The h Bar

12:20 AM

I would appreciate if someone is able to help me by answering this question

0

Q: Two angular velocities on two segments connected by a hinge joint differ only by the joint angle velocity and a (time-variant) rotation matrix

I was reading this article called "Joint Axis and Position Estimation from Inertial Measurement Data by Exploiting Kinematic Constraints", but I'm not understanding one part, which doesn't let me proceed in the reading of the same. From the physical point of view, we have the following situation...

user228700

4:52 AM

@JohnR: Morning! :-) Here's my to-read list for the summer:

user228700

user228700

It's embarrassingly short, yes, but I don't want to overwork myself. Besides, I think it would be better for me to spend longer with good books than race through easy reads.

John Rennie

@Kaumudi.H I haven't read any of those.

user228700

Huh? Not even The Giver?

John Rennie

Who wrote The Giver?

user228700

4:56 AM

Lois Lowry

user228700

The Giver Quartet

The Giver Quartet is a series of four young adult novels by Lois Lowry. The quartet consists of The Giver (1993), Gathering Blue (2000), Messenger (2004) and Son (2012). The first book won the 1994 Newbery Medal and has sold more than 10 million copies. The story takes place in the world of the Giver. Each book has a different protagonist, but is set in the same futuristic era. == Plot overview == === The Giver === The Giver is a 1993 American children's novel (generally Young Adult or older) by Lois Lowry. It is set in a society which is at first presented as a utopian society but gra...

John Rennie

By 1993 I was already too old for young adult books :-(

user228700

EEK, forgot to add All Systems Red. Just did. Anyhoo, what is that book series you'd recommended to me about a person living the same life over and over?

user228700

@JohnRennie :-/ Hmm, OK...

user228700

Mar 5 at 11:03, by John Rennie

There is a really good book you should read by Kate Atkinson and called Life After Life

user228700

5:02 AM

AH, there it is!

user228700

Wokay, added three more books to the list. That's it, no more!

John Rennie

All Systems Red is a novella really, and it's a very quick and easy read.

user228700

@JohnRennie I see. The Velveteen Rabbit is a children's book :-P An easy 15-minute read.

John Rennie

I wouldn't dismiss the quick and easy reads. Sometimes it's nice to have a book you can just pick up and sprint through without having to work at it.

user228700

Yes, of course. I'm not doing any dismissing :-) I said that I think it would be better for me to sit with some of the tougher reads this summer.

John Rennie

5:06 AM

If you like bittersweet endings then The Death House by Sarah Pinborough is an excellent read. Although I don't think it's specifically described as young adult it is really.

user228700

Well, tough relative only to the quicker reads.

user228700

@JohnRennie I don't restrict myself to the YA genre, you know...

John Rennie

I think Life After Life is a very, very good book though it can be hard going at times. It is most definitely not young adult!

user228700

But I will be sure to check it out, thank you :-)

John Rennie

½ a day to go now? :-)

user228700

5:09 AM

@JohnRennie I see. I've added it to the list so I will let you know how it goes! I might not find it at the library so I might just actually buy it. After having read some on a screen, I'm finding that I'd much rather read the physical copies; I find it hard to finish softcopies...

user228700

@JohnRennie Yeah! :-)

John Rennie

My niece prefers real books as well.

user228700

I see :-)

John Rennie

I'm genuinely not fussed. I do still read physical books, usually when someone has given me a book, but I'm just as happy reading on my tablet.

user228700

Like I said, I find it more difficult to engage with the text on screen as actively as I would on paper, which subsequently at least partially results in this inability to actually finish the book.

user228700

5:15 AM

I read both Fangirl and Eleanor & Park on screen.

user228700

The latter was a delightful book, which is why it wasn't a pain to read it on my laptop but the former, well, that book sort of sucked, which added to the misery of having to read it on my (now dead) tablet.

user228700

Anyhoo :-) I'd better get back to revision. I'll see you tomorrow, then!

John Rennie

See you later.

@BernardoMeurer this is pretty much how Windows does it if you're writing Windows apps in C/C++. The downside is the overhead of processing definitions you don't need for every file, but with modern compilers that overhead is pretty small.

