Spectral parameters of the quantum Yang-Baxter equation

We show that one can naturally associate with any solution R of the quantum Yang-Baxter equation a set L(R) of spectral parameters. A general algebraic procedure for reconstructing L(R) from R is proposed. It turns out that in general L(R) is a non-commutative semigroup, whose idempotent elements give rise to other solutions of the quantum Yang-Baxter equation. Some examples and applications are discussed. (orig.)