28 AM
@JohnRennie I have to say, for all my dislike of Windows, it does handle hardware failures really well
 
12:47 AM
@0celo7 that's interesting
did they run out of old ships to shoot at?
An artificial reef is a man-made underwater structure, typically built to promote marine life in areas with a generally featureless bottom, to control erosion, block ship passage, or improve surfing. Many reefs are built using objects that were built for other purposes, for example by sinking oil rigs (through the Rigs-to-Reefs program), scuttling ships, or by deploying rubble or construction debris. Other artificial reefs are purpose built (e.g. the reef balls) from PVC or concrete. Shipwrecks may become artificial reefs when preserved on the sea floor. Regardless of construction method, artificial...
this kinda thing
 
Pro tip fellas: never, never, NEVER unplug a drive or allow system failure during low-level operations.
It's harder to fix than I imagined
After two days I finally recovered this bricked drive
 
1:05 AM
@BernardoMeurer unlike you, we actually listen to the folks like you who tell us not to do stupid shit like that
¯\ _(ツ)_/¯
 
@EmilioPisanty I am the guy who tells you not to do it :P
Someone has to try it :P
 
@BernardoMeurer Like you didn't know it was a bad idea
 
In my defense it was half-needed
 
just sayin'
 
I was creating a ZFS pool on a drive and my girlfriend decided she had other plans than waiting
I ain't confronting her because I need to wait on ZFS ;P
Shit I broke it
again
AH
I'm throwing this drive away
it's dead
 
1:15 AM
@BernardoMeurer quitter
 
@EmilioPisanty I know how to fix it
 
You gonna give up that easily?
 
Boot into a vanilla kernel with the default scheduler, dd /dev/zero into the block device, and wait
problem is writing 500GB through a USB2 link takes like 16h
This drive costs like $10, my 16 hours is worth more than $10
The problem is that the bfq IO scheduler causes the -ck kernel to panic when a block-dev driver hangs; which this drive does because it has a corrupt superblock somewhere that I cannot get rid of
[ 1226.710194] INFO: task kworker/u16:3:28760 blocked for more than 120 seconds.
[ 1226.710200]       Tainted: P        W  O     4.15.18-1-ck-ivybridge #1
[ 1226.710201] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 1226.710203] kworker/u16:3   D    0 28760      2 0x80000000
[ 1226.710218] Workqueue: events_freezable_power_ disk_events_workfn
[ 1226.710221] Call Trace:
[ 1226.710236]  ? __schedule+0x7d3/0xe20
[ 1226.710243]  schedule+0x32/0xc0
[ 1226.710249]  io_schedule+0x12/0x40
See ^
Oh, I know what to do!
I have a NetBSD machine!
 
1:38 AM
Yeah, apparently my custom kernel was the issue
preliminary results
Yep, the problem is bfq :)
Pro-tip: If you have a drive with shitty sectors, don't use an asynchronous scheduler :)
 
2:01 AM
I have 18 reputation but I can still talk here
 
@EmilioPisanty this reef is crazy
these people just dumped 2,000,000 tires in the ocean
complete madlads
and now when there's a big storm they get scattered everywhere and destroy all of the natural reefs
 
2:14 AM
I'm temped to start collecting statistics about questions that involve the concept of centripetal force/acceleration. I conjecture that nine of of ten times they can be resolved by (getting the the OP to believe/understand that) "the system is not in equilibrium!"
 
rob
@Abhinav You also have reputation on Mathematics. That's the difference.
 
vzn
@0celo7 lol since when are you concerned about the environment? your chat record shows quite the opposite sentiments repeatedly :P
 
@EmilioPisanty There, now I have a raspberry pi wiping the drive for me
 
2:35 AM
@rob So it works like that.Thanks for telling me
 
I feel a warmth inside
I am going to be live studying category theory later
I feel like I will make a lot of progress tonight. Will begin in an hour
Ok let me grab a bottle and start. Will be making strides in the associated fora.
* a bottle of water that is * I don't drink alcohol (anymore hehe)
alright
 
3:02 AM
Actually, let me just read and scribble first
 
 
3 hours later…
Sid
6:10 AM
@JohnRennie HELP required!!
 