Rumplestillskin

5:54 AM

Hello all! Does anyone have any experience in PPN formalism for the field equations of general relativity? If so, would you mind checking out my recent question. There is a cold hard +50 bounty awaiting whomever puts forth a comprehensible derivation.

Slereah

6:56 AM

hey hey

DanielSank

@BernardoMeurer In my experience, that is the transpose of how code should be organized.

Slereah

Just put all your code in a gigantic single C file

Slereah

7:14 AM

Classification of electromagnetic fields

In differential geometry and theoretical physics, the classification of electromagnetic fields is a pointwise classification of bivectors at each point of a Lorentzian manifold. It is used in the study of solutions of Maxwell's equations and has applications in Einstein's theory of relativity. == The classification theorem == The electromagnetic field at a point p (i.e. an event) of a Lorentzian spacetime is represented by a real bivector F = Fab defined over the tangent space at p. The tangent space at p is isometric as a real inner product space to E1,3. That is, it has the same notion of vector...

Why have I never heard of this

Slereah

7:47 AM

Sulla teoria e sulla classificazione delle omografie in uno spazio lineare ad uno numero qualunque di dimensioni

Good thing Italian just sounds like bad French

Kenshin

Let philosophy hour begin

Slereah

>> philosophy.stackexchange.com

Kenshin

If one subscribes to "existentialism", does this mean "morality" is now a choice?

Slereah

Kenshin

I'm a physicist tho

I want the opinion of physicists

they're more logical

yuggib

8:01 AM

@Slereah At least italian was not ruined by the influence of anglo-saxon languages (at least up until the late twentieth century).

Slereah

please, it's the other way around

French corrupted English

Have you ever read pre-french corruption english

yuggib

they clearly corrupted each other

Slereah

Yore folk, such as the British builders of Stonehenge, mealfully wondered about the heavens. The first folkdoms, such as those of Sumer, Midrike, Egypt and the Mayas, sometimes built big losseners, where they would keep watch on the heavens.
These folkhoods knew much about the shrithing and setting of the stars and wanderers, and often drew bilds of them. The Olden Greeks cleaved the night sky into starbilds, still ongot by roomlorers and starcrafters to this day. However, they were also unaware of the true workings of the heavens; Aristotle believed the Sun whirled about the Earth

yuggib

ye aulde english?

Slereah

The coming of Einstein was one of the biggest leaps in tunglecraft. His Beholding of onlay showed that sweerdom is a forthmake of the bendings of roomtide made by bulk, and also showed how bulk and dodrive were the same. It also unraveled the wonder of the speed of light; showing how as things shrithed almost at that speed, it would both slow its tide and gain bulk. Edwin Hubble later found out that stars were not huddled in one cluster, but set out in shedded clusters known as starswirls.

Good old Einstein and his Tunglecraft

yuggib

8:06 AM

Hie dygel lond
warigeað, wulfhleoþu, windige næssas,
frecne fengelad, ðær fyrgenstream

under næssa genipu niþer gewiteð,
flod under foldan. Nis þæt feor heonon
milgemearces þæt se mere standeð;
ofer þæm hongiað hrinde bearwas,
wudu wyrtum fæst wæter oferhelmað.

þær mæg nihta gehwæm niðwundor seon,
fyr on flode. No þæs frod leofað
gumena bearna, þæt þone grund wite;
ðeah þe hæðstapa hundum geswenced,
heorot hornum trum, holtwudu sece,

feorran geflymed, ær he feorh seleð,

Slereah

Beowulf?

yuggib

yep

Slereah

Old french is fairly unreadable too although a bit less than old english

yuggib

old italian is perfectly readable

Slereah

Mama mia

yuggib

8:08 AM

that is even wrongly spelled

Slereah

That is a spicy meatball

Que maint conteres vos aconte,
Conment Paris ravi Helayne,
Les maux qu'il en ot et la paine,
De Tristram qui La Chievre fist,
Qui assez belement en dist
Et fables et chançons de geste,
Romanz de lui et de sa geste,
Maint autre conte par la terre.
Mes onques n'oïstes la guerre,
Qui mout fu dure de grant fin,
Entre Renart et Ysengrin,
Qui mout dura et mout fu dure.

ye olde french

yuggib

This I can understand pretty well (compared to old english)

Slereah

yeah it's mostly a few words and verbs that are weird

John Rennie

Even middle English is hard. Try reading Chaucer.

