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Website 2.0

Over the past few years, I neglected the content of this website somewhat. So many things to do, so little time. But in part this was due to the hard time that the chosen CMS, Drupal, was giving me. Yesterday I moved the Website to Drupal 7, and things appear to work better. For a math website, it is a must to have formulas. The package DruTeX has become obsolete, and the current rendering is done using MathJAX, which is both more secure (rendering of TeX happens in user's browser) and more reliable way to render random formulas, such as this one: $$ P(G,x) = \sum_{A\subseteq E} (-1)^{|A|}\, x^{k(A)+|V| - |\bigcup A| } $$ which expresses the chromatic polynomial of the graph $G=(V,E)$ as a sum over all edge subsets $A\subseteq E$ of the edge set of $G$. Here, $k(A)$ denotes the number of connected components of the subgraph $G'=(|\bigcup A|, |A|)$ of $G$. Note that $|X|$ denotes the cardinality of a set $X$. This is a formula related to the Tutte polynomial, and... to the class on Combinatorial Mathematics, which I just finished teaching.