The h Bar

ManishEarth

01:04

@crazy note that classical mechanics= Lagrangian/Hamiltonian mech, not pulley mass problems :p There's a whole lot of formulism that gets useful later on.

Do classical and linear algebra, then QM (Introductory+couple more courses worth; you want to go from schrodinger to H atom to operator formulism to Dirac's eqn and beyond.) Sakurai 1+2 works, or Beiser+Dirac, at least for getting a good qm foundation.

Electromag is also something you can delve into. Feynman has some great chapters, from there you can go to Griffiths/Jackson.

Optics: E. Hecht is an awesome book.

You probably want a course that looks at ODE's from a lin alg POV. We had a half sem one and it was really helpful.

For GTR there are many self contained books, but it might be easier to familiarize yourself with tensors first.

As for edX/Coursera, I dunno. Quality varies from course to course. I prefer books, but my friends who have taken courses have had both good and bad experiences with it.

user54412

01:23

@ManishEarth there are ODE courses not based on linear algebra?

user54412

but why??

ManishEarth

01:47

@chris There are some that deal with a random bunch of methods. Our first half sem ODE course was only half lin alg related.

ManishEarth

02:57

@chris Oh, also, in case you are specifically analysing nonlinearity, then aside from the Jacobian you don't really touch linear algebra.

user54412

03:18

well, indeed - nonlinearity is terrible

user54412

also basically intractable anyway

Crazy Buddy

@ChrisWhite If that's only the case, it's cool with me. I'm confident that I'll finish off a few topics within these two years ;-)

@ChrisWhite For instance, khan academy -- most of the things are easy. Yeah, armed with that, I surfed through the archived courses in edX (E&M from MIT) yesterday. It appeared quite nice. The thing is, if we intended to cheat a little bit, we can, and of course eliminate the challenges easily. Only if we decide to not Google about that, and think a little bit - the course might be worthy...

@dmckee I'll try that for sure, and rant here about my experience later :P

@ManishEarth HEY..!!! I know that. Just that I haven't taken a course on that. But, I've some experience in Phys.SE :P

@ManishEarth Yeah, books are always safe & secure. Phew, I got book suggestions. Maybe I should bookmark this convo :)

Okay, thank you guys @ChrisWhite @dmckee @ManishEarth and @BrandonEnright (for yesterday's chat) ;-)

I miss only one... @DavidZ

user54412

03:33

@CrazyBuddy are you going for the opinions of all the chat regulars?

Crazy Buddy

@ChrisWhite Nah, I'll just keep those in mind :)

I'm not going anywhere :P

@ChrisWhite: I'm somewhat interested in hearing your history... Like, how's schooling & colg. there, what did you do after high school and enter now into Ph.D

You're not gonna sleep anyway :P

And you too @ManishEarth :)

Kyle Kanos

We're scientists, we don't sleep

5

user54412

I don't know how interesting my history is

user54412

I went to a small public high school - nothing special, no record of any remarkable academic acheivements

Crazy Buddy

@ChrisWhite Duh, I'm already sick of that here :D

user54412

03:39

somehow - probably an admissions committee mistake ;) - I got into Caltech

Crazy Buddy

@KyleKanos Yeah, I know ;-)

user54412

and there I proceeded to immerse myself in math, science, philosophy, and just thinking for 4 straight years

Crazy Buddy

@ChrisWhite Wait... So, the colleges there - we can try all the courses, all at once? o_O

user54412

@CrazyBuddy curricula here are much more freeform than in India

Crazy Buddy

ah... (sigh) :/

okay, go on... :)

user54412

03:41

there are required classes, but every college I know has plenty of choices for electives, both in your major and importantly outside of it

user54412

usually at least

Crazy Buddy

mmm...

user54412

a counterexample is ChemE at caltech - they had so many requirements they couldn't take anything else - so I guess it does happen

Crazy Buddy

hehe :D

user54412

the US emphasizes a broader, more "well-rounded" education compared to India or even to Europe

user54412

03:43

most college students here just go to college because it's expected that everyone goes to college these days, at least everyone middle class and upward

user54412

so most just bumble along for 4, 5, maybe 6 years, trying to figure out what to do with themselves and their parents' money