Slereah

Is that the Canterbury Tales guy

yuggib

8:12 AM

@JohnRennie can you read old english?

John Rennie

It is at least obviously English, unlike Old English, but it's still hard to understand.

@yuggib No.

@Slereah yes

yuggib

@JohnRennie Is it studied in schools anymore (or ever)?

Slereah

I think english books start at Shakespeare in schools

John Rennie

@yuggib it was in 1977 when I did O Level English :-)

yuggib

@JohnRennie old english I was meaning

Slereah

8:14 AM

I mostly remember what we read in school

They loved making us read Zola and Hugo

the most boring books

Never make school children read authors that were published in newspapers

ie paid per page

Mithrandir24601

@yuggib I didn't do it in school (yeah, started at Shakespeare), but they might have looked at it in A-level

John Rennie

@yuggib no, or at least not at O Level (age 16). You might study Old English if you do A Level English (age 18) and I'm sure you would if you do an English degree.

Slereah

Beware, Chaucer is nothing but FILTH

John Rennie

We'd still be speaking Old English if it wasn't for the bloody Normans :-)

Slereah

Normans get out

yuggib

8:17 AM

@JohnRennie I see. We still study latin during all high school

Slereah

Mamus mius!

John Rennie

@yuggib We did two years of Latin but gave it up unless pupils studiedfor the O levels.

It was actually quite fun to do a bit of Latin, though I'm not sure it's been much use to me over the years.

Mithrandir24601

@yuggib I think the school I went to just started latin classes up a few years ago - not sure if it was a success or not

Slereah

School also made us read the early 20th century absurd drivel

Like Ubu Roi

Which I'm sure was hilarious when it came out 120 years ago

Mithrandir24601

@JohnRennie reading the Principia?

yuggib

8:20 AM

We cannot choose...it's five years of latin, five hours per week (compared to two/three of mathematics and two of physics (only in the last three years)) ;-P

Mithrandir24601

OK, that's a bit much :/

yuggib

And that is the "scientific" program; I'll let you imagine the "classical studies" program

John Rennie

@Mithrandir24601 no-one reads the Principia unless they're studying the history of science or they're a masochist :-)

yuggib

@JohnRennie which Principia ? the interesting or the boring ones?

Mithrandir24601

@yuggib :o Oh dear. Oh dear

Slereah

8:22 AM

The Principia Discordia

I've read Russell's Principia Mathematica

Not all of it, but I redid by hand the first 14 chapters or so

yuggib

^ those are the interesting ones ;-P

Mithrandir24601

I was talking about Newton's Principia Mathematica, but whatever works :P

yuggib

@Mithrandir24601 to be fair, russell's ones are not in latin

Mithrandir24601

Where's the fun in that?

Slereah

There's a 2008 math paper in latin

yuggib

8:25 AM

I think that, apart from the pope and very other few exceptions, nobody in the twentieth century wrote in latin

Slereah

2006, actually

link.springer.com/chapter/10.1007/0-8176-4478-4_18

Well the Vatican has its own science paper

yuggib

@Slereah latin is still official language of the vatican iirc

Slereah

it is

pas.va/content/accademia/en.html

The modern publications are in english

very sad

Slereah

9:33 AM

Oh god, Lagrangians require jet bundles

Kill me

"Let $Z$ be a manifold"

Who is this madman

Bernardo Meurer

@JohnRennie Halp

John Rennie

@BernardoMeurer morning. What's up?

Bernardo Meurer

@JohnRennie Good morning John :)

So, nice advancements to my final project, I have my parsers almost done :^)

I have decided to store the CSV entries in a doubly linked list

And I've written all the functions for it, push, reverse, remove, print, etc

@JohnRennie Can you test-run it?

John Rennie

9:49 AM

OK ... ?

Bernardo Meurer

I'm afraid one of the parsers isn't 100%

John Rennie

@BernardoMeurer yes of course. Is it on github?

