## Search found 46 matches

Fri Sep 29, 2017 7:24 pm UTC
Forum: Coding
Topic: code for melting computer
Replies: 7
Views: 8140

### Re: code for melting computer

Ooh, I know this one! Modern computers have very good thermal throttling - ie, when they get hot, they slow way the fuck down to avoid overheating. Old CPUs (10+ years old by now) didn't always have thermal sensors, so you could get them to burn up by running even fairly standard programs without a ...
Tue Oct 27, 2015 8:26 am UTC
Forum: General
Topic: Sleep-time holodeck experiences
Replies: 3403
Views: 751110

### Re: What were your dreams last night?

In my dream last night, I was at some sort of garden party thing, in a big marquee with lots of tables and chairs set out and with the floor just being grass. There were a couple of people making sure only people on the invite list could get in. One looked kind of like Shirley from Community, and we...
Tue Sep 15, 2015 2:28 pm UTC
Forum: Mathematics
Topic: Math: Fleeting Thoughts
Replies: 427
Views: 147063

### Re: Math: Fleeting Thoughts

Can you look at M different sums of size N? What do you mean by that? If it's just "Can you sample M different values from the sum distribution", then yeah, you can do that. For uncorrelated variables, the variance of the sum is equal to the sum of the variances. [citation here] So if you...
Tue Sep 15, 2015 11:36 am UTC
Forum: Mathematics
Topic: Math: Fleeting Thoughts
Replies: 427
Views: 147063

### Re: Math: Fleeting Thoughts

Fleeting thought: Let's say you have some probability distribution X, but you can't sample it directly. Instead, you can only sample the sum of N independent variables, each with distribution X. How would you estimate, say, the variance of X based on that? Context: I've written a (very basic) benchm...
Sun Sep 06, 2015 12:20 pm UTC
Forum: General
Topic: Blistering blue barnacles
Replies: 28601
Views: 3423442

Relevant story: There was a person in my school who had moved from the south (of England) to the north (where we were). His first and last names formed a fairly "normal" name by our standards. His two middle names, on the other hand, were really posh. So we used to joke that that was the n...
Sat Aug 01, 2015 2:19 pm UTC
Forum: Mathematics
Topic: Favorite math jokes
Replies: 1452
Views: 482828

### Re: Favorite math jokes

Then you can prove that zeta(1)=infinity, without assuming that there are infinitely many primes. (though that's hard, and the usual easy proof uses the fact that there are infinitely many primes) Huh? The usual easy proof of the divergence of zeta(1) is Nicole Oresme's proof using comparison of th...
Fri Jul 31, 2015 8:40 pm UTC
Forum: Mathematics
Topic: Favorite math jokes
Replies: 1452
Views: 482828

### Re: Favorite math jokes

Pretty sure I never saw this one here... Theorem: 5!/2 is even. Proof: 5!/2 is the order of the group A5. It is known that A5 is a non-abelian simple group. Therefore A5 is not solvable. But the Feit-Thompson Theorem asserts that every finite group with odd cardinal is solvable, so 5!/2 must be an ...
Tue Jul 07, 2015 11:12 am UTC
Forum: Science
Topic: How can gluons interact via color force?
Replies: 8
Views: 2584

### Re: How can gluons interact via color force?

I don't know enough about the strong force to answer your question exactly, but I can give you a classical explanation - in other words, I'm going to treat QM as if it worked with ordinary probabilities. Technically that isn't quite how it works, but I think it's close enough to explain what's going...
Mon Jun 01, 2015 10:47 pm UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9968
Views: 1951349

### Re: Coding: Fleeting Thoughts

Yeah, about once every 6 months I get anxious about floating point errors that could propagate badly through whatever code I'm writing at the moment. Then, after carefully going through worst-cases, I conclude that FP error is really insignificant, and vow to never doubt them again. Makes me wish I...
Tue May 19, 2015 4:40 pm UTC
Forum: Mathematics
Topic: Favorite math jokes
Replies: 1452
Views: 482828

### Re: Favorite math jokes

The first paragraph of the latest Good Math, Bad Math post seems relevant to this thread: Yesterday, a friend of mine from my Google days, Daniel Martin, sent me a link, and asked to write about it. Daniel isn’t just a former coworker of mine, but he’s a math geek with the same sort of warped sense ...
Wed Apr 29, 2015 10:42 pm UTC
Forum: General
Topic: [SAFESPACE] LGBTIQQA Thread - Queer Support!
Replies: 8247
Views: 1425366