Kyle Kanos

I paid for my education

My wife got a scholarship

Crazy Buddy

@ChrisWhite Meaning? the system is quite strong? I guess Manish has some bad experience. He's lucky he didn't join any colleges controlled by state gov. -_-

Kyle Kanos

I took 5 years, she took 3.5

user54412

@KyleKanos cool - I think you'll agree that's not too common these days, though

Kyle Kanos

03:46

@ChrisWhite Most of the students I teach are having mum & pup paying for ti

*it

Crazy Buddy

@ChrisWhite Ugh... That happens here too -_-

user54412

@CrazyBuddy meaning students here are expected to just "know more" after college, whereas elsewhere they are expected to "know how to do their job"

user54412

I'm not saying one system is better than the other - but they are quite different

Crazy Buddy

@ChrisWhite yeah, I get that...

@ChrisWhite Nah, but I can safely say it's much better than mine :D

user54412

well, you never know quite what you'll learn from college until you're older and looking back on it

user54412

03:49

I can say that I never learned time management skills, for instance, but on the other hand I had any fear of not knowing something beaten out of me - there's no such thing as a task so big I'm afraid to try, since I got used to failing at hard things all too many times

user54412

or the undergrads here, I feel, learn very useful networking and policy-making skills just from interacting with each other cough @DavidZ

Crazy Buddy

@ChrisWhite As far as me, my colg. is the reason that I got into Physics. I mean, I hate the environment there, which is what made me involve in Phys.SE (I got lucky, for once) :D

@ChrisWhite "Failing most of the time" -- that happens during physics courses. Right? :P

Brandon Enright

@ChrisWhite Caltech was my dream school. Was pretty devastated when I didn't get in. I got in to UC San Diego though, probably due to an admission mistake. It turned out to be perfect for me though and I realized about halfway through my college career that because I was such a bad student, it was probably good that I got into a non-top-tier school. I'm pretty certain I would have failed out of Caltech.

David Z

@ChrisWhite well some of them. I don't know if I'd count myself among them.

Crazy Buddy

@ChrisWhite heh, yeah that too :D

user54412

03:54

@BrandonEnright or been made very bitter - caltech alums are notoriously resentful of the school - it works very well for some students, but many would have been better off at more "normal" schools

user54412

@CrazyBuddy when applying for grad schools, a lot of them wanted me to compute my physics-courses-only GPA, in addition to my overall GPA - it was then that I realized I got lower grades in physics than anything else :P

user54412

@BrandonEnright also, I though Pasadena had perfect weather, but everyone from San Diego/La Jolla thought the weather in Pasadena just wasn't that good ;)

David Z

@ChrisWhite oh cool, I'm not the only one :-P

Kyle Kanos

@DavidZ Me too

Crazy Buddy

Great... Everyone's a professional physicist, but failed to obtain the grades :P

Kyle Kanos

03:58

No, we failed to obtain grades in things outside physics

Brandon Enright

@CrazyBuddy Grades are a poor measure of ability, intelligence, or likelihood of success.

Crazy Buddy

@VanishedUser: I think you missed a point (intentionally??). In my profile, there's a strikeout mentioning that I'm currently learning Physics and if you've noticed my messages in h-bar (where I will be, most of the time), you would've known that I hate my engineering course terribly. And, as Manish said, an engineering degree doesn't explain our interest (nor our knowledge) in Physics. Just like the "rep. score" which is a rough measure of our contribution to SE, the degree is a rough measure of our contribution to engineering ;-) — Crazy Buddy Nov 1 at 3:46

Kyle Kanos

@BrandonEnright Debatable on the last aspect, depending on your definition of "success."

Brandon Enright

@KyleKanos Yeah I'll have to concede that point. There are many measures of success.

user54412

I suppose (not sarcastically) that being able to get good marks in some system, however arbitrary, is a useful skill

Crazy Buddy

04:02

So, @Brandon (/cc @Chris) - regarding the admissions, where are they held? Well, my admissions are based on a cut-off scheme, where they let in loads of people into colleges based on their marks obtained during the last (12th) grade of high-school

Brandon Enright

@ChrisWhite agreed. It's a great measure of ability to follow directions or stick-to-it-ness.

