Wolfram Mathematica

acl

12:16 AM

@belisarius would you believe, I didn't remember what a discriminant was?

belisarius

@acl Me neither

acl

I read the question and your answer to it and, as a matter of principle, didn't look it up and tried to remember. in the end I gave up

belisarius

but it is the radical for solving polys

acl

yes :)

belisarius

was high school jargon

acl

12:18 AM

it's strange how this stuff slips out of your mind and becomes automated after a while

recently a mathematician acquaintance asked me why one needs to time-order operators in many-body quantum mechanics or field theory. I started forming an explanation and realized how long the trail to the bottom is, if you haven't thought about it before

so I said "god made it this way"

(although I guess "the matrices don't commute" should do it from a technical standpoint)

@belisarius I was wondering what residue could be here; any ideas?

belisarius

12:45 AM

@acl I thought he is dealing with nuclear reactor waste :)

R.M

@acl I guess they just show the stuff that's currently popular (in the English speaking world)... I grew up watching Bill Nye the Science Guy

acl

@R.M seems like I barely escaped that :)

also british programmes where more likely to be shown

@belisarius I couldn't find anything by googling and thought that strange

belisarius

@acl No, really I can only speculate ...

acl

@belisarius yes of course

R.M

@belisarius apparently everyone here must be a physicist who can appreciate his stuff and understand it to provide mma help

acl

12:51 AM

@R.M well I am a physicist but I still don't know. but I guess he felt that he was being attacked. happens

and so is bel

belisarius

@R.M I think that is the biggest intelligence challenge: to adapt your discourse to your audience

acl

@belisarius I think it is also a sign of scientific maturity (without meaning any offence to anybody!)

to realise that you have this viewpoint but not everybody does

well, not just scientific obviously

belisarius

@acl Notwithstanding that, I appreciate questions posed like "I have this specific Mma problem ... and the motivation is .... ".

R.M

I agree, it's not always easy... I've been in situations before where I'm like "Guys, you all get what I'm saying, right? This should be obvious stuff..." and they all have a blank stare on their faces. That was a while ago though, when I started grad school. Now I just avoid talking if I know the audience is not right or if I know I can't explain it simpler

acl

certainly, it may be interesting to know the background.

belisarius

12:57 AM

@R.M Then you have some geniuses (I know less than a handful of them) that can explain everything to everyone. But you need to have a razor blade in your mind to do that

acl

@belisarius in technical matters, I think you just need to have thought about everything to the bottom at some point. most people don't and it's hard

it's not a question of intelligence but of attitude (or so I claim :) )

R.M

@belisarius I just go the Feynman route... not the dozens of videos where he explains everything beautifully, but the one magnets video where he essentially says "If I explain 'How', it'll just lead to another 'Why' and if we go deeper, you don't have the expertise to comprehend it. So let me just stop it right here and say they're awesome, but I can't explain it"

belisarius

@acl may be. I saw a guy explained BCS to a bunch of 14 yo. They ended up understanding what a physical model is. Wonderful.

acl

@belisarius I hope it didn't involve couples dancing through each other. If I hear that one more time I'll scream

belisarius

@R.M Well, Feynman was a master doing that!

@acl No, it was a pure abstraction, as it should be. The only thing he did not do was the math.

acl

1:03 AM

but seriously, I think this really has to do with sitting down and thinking about what it is you're actually doing, and reducing it to concepts closer to "reality" until you end up with visualisable things

even though in practice you're just moving symbols around on a piece of paper

belisarius

@acl Hehe ... Can you do science in another way?

acl

@belisarius I think most do (although to get in the feyman spirit, it's cargo cult science--but who asked for my opinion anyway?)

hey that's what feynman says in that video too, it's all about what we accept as "obvious"

belisarius

@acl Once you are doing quantum whatever, if you don't rethink your problems from the very principles, you are soon lost in a pool of inconsistencies and brackets

acl

@belisarius mostly kets, unfortunately

belisarius

:)

acl

1:09 AM

I am now at 3:43 in that video, where he talks about "why does water expand when it freezes". that question was pivotal for me: I asked my physics teacher when I was 13 and she said "because it does"

that taught me something!

belisarius

Mpemba effect

The Mpemba effect is the assertion that warmer water can sometimes freeze faster than colder water. Although there is anecdotal support for the effect, there is no agreement on exactly what the effect is and under what circumstances it occurs. Historical observations Similar behavior was observed by ancient scientists such as Aristotle, "The fact that the water has previously been warmed contributes to its freezing quickly: for so it cools sooner. Hence many people, when they want to cool water quickly, begin by putting it in the sun. So the inhabitants of Pontus when they encamp on the ic...