### Re: [SAFESPACE] LGBTIQQA Thread - Queer Support!

Hmm, update on my gender-y stuff: I'm now pretty damn sure that 'agender' describes me. Still going to have to get used to identifying that way, but there you have it. Yay :D As for pronouns, well, I'm probably okay with any, with a minor preference for 'he' (due to familiarity more than anything el...
Wed Apr 29, 2015 6:54 pm UTC
Forum: Mathematics
Topic: Collections of classes
Replies: 3
Views: 1511

### Re: Collections of classes

If I'm understanding it properly, what you're proposing is basically a form of type theory , where each "type" has a full copy of (say) the ZFC axioms, and so has a full hierarchy of sets inside it. Then you'd have extra axioms governing the interaction between the types, eg. "The col...
Thu Apr 09, 2015 6:14 pm UTC
Forum: Science
Topic: An Ounce of Sunlight
Replies: 6
Views: 1872

### Re: An Ounce of Sunlight

One problem I can see: You've said human skin reflects ~0.8% of the light that falls on it. But what about the other 99.2%? It certainly isn't transmitted, so presumably it's absorbed (unless I've forgotten something). And absorbing light should provide half of the momentum you'd get if you reflecte...
Sun Mar 01, 2015 12:22 pm UTC
Forum: General
Topic: [SAFESPACE] LGBTIQQA Thread - Queer Support!
Replies: 8247
Views: 1425366

### Re: [SAFESPACE] LGBTIQQA Thread - Queer Support!

That's not far from how I gender myself (or don't). I'm mostly mostly agender, but being femaled is acceptable. (Demigirl is a decent word. I should remember it.) Since last time I posted here, I seem to have been going in a similar direction myself. It's pretty clear that I could identify as agend...
Sun Mar 01, 2015 12:13 pm UTC
Forum: Mathematics
Topic: Independent components of Christoffel Symbols
Replies: 15
Views: 5647

### Re: Independent components of Christoffel Symbols

z4lis: Ah, that makes so much sense! What I think you're saying is: A priori, we have 64 independent components in each of Γ abc and g ab,c , but then symmetry (of gamma and g) reduces them to 40 each. Finally, metric compatibility gives 40 equations involving *both* Γ abc and g ab,c , so fully dete...
Fri Feb 27, 2015 3:32 pm UTC
Forum: Mathematics
Topic: Independent components of Christoffel Symbols
Replies: 15
Views: 5647

### Re: Independent components of Christoffel Symbols

For completeness: I am one of the people eSOANEM mentioned as helping with this. Specifically with the conclusion that there should be at most 30 independent components to Γ. This part should be fairly standard GR tensor manipulation, and it's probably worth other people checking. Take the usual exp...
Sun Jan 18, 2015 8:42 pm UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9968
Views: 1951349

### Re: Coding: Fleeting Thoughts

FT: This video is super cool! It is an hour+ long, so here's my rough summary: they took a method originally used for sampling from (complicated, high-dimensional) probability distributions and turn it into a directed search algorithm (for complicated, high-dimensional search domains). Then they bui...
Fri Jan 02, 2015 9:21 pm UTC
Forum: Mathematics
Topic: unique description of circle
Replies: 21
Views: 5237

### Re: unique description of circle

I think it takes one number to fundamentally specify a circle. Any two circles with the same radius is congruent. So all you need to give is the radius. The other numbers are not specifying the circle itself but rather the location of the circle with respect to a coordinate system. Well, at that po...
Fri Jan 02, 2015 5:21 pm UTC
Forum: Mathematics
Topic: unique description of circle
Replies: 21
Views: 5237

### Re: unique description of circle

This is probably on some level a restatement of what other people have been saying, but here's my take on things: If we're trying to find a specific circle, we have three unknowns a, b, and r to find. Then for each point (x, y) we are given which is on the circle, we get one equation in those three ...
Fri Jan 02, 2015 4:56 pm UTC
Forum: Mathematics
Topic: Mathematical Induction - Help for a Beginner?
Replies: 75
Views: 12455

### Re: Mathematical Induction - Help for a Beginner?

I should also point out that I don't understand how to manipulate the symbols to arrive at the solution. The text I'm working from has the following solution: 1 + 2 + 3 + . . . + k + (k + 1) = k(k + 1)/2 + (k + 1) = (k + 1)(k/2 + 1) = (k + 1)(k + 2)/2 Can anyone help me figure out what happened abo...
Mon Dec 29, 2014 6:55 pm UTC
Forum: Science
Topic: (New) Neutrinos = Tachyon?
Replies: 19
Views: 5263