@Sid whats up?
 
Sid
I hope you are okay with magnetic circuits..
 
Magnetic circuits. Hmm. Well, what's the question?
 
Sid
Suppose, we are given flux through the airgap and Area of Cross section of the air gap. Then, we can find flux density. And from a table given to us, the corresponding values of Magnetic field strength for different values of flux density are given
 
OK ...
 
Sid
6:17 AM
From this, we can find the permeability. However, the flux density that I get from calculation is, say 0.5. But, the value of H (Magnetic field strength) corresponding to 0.5 isn't given in the table. But that of 0.4 and 0.6 are given.
How do I calculate the value of H corresponding to 0.5?
 
Graph the figures you are given then estimate the value for 0.5 by interpolation?
 
Sid
Won't that be approximation?
 
I'd draw the graph and see what it looks like. It might be linear in which case you'd get a pretty accurate value.
 
Sid
No, it's not linear. If it had been, I wouldn't have been asking you..
I did draw the graph and approximated the value of H. My final answer of current came out to be about 2mA more than the answer given in the book
 
Unless you know some formula that relates H to the flux density I'm not sure what more you can do. Does the curve look like anything obvious? A parabola for example?
 
Sid
6:32 AM
Well, it's sort of straight line.
(How do you upload pictures in mobile version of chat?)
 
6:51 AM
@Sid Upload to imgur and post the link?
Or use the desktop version of the web site
 
Sid
7:07 AM
I will post once I am in the vicinity of a laptop
 
Morning my dudes
 
How to write a good answer so to get votes....my answers are not good results
getting*
 
 
2 hours later…
9:23 AM
@JohnR: Hi! :-) You around?
 
Morning :-)
 
How's it going?
 
Though i'm only around for a few minutes as I have deliver a laptop (one I've fixed)
@KaumudiH Mondays aren't my favourite day, but it's OK. The weather is nice :-)
 
@JohnRennie Ah, haha, yet another has fallen victim! :-)
@JohnRennie Cool :-)
 
I do the washing on a Monday morning but it's mostly done so that's Ok too :-)
How is life in Kochi? I guess the exams are about to start - or shouldn't I mention that? :-)
 
9:26 AM
Actually, in a stunning turn of events, I find myself in Chennai again!
 
Ah, do go on ...
 
(That's why my replies aren't coming in minutes later, haha.)
@JohnRennie Well, it turned out that I had a few days of study holidays left, so I came back home with my parents.
 
Presumably the theory is that you'll use the peace and quiet to get lots of work done? :-)
 
I will be leaving on Wednesday, and they will follow either this Sunday, or the next Saturday.
@JohnRennie Sort of :-)
 
How are the plans for the move to Kochi going?
 
9:29 AM
Great! We've found an excellent apartment, my Father's been looking into Packers & Movers options, and I'm vacating my room at the hostel this Friday, right after my exam, and taking my stuff to the new house!
I'll be staying there on my own until my parents move in with all the stuff, but I'll still have a few essentials from hostel to live on till then- a bed, a bucket, soap, etc.
 
@KaumudiH have they sorted out the Internet connection? You have to take care of the important things first!!!
 
No, no, they have not :-) Not to worry, I'll be able to use my mobile as a hotspot till they do.
You're not adequately excited about "I'm vacating my room at the hostel this Friday..."
 
How far is it from MEC? What's the travel time like?
 
VACATING MY ROOM AT THAT WRETCHED HOSTEL, JOHN!
 
@KaumudiH Free! Free, at last!! :-)
 
9:33 AM
:-D Yes!
@JohnRennie Around 5 Kms, so roughly 20 minutes (on a scooter my parents are going to buy me soon!), give or take.
 
You'll be able to go out after 6 p.m. How will you cope with the freedom after your long incarceration? :-)
@KaumudiH Cycle distance?
 
