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Hash Week! (Part 3)
Posted by Matt Springer on October 10, 2012 Over the last two days we’ve talked about hash functions and their uses in cryptography and elsewhere. Remember that an ideal hash function is basically what cryptographers call a random oracle – given an input, it produces a random number in some range. (In practice this range is always [0,2^(2^n)], with n usually equal to…
Hash Week! (Part 2)
Posted by Matt Springer on October 9, 2012 Yesterday we looked at hash functions. As you recall, they’re functions which take an input and generate a random-seeming output. As a quick example, here’s the output of the SHA-256 hash function for the name of the Scottish physicist James Maxwell and a misspelling thereof: SHA256(“James Clerk Maxwell”) = 2667629603913530690117759428994407894024237387971995154086108064226397\ 5353322 SHA256(“James Clark Maxwell”) =…
Hash Week! (Part 1)
Posted by Matt Springer on October 8, 2012 Last week NIST anounced the winner of its Cryptographic Hash Function Competition. After five years of review and many rounds of discussion and elimination, the winner is a hash function called Keccak, and its developers deserve many congratulations. It’s a shame hash functions aren’t better known in the general public, because not only are they…
A Raman Rainbow
Posted by Matt Springer on October 1, 2012 Hey, how about that! Three people in our optics group here at Texas A&M (Professor Alexei Sokolov, postdoc Miaochan Zhi, and grad student Kai Wang) had a photograph from one of their optics experiments make the Optics and Photonics News Image of the Week: The crystal in the foreground is being hit by two pulses…
Magneto and Momentum
Posted by Matt Springer on September 24, 2012 There’s this grim and affecting scene in both X-Men and X-Men: First Class – a young Erik Lehnsherr watches his family hauled away by Nazis through the gates of a concentration camp. He’s being dragged away by the Nazi guards, and he uses his magnetic powers for the first time to grab the gates with…
How Single-Colored Is A Laser?
Posted by Matt Springer on September 17, 2012 In most books or articles that talk about lasers, you’ll see a definition of laser light in terms of “coherence”. But coherence is sort of a term of art, and the books will go on to explain coherence in terms of the waves being in sync with each other, or the emitted light being very…
Some Cute Math
Posted by Matt Springer on September 14, 2012 Back before my now-ended blogging hiatus, the server machinery that keeps ScienceBlogs running was not so snazzy as it is now. Now it’s running a WordPress implementation that includes LaTeX support. LaTeX is a free environment for (among other things) typesetting mathematics. Let’s give it a test run: I actually came across the above expression…
Armstrong in Orbit
Posted by Matt Springer on September 10, 2012 If you’ve been reading ScienceBlogs for a while, you might remember this little physics blog I used to write. It and I sort of vanished off the internet for a long while. More than a year, I’m sad to say. Long story short, being a grad student takes up a huge amount of time. While…
Spherical Waves and the Hairy Ball Theorem
Posted by Matt Springer on August 12, 2011 Boy howdy do we love spheres in physics. Sure we might tell you that the reason involves deep truths in topology, and symmetry, and group theory, and all that mathematical arcana, and in fact there’s a lot of truth to that. But if we’re completely honest, or at least if I’m completely honest, I have…
Sunday Function
Posted by Matt Springer on August 1, 2011 A reader asked me about the hyperbolic trig functions, sinh(x) and cosh(x). What are they for, and do they have an intuitive interpretation in physics? That’s a pretty good question. After all, most of the time you first meet the hyperbolic trig functions in intro calculus, where their rather odd definitions are presented and then…