### Re: (New) Neutrinos = Tachyon?

I've been told that, in quantum field theory, you can't have tachyons in the sense of "things which travel faster than c". For a start, this post from the Usenet Physics FAQ was posted to the Hacker News thread about the article from the OP. Another way I've been told to look at it is that...
Mon Dec 22, 2014 8:01 pm UTC
Forum: Science
Topic: Fermi's Golden Rule and laser rate equations
Replies: 5
Views: 3257

### Re: Fermi's Golden Rule and laser rate equations

In reference to OP's original question: I would've thought that, if you're assuming the particles don't interact with each other (much), then Fermi's Golden Rule would apply as long as the transition rate for a single particle is small. In other words, what matters is (say) how likely a particle whi...
Mon Oct 27, 2014 6:28 pm UTC
Forum: Mathematics
Topic: Favorite math jokes
Replies: 1452
Views: 482828

### Re: Favorite math jokes

Why did the topologists insist that their relationship had lasted "up to and including the point of the breakup"? They wanted closure That's brilliant :D I don't have any good jokes, but I did remember there's a page with quotes from some of our lecturers. Here are a few of the funnier on...
Wed Oct 22, 2014 9:11 pm UTC
Forum: Mathematics
Topic: How many ways can you prove x + 1/x >= 2?
Replies: 23
Views: 16195

### How many ways can you prove x + 1/x >= 2?

This is a fun game one of my friends just told me about: How many different proofs (for some meaning of "different") can you find of the fact that if x > 0, then x + 1/x >= 2? The guy who told me about it reckons he has at least 8. I'll start with a couple of simplifications: x=1 is obviou...
Sun Oct 19, 2014 4:33 pm UTC
Forum: General
Topic: [SAFESPACE] LGBTIQQA Thread - Queer Support!
Replies: 8247
Views: 1425366

### Re: [SAFESPACE] LGBTIQQA Thread - Queer Support!

Natashatasha: I can't really comment on most of what you said, aside from offering sympathy and internet hugs (but only if wanted). But there were a couple of things I wanted to say: I don't really want to worry you people or wear on your good will or make you think I'm seeking attention orr just wa...
Fri Oct 03, 2014 1:37 pm UTC
Forum: General
Topic: [SAFESPACE] LGBTIQQA Thread - Queer Support!
Replies: 8247
Views: 1425366

### Re: [SAFESPACE] LGBTIQQA Thread - Queer Support!

Is it actually necessary to choose? There was a lovely essay on a now-deleted blog about folks like myself who are "gender apathetic" - maybe we do or don't identify as male or female, completely or incompletely, but we just don't given enough of a shit to actually change pronouns, adjust...
Wed Sep 17, 2014 10:12 pm UTC
Forum: Mathematics
Topic: Math: Fleeting Thoughts
Replies: 427
Views: 147063

### Re: Math: Fleeting Thoughts

Hmm, that is the impression I was getting from a couple of other people too, that numerical stuff is better to pick up as and when you need it. In that case I'd probably be most interested in either the classical or quantum field theory courses. There's also one slight complication I haven't mention...
Wed Sep 17, 2014 9:31 pm UTC
Forum: Science
Topic: Fuck Dark Matter; It's a sprinkler, not a whirlpool.
Replies: 135
Views: 26713

### Re: Fuck Dark Matter; It's a sprinkler, not a whirlpool.

I went away from the fora for a while and seem to have missed all the fun in this thread! However, I do have one question for the GR people around here, based on something skolnick1 said on the second page: When you accelerate an electron, you get Bremsstrahlung, or "braking radiation", o...
Wed Sep 17, 2014 9:08 pm UTC
Forum: Science
Topic: Fuck Dark Matter; It's a sprinkler, not a whirlpool.
Replies: 135
Views: 26713

### Re: Fuck Dark Matter; It's a sprinkler, not a whirlpool.

I went away from the fora for a while and seem to have missed all the fun in this thread! However, I do have one question for the GR people around here, based on something skolnick1 said on the second page: When you accelerate an electron, you get Bremsstrahlung, or "braking radiation", op...
Wed Sep 17, 2014 8:48 pm UTC
Forum: Mathematics
Topic: Math: Fleeting Thoughts
Replies: 427
Views: 147063