Bernardo Meurer

Yep, github.com/bemeurer/prog/tree/master/project02

You should have access to that

John Rennie

That link gives me a 404 error

Bernardo Meurer

github.com/bemeurer/prog

Try this one, it's project02

(Make sure you're logged in)

John Rennie

9:55 AM

Ah it was failing because I wasn't logged in. Give me a mo while I remember the syntax for git clone ...

@BernardoMeurer: huh, why doesn't git clone git://github.com/bemeurer/prog.git prog work?

Oh, because it's a private repository. Hang on, I'll clone using the key pair.

Bernardo Meurer

Hm

Over here I just do git clone URL and it asks me for username and password

John Rennie

Ah, OK, that's working.

Slereah

"A system of $k$-order partial differential equations on a fiber bundle $Y\to X$ is defined as a closed subbundle $\mathfrak E$ of a jet bundle $J^k Y \to X$."

Help

Bernardo Meurer

Oh, dangit, it may not work for you because of strsep()

John Rennie

@BernardoMeurer: I can't build it I'm afraid because it uses SDL which isn't available in Windows

Bernardo Meurer

10:01 AM

@JohnRennie Ah, I'm not using any of those, just take them off

They're just there 'cause I'll need them later

John Rennie

utils.c(52): error C2059: syntax error: '}'

Bernardo Meurer

wat

Ah

Are you using C99?

John Rennie

MSVC 2015

Bernardo Meurer

ID newID = {};

It's saying that this initializer for structs is illegal

John Rennie

parser.obj : error LNK2019: unresolved external symbol _strsep referenced in fun
ction _parseStations
utils.obj : error LNK2019: unresolved external symbol _strptime referenced in fu
nction _mkDatetime
utils.obj : error LNK2019: unresolved external symbol _asprintf referenced in fu
nction _IDToStr
main.exe : fatal error LNK1120: 3 unresolved externals

Bernardo Meurer

10:04 AM

Dangit

It's all POSIX stuff

:P

You should get cygwin John

It's black magic, but it works

Anywho

The problem is at parseTrips over in parser.c

It should work just as well as parseStations but it seems to not include much of the file

Ah

I think it was an issue in my IDE's terminal :^)

Slereah

@0celouvskyopoulo7 So it turns out the presentation I did on differential geometry in school, jet bundles were indeed necessary to prove that geodesics are the shortest curves

$$\delta L = \sum_{0 \leq | \Lambda |} (-1)^{|\Lambda|} d_\Lambda (\partial_i^\Lambda \mathcal L) \theta^i \wedge \omega$$

I am ready to die

Bernardo Meurer

10:19 AM

@JohnRennie Can I have a struct in foo.h with a function pointer to a function in foo.c? I would think no

John Rennie

Yes, I don't see why not. You just need to know the function type when writing the struct declaration. You can't initialise the pointer in the header file.

Bernardo Meurer

Ah, right

Hm

I guess my function newStationNode in utils will be the initializer :)

To work!

John Rennie

A function pointer is just a variable. You need to set it yo the function, but of course you can't do that at compile time because the address of the function isn't known.

Hi @nbro. Did you see my comment about proper acceleration?

nbro

@JohnRennie Hi, I guess I missed it...

John Rennie

yesterday, by John Rennie

@nbro: GR gives us an expression for the four-acceleration, and this includes both terms due to non-inertial motion and due to spacetime curvature: $$ a^{\mu}= \frac{du^{\mu}}{d\tau}+\Gamma^{\mu}_{\alpha \beta}u^{\alpha}u^{\beta} $$

Bernardo Meurer

11:06 AM

@dmckee Is it okay if each element of my linked list has a pointer to head and tail?

This way I can avoid O(n) brouhaha whenever I want to do something in reverse

Sha Vuklia

Guys, say we have a uniformly charged sphere. I see it makes sense to assume the charge density is finite. However, what would go wrong if we assume a finite charge density in the interior of the sphere, and a charge density described by the Dirac delta function at the surface? To me it seems that we would still have a finite charge, so I'm guessing the distribution wouldn't be uniform. How to make this a bit more rigourous, tho?

John Rennie

@ShaVuklia I'm not sure I see the problem. You can have any charge density function you want as long as it integrates to a finite value.

