Coefficients of Catalan States of Lattice Crossing I: ${\mathrm{\Theta }}_A$-state Expansion

Plucking polynomial for plane rooted trees was introduced by J.H. Przytycki in 2014. As it was shown later, this polynomial can be used to find coefficients $C(A)$ of Catalan states $C$ of $m\times n$-lattice crossing $L(m,n)$ without returns on one side. In this paper, we show that $C(A)$ for any $C$ can be found by using ${\mathrm{\Theta }}_A$-state expansion which represents $C(A)$ as a linear combination of coefficients of Catalan states with no top returns over $\mathbb{Q}(A)$. We also provide an algorithm for finding ${\mathrm{\Theta }}_A$-state expansions and examples of its applications. Finally, an example of a Catalan state with non-unimodal coefficient is given.