acl

@belisarius yes I've read that. funny

belisarius

@acl and ... true

acl

that's a nice video. feynman was charismatic

(I realize that this is a trivially true observation)

belisarius

@acl Did you read something about his "Tuva project"

acl

1:15 AM

@belisarius I think so. must have been a pretty dangerous person to be around

belisarius

In the middle of cold war, he wanted to visit the city where soviets were doing their nuclear research because he had a bet on the existence of that city

acl

@belisarius ha

belisarius

Also, his adventures with prostitutes and the such are worth reading

acl

@belisarius I vaguely remember those

surely you're joking mr feynman and so on

belisarius

yep

acl

1:20 AM

also I liked QED: the strange theory of light and matter

I am not sure I understood it much better later

belisarius

He was a bright man

acl

@belisarius I think more relevantly he had a uniquely literal way of approaching things, at least, as far as his work on helium is concerned

reading his papers, he just takes things literally and pushes to the end. you keep thinking you could have done it, but it's too far. it takes too much courage. or, anyway, it looks that way (and remember I am looking at it from 50 years in the future!)

but really, the helium stuff is just a few simple arguments which conclude that the partition function shows a transition. it's extremely clear once you see it

belisarius

@acl Only a few can reason like that. Landau being my favorite

acl

@belisarius landau is my hero

belisarius

Take two silly arguments, and explain why galaxies rotate

:)

acl

1:26 AM

but that is different, if you read his papers (and books but this is clearer in the papers, although they are very old style of course and so hard to read) he reasons strictly within the bounds of his equations, although with huge gaps in the reasoning that you probably need to be landau to perform

@belisarius and deform some contour of integration in some incomprehensible way, yes :)

belisarius

@acl It's those huge gaps in his books that allow you to grow. Once you can fill the gap, and understand why it was obvious for him, you are two inches taller

acl

@belisarius yes I think L&L have made me what I am as a physicist, although this may not actually be an endorsement :)

belisarius

@acl It is. For you. :D

acl

in fact I first met L&L in my first year studying physics when I was giving a short talk (you were supposed to practice giving talks). I read about the principle of least action in feynman's lectures on physics, and decided to explain that. so I read about it in the lectures on physics, thought very hard and understood

then I saw it explained in half a page, in vol 1 of L&L. in fact, the second and third paragraphs in the entire book!

I was hooked of course, and it all went downhill from there

(as an aside, an interesting observation: I have written more than twice as many papers as pauli!)

belisarius

@acl We had Goldstein and L&L in our first mechanics course. I found Goldstein very boring, and it was queer how he could use 100 pages to explain exactly those 2 paragraphs

acl

1:36 AM

@belisarius luckily we were not taught anything at all about hamiltonian or lagrangian mechanics, so I learnt it by myself. suited me just fine

belisarius

@acl Pauli was a particular guy

Sommerfeld asked Pauli to review the theory of relativity for the Encyklopädie der mathematischen Wissenschaften (Encyclopedia of Mathematical Sciences). Two months after receiving his doctorate, Pauli completed the article, which came to 237 pages. It was praised by Einstein; published as a monograph,

acl

@belisarius on the other hand L&L cheat. for instance they say "take a deviation from the path, \delta x(t), and take it small; then blah blah"

but if you look at what they do, they silently also take the time derivative of delta x to be small

belisarius

@acl They are doing physics, not math

acl

@belisarius nevertheless, I have written more papers. I thought that's the only thing that counts?

@belisarius but it's a physical assumption: you are cutting off the short-scale physics, which is reasonable. they just don't mention it

or look at their derivation of the euler equation in flud dynamics. it's also not correct

but anyway I am not bad mouthing them, as I said, landau is my hero!

belisarius

I love those exercises on L&L where they say something like "be careful, this is a PhD thesis"

acl

1:40 AM

@belisarius in fluid mechanics, they casually ask you to solve some equation

turns out the solution is to do a cole-hopf transformation which turns it into the diffusion equation which is linear...

it's good to look at other books to get a sense of what is reasonable!

@rojo hi red one

Rojo

@acl Hi acl

and belisarius, and everyone

belisarius

@Rojo HI!

Rojo

2:16 AM

What's up

Mr.Wizard

Anyone here?

belisarius

@Mr.Wizard Let me see

yes!