@CrazyBuddy Every country is a bit different. Within a country, every school is a bit different.

Crazy Buddy

@BrandonEnright I thought the country's scheme of letting into colleges might be the same. No?

Kyle Kanos

@CrazyBuddy I think most US universities base it on cumulative GPA from your HS (grades 9-12) and your SAT scores

Crazy Buddy

ah...

Kyle Kanos

But there's different standards of what is an acceptable lower limit on GPA & SAT scores

David Z

04:03

@CrazyBuddy Each university is free to determine who it wants to admit by whatever criteria it wants

user54412

the ~~smaller the school~~ fewer the applicants the more time they have (in theory) to research the applicants, like by reading recommendations

Kyle Kanos

I've seen some that have accepted a minimum 2.5 GPA and an 800 on the SAT (out of 1600). I've also seen some that require 3.2+ GPA and 1200+ GPA

David Z

A lot of universities don't have explicit GPA or SAT score cutoffs.

Well, some, at least. Maybe a lot.

user54412

indeed - schools like to have at least a few "interesting" or "unique" people too - students who stand out, even if not academically

Kyle Kanos

@DavidZ When I was applying for undergrad, they definitely were publishing those values...at least the upper-tier Unis

David Z

04:07

Hm, I seem to remember Princeton saying that they don't have explicit cutoffs.

Of course the median SAT score of the people they did admit was probably something like 1500+ out of 1600, so they didn't need cutoffs anyway...

user54412

@DavidZ and I seem to remember Princeton rejecting me, whatever my scores were

user54412

;)

Crazy Buddy

@ChrisWhite What? Why? :D

David Z

@ChrisWhite well it is kind of like a lottery. Though I would argue you got the better experience there anyway.

Kyle Kanos

Well, I've got to be off. One of the twins is awake and needs her mommy.

user54412

04:09

@KyleKanos see ya

David Z

A PhD from a top university carries a lot more weight than a bachelor's degree from the same school.

@KyleKanos see you

Crazy Buddy

@KyleKanos C'ya later :)

Brandon Enright

@DavidZ I totally agree with this.

user54412

@CrazyBuddy indeed it is a lottery - "top" schools receive 5, 10, 20 times as many applicants as they have room for, and most of those who bother applying are capable of doing well there

David Z

@BrandonEnright and to clarify (perhaps you knew), I mean the relative amount by which a PhD from a top school is more impressive than the average PhD far exceeds the relative amount by which a bachelor's degree from a top school is more impressive than the average bachelor's degree.

Crazy Buddy

04:13

I guess I'd have to do more research on foreign colleges. They're very different in a lot of ways :D

Brandon Enright

@DavidZ Yeah "normalizing" the degree.

user54412

@CrazyBuddy have you considered at all applying to study abroad for a summer?

Crazy Buddy

@DavidZ That really takes my time (to understand) :)

user54412

I don't know how common it is, or how likely there is to be funding/available positions, but it might be worth looking into

Crazy Buddy

@ChrisWhite Um, pardon me but I don't understand. What's summer?

user54412

04:16

@CrazyBuddy hmmm, do you not get off for ~3 months, June-August or something?

user54412

I mean, I know it's always hot there ;)

Crazy Buddy

@ChrisWhite Nah... My sem (usually) ends on July. And, the next sem starts on Aug. Duh...

user54412

wow - intense

Crazy Buddy

@ChrisWhite And, we don't usually get the whole vacation. Last time, we had a NSS camp (like go to a village, clean the streets, etc.)

... which sucked 10 days of my vacation -_-

user54412

to American students, aged all the way 6-21, a 3-month summer vacation is like a basic human right

Crazy Buddy

04:20

(sigh)

user54412

well at least you're being productive

Crazy Buddy

I hope so. And, can you expound what "summer" means? :D

Is that, a kind of... research?

Brandon Enright

@CrazyBuddy For grad students it usually means research but "summer" in the US is really just 3 months of time you're not in school you can do pretty much whatever you want.

Crazy Buddy

@ChrisWhite: So, that 3-months is enough to have a course in the abroad?