@JohnRennie :-D Hahaha, yes!
The apartment's on the 17th floor, inside a gated community of four other buildings. So, they have a gym, a swimming pool, a shopping complex, a cafeteria, etc.
@JohnRennie True, but the roads are too hilly to cycle on.
 
@KaumudiH Wow, that's a step up from the hostel!
Do you have free use of the gym and swimming pool, or do you have to pay?
 
@JohnRennie "Free". We'll be paying Rs. 3000 for maintenance every month, which includes all this stuff.
 
@KaumudiH ah, I just noticed you said in an earlier post that you were getting a scooter.
 
9:37 AM
Second hand, but still!
 
@KaumudiH In the UK that would be really cheap - I don't know how it is in Kochi.
 
Eh, it's not too cheap by modern standards over here, but not too expensive, either. Affordable.
 
@KaumudiH I don't think I've ever owned a brand new motorcycle or car. I actually quite like driving a slightly battered car as I feel I don't have to be ultra careful with it.
 
Oh, what, I thought your car was new when you bought it!
 
@KaumudiH No. I do so little driving these days that it wouldn't be worth spending lots of money on a new car. I tend to look for cars that are about ten years old but with a low mileage.
 
9:40 AM
Ah, I see!
 
Those tend to be cheap, and as I said it allows me to be careless with them without feeling guilty.
With a brand new car I'd be terrified of scratching it.
 
Can anyone tell me how can I represent acceleration in respect to distance $x$ ...? Like , *x double dot *...
 
@JohnRennie Right, like that time it hit that tree in your driveway :-P
 
@KaumudiH ah, erm .. yes :-)
And I managed to back into a wall so the corner of the rear bumper is bent now. Oh well :-)
But the car just passed its MOT with no repairs needed so it's good for another year.
 
@JohnRennie x'D When did this happen?
 
9:43 AM
@KaumudiH A while back. I was at my Mum's and we were visiting a friend of hers who is in a care home. When I was backing out of the parking space there was a low wall - so low I couldn't see it through the rear window.
 
@NehalSamee x double dot is quite correct-acceleration is the double derivative of distance with respect to time.
@JohnRennie Oh, dang.
 
But it's OK - just a slightly bent bumper. Hardly noticable given all the other dents on the car :-)
 
:-) Right...
 
That's the thing about an old car. You don't care if you add another dent or two.
 
I like your car. It's cute :-)
 
9:44 AM
@KaumudiH Ah , sorry... I couldn't complete it ... Using Math jax ...
Of course ...
 
@NehalSamee Ah, you wanted the MathJax for it?
 
It is a nice car. I don't get attached to cars like some people do, but I will be sorry when it finally dies of old age.
 
@JohnRennie :-) How old is it now?
 
@KaumudiH yeah ...
 
@NehalSamee $\ddot{x}$ or $\frac{d^2x}{dt^2}$
@KaumudiH 15 years!
 
9:45 AM
@JohnRennie Thanks ...😄
 
@JohnRennie Wow! :-o That's not normal for a car, no?
 
Modern cars last ages. It's not uncommon to see 20 year old cars.
What tends to happen is they get gradually more expensive to keep running, then eventually something big and expensive goes wrong and it's cheaper to buy a new car than fix the old one.
 
Wow, I see. My Dad's car is now...almost 10 years old, and works just fine! Guess we'll be seeing loads more of him (the car), thank God! It's such a good car.
@JohnRennie Ah, right, right.
 
Anyhow I need to go. My drier has just pinged to say it's finished, and I need to get the clothes out then dash off with the laptop.
 
How's the new cycle doing?
Ah, OK :-) Catch you later!
 
