Category Mathematics
Ahlswede-Zhang identity
This post is about Sperner systems and about turning the famous LYM inequality into an identity. Typically, people refer to this inequality as the LYM inequality (Lubell-Yamamoto-Meshalkin) but it is worth pointing out that the inequality follows as a corollary from the more general Bollobás inequality. While thinking of this inequality I asked myself about the cases that […]
Double counting
Double counting is a simple yet so powerful way to prove non-trivial theorems. Here, we present some applications of the double counting principle. Our main source is the excellent book “Extremal Combinatorics” by Stasys Jukna [1]. A newer edition from the one in the picture (which shows the book I have) is also available now. […]
Large Girth and Chromatic Number
Paul Erdös is an inspiring figure. Not only for mathematicians and computer scientists but for everyone. His simplicity, his love for his friends, for music and of course for mathematics indicate a man who followed his feelings which had the word love in them. If you get to meet people that knew him personally and […]
tsourakakis.com 