Brandon Enright

@CrazyBuddy "Summer abroad" for 2-3 months is really common for US and Europe.

user54412

04:24

@CrazyBuddy lots of profs at research-heavy universities also take on students for helping on small research projects for those months, so it's not always classes

Crazy Buddy

ah...

user54412

I spent a total of 3 summers doing research, and the other 13 or so summers of my youth were spent vegetating on a couch

Crazy Buddy

lol :D

Okay, nice chat with you all... Thank you guys :)

I'll better bookmark this conversation as a whole :D

@ChrisWhite Regarding that, I really honor my classmates. They're pretty much okay, with the system unlike me, who can't (in any way) accept that that's the way to survive :)

@DavidZ: Is it okay to disgrace people with conversation titles?

Coz.. I'm seeing a convo having such a name

davidz-has-fallen-to-the-evil-side

Sep 28 at 1:31, 2 hours 31 minutes total – 30 messages, 5 users, 2 stars

Bookmarked Oct 2 at 9:17 by DIMension10

David Z

04:41

rofl

@CrazyBuddy I'm pretty sure that's not okay

Crazy Buddy

hehe :D

user54412

@DavidZ is... Anakin Skywalker??? o.O

David Z

oh I wish

because then I could use the Force

and have a lightsaber

user54412

the fact that physics hasn't yet given us the Force or lightsabers reflects badly on the field

David Z

yeah... well but honestly, once those things actually happen we might as well be done with physics

The entire purpose of the field is clearly just to reinvent Star Wars :-P

Anonymous

04:54

Hey everyone!

David Z

hi

Anonymous

I have a question about amplifiers, can anyone help?

Namely, just how do amplifiers modulate power supply signals?

Crazy Buddy

^^^ Maybe Electrical Engineering can help on that, right?

Anonymous

Oh I guess it can just create a signal from the power supply couldn't it...

Oh I guess... I always just think everything is physics lol

user54412

some physicists are good with circuits, many are not

Anonymous

04:55

:(

David Z

EE has a reasonably active chat room I think.

Anonymous

It looks like it, but no one is on right now...

user54412

it's late in the US, pre-dawn in Europe

Crazy Buddy

@ChrisWhite Well, I'm good at ripping off the circuits. A few of my mates are afraid to come near me in our practicals lab, as it's always risky :D

user54412

@CrazyBuddy my experiments with electronics had two outcomes - (1) I blew my house's fuse when I dropped water onto a lit lightbulb and it exploded, and (2) I learned very early that 9V batteries set steel wool on fire just via contact

4

David Z

04:58

oh cool I have to try that

Crazy Buddy

@ChrisWhite LOL, cool... I haven't tried the second one though :P

user54412

@DavidZ ummm.... the lightbulb was more dangerous than it sounds...

user54412

but I learned from EE's in college that it's actually common practice to touch a 9V to some steel wool to see if it's charged

David Z

well in a controlled environment of course ;-) I was thinking more of the 9V battery and steel wool because I have those handy

reminds me of the time I put aluminum foil in the microwave

by accident, but I was tempted to do it again and take video

Crazy Buddy

In my childhood, I'm always fond of light bulbs. I've broken many light bulbs to see how it works. Didn't have the slightest idea that the filament is the thing that's responsible (each time I break the bulb, I just lose the filament, and I just ignore it :P)

Anonymous

05:01

I can't ge tmy steel wool

to light... I dunno why

Crazy Buddy

@DavidZ you have the video? I'd like to watch it :)

David Z

no, I said I didn't actually take the video

Crazy Buddy

Ow... :D

user54412

@Anonymous try concentrating the current in as narrow a chokepoint as possible - if even a single stand doesn't ignite, then either you have ridiculously low gauge steel wool or the battery is dead

Anonymous

05:14

Is low gauge thick?

Crazy Buddy

@ManishEarth: You're lagging behind. You have a lot to read :D

user54412

@Anonymous yes, for bizarre historical reasons

user54412

Wire gauge

Wire gauge is a measurement of how large a wire is, either in diameter or cross sectional area. This determines the amount of electric current a wire can safely carry, as well as its electrical resistance and weight per unit of length. Wire gauge is applicable to both electrical and non-electrical wires, being important to electrical wiring and to structural cable. Types Gauges may be broadly divided into two groups, the empirical and the geometric. The first includes all the older gauge measurements, notably the Birmingham (B.W.G. or Stubs) and the Lancashire. The origin of the B.W....