Mr.Wizard

:D always the jester...

belisarius

@Mr.Wizard The salt of life

Rojo

@Mr.Wizard Here too

Mr.Wizard

2:28 AM

I posted what I thought was a pretty good answer, but it failed to get any votes. Besides feeling mildly disappointed I'm wondering if it either (a) it's broken/doesn't work, or (b) I could somehow explain it better.

0

A: MapThread over sublists of different length

Since MapThread accepts a level specification, I think our ragged MapThread function should too. raggedMapThread[f_, expr_, level_Integer: 1] := Apply[f, Flatten[expr, List /@ Range[2, level + 1]], {level}] Example: a = {{{67, 47}, {5, 99}, {70, 44}, {9}}, {{75, 70}, {61}, {16, 23}, ...

belisarius

Should we migrate this?

0

Q: How do I transform a rasterized graphic's coordinates back to its original ListPlot data coordinates?

From this question I successfully made an elliptical fit for my data. However, when I try and collect the datapoints within the ellipse via this question the coordinates of my ellipse correspond to an ellipse of a rasterized image of my listplot data and not the original. How can I transform or s...

Mr.Wizard

@belisarius Probably so, at is already references a question on this site, and it looks pretty good. I'll flag if you agree.

belisarius

@Mr.Wizard go ahead!

Mr.Wizard

By the way I'd like to know the answer to this question myself:

1

Q: CA Random 3 colors

Does exist a Cellular Automata Rule that is RANDOM (like the rule 30) and has 3 colors?

mathematica cellular-automata

belisarius

@Mr.Wizard Well, I don't understand the question ...

Rojo

2:33 AM

@Mr.Wizard Just got your upvote

Mr.Wizard

@belisarius Rule 30 CA produces pseudo-random (binary) data (down the middle column). Is there a 3-level rule that does the same?

belisarius

@Mr.Wizard Where can I see an example of a three level rule?

Mr.Wizard

The documentation has examples. Here's one:

ArrayPlot[CellularAutomaton[{50257, {3, {3, 1, 3}}}, {{1}, 0}, 50]]

belisarius

ok, thanks!

Mr.Wizard

@Rojo Thanks! Do you see how I might improve it?

Rojo

2:43 AM

@Mr.Wizard Perhaps you could add the solution to the question using it

but in any case, I think the quality of the answer is not to blame for the lack of votes, but the lack of visibility

I just got another upvote on the reopened question :)

and about 4 upvotes on the eternal question of the multiple undos

I think I'll give it a shot myself, humm

belisarius

@Rojo If you get multiple undos working and robust, WRI will buy your code (Or they will stab you to death)

Rojo

@belisarius I guess it doesn't need to be perfect to be useful

belisarius

@Rojo messing with the FE interface with buggy code is a dangerous way of working :)

Rojo

@belisarius Danger is fun

Mr.Wizard

@Rojo If "just" means 30 minutes ago that was mine. :-)

@belisarius LOL -- I think.

@Rojo I could do that, but it wouldn't showcase the feature of the function. What about this? (using my a data):

Rojo

2:50 AM

@Mr.Wizard "just" is applied to the invisible "realised"

Mr.Wizard

raggedMapThread[{##} ~Count~ _?OddQ &, a, 2]

Rojo

so

probably it was 30 mins ago

@Mr.Wizard I don't know, you already have a couple of examples to show the full extent of your solution, with level spec. But I think it's necessary even if it's obvious to answer the question

Mr.Wizard

Okay, will do.

Rojo

Btw, does anyone know if NotebookDynamicExpression can do independent updates

?

I don't think so

@Mr.Wizard, I just had a flashback

Did you get to test the scheduled task thing I once did and already forgot about?

Mr.Wizard

I just updated my raggedMapThread answer; please tell me if it reads better now.

@Rojo Despite seeing that here I don't think I've ever used it, therefore I have no idea.

Rojo

3:01 AM

@Mr.Wizard You owe me a bounty if it works. And if it doesn't, I already don't remember a thing of the code to debug it, ;D

Mr.Wizard

@Rojo I tried your code but rather quickly it hard-crashed Mathematica 7 and I couldn't figure out why. I realized that you were probably in no position do debug that, so I shelved it. I'm sorry I didn't say this sooner.

Rojo

@Mr.Wizard It's ok, I'm in less of a position to debug it now

Mr.Wizard

"Despite seeing..." referred to NotebookDynamicExpression.

