On $S$-units for valuations of the second degree in hyperelliptic fields

In this paper we propose a new effective approach to the problem of finding and constructing non-trivial $S$-units of a hyperelliptic field $L$ for a set $S=S_h$ consisting of two conjugate valuations of the second degree. The results obtained are based on a deep connection between the problem of torsion in the Jacobians of hyperelliptic curves and the quasiperiodicity of continued $h$-fractions, that is, generalized functional continued fractions of special form constructed with respect to a valuation of the second degree. We find algorithms for searching for fundamental $S_h$-units which are comparable in effectiveness with known fast algorithms for two linear valuations.