The h Bar

G. Bergeron

00:00

spinodal decomposition?

Skyler

@G.Bergeron nvm then

its the opposite of diffusion in someways, when your free energy prefers seperation

you originally actually start off by learning it as a diffusion with a negative D, but then since you would reach a singularity you need to introduce a higher order correcting term

G. Bergeron

00:20

Cool but yeah, I never read on that, just now.

Skyler

00:47

@DanielSank bro are you running that linear alg room with heather?

or maybe its @heather

Skyler

01:02

@G.Bergeron quick question

are you familiar with dislocations?

G. Bergeron

a little bit, but better be quick, I'm fighting with five mathematica notebook right now

Skyler

np, I just came across a question related to partial dislocations (frank disloccations)

It asks: Are Partial dislocations of this type edge dislocations?

basically frank dislocations are when you have an edge dislocation split into two half offset planes

full edge: 1 discontinuity offset by 1 burger vector $b$
splits into
partial: 2 discontinuities offset by same total burgers vector, but each is part of the $b$ is split into a vector sum

I'd say yes but the question seems too easy...

heather

@Skyler, DanielSank is the teacher, I most certainly could not be =)

Skyler

@heather someone should accept my request to join that room then

heather

@Skyler, okay

I don't know if I can, I think @DanielSank is the only person who can

G. Bergeron

01:07

not a question about linear algebra

Skyler

@G.Bergeron not related to us, just kinda wanna talk about it too

G. Bergeron

pl

ok

heather

@Skyler, yeah, @DanielSank is the only room owner

G. Bergeron

but to the question... I'm thinking

Skyler

@heather, tell Dan I'll bribe him with some of my notes specifically geared for what you guys are talking about

since it seems like he's forgotten to check this chat room

heather

01:18

will do =)

DanielSank

@Skyler Yeah. Added you.

@BernardMeurer catch me in my mornings.

Maks

@G.Bergeron Hey ! Remember me ? I've recently read waves travel at the speed of ligth, do all waves travel at the speed of light ? Or only some of them ? And can I ask you some questions about them ?

Skyler

@Maks quick counter-question, what's a wave?

in the broadest sense

Maks

Radiation ? I actually dont study physics, I'm just a curious person

Like, energy ?

I really dont know

Skyler

@Maks but then sound is usually considered a wave too

isn't it?

Maks

01:33

@Skyler yes...

It isnt ?

Skyler

@Maks but we have a different speed of sound

than that of light

yea

Maks

Right, why is that ?

Skyler

so waves are generally our way of describing some kind of movement of something

I'm pretty sure, like you said, it always involves the transfer of energy.

Maks

But lets say radios waves, they move at the speed of light

G. Bergeron

@Skyler Isn't this essentially three orthogonal edge dislocations?

Maks

01:38

?

Skyler

@G.Bergeron maybe i said something a little wrong, picture a $b_1$ and $b_2$ vector that add up to a burgers vector, now the edge dislocation that usually is offset by $b$ can instead form a region offset on both sides from the rest of the media by $b_1$ and $b_2$

@Maks in a broad sense, we are describing the movement of photons when we deal with these Electromagnetic Waves

thats simplifying on many levels, but photons have an interesting property of being massless, so they are required by the conditions of space time to propogate through empty space at $c$

Maks

But why does sound travel slower than light if its massless ?

Skyler

the speed of light

Maks

Sound isnt massless ?

Skyler

@Maks maybe something different is moving, what do you think sound is

like if a kid came and asked you why am i hearing sound

whats the best answer you could give them, and dont feel shy about your answer

Maks

01:43

I would google that hahaha

Mmmh

as far as I know

sound is a wave

Skyler

do you play any instruments, say a guitar

Maks

its like, you "configure" the air so that your ear can hear something depending on the properties of the wave

I do actually

Skyler

@Maks so describe what happens when you strike a note

just at whatever level you want

Maks

The strings vibrate, and output a sound ?

Skyler

@Maks ok, so we have some kind of movement

Maks

01:46

Yes..