Rojo

Oh, ok

belisarius

@Rojo Flagged for mod attention. Bounty Bullying

Rojo

3:02 AM

@belisarius Haha

Mr.Wizard

flag dismissed as unhelpful

Rojo

If I should bully someone

belisarius

@Rojo That was a really nice piece of code

Rojo

it would be stackexchanger

He didn't give me a bounty because he wanted to wait just to see what other answers came up, and then he just couldn't

I also have no idea how bounties work, never gave one

@belisarius Thanks

Working on the undo now, let's see what happens

belisarius

4

Q: Start Bounty fails

I am trying to start a bounty on this question of mine I get to the start bounty window: But nothing happens when I press the "Start Bounty" button. Is there something wrong with the question? My browser? Should I start a bounty on this question to get an answer? Edit Changed to bug sin...

bug bounty

Mr.Wizard

3:07 AM

@Rojo You should; it's a good exercise and helps the community. I'll pick another question or answer I like this week and put a +50 on it, just to "put my money where my mouth is" as they say.

@belisarius Oh nuts, I forgot about that. I hope it's fixed, or fixed soon!

Rojo

@Mr.Wizard Yeah, I want to bounty something too

belisarius

@Mr.Wizard let me try if they fixed it

Rojo

I guess that's the only way around those unseen late answers that get no credit

Good habit

Mr.Wizard

@Rojo for what it's worth I just recreated the crash with ScheduledTasks. I get this error message within the Notebook:

Unset::norep: Assignment on Global`private`extraTasks for Global`private`extraTasks[1] not found. >>

Rojo

@Mr.Wizard When you do what

Mr.Wizard

3:10 AM

Then I get a Windows crash dialog: "Mathematica Kernel for Windows has stopped working"

belisarius

@Mr.Wizard Nope, it is not fixed yet

Mr.Wizard

After evaluating your code, I ran the first three lines, waited maybe ten seconds, then ran the removeScheduledTask line:

runScheduledTask[x = DateString[]];
Dynamic[x]
Dynamic[Refresh[DateString[], UpdateInterval -> 1]]


removeScheduledTask[scheduledTasks[]];

Rojo

Let me try

Mr.Wizard

I repeated this process a couple of times and it crashed. It doesn't crash every time, or at a predictable interval, so I believe it may be a Kernel bug.

Rojo

Perhaps periodicals where buggy in v7, who knows

but I'll better save my notebooks before testing that

Mr.Wizard

3:13 AM

That's what I fear: not ready for prime time.

Oh, the error is not the same every time (I remember now). This time I got this:

Mathematica has detected an internal error:
  FreeExpr() called on live expression.

Followed by a different Windows error dialog:

Microsoft Visual C++ Runtime Library

   Runtime Error!

   ...MathKernel.exe

Rojo

Now, how would I do that on purpose I haven't the slightest idea

Saved. Time to test

I see a bug, but

a regular bug

Not a crash so far

Mr.Wizard

I just realized something probably quite relevant. When it doesn't crash the Dynamic[x] counter continues to change even after running removeScheduledTask[scheduledTasks[]]; -- it's my understanding that it should not. Maybe attempting to run the same event multiple times causes the problem?

Rojo

Yeah

That's what I meant

but in any case, if it does'nt serve you, what's the point in fixing it

Mr.Wizard

Do you suppose it's possible that the problem is running multiple runScheduledTask[x = DateString[]] tasks at once? Maybe v8 adds protection against that which v7 lacks?

It would be interesting to me to see if fixing that (if possible and not a lot of work) fixes the crash too.

Rojo

@Mr.Wizard It shouldn't be, this bug is probably my fault

Ok, I'll take a look later, after playing around with the undo

Be attentive to pings

Mr.Wizard

3:22 AM

Wow, you're really biting into Multiple Undo? You're a brave man.

Rojo

No

I'm just ignorant

I won't know the difficulties and subtleties until I've wasted my time

Mr.Wizard

Honestly, speaking from experience that's a great way to learn.

Rojo

I hadn't tried before because of Leonid's comments

but he clearly moved on and is quite busy

I hope you are both around if I need your opinions or tests on the undo things

Mr.Wizard

@Rojo I'm going to be doing other things too, but I'll try to check in now and again.

Verbeia

3:43 AM

Woo hoo, just clicked over 9000!

Mr.Wizard

4:25 AM

@Verbeia Nice. :-)

R.M

5:01 AM

@mr.w is a biglist tag necessary? Two of the questions are mistagged...