Anonymous

Anyone know the historical reasons?

user54412

it used to count how many times the wire was drawn out, getting thinner each time

Anonymous

05:22

I see....

Drawn out? You mean like in production?

user54412

yeah

ManishEarth

05:55

@ChrisWhite terrible but fun!

@ChrisWhite My physics scores are all over the place. I got a 7(/10) in special relativity, even though I was really comfortable with the course and I think I understood everything. Screwed up on the tests badly though, apparently I suck at calculating out Lorentz factors

@ChrisWhite Most schools in India have a month long winter vacation and 1.5-2 months of "summer". (summer=dry season, doesn't exactly coincide with the US summer). But we also have tons of vacations scattered throughout the year. National holidays, Hindu holidays, Muslim holidays, and one Sikh and Parsi holiday each. Also some local holidays, depending on the school.

Crazy Buddy

@ManishEarth You mean, school==colg.?

ManishEarth

yeah both

Crazy Buddy

@ManishEarth Then, you're wrong. You don't count the extra classes, which most of the schools have (even my colg. compels us for extra classes - Saturdays) sigh :/

ManishEarth

06:12

@CrazyBuddy Hahaha points and laughs

@CrazyBuddy There are also quite a few good astro(nomy|physics) programs in India for UGs

there's the pulsar radioastronomy summer camp

Crazy Buddy

@ManishEarth And, it gets worse -- when they fear us that they'd take those days into account for attendance, and sometimes they forget -_-

@ManishEarth Dunno about that. Are there any?

ManishEarth

Ooty Radio Telescope

The Ooty Radio Telescope is located in Muthorai near Ootacamund (Ooty), south India. It is part of the National centre of Radio Astrophysics (NCRA) of the well known Tata Institute of Fundamental Research (TIFR) which is funded by the Government of India through the Department of atomic energy. The Ooty Radio Telescope (ORT) is a 530 m long and 30 m wide Cylindrical Paraboloid telescope. It operates at a frequency of 326.5 MHz with a maximum bandwidth of 15 MHz at the front-end. Design The Ooty Radio telescope has been designed and fabricated with domestic Indian technologica...

Crazy Buddy

@ManishEarth Nice attractive image. Can safely say that it's India :D

ManishEarth

NCRA has some other camps

Crazy Buddy

ah... Anyways, c'ya later @Manish. Power shutdown in 10 mins... (started again) :/

Feeling "WHERE TO SHOW THE WRATH" -_-

@ManishEarth Wait... I totally forgot to see the name. I've visited Ooty twice (sigh again)

... but, didn't know that there's a telescope in our state, DUH...

ManishEarth

06:19

@CrazyBuddy They have a summer camp every year for UGs. One of my friends went there, observed and analysed some pulsars and learned a lot about radioastronomy in general

NCRA has some summer/winter camps too, but I don't know of any specifics

Oh, also, if you do learn GTR on your own, there is scope for astrophy projects in my college too.

Crazy Buddy

Gee, thanks. I should gather a few, and visit that telescope :D

@ManishEarth Your colg. has projects on GR? o_O

ManishEarth

@CrazyBuddy Well, astrophysics, but yeah

Crazy Buddy

Oh my... I didn't know that

ManishEarth

@CrazyBuddy phy.iitb.ac.in/~yajnik for example

There are more, but can't recall them off the top of my head

There are some who dabble in AstroPhy but mainly work in particle physics or TP

Crazy Buddy

Oh, nice :)

ManishEarth

06:25

@Anonymous transistors are magic

@CrazyBuddy rac.ncra.tifr.res.in/ContactUs.html

Crazy Buddy

@ManishEarth Thanks. Um, it says that I should apply to them briefing out my telescope time and my experiment (??) -- Do they mean that I need some experience in the past with RTs? o_O

ManishEarth

@CrazyBuddy no, that is if you want to apply for telescope time . Ask them for details about summer camps.

