This is Ferdinand Ihringer’s math blog. I am a postdoctoral researcher in mathematics. I started this blog at the end of 2017 because (1) I wanted to have a math blog for some time and (2) I wrote in a funding application that I will use a blog to present my results.

In (algebraic) combinatorics there is a bound on the size of an independent set in a graph which is often call *Hoffman’s bound*. Variations of this bound I use very often in my work. Chris Godsil usually refer to the same bound as *ratio bound*. In a philosophical context ratio can also mean reason. Unlike in mathematics, in the real world reason itself has its limits. So there is another ratio bound for. That is why I like the word.