Decide as you see fit.I won't be around to answer you/reason with you for a while

belisarius

5:40 AM

@R.M Are you getting married too?

Mr.Wizard

7:36 AM

@R.M I don't know. I didn't realize two questions were mis-tagged, but I saw the tag description and I thought I'd give it a change by including my own question. Like other tag experiments if it doesn't take off we can delete it later.

Rojo

9:43 AM

@belisarius You're around?

belisarius

Yep, for a few seconds more

Rojo

Ok

I think I did this a way that can never be too efficient, but anyway... We'll see

How do we share code that's not so short?

Oh, that paste bin

belisarius

like ... how many lines?

Rojo

Not so many

belisarius

ideone, pastebin

Rojo

9:45 AM

just big enough to be very ugly in here

belisarius

but I am going to bed now

too tired

Rojo

pastebin.com/UZwU4AGA

Just test it for a min before

After running that, run setUpUndo[InputNotebook[], {"Input", "Text"}];

belisarius

but ... all those In[xx]??

Rojo

Oh crap

Ok

You can go to sleep then

:P

belisarius

ok. sorry, but I am reaaly tired

see ya

Rojo

9:49 AM

Sleep well

@Mr.Wizard

belisarius

bye

Rojo

You around?

Rojo

10:10 AM

Ok, when you're around, put this in a .m pastebin.com/TVD9U20H, and then do something like Needs["Undo`"]; SetUpUndo[InputNotebook[], {"Input", "Text"}]; Then, write some stuff, erase, write more blabla in Input or Text cells, and alt+left click on the cells to undo

There are a couple of leftover cells that serve no purpose there, but it's a draft. I mainly want to know how it works

Silvia

11:59 AM

@Rojo alt+left clicking undo the input, but at the same time my cursor disappeared

Hi @acl :)

acl

@Silvia hi!

wow, undo?

Silvia

I'm never brave enough to try undo myself :)

Rojo

1:57 PM

@Silvia You around?

Silvia

2:08 PM

@Rojo yes

Rojo

Hey :)

So you tried that code...

Does it always make your cursor disappear?

Silvia

missed the notification with my speakers turned down

Rojo

@Silvia it's ok. I sometimes don't even get pinged, don't know why

Silvia

:)

@Rojo Yes but everything else looks fine. I can input and evaluate as normal

Rojo

@Silvia Humm

I have MMA 8.0.4, Win7x64

and that doesn't happen. Or at least definately doesn't always happen

And you can undo properly apart from the ShowSelection going to False?

Silvia

2:24 PM

@Rojo me too

@Rojo Let me try it now :)

something strange happened @_@

Rojo

@Silvia Hope you saved your work

Save your work, don't have too much faith in me, hehe, I had barely tested it before sharing... The approach is probably very inefficient, so I just wanted to check how it worked for others in general before putting more time to that

Silvia

I created a Text cell and an Input cell. Then I alt+left clicked the Text cell, it was then be replaced by the contents of the Input cell. But I can't reproduce the phenomenon @_@ I'll try more.

Rojo

That's ugly

Silvia

@Rojo I used to think of saving history input in a special invisible notebook.

Rojo

@Silvia Yeah, that's what I tried

Silvia

2:35 PM

@Rojo what a coincidence LOL

Rojo

In fact

you could debug it for me

quite easliy

by making that notebook visible

It should have the same name of your notebook, appending a _undoData

Each cell's history is saved in a cell group delimited by a Start and End cells, celltagged with the CellID

Silvia

It sounds great. I'll check your code and see what I can do. But I have to say I'm not familiar with notebook programming..

For loading the package afresh, will I need to restart the frontend or just restart the kernel?

Rojo

I guess you can just open a new notebook

and run the Setup

Silvia

I see

Ok I see the problem.

It seems the cached contents are recovered in a reversed order as they were cached. So if I perform the undo-click by random orders, there will be a mistaken replacement.

Rojo

2:55 PM

That's weird, doesn't happen to me

I mean, you write a long text cell, then you start undoing

and you recover the stuff in the wrong order?

Silvia

!Mathematica graphics

Rojo

@Silvia I see

The problem is another one

You aren't getting separate cell groups for the two cells

Silvia

This shows what happened. I created two Text cells. They were cached perfectly. Then I undo-ed the first one.

@Rojo yes it looks so

Rojo

put

it to show the cell tags on the undo notebook

Perhaps your original notebook doesn't have CreateCellIDs to True?

