String Compression in FA-Presentable Structures

Abstract

We construct a FA-presentation $\psi: L \rightarrow \mathbb{N}$ of the structure $(\mathbb{N};\mathrm{S})$ for which a numerical characteristic $r(n)$ defined as the maximum number $\psi(w)$ for all strings $w \in L$ of length less than or equal to $n$ grows faster than any tower of exponents of a fixed height. This result leads us to a more general notion of a compressibility rate defined for FA-presentations of any FA-presentable structure. We show the existence of FA-presentations for the configuration space of a Turing machine and Cayley graphs of some groups for which it grows faster than any tower of exponents of a fixed height. For FA-presentations of the Presburger arithmetic $(\mathbb{N};+)$ we show that it is bounded from above by a linear function.