I shall also ask my friends for links/details, I'm sure they have them

Crazy Buddy

ah... will do :)

oh, okay fine ;-)

Hmm... Strange. No power shutdown yet... O_O

Brandon Enright

06:41

@CrazyBuddy Sad that's strange :-/

Have a good day. I'm heading to bed :-)

Crazy Buddy

@BrandonEnright What the... Grr..!!!

@BrandonEnright Good night ;-)

Physics Meta

13:02

0

Q: Do we need/want an overarching books question?

The current tag wiki for the books - now resource-recommendation - tag includes, in its final paragraph, the request that If you question is about resource-recommendations, please add your question to the book list as well. I just gave that tag wiki a make-over to bring it in line with the ...

Emilio Pisanty

14:17

@ManishEarth @DavidZ I submitted edits to two tag wikis. Could you take a look?

Crazy Buddy

21

A: How to prove $\sum_{n=0}^{\infty} \frac{n^2}{2^n} = 6$?

First observe that the sum converges (by, say, the root test). We already know that $\displaystyle R := \sum_{n=0}^\infty \frac{1}{2^n} = 2$. Let $S$ be the given sum. Then $\displaystyle S = 2S - S = \sum_{n=0}^\infty \frac{2n+1}{2^n}$. Now use the same trick to compute $\displaystyle T := \...

I think I'm unable to get this answer... :/

Anyone interested?

Crazy Buddy

14:39

@ManishEarth: Gotcha... Come here you!!! :D

How did he simply write this out? $S = 2S - S = \sum_{n=0}^\infty \frac{2n+1}{2^n}$

Or, am I missing something?

Kyle Kanos

@CrazyBuddy Yeah, I'm not following what he's doing either. Not sure how $2n^2-n^2=2n+1$. Or how $2n-n=1$

Crazy Buddy

Oh my... I was pondering on that step for about 20 mins or so. Looks like I'm not the only one who's confused :P

Crazy Buddy

15:43

Waaa??? O_O

Servicing, maybe...

But, that can redirect to a kind page. No? :D

Kyle Kanos

Maybe Anonymous got them?

Crazy Buddy

huh?

Kyle Kanos

Anonymous (group)

Anonymous (used as a mass noun) is a loosely associated international network of activist and hacktivist entities. A website nominally associated with the group describes it as "an internet gathering" with "a very loose and decentralized command structure that operates on ideas rather than directives". The group became known for a series of well-publicized publicity stunts and distributed denial-of-service (DDoS) attacks on government, religious, and corporate websites. Anonymous originated in 2003 on the imageboard 4chan, representing the concept of many online and offline community u...

Crazy Buddy

Oh.. hehe :D

Pulsar

15:56

@CrazyBuddy It looks correct, but he should've used more intermediate steps for clarity. $S=\sum_{n=1}^\infty\frac{n^2}{2^n}$, because the term with $n=0$ is zero. Then $2S = \sum_{n=1}^\infty\frac{n^2}{2^{n-1}}$. Take $m=n-1$, then $2S = \sum_{m=0}^\infty\frac{(m+1)^2}{2^m} = \sum_{m=0}^\infty \frac{m^2+2m+1}{2^m}$. Subtract $S$, so that $S=\sum_{m=0}^\infty \frac{2m+1}{2^m}$.

Kyle Kanos

@Pulsar That makes a lot more sense (though I had to copy & paste into my (already open) latex editor to read that)

Crazy Buddy

@Pulsar Gee, thanks. really makes sense ;-)

@KyleKanos We use chatjax :)

4

Q: MathJax in chat (ChatJax offshoot)

This is an offshoot of ChatJax, which enables MathJax along with mhchem on chat. Copy the text below: javascript:(function(){if(window.MathJax===undefined){var%20script=document.createElement("script");script.type="text/javascript";script.src="https://d3eoax9i5htok0.cloudfront.net/mathjax/lat...

discussion mathjax

Kyle Kanos

Hmm. $F=ma$.

Nope

Crazy Buddy

@KyleKanos You've to make a bookmark of that javascript...

And, click it once a new latex'ification has appeared ;-)

BTW, it should be noted that chatjax will be disabled once you refresh the page :)

Kyle Kanos

I made it a bookmark, just clicked it.