Sha Vuklia

@JohnRennie Well, my question is if we still have a uniform charge distribution, if we choose our charge density to be finite in the interior, and described by the Dirac delta function on the surface. Because as far as I know, in the case of uniform charge distribution in a solid sphere, we have zero charge on the surface, because our charge density if finite. However, if we described the charge density by the Dirac delta function, we would not havr zero charge on the surface.

ACuriousMind

@ShaVuklia No, that's not uniform (and that charge density does not really make sense- you have a charged sphere but a part of the charge is confined exactly to the surface?

John Rennie

If you have a uniform charge distribution then $\rho(r)$ would be a step function and it's value isn't defined at $r = R$ (R = radius of sphere).

But that doesn't matter because the edge of the sphere has zero volume so the charge contained within it is necessarily zero.

Sha Vuklia

11:20 AM

Yea I see it now

I donno why I was confused

Sir Cumference

Why does LaTeX first load as really small text, then as bigger text?

Sha Vuklia

If you just decrease your volume, the charge will decrease, so it can never be non-zero on the surface

(volume of a Gaussian surface that encloses part of the sphere surface)

Bernardo Meurer

@JohnRennie These doubly linked lists with head and tail pointers are mushing my brain

John Rennie

Doubly linked lists shouldn't present any problems.

Any linked list requires careful management to avoid mangling the links, but double linking isn't any harder than single linking.

Bernardo Meurer

@JohnRennie It's just that I'm trying to embed the head and tail pointers into the list

typedef struct tripnode {
    trip data;

    struct tripnode *prev;
    struct tripnode *next;

    struct tripnode *head;
    struct tripnode *tail;

    void (*headInsert)(struct tripnode *self, trip data);
} trip_n;

And it's a bit confusing at first

John Rennie

11:35 AM

The prev pointer is null and the head and the next pointer is null at the tail.

Bernardo Meurer

Yes

John Rennie

You store the head and tail pointers in every list element?

Bernardo Meurer

Uhum

It makes things easier after you've implemented the functions

Is that a bad idea?

John Rennie

Well it means if the tail changes because a new element is added you have to go all the way through the list and update every element with the new tail pointer.

Bernardo Meurer

Because then I can do all my operations on the whole list just passing any element of the list :^)

Shit

I had not thought of that

Goddamit

John Rennie

11:37 AM

I must admit it isn't obvious to me why a linked list is the best solution in this case. I'd have used an array to store the data.

Bernardo Meurer

Because I want to get fancy

John Rennie

If necessary use a second array of the same dimension as an index for things like sorting.

Bernardo Meurer

i.e. harvest points by using what we learned in class

Goddamn

I thought I was super smart

With that those head and tail pointers

nope, lel

THEY CAN BE A DOUBLE POINTER

AHA!

Bingo

AH!

Can't I just have two bools

head and tail?

Ah, that doesn't help me

Dammit

Balls

John Rennie

The head is uniquely identified by prev being null. Likewise the tail by next = null. Why would you need extra bools?

Bernardo Meurer

Yeah, exactly, why I said it didn't help me :P

I can make the head and tail things be double pointers to an external variable

This way I can still call operations by just passing any node

John Rennie

11:44 AM

I've never seen that done in an implementation of a linked list.

Bernardo Meurer

Do you understand why I want it though?

John Rennie

The head is normally stored ina variable because it never changes, and the tail is found by navigating the list.

Bernardo Meurer

Yeah, I will store it in a variable, but all the elements will have a pointer to that variable

Well, the variable is a pointer to head and everyone points to that pointer

POINTERS WOOHOO

John Rennie

Presumably you want a quick way to find the head or tail when given any member of the list?

Bernardo Meurer

Yes, as well as being able to pass any node to it's function pointers and have them work

i.e. inserting at head passing a middle node

John Rennie

11:47 AM

I guess storing a pointer to a pointer to the head/tail in every list element is a way to do this, though obviously at the expense of extra storage space.

Bernardo Meurer

Meh, a pointer is what, 8 bytes?

Good lord, this is going to be a mess :D

John Rennie

Are you allowing adding at the head to you can build a sorted list?

i.e. you sort when adding the new element

Bernardo Meurer

Yeah, I can add at head and at tail

my CSV's are already sorted though, so as long as I invert the list after reading it's sorted

John Rennie

You normally wouldn't add at the head, though if you're sorting as you build the list I can see why you would want to.

