Archive for July, 2007

SIGGRAPH 07

Posted in Computing 3 years, 1 month ago

SIGGRAPH 2007 Poster

SIGGRAPH has to be the most prestigious conference for graphics research. While preparing for my talk last week, I came across this incredible resource for papers on the web. This is in many ways so much better than the official conference proceedings (links to the official homepages for example.)

SIGGRAPH 2007 papers on the web.

My CUMC talk

Posted in Activity 3 years, 1 month ago

My talk at the CUMC last week was well received. It so happened that it was scheduled on the last day — I got a chance to see some of the other presentations and assess the level of depth presented.

Applications

I was surprised to see that variational calculus and some analysis material is optional in the undergraduate curriculum, but we’ll debate that some other day…

The problem with conferences is that you tend to become mentally exhausted towards the end of four or five days of absorbing information non-stop.

Anyways, check out the outline of what I presented, geared towards a general audience. Someday, I’ll learn how to upload presentations…

Random Facts

Posted in Physics 3 years, 1 month ago

Some random math facts that I came across last week.

Poincaré group

The Special Euclidean group combines rotations and translations in Euclidean space. The SE group is an isometry, which means it preserves angles and distances.

In special relativity, the 4-vectors are three space variables and one time variable. Rotations in this space can be generalized to the Poincaré group. Instead of having sines and cosines in the rotation part as in SE, they have hyperbolic sines and cosines.

The norm of a vector is defined through its inner product:

 ||x|| = \sqrt {\langle x,x \rangle}

which in special relativity is

 \langle (x,y,z,t), (x,y,z,t) \rangle = x^2 + y^2 + z^2 – t^2

A friend pointed out that the Lorentz transformation was only recently proved to be linear.

Geodesics and Metrics

One of the most beautiful things I learnt in the last few weeks is the connection between geodesics (shortest paths) and metrics in that space. If g(t) is a geodesic path and v(t) is the velocity of the path:

v(t) = \frac{d g(t)}{dt}

then the metric is defined by

d^2 = \int ||v(t)||^2 dt

Moreover, the path satisfies the Euler-Lagrange equation. This was first shown by Arnold in a hydrodynamical context, and subsequently borrowed by control systems and computer vision folks.

A Poor Joke

Two functions e^x and x^2 were going in a car. x^2 looked ahead and said, “Oh shit! There comes a differential operator.” e^x says with a smirk, “It can’t do nothing to me!” On approaching the differential operator, it says “Haha! I’m d/dy.”

As narrated to me by a random math major last week…