Welcome!

This is the personal website of Armin Straub.

Currently, I'm studying mathematics at Tulane University, New Orleans. My PhD advisor is Victor H. Moll, and my research area is an exciting mix of combinatorics, special functions and computer algebra.

This website is about to replace my old one.

Visiting Grinnell, Iowa

Sun, 06/14/2009 - 20:01 — arminstraub

At Grinnell…

Apollonian circle packings in Mathematica

Fri, 06/12/2009 - 18:33 — arminstraub

Today, I have been playing a little bit with Apollonian circle packings. Here is the code I wrote in Mathematica to visualize such packings (see below for an example).

Attachment: 
application/mathematica icon
apolloniancirclepackings.nb
read more »

Fast q-binomials in Mathematica

Wed, 06/10/2009 - 21:33 — arminstraub

Recently, I have been doing experiments involving q-binomial coefficients in Mathematica. Starting with version 7, Mathematica is prepared for some q-business; in particular, there exists a function named QBinomial giving the q-analog of Binomial. However, this implementation turned out to not be fast enough for my needs. Here is an alternative approach which is not only way faster but provides a full factorization. read more »

Math department picture 2009

Tue, 05/19/2009 - 08:41 — arminstraub

The Tulane Mathematics Department as of April 27, 2009. Unfortunately but naturally, a few people are missing.

Using the Google Chart API

Sat, 05/16/2009 - 15:24 — arminstraub

The following graph is dedicated to my brother Benjamin.

 read more »

A trick for playing a multivariate integral

Wed, 05/13/2009 - 14:35 — arminstraub

For suitable functions f the integral

$$ \int_0^{\infty} \int_0^{\infty} \ldots \int_0^{\infty} \frac{dx_1 dx_2 \cdots dx_n}{(f(x_1) + f(x_2) + \ldots + f (x_n))^{k+1}} $$

is equal to

$$ \frac{1}{k!} \int_0^{\infty} t^k \left( \int_0^{\infty} e^{- t f(x)} dx \right)^n dt . $$

To see why this is true, start with the last integral and write the n-th power of the inner integral as a multiple integral over variables x1, …, xn. Then change order of integration and evaluate read more »

The "What Is...?" column

Wed, 04/29/2009 - 19:26 — arminstraub

I very much enjoy reading the "What Is…?" column in the Notices of the AMS. Unfortunately, there seemed to be no index to this column. I have therefore created this one in the hope that it'll be helpful to others as well.

  1. What is…an amoeba? — Oleg Viro, September 2002
  2. What is…the monster? — Richard Borcherds, October 2002
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Des Herrn Geburt

Mon, 12/22/2008 - 10:31 — arminstraub

Der Mensch war Gottes Bild.
Weil dieses Bild verloren,
Wird Gott, ein Menschenbild,
In dieser Nacht geboren.

Author: 
Andreas Gryphius

Positivity of Szegö's rational function

Thu, 05/22/2008 - 20:09 — arminstraub

This article has been published in Advances in Applied Mathematics (Volume 41, Issue 2, August 2008, Pages 255-264) and is available at doi:10.1016/j.aam.2007.10.001.

Errata and addenda are contained in an additional document.

Attachment: 
application/pdf icon
positivity.pdf
application/pdf icon
positivity-addendum.pdf
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