Bernardo Meurer

Maybe I should just read the file backwards le

I add at head because I didn't have a tail pointer before, and it's MUCH faster to add at head then

so I added at head and inverted after

John Rennie

11:53 AM

That is a bit bizzare

Bernardo Meurer

Yes

Which is why now that I have a tail pointer I can just add at the tail

John Rennie

Most of us would just keep the address of the current tail in a separate variable.

Bernardo Meurer

Yep

@JohnRennie How do people do those C functions with variable arguments? Like, say, printf can take any number of arguments depending on the string

John Rennie

@BernardoMeurer In general it's a good idea to code in the obvious way because other people reading your code will expect you to code that way. If you work on a collaborative project not using the obvious solution will not make friends and influence people.

Bernardo Meurer

So, not make everyone point to head and tail?

nbro

11:57 AM

@JohnRennie I must be honest I'm not familiar with general relativity...at the same, I'm wondering why some people define proper acceleration as the acceleration measured from an inertial frame of reference... Is this last version a special relativity version?

John Rennie

@nbro Proper acceleration is not the acceleration measured from an inertial frame of reference, it is the acceleration measured in the rest frame of the observer.

The rest frame of the observer isn't an inertial frame if the proper acceletration is non-zero.

Sha Vuklia

Guys, do we know what the electric field is on the surface of a charged hollow sphere? I know that we have a discontinuous electric field (the difference between the upper and lower perpendicular electric components is $1/\epsilon_0\sigma$, if you are close enough to the surface), however, what about at the point of discontinuity? Is it "infinite" there?

John Rennie

The discontinuity doesn't exist in reality - it's an idealisation. In real life charge distributions always change smoothly. So handling charge localised in a 2D surface is always an unphysical approximation.

Slereah

Gauss theorem

Sha Vuklia

I understand it's not realistic, but I was wondering what the theoretical/ideal value then would have been

ACuriousMind

12:07 PM

@ShaVuklia It's best to think about it as "undefined". I can't imagine an actual situation where that value would matter - if you are close enough to the sphere that it matters what the value there is, it's likely that the approximation of the sphere as being infinitely thin breaks down anyway.

Sha Vuklia

Ok, sounds good @ACurious

Slereah

The theoretical value of the field at the discontinuity is gonna be the value outside

Sha Vuklia

there are two values outside, so I'd go with undefined too

Slereah

and then drop to $0$

you can define it as a distribution

nbro

@JohnRennie Well, maybe I'm misinterpreting this Wiki article en.wikipedia.org/wiki/Proper_acceleration, but it says "It is thus acceleration relative to a free-fall, or inertial, observer who is momentarily at rest relative to the object being measured.", even though here it also says that the observer is at rest relative to the object being measured, which I suppose is equivalent to your statements, but, at the same time, the sentence also says that the observer is inertial...

Kenshin

12:17 PM

Yo dawgs

nbro

Another point from en.wikipedia.org/wiki/Inertial_frame_of_reference: "an accelerometer moving with any of them (i.e. inertial frame of reference) would detect zero acceleration.", where here acceleration is supposed to be proper acceleration, since an accelerometer measures theoretically proper acceleration

Kenshin

If i accelerate beyond the speed of light, do I go back in time?

0celouvskyopoulo7

@Slereah you do not need fucking jet bundles

and geodesics are not the shortest curves; the shortest curves are geodesics

Slereah

Well no, not for a general connection

0celouvskyopoulo7

who cares about a general connection?

send me this thing pelase

Slereah

12:25 PM

Ehresmann

arxiv.org/pdf/0908.1886.pdf

0celouvskyopoulo7

Fucking physicists

You know they are the worst

They either do it completely wrong

Or with so much overkill it't stupid

Sha Vuklia

^ you can't live with them or without them :P

Slereah

how would u solve a differential equation without the jet bundle, mister funny man

0celouvskyopoulo7

@Slereah I do it all the time

amazon.com/Elliptic-Partial-Differential-Equations-Second/dp/…

just use that

Slereah

Local mom solves PDEs without the jet bundle

Geometers hate her!

