# Anders Claesson: On the problem of Hertzsprung and similar problems

**Time: **
Wed 2021-04-21 10.15 - 11.15

**Location: **
Zoom meeting ID: 654 5562 3260

**Lecturer: **
Anders Claesson (University of Iceland)

Abstract: Drawing on a problem posed by Hertzsprung in 1887 (sometimes called the n-kings problem), we say that a permutation w contains the Hertzsprung pattern u if there is factor w(d+1)w(d+2)...w(d+k) of w such that w(d+1)-u(1) = ... = w(d+k)-u(k). Using a combination of the Goulden-Jackson cluster method (which we explain) and the transfer-matrix method we determine the joint distribution of occurrences of any set of (incomparable) Hertzsprung patterns, thus substantially generalizing earlier results by Jackson et al. on the distribution of ascending and descending runs in permutations. We apply our results to the problem of counting permutations up to pattern-replacement equivalences, and using pattern-rewriting systems---a new formalism similar to the much studied string-rewriting systems---we solve a couple of open problems raised by Linton et al. in 2012.

Zoom meeting ID: 654 5562 3260

Zoom meeting link: https://kth-se.zoom.us/j/65455623260