9:48 AM
Bye :-)
 
10:38 AM
ZFS is kind of amazing
@0celo7 50% confirmed for Brazil
Just getting things set-up with Standard Cognition
Should be in Rio from August 2-25
 
11:08 AM
Can anyone help me out with some index notation: I've got the following expression $$ -4/c^2 \mathbf{v} \times (\nabla \times \mathbf{w}).$$ So far I've re-written it as $$ \mathbf{v} times (\epsilon_{ijk} \partial_j w_k)$$ but I'm not really sure how to handle the rest any suggestions. I know I want to get it so that we can write it in terms on Kroneckers deltas but I currently having a brain fart. $$ \mathbf{v} $$ is used to denote a boldface vector and the $$-4/c^2$$ is just a constnat
 
You can rewrite the levi-civita tensor as a sum of Kronecker symbols
Also I don't know what you want to prove so that doesn't help
 
11:34 AM
Ah I got it! When you don't use something for a while the tricks fade away! Thanks @Slereah
 
12:03 PM
@BernardoMeurer sick dude I’m going earlier than expected
We’re gonna have 4 days to ruin my life before the conference
@vzn that shows you just don’t know anything about me
@ACuriousMind unexpected porno imgur.com/a/uB4aPIW
 
is this the new post apocalyptic waifu simulator that you're playing
 
replaying the witcher 3
 
Witcher than what
 
admittedly the name doesn't make sense
especially because you're not a witch hunter
 
 
1 hour later…
1:20 PM
Hello, everyone.
Can you people suggest me some resources (books, webpages etc.) to learn physical simulation?
 
@EmilioPisanty oh, I remember you wondering what I was talking about when I brought up finite-gap potentials at one point. while looking up something else, I found a pretty good discussion (or at least one which isn't completely obscure) in one of Arnold's books: books.google.com/…
 
@Semiclassical goodness
 
yeah, i came upon that pretty randomly
but it's about as good as one would hope for
the lead-up to it is some inverse scattering transform stuff, but if you take that eigenvalue problem for granted then I think it's pretty self-conntained
 
that's horrifying
but more importantly
lunch calls
 
@EricSilva tfw Sougi shows up in research
It’s a small world
Oh no this is P. E. Soug
False alarm
 
What
 
It's a Sougi meme created by the UCians
 
hello balarka
 
2:16 PM
h
 
Help
 
Hello there
 
My current job mission is working on some VBA application developped by some company
The help I need is for someone to shoot me
 
is assisted suicide legal in france?
i won't do it otherwise
 
2:17 PM
come and find out
 
im a law-abiding citizen
 
Have you ever analysed VBA code on an excel file written by people who don't know anything about programming
 
Admittedly not
 
i am reading torque and stuff like that from hrk
but they only consider tension force, but not lateral force in rod
so ain't the calculations a bit off ?
 
those calculations that you deleted did seem off
 
2:19 PM
lol
no I mean for two particle rod configurations like this, shouldn't lateral force produces a change in calculations ?
 
@BalarkaSen yo i hrd you like indices
 
Besus Brist
 
Morning folks
 
@0celo7 souganidis is p.e. soug
Takis is his nickname
 
(hence why the meme was relevant)
 
2:31 PM
@EricSilva oh
He has an MCF paper
 
2:42 PM
Can anyone tell me if a charged particle is in motion in a place where both electric and magnetic field exist , then will its path be circular ? And if yes , then will I count only magnetic force for finding its radius ?
 
depends on the electric and magnetic field.
There's a famous setup where the path will be helicoidal
 
@Slereah VBA in Excel? That's what I get paid £500 a day to do :-)
 
@JohnRennie You poor man
 
It's all money :-)
 
Those people don't use any variable names for rows and columns for the most part
I'd rather prostitute myself
 
2:51 PM
@Slereah Shooting is too good for them
Either use named cells or ranges, or at least define some const values with the row/column numbers.
 