Skyler

if you have a rubber band try plucking that and you can hear a small noise

so the moving string is vibrating in the air, and it sounds (har har) like something is being disturbed with it

specifically, the air

Maks

So... sound is just vibrating air ?

Skyler

@Maks its vibrating matter

whatever our ears can get in touch with and vibrate accordingly to triggers sound

since we walk in air thats mainly how the interaction is heard by humans

we can hear in pools though so clearly sound goes through that too

but its different

Maks

Then they're not waves

Skyler

since the medium is different

@Maks why not?

Maks

01:56

Waves with matter ?

heather

02:07

the avatars off to the left really fit with the Christmas season =)

Maks

02:20

@Skyler I've just read that waves are particles, and depending on if those particles have or not mass they can travel at the speed of light

is that correct ?

Skyler

@Maks physicists have a different notion of particles than the lay person

for example, we could say that sound is carried by a "phonon", but the phonon isnt a particle in the strictest particle physics meaning

DanielSank

Wow, pycharm is indexing all the things...

Skyler

@DanielSank indexing what?

and whats the master file @DanielSank

for the zip?

starts compiling everything

gets error messages for everything in root

Sir Cumference

02:39

Anyone know the answer to this?

0

Q: Why didn't the Big Bang produce heavier elements?

Shortly after the Big Bang, temperatures cooled from the Planck temperature. Once temperatures lowered to 116 gigakelvins, nucleosynthesis took place and helium, lithium and trace amounts of other elements were created. However, if the temperatures were so high shortly after the Big Bang, why we...

Solenodon Paradoxus

02:52

Hello to everybody

So it is official: I am moving to Sydney. Any advice from people from Australia (and others)? :)

What I have so far:
* Don't touch snakes & spiders (duh)
* Watch out for crocodiles
* Protect yourself from the sun

DanielSank

@Skyler source files.

Skyler

@DanielSank whats the master file

DanielSank

@Skyler go to the finite dimensions chapter and build main.tex after running the Python script to make the figures.

Skyler

oh ok

DanielSank

You need Inkscape too.

brb

Skyler

02:56

its been a while since i had inkscape

getting now

@DanielSank main.tex in there says its missing macros.tex

DanielSank

03:16

@Skyler ah, I know why: that git repo uses submodules.

You have to pull down the submodule.

Try git submodule update.

(There's already an issue filed that I need to explain that in the readme file)

Skyler

@DanielSank never really used git before on a windows system (barely did on unix forever back)

DanielSank

Oh, you're on Windows?

vzn

@SolenodonParadoxus why are you moving there? are you going to school? secret is in oz...

Skyler

@DanielSank surprising I know

DanielSank

Are you using git bash?

Skyler

03:18

downloading it now

(unless theres another way)

DanielSank

You can use git from the Windows command line as far as I know.

It's been a while though.

...and I used git bash.

Skyler

time to see how it goes

DanielSank

Git submodules are a total PITA.

Skyler

OMG, it even installed its own Linux like terminal

DanielSank

Yes, that's what git bash is for!

Skyler

03:24

this is the best thing ever

DanielSank

Yep.

It even has stuff like grep built in.

Skyler

@DanielSank first I have to pull your git repo before i can update submodules right?

DanielSank

You have two options.

1) Do git clone --recursive to get the submodule when cloning.

2) Clone and then do git submodule update.

Skyler

so first how did I actually first clone the repo

do i use the url, a special hash, or etc. I've forgotten what little I knew

DanielSank

You clone with the URL.

git clone github.com/DanielSank/repo_name.git

Or you use a GUI if you want.

Skyler

03:35

@DanielSank psh... GUIs for casuals

DanielSank

::shrugs::

Skyler

ugh, i didnt remember to put the recursive flag, how doI remove I clone

herp derp

DanielSank

don't remove it

Just go into it and git submodule update.

To remove a clone you just delete the directory, but you don't need to do that.