0celouvskyopoulo7

12:30 PM

Seriously though, the jet bundle is not necessary.

Slereah

Yeah I am wondering what it's for

0celouvskyopoulo7

On what page is it claimed they are necessary for whatever

Slereah

Well they define the Lagrangian via bundle wizardry

And in my proof of geodesics during that presentation I did use the length function

which is roughly a lagrangian

0celouvskyopoulo7

Serious question

Have you actually read O'Neill's material on geodesics

Slereah

I think so?

0celouvskyopoulo7

12:34 PM

You do NOT need the jet bundle, you do it via an old-fashioned variational technique, or the Gauss lemma or whatever

Slereah

I don't really read O'neill in order so it's hard to say

I know

I am just sayin'

you could

And that professor back then mentionned it

that the method I used was to be done properly via jet bundles

0celouvskyopoulo7

"properly"

That's like saying the correct definition of group is a "groupoid with one object"

It's an overcomplication

Slereah

well, is it not

0celouvskyopoulo7

@Slereah Yeah and Picardy-Lindyhop is really just elliptic regularity theory

Don't bother with ""proper"" proofs

Slereah

what would u say the proper definition of the Lagrangian on a manifold is

0celouvskyopoulo7

12:38 PM

What Lagrangian?

@ACuriousMind Please help

He's not making sense

Slereah

The lagrangian in general

0celouvskyopoulo7

I don't know about Lagrangians in general. In Arnold there are no jet bundles. Some people have jet bundles. For what reason, I cannot say.

Slereah

I am unsure

Maybe it's easier for like gauge theory

Kenshin

I flip a coin 99 times and it is heads

what is the chance of heads comnig up on the next flip?

0celouvskyopoulo7

1/100

Kenshin

12:48 PM

realli?

Sha Vuklia

1/2?

Slereah

100%

Kenshin

the book says there's two people

Dr. John the man of science, he says 50%

Sha Vuklia

doesn't it depend on how you ask the question?

Kenshin

and Fat Tony, he says it is a loaded coin

Sha Vuklia

12:50 PM

or maybe the coin has heads on both sides

Kenshin

And @0celouvskyopoulo7 is in between

yes good point @ShaVuklia

now ur thinking like fat tony

Sha Vuklia

XD

0celouvskyopoulo7

Fat Tony sounds like a sicilian

I trust him with a bet

Kenshin

I wouldn't trust if he was flipping the coin tho

ACuriousMind

@0celouvskyopoulo7 It's the name of a mafia boss in The Simpsons...

0celouvskyopoulo7

12:58 PM

@ACuriousMind Why would I know that?

And how come you respond to that and not Sam's ramblings

Kenshin

Hi @JohnDuffield

Slereah

I'm sure most Americans know more characters from the Simpsons than from the Bible

Homer Simpson is of course the equivalent of biblical Esau

Selling his birthright for a bowl of lentils

AccidentalFourierTransform

1:34 PM

lentils are good

except if they are cursed

that's bad

Avantgarde

who cursed them lentils

AccidentalFourierTransform

they contain potassium benzoate

Avantgarde

is it bad?

AccidentalFourierTransform

yes

you may go now

Secret

[random question] We know that string theory often give the impression of a physical theory that look so much like it should be in mathematics, but are there examples where the opposite happens?

Avantgarde

1:40 PM

where should I go?

Lentils are good

AccidentalFourierTransform

imdb.com/title/tt0758368/quotes

Bernardo Meurer

@JohnRennie Still around?

Avantgarde

oh simpsons. I never watched/liked that

AccidentalFourierTransform

ಠ_ಠ

nbro

1:55 PM

Reposting this question here with the hope somebody qualified can help me.

0

Q: Two angular velocities on two segments connected by a hinge joint differ only by the joint angle velocity and a (time-variant) rotation matrix

I was reading this article called "Joint Axis and Position Estimation from Inertial Measurement Data by Exploiting Kinematic Constraints", but I'm not understanding one part, which doesn't let me proceed in the reading of the same. From the physical point of view, we have the following situation...

rotation angular-velocity gyroscopes

Bernardo Meurer

@dmckee @JohnRennie Someone save me, I have angered the pointer gods

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