Alas not
 
@Slereah me too, but I fear there would be little demand for my services
 
It's a giant seething mass of "if" statements with random numbers for rows and columns
Debugging it is fairly tough
also they don't seem to understand factorization
 
Excel has a primitive object system. There's no inheritance but it does a decent job of encapsulation.
 
there's a bunch of If sheet1.Cells(i, n).value = "" Then
sheet2.Cells(i, n).value = 0
Else
sheet2.Cells(i, n).value = sheet1.Cells(i, n).value
End If
Like dozens of them
 
3:16 PM
@EmilioPisanty lol, I don't think it's that bad
especially if you look specifically at the case considered at the bottom of page 274, where $L=-\partial_x^2 +u(x)$ with $u(x+T)=u(x)$. (the second operator in that case is the discrete translation operator)
 
Hey guys while reading an article about the unusual characteristic of Projectile motion I came to know that for angle greater than 70.5288 ° the projectile starts oscillating. And we can find two points where the radial vectors magnitude is same. When I was reading the proof of this phenomenon I saw they used radial velocity =dr/dt= 0 then kept proceeding. But how could the radial velocity be zero? See the pictures
 
then being finite-gap amounts to "the dispersion relation is $\epsilon^2=f(k)$ with $f(k)$ being a rational function"
 
@ffahim They're looking for the moment of time where the distance of the particle from the origin is maximum
so you want to find the critical point for the function $r(t)$.
ergo, you want the time at which $dr/dt=0$
That's no different than saying that, if you toss a particle vertically upwards, then the height is maximum at the moment when $v_y=dx/dt=0$
it's true for some particular moment in time, not for all times
 
@0celo7 I am aware
 
3:25 PM
@Semiclassical what zero velocity has to do with the maximum radial distance since the radial velocity never becomes zero only the vertical component of velocity is zero at maximum point still there is no zero velocity. Can you please elaborate more
 
if i'm throwing it straight up, then there certainly is zero velocity when the particle's height is maximized
presumably, though, what they mean is precisely that the radial component of the velocity is zero
that's why they write $dr/dt$ not $d\vec{r}/dt$
$r$ is the distance from the origin. it's not a vector. hence dr/dt is not a vector quantity.
 
Oh I see. I am sending another picture, what does that mean by the line I circled
@Semiclassical "" radial velocity goes to zero and changes sign""?
 
radial velocity = radial component of velocity
so the distance from the origin goes from increasing to decreasing or vice versa
 
Radial means vertical component?
 
radial means distance from the origin
but they're not really spelling that out
if you want to think in terms of vectors (as they're language suggests) you really need to think of your vectors as being in polar coordinates rather than Cartesian coordinates
 
3:36 PM
So how does it change sign? Since it's not a vector
I got that r represents here the radial distance fine, and when finding out two equal radial distance and showing that the change in distance is zero hence the radial velocity (speed) is zero, but what sign flip has to do anything with that
 
because the distance goes from being increasing to decreasing, i.e. dr/dt>0 to dr/dt<0, or vice versa
 
Thank you so much, now it's clear :) @Semiclassical
 
the point is that, initially, the distance of the particle from the origin is definitely increasing
and if you wait long enough, then it'll also definitely be moving away from the origin
but, apparently, if the initial angle is steep enough then there'll be a time interval in which the particle's radial distance is decreasing. for that to happen, you need for dr/dt to go from being positive to negative (and ultimately back to positive)
 
3:58 PM
this is....
 
yeah...
 
not all that informative
 
it's a bit disappointing, yes. I more meant that the context they're setting is not so strange
 
@Semiclassical not an unsurmountable problem though
 
ya
and if you look at the stuff they do ahead of that, you can imagine where they're going with it
 
4:00 PM
I guess it's a matter of time before IT catches on and kills that route to the secret Russian cache of wisdom
but for the time being, life is good
 
loool
 
@Semiclassical used to be gen.lib.rus.ec worked, but then it stopped was killed by IT
currently the .io domain still works
@Semiclassical It doesn't accent Lamé correctly
srsly wtf
but more seriously now
> There is a large class of periodic or quasi-periodic finite-gap (algebro-geometric) potentials $u(x)$ such that all but finitely many of their forbidden zones have length zero. Then the Riemann surface $\Gamma$ of the corresponding Bloch-Floquet function has genus $g$, where $g$ is the number of forbidden zones of finite length.
they're kidding, right?
that's ridiculously strong
 
or maybe not?
heck, maybe it's just exactly what you'd expect from simple examples?
 