Skyler

got it

is there a way to open with the text editor you bind to git

like an open command?

that defaults to the right thing

DanielSank

You want to tell git what text editor to use?

Skyler

03:40

@DanielSank i already did that (I'm pretty sure)

DanielSank

So what are you asking? I'm confused.

Skyler

what is the open command that git needs to open it with that editor

DanielSank

@Skyler I'm not sure what you mean.

Skyler

@DanielSank whats your editor for git?

DanielSank

vim

At some point I had it set up on windows to use Notepad++.

I had to do something a little funky to make that work.

Skyler

03:44

@DanielSank basically trying to do that now

looks like it takes a little hacking

but im trying to do it with sublime text, which is an AMAZING editor btw

and probably has a few plug ins to help facilitate that

vim is nice and all but i highly recommend giving sublime text a try as well

its cross-platform too

DanielSank

If I can learn a few little things with vim, I'll be happy forever.

I don't know how to manage code folding yet. That's the biggest issue.

I also need to learn how to do multiple files at once.

I do like pycharm though, because it's a good IDE and it has a vim mode so I get the best of both worlds.

I simply cannot work with editors that don't have vim mode any more.

It's not just a preference, my hands can't take it.

I had bad hand pain a while back and vim was part of the solution.

Skyler

sublime text also has a plugin to support vim

called vintage

DanielSank

Oh, cool.

Skyler

it might be VI though, so I cant speak to how different those two are

and even though its not "free" it has an infinite free trial

DanielSank

TBH, for now I'm focusing on learning vim's features.

I want to make that investment.

See, that's the thing: vim is open source free software, and it's awesome.

I'm willing to spend a bit of time learning to use it.

Skyler

03:50

ill know who to ask for vim questions

DanielSank

That plus pycharm for certain refactoring tasks.

Pycharm can do some things that vim simply cannot.

Skyler

@DanielSank like?

DanielSank

Refactoring.

Pycharm is smart enough to rename functions, etc.

You can almost do this in vim, but only if you're a regular expressions ninja.

There are, however, plugins for vim that do all kinds of stuff.

Done with Russian lessons. Going to play guitar. Bye, everybody!

Solenodon Paradoxus

@vzn I am coming to work at Google

Skyler

@SolenodonParadoxus where?

Solenodon Paradoxus

03:57

@Skyler Sydney

Skyler

@SolenodonParadoxus congrats, you supply the ticket and ill do the housewarming party

=P

Solenodon Paradoxus

@Skyler where do you live? :)

Skyler

California

>_<

when do you start though?

and whats the project

Solenodon Paradoxus

Feb-March

It doesn't matter :)

Skyler

heheh

google seems to really like to pull in a lot of physicists

cant blame em but still a bit surprising

right @DanielSank?

Solenodon Paradoxus

04:02

I remember @MAFIA36790 wondering why physicists take IT jobs

- They took our jawbs!

Skyler

google isnt just a IT job

its an "It" Job =)

jesus Solenodon, just clicked on your qcomputing "notes"

didnt know brief meant small books

@SolenodonParadoxus are all of them that long?

Solenodon Paradoxus

What are you talking about?

Lecture notes by Ronald de Wolf?

Skyler

@SolenodonParadoxus yea

oh wait, this is a just a collection

Solenodon Paradoxus

@Skyler well whenever I find a freely distributed pdf helpful, I store it on my site

Its nice because I can keep track of them and return to them anytime I want to

You searched a tag, it would show you both my notes and library entries

Skyler

yea, more convenient than a folder on computer

ooh Polchinski

DanielSank

04:21

@Skyler eh?

Skyler

@DanielSank talking about how google seems to be a magnet for sucking in physicists

on that end, you have a new sort of kinda a coworker

DanielSank

@Skyler meh, physicists are often trained to solve problems, and we know math.