Silvia

3:14 PM

@Rojo yes it's not set to True.

Rojo

@Silvia Weird, I'll look into it. Try setting it manually. Thanks a lot! :)

Silvia

You are welcome :)

Rojo

@Silvia Who knows... SetOptions[#, CreateCellID -> True] & is supposed to be run when you SetUp

on the parameter notebook object

No clue. Breakfast needed, brb

Silvia

@Rojo I looked the notebook's options, there is a UndoPrivate`CreateCellID -> True`.

Rojo

OHHH

You're a great remote debugger

Perhaps just in some systems CreateCellID requires the full context then... System`CreateCellID's

:) (ugly)

If you set that manually it works fine?

Silvia

3:29 PM

@Rojo Have a good breakfast. I need to have some midnight snack too :)

Rojo

@Silvia Ok, I was abusing already

Thanks again

Silvia

@Rojo yes it works fine now

@Rojo welcome again :)

Rojo

4:43 PM

Good

Rojo

7:21 PM

I never thought I'd write /. HoldPattern@\[Infinity] -> \[Infinity]

belisarius

8:33 PM

Infinite monkey theorem

The infinite monkey theorem states that a monkey hitting keys at random on a typewriter keyboard for an infinite amount of time will almost surely type a given text, such as the complete works of William Shakespeare. In this context, "almost surely" is a mathematical term with a precise meaning, and the "monkey" is not an actual monkey, but a metaphor for an abstract device that produces a random sequence of letters and symbols ad infinitum. The relevance of the theory is questionable—the probability of a monkey exactly typing a complete work such as Shakespeare's Hamlet is so tiny tha...

Rojo

9:16 PM

@belisarius Haha, that's not exactly why I typed it

belisarius

@Rojo Just trying to help you to explain mother Nature

belisarius

9:42 PM

waaaay too localized

-2

Q: problem with NDSolve

Here is the code I want to solve the equation: Clear["Global`*"] ta = 30; rha = 0.2; altitude = 0; p = 101325 (1 - altitude 2.25577 10^-5)^5.2559; roair = p/(287 (ta + 273.15)); tka = 273.15 + ta; c1 = -7.85951783; c2 = 1.84408259; c3 = -11.7866497; c4 = 22.6807411; \ c5 = -15.9618719; c6 = 1.80...

differential-equations numerical-integration

@acl Hiya!

acl

@belisarius hi! just discovered that to approximate an integral by a sum you need very small discretisation steps. took me half a day

@Rojo when would you need this?

Rojo

@acl Hello acl

What are you referring to?

belisarius

@acl Errr ... Integrals are limits, yes

acl

@Rojo /. HoldPattern@[Infinity] -> [Infinity]

@belisarius I know:) I mean, I was approximating a series as an integral in my head without thinking about it and of course the numerics didn't agree

belisarius

@acl He is shuffling keywords. Weekend fun

Rojo

9:48 PM

Ah, well, I used it to fix a bug on a question of Mr.Wizard, of implementing scheduled tasks. The issue with Infinity is that it evaluates to DirectedInfinity[1]

acl

oh your're right

who'd have thought

belisarius

An Infinity by other name (TM)

Rojo

Yeah

belisarius

@acl With oscillating functions it usually works without much care

acl

@belisarius did you compose this yourself? very impressive

Rojo

9:50 PM

and DirectedInfinity[1]

parses as Infinity

so it get's messy

Weird design

acl

@Rojo probably a reasons somewhere

belisarius

@acl Yes. I am selling marketing material to WRI.

acl

@belisarius example: Exp[-I*en*m/size], summed over m=1 to size for large en

belisarius

@acl hehe

"large en" :D

acl

it's equivalent to the integral when size is larger than eg 10*en

@belisarius well the original problem I had was a many-body hamiltonian driven periodically in time. so I had some gigantic matrices multiplying some eigenstates multiple times etc, and I wasn't getting the asymptotics I expected. turns out my system size was too small

nice way to spend my sunday. luckily the girlfriend is on a business trip so am free

belisarius

9:54 PM

Enlarge your system and switch to statistics :)

acl

@belisarius my analytical calculations are for infinite systems, actually

it's the numerics that I have trouble with

and actually this is an attempt to develop stat mech for nonequilibrium systems, so what you say is precisely what I am trying to do :)

belisarius

That remind me a joke (but true story). My friend (Argentinian too) was talking with her physician in the US about the difficulties of being expat, language, etc. And she came out with I have problems with my bowels ...

Transcript for