It's a strong condition, but so is a high-order polynomial having rational solutions
 
4:05 PM
[91] P. Pechukas et al. Analytic structure of the eigenvalue problem as used in semi-
classical theory of electronically inelastic collisions. J. Chem. Phys. 64 no. 3, pp.
1099–1105 (1976).
[92] J.-T. Hwang and P. Pechukas. The adiabatic theorem in the complex plane and
the semiclassical calculation of nonadiabatic transition amplitudes. J. Chem. Phys.
67 no. 10, pp. 4640–4653 (1977).
^ i.e. the stuff in those papers
particularly the first one
 
can you see the discussion on page 278?
the point is more or less that, in that scenario, the variational aspect of the problem basically forces you to get a finite-gap solution
 
@Semiclassical I've got the full pdf now
 
which part of p278?
 
the P-F model
specifically the point about the 'first case' they considere
 
4:10 PM
@Semiclassical that's horrifying
 
lol
it's basically an electronic lattice with elastic energy as well
so that the lattice can lower its energy either by organizing the charge in a certain way or by deforming the lattice
I dunno why they use that interaction function though if I'm honest
this is something you definitely hear about in solid state courses, but i dunno how much play it gets outside of that
The other thing I'll confess is that the analytical details for these stories always slew me
just too much
 
 
2 hours later…
6:12 PM
Yo @Semiclassical that Riemann-surface thing
any chance for a 2D treatment?
i.e. the Riemann surface of the eigen-energies of graphene & related materials?
 
6:48 PM
Is pi=2.0 on a sphere?
 
On a sphere, the relation between the perimeter and area of a circle depends on its radius
Consider the three cases : an infinitesimally small circle ($A \approx \pi r^2$), the circle that covers half a sphere ($A = 2\pi$ for $r = \pi / 2$, so $A = 4 r$)
And the circle that covers the entire sphere
Wait that sounds wrong
Hm
 
@EmilioPisanty wish I knew tbh. At the very least you’d now have the k-vector as 2D rather than 1D, which would seem to mean you’d end up not with a surface in C^2 but in C^3...which, yikes
 
Ah yes, the area of the sphere is $4 \pi R^2$, so the half sphere is $2 \pi R^2$, with a radius of the circle of $(\pi/2) R$
 
@Semiclassical yes, that =/
alas, saddle-point analysis for HHG in graphene has landed on my plate
 
So the relation would be... $A = 8 R^2 / \pi $?
 
7:01 PM
in this vein you might like : arxiv.org/pdf/0901.0050.pdf
 
4
Q: Area of a circle on sphere

Markus KlyverOn a (flat) Euclidean plane, the area of a circle with a radius $r$ can be described by the function $A(r) = \pi r^2.$ But how can one describe the area of the same circle on a spherical manifold? Assuming that the radius of the sphere is an Euclidean distance of $d,$ how would $A(x)$ look? I'm...

Here's the relation apparently
 
But how to get a Riemann-surface type logic...
(One idea which I think would work is to take one of the k-components as fixed. But that’s quite a strong restriction)
 
and apparently the perimeter is given by
$$P = 2\pi R \sin\left(\frac{r}{R}\right)$$
So if you define $\pi' = P / 2R$, then $$\pi' = \pi \sin(r/R)$$
So the value of $\pi'$ is anywhere between $\pi$ and $0$
Since in the limit $r \to 2\pi$ (a circle that is the entire sphere), the perimeter goes to zero
 
7:37 PM
I bet Ayou get a similar idea when you look at the perimeter of a spherical triangle vs it’s area
Though that’s a bit involved since the area is governed by the angles of the triangle and it’s perimeter by the sides
 
8:17 PM
What's an example in classical physics where operators do not commute?
 
8:31 PM
@0celo7 u there
 
maybe
 
flip we pinged each other simultaneously but in the wrong rooms
dude check out the math mod's office chat room
so much spice and curry there
 
link?
 