Skyler

@DanielSank id say its more that were trained to think "in problem"

i mean in a loose sense we generally first just eigensomething the crap out of everything

cant do that? Taylor Expand

nope? how about orthogonalization and fourier series, limiting conditions, etc

still nothing? well at least if im a smart professional physicist before i did all this I made a rough model in programming and have several more tricks up my sleeve for the particualr problem

since im clearly lacking in one or both of those i forgot that until now =P

DanielSank

I get what you're saying and I totally agree.

Skyler

@DanielSank btw

what is your workflow for solving a challenging problem

is there a generalized way you've developed yet

Solenodon Paradoxus

04:37

OMG I've just realized that my workflow is to blindly stumble upon things until something comes up...

You'd be surprised how often it worked for me :)

Skyler

from what i remember talking about with regards to your work im sure some problems fall into larger groups

@SolenodonParadoxus i do that, but i have probably ~100 sets of notes from various seminar lectures I peruse through here and there,

i still know this one talk i sat in on at caltech, from this dud at tel aviv, talking about diffusion mapping algorithms, is going to be really useful for something I want to do in the future

not sure what though

@SolenodonParadoxus so sometimes its a bit of the reverse for me too

@SolenodonParadoxus just 2 days ago I found Dan inadvertantly had half solved a simulation I wanted to set up, I came up with the idea while going to sleep the night before

vzn

@SolenodonParadoxus congratulations! what prj, do you know yet? was just surfing your website lately too, impressive collection...

G. Bergeron

04:54

Mathematica internal ordering can be a major pain in the ass!!!

I know they want order functions to return something but in general you cannot rely on this ordering for manipulation purpose, but nevertheless they apply it implicitly between operations >:(

But then when you try to track how a quantity evolves under several transformations, it secretly permutes everything... RAAAR

Sorry, I needed to vent... It's been several hours I'm balancing and tracking normalization factors for fairly complicated expressions.

ACuriousMind

@Slereah I'm not sure I understand the question - any separable Hilbert space will be unitarily isomorphic to $L^2$.

Slereah

yes, obviously

But

Is there another mathematical structure with the same properties, as well

G. Bergeron

05:12

@Slereah Well no, since from the axioms you get only one, up to equivalence, as he said

Slereah

well yes, but can $\mathcal{L^2}$ be isomorphic to another interesting math structure, is my question

G. Bergeron

Hmm...

Slereah

By which I mean the QM Hilbert space, by the way

No boring hilbert space like $\Bbb R$

ACuriousMind

@Slereah Sure, you might decide that any of the other separable Hilbert spaces is "interesting" :P

G. Bergeron

We can prove this thing by considering the vector space of formal power series in $X$

And demanding that those series converges as power series of a real variable

This defines the notion of infinite span and leads to a countable basis

So that it is isomorphic to it's dual

I think this make the structure pretty ''rigid''

!!! The subway is gonna close, I gotta run!!!

vzn

05:28

any debroglie-bohm fans or anti copenhagenists around? naysayers? just ran into this amazing site/ ref, whaddya think? substantial electron-cloud like replication via emergent behavior in oildrop experiments dotwave.org/… / Gilet, Phys Rev E

Skyler

05:49

@DanielSank the submodule thing didn't work

and ironically I actually wanted to ask you the steps you should take to solve a particular pde using fourier transforms

hey @JohnRennie

John Rennie

Morning :-)

Skyler

care to help a distraught soul looking at a PDE and rusty on the method to solve it?

Top is the initial condition for a diffusion problem

last is meaningless here

and the middle is what im pretty sure happens as you time evolve it

until it stabilizes to $\frac{C_0}{2}$

how did I solve this by PDE by fourier transform method

$\frac{dc}{dt}=D\frac{d^2c}{dx^2}$

(also would be willing to solve by Laplace Transform, just want to relearn how to properly apply transform methods to PDEs since i forgot)

howdy @SirCumference

Sir Cumference

Hiya

Skyler

how do you do

Sir Cumference

Good

Say, is this question sensical at all?

Slereah

05:59

it seems pretty nonsensical

Skyler

wat

yea, what :34078270 said

Sir Cumference

Not sure if "electroscopy" is even a field

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