$F=ma$

Still nothing :/

Crazy Buddy

16:09

^^^ Works for me...

What browser do you use?

Kyle Kanos

Opera 12.16

Crazy Buddy

Well, it works in FF & Safari (I'm sure)... Haven't tried it in Opera :/

Kyle Kanos

Just opened up FF

$F=ma$

Nope there either

Crazy Buddy

What?!!! O_O

Kyle Kanos

I run Linux

Maybe that is the reason?

Crazy Buddy

16:12

No, @Manish uses linux (I guess)

Kyle Kanos

Hmm

No big deal

Crazy Buddy

brb after dinner... will get back to that later ;-)

Qmechanic

17:06

@BrandonEnright : I think chat (as opposed to meta) is fine for such minor tag issues.

ManishEarth

18:19

@CrazyBuddy /cc @KyleKanos I use both

Kyle Kanos

@ManishEarth Both Linux & Opera?

ManishEarth

18:38

@KyleKanos Nah, Linux&Windows

Kyle Kanos

@ManishEarth Got it.

Writing cover letters suck

Crazy Buddy

18:54

@ManishEarth You already use 3 PCs... o_O

Kyle Kanos

I don't really know anyone who uses Windows these days. All of my colleagues are either on Linux or Mac

ManishEarth

@CrazyBuddy dual boot

@KyleKanos gaming, Mathematica, etc

My laptop is far from a gaming laptop, but it's good enough to run AOE3 multiplayer :)

Kyle Kanos

IDK what AOE3 means....

The last video game that I played was Final Fantasy XII on my PS2. I sold that 3 or 4 years ago.

ManishEarth

@KyleKanos Age of Empires 3. It's one of those real time strategy games, where you build a base, collect resources, make army, and attack the enemy. Pretty fun with friends.

I also play a lot of indie games if I get time, they're usually fun and don't eat up too much time.

Kyle Kanos

I've played RTS's before, Warhammer 40K: Dawn of War. That was literally a decade ago.

ManishEarth

19:05

wow

Kyle Kanos

I'm an active researcher and also a father of 4, so playing video games isn't something I have time for

ManishEarth

Hah. I'm a student, also pretty busy, but in vacations and on some fridays we all get some time to play.

Brandon Enright

Hmm just read a question by Ron and either I don't "get" it or it doesn't sound right:

1

A: Why exactly does current carrying two current wires attract/repel?

Your question is assuming that the electrons are weakly interacting with the nucleus. The interaction with the nucleus is extremely strong. It is better to ask instead why do we have conductivity at all. Electrons are so tightly bound to nuclei of atoms, why should a tiny external electric field ...

"So there must be an additional attractive force due to the currents in the wires". What is he referring to here?

Is he just referring to the magnetic field generated by the current?

Anonymous

Hellllloooo

How do you describe the evolution of a wave function after a potential is removed?

Brandon Enright

@Anonymous With math :-p

Anonymous

19:15

Well yeah, but I mean how can I go about it?

If I have something in like a harmonic potential, and then I remove the potential, how do I go about describing the weird changing period?

Brandon Enright

@Anonymous I'm just being snarky. I can't help you. It's been too long since I took an QM classes or sat down and did that sort of math.

Anonymous

Nooooo @BrandonEnright

Kyle Kanos

@Anonymous Suppose $H_1$ is your original Hamiltonian and $|\psi_1\rangle$ represents the state (wave function) that satisfies $H_1$. Wouldn't you just use $\mathcal{U}(H_2)|\psi_1\rangle$ where $\mathcal{U}(H_2)$ is the time-evolution operator with the new Hamiltonian?

Anonymous

Sounds golden, but I've never used the time evolution operator :/

I learned about it, but it looked like too unwieldy a beast

Kyle Kanos

Isn't it just $\mathcal{U}(H)=\exp\left[-iHt/\hbar\right]$?

Anonymous

19:25

Is there a way to view the latex not in latex form?

Kyle Kanos

Supposedly here, but it didn't work for me: meta.chemistry.stackexchange.com/questions/89/…

Anonymous

Yeah I think that's the operator...

Just so magic...

Anonymous

22:20

Are quantum waves dispersive?

davidz-has-fallen-to-the-evil-side

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