@BalarkaSen I dont get iot
 
8:37 PM
Me neither. It's too much condensed drama
My brain doesn't have enough water to liquify it in the right proportion
 
are those bots in there
wtf is that conversation
 
our collective IQ is too low for us to understand the conversation, admit it
 
my brain is kind of fried rn
so idk
 
9:03 PM
@0celo7 looool @ math mods office
 
vzn
Apr 14 at 14:29, by 0celo7
From my perspective the climate scientists are evil
 
Low tier argument, there's more to environmentalism than climate science
I can care about people polluting the ocean but dispute global warming
Not saying that I am, but I could do that
 
Lol
 
vzn
hypothetically speaking. anyway maybe should know better than to take any of your stated positions seriously, incl/ maybe esp on "serious" issues... based on my knowledge of you...
 
Indeed.
You should change your name to vsn
Very Serious Name
 
vzn
9:14 PM
actually was slightly )( triggered by the glimmer )( of conscience, maybe should forget about the whole thing... whatever
 
Do you always write your comments with bra-ket notation?
 
vzn
@Lozansky hi, probably more when bored/ aimless. so are you physics student?
 
No, just a lowly engineering student
 
vzn
@Lozansky cool question, wonder myself the answer to that question, think itd be great if you could formulate it for the main site, dont think it has been studied much, suspect there are examples/ analogies. have found "at least 1" from long research over yrs.
@Lozansky what kind
 
@vzn Physics!
 
vzn
9:26 PM
@Lozansky great, what year/ country? studying QM already?
 
3rd year/Sweden. Yeah, it's only an introductory course tbf
 
vzn
@Lozansky still worthwhile am sure
 
10:20 PM
@Lozansky the usual example is for rotations, namely that the order in which you rotate a solid object with respect to the x-, y-, z-axes makes a difference as to the final orientation
Another analogue is passing light through polarizing filters at angles
Suppose you have three polarizing filters: one horizontal, one vertical, and one at 45 degrees to both
If you put the filters in that order, no light passes through the first two and so nothing comes out
But if you put the 45 degree filter between the two others, then light will pass through all three. (The intensity will low—only 1/8th of the initial incident intensity if I remember right—but it’s not zero.)
So the order in which you place the filters makes a difference to whether all the light is filtered
(People like to use this as an analogue for the Stern-Gerlach experiment. It’s not a perfect analogy but it does have merit.)
@vzn oh. Does the name John Bush ring a bell with you?
 
vzn
10:35 PM
@Semiclassical yes, found his excellent survey on PWH, cited in here, have been calling it the Couder-Bush theory recently, real pioneers =D math.mit.edu/~bush/?page_id=484
 
Then you’ll probably wish you were on campus here Thursday: physics.umn.edu/events/calendar/spa.all/thisweek/index/…
 
vzn
@Semiclassical way cool, another rabbit out of the hat, youre going for sure right? you really picked an outstanding school for physics =D ... wondering, did you look at any others? did you do your undergrad degree there too?
 
Yeah, I am, and I may get a chance to talk with him separately. (I did my degree at a liberal arts college which was within walking distance)
I will point out that this is a bit of a one-off—pwh is not a common topic of study in physics
 
vzn
@Semiclassical he seems to be sufficiently conservative in his claims/ demeanor/ reputation to not arouse any serious opposition so far :P
@Semiclassical the lecture is a one-off for you to attend or the dept to hold?
 
So I wouldn’t read_ too_ much into the school’s view on it from their invitation. It’s complicated
The latter
I’m an easy mark for talks like that
 
vzn
10:43 PM
@Semiclassical not sure what you mean by "its complicated". its physics, period. (and have strong feeling, much more in the future.) as for "easy mark," (lol) either that or youre way ahead of the curve™ :P
 
I mean that Bush being invited isn’t synonymous with an endorsement of such work, either in terms of its meaning or in terms of whether anyone here will start exploring it
So the institutional aspects are a bit harder to gauge
 
vzn
@Semiclassical "endorsement"? the university probably does not really "endorse" any work except their own, so to speak. & isnt that really a peripheral issue anyway? :|
 
True enough
 
vzn
thx for the good news =D
 

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