G5 Artikkeliväitöskirja

An Algebraic Approach to Nivat's Conjecture




TekijätSzabados Michal

KustantajaUniversity of Turku

KustannuspaikkaTurku

Julkaisuvuosi2018

eISBN978-952-12-3737-9

Verkko-osoitehttp://urn.fi/URN:ISBN:978-952-12-3737-9

Rinnakkaistallenteen osoitehttp://urn.fi/URN:ISBN:978-952-12-3737-9


Tiivistelmä

This thesis introduces a new, algebraic method to study multidimensional configurations, also sometimes called words, which have low pattern complexity. This is the setting of several open problems, most notably Nivat’s conjecture, which is a generalization of Morse-Hedlund theorem to two dimensions, and the periodic tiling problem by Lagarias and Wang. 

We represent configurations as formal power series over d variables where d is the dimension. This allows us to study the ideal of polynomial annihilators of the series. In the two-dimensional case we give a detailed description of the ideal, which can be applied to obtain partial results on the aforementioned combinatorial problems. 

In particular, we show that configurations of low complexity can be decomposed into sums of periodic configurations. In the two-dimensional case, one such decomposition can be described in terms of the annihilator ideal. We apply this knowledge to obtain the main result of this thesis – an asymptotic version of Nivat’s conjecture. We also prove Nivat’s conjecture for configurations which are sums of two periodic ones, and as a corollary reprove the main result of Cyr and Kra from [CK15].



Last updated on 2024-03-12 at 13:19