### Re: Math: Fleeting Thoughts

Something of a first-world problem, but my university offers far too many interesting modules for next year. I think I have a rough idea what I'm going to do, there's only really one or two things I'm undecided on. In fact, maybe some of you could be of help: Does this course (description quoted bel...
Wed Aug 13, 2014 10:27 am UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9968
Views: 1951349

### Re: Coding: Fleeting Thoughts

Well here's the thing: I don't need the values I get out to be sorted, I just need them to be the smallest ones (they just get summed anyway, so order doesn't matter). And doing it on a vector unit means you have some really annoying requirements. The main one is that you don't have compare-and-bran...
Tue Aug 12, 2014 8:46 pm UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9968
Views: 1951349

### Re: Coding: Fleeting Thoughts

Which heap algorithm do you use? Some complex heaps like Fibonacci heaps have very good theoretical properties, but in practice simple binary heaps are orders of magnitude faster. It's a fixed 4-level binary heap (ie, it always has 15 elements in). I was considering trying a ternary heap and seeing...
Mon Aug 11, 2014 6:12 pm UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9968
Views: 1951349

### Re: Coding: Fleeting Thoughts

Oh wow, that's impressive! Do you need every file in every build, though? Because I'd be very tempted to partition the rules up (in a similar way to how you'd do recursive make) and then only include the rules for the files you need. That could be based on the build target, static configuration or b...
Tue Aug 05, 2014 10:24 pm UTC
Forum: Science
Topic: Computational modelling of fields
Replies: 8
Views: 2668

### Re: Computational modelling of fields

Oh, I see what you mean now. I meant that the algorithms were O(txyz) where t, x, y, z are the number of points in each direction, while you were thinking of the overall size of the region. In that case, yes, as you increase the total size you'll have to decrease the spacing so it scales super-linea...
Tue Aug 05, 2014 8:08 pm UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9968
Views: 1951349

### Re: Coding: Fleeting Thoughts

Thesh and Yakk: Oh, I've read far too many accounts of people trying to "fix" legacy systems to try that ;) Though thanks for the reminder, it's a lesson worth repeating! In this case it's a little different. I'm having to add features in order to support the work I'm supposed to be doing,...
Tue Aug 05, 2014 7:28 pm UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9968
Views: 1951349

### Re: Coding: Fleeting Thoughts

Ever experience that? The desire to push someone aside and be like 'Nonono, get off, you're done, let me do this the right way'. Oh so very very much. In particular, one of the programs I'm working on as part of my internship. To be fair, the way it's designed it isn't necessarily bad per se , it's...
Tue Aug 05, 2014 7:08 pm UTC
Forum: Science
Topic: Computational modelling of fields
Replies: 8
Views: 2668

### Re: Computational modelling of fields

One hopes that, by performing simulations on larger and larger lattices, while making the lattice spacing smaller and smaller, one will be able to recover the behavior of the continuum theory. I was hoping it was possible to keep the simulation's scalability to be linear to the number of space-time...
Sat Aug 02, 2014 12:58 pm UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9968
Views: 1951349

### Re: Coding: Fleeting Thoughts

Thesh: I quite like Haskell's way of dealing with the eternal problem of error codes vs. exceptions, so I've made a fairly straight translation of your first example: import Control.Monad.Except import System.Exit data MathError = DIVIDE_BY_ZERO deriving Show divide :: Int -> Int -> Except MathError...
Fri Aug 01, 2014 4:53 pm UTC
Forum: Mathematics
Topic: What's your favorite platonic solid?
Replies: 21
Views: 4963

### Re: What's your favorite platonic solid?

Mine's the dodecahedron. It's such a sexy shape. xD In which case you'll probably like this : by drawing lines on (the surface of) a dodecahedron, you can outline five different cubes. Not only is it kind of cool, but it's quite a good lead in to some really interesting bits of group theory. Unfort...
Thu Jul 31, 2014 10:14 pm UTC
Forum: Mathematics
Topic: What's your favorite platonic solid?
Replies: 21
Views: 4963

### Re: What's your favorite platonic solid?

Mine's the dodecahedron. It's such a sexy shape. xD In which case you'll probably like this : by drawing lines on (the surface of) a dodecahedron, you can outline five different cubes. Not only is it kind of cool, but it's quite a good lead in to some really interesting bits of group theory. Unfort...