## Pavel Pt\'ak, Hans Weber

*Relatively additive states on quantum logics *

Comment.Math.Univ.Carolinae 46,2 (2005) 327-338. **Abstract:**In this paper we carry on the investigation of partially additive states on quantum logics (see [2], [5], [7], [8], [11], [12], [15], [18], etc.). We study a variant of weak states --- the states which are additive with respect to a given Boolean subalgebra. In the first result we show that there are many quantum logics which do not possess any 2-additive central states (any logic possesses an abundance of 1-additive central state --- see [12]). In the second result we construct a finite 3-homogeneous quantum logic which does not possess any two-valued 1-additive state with respect to a given Boolean subalgebra. This result strengthens Theorem 2 of [5] and presents a rather advanced example in the orthomodular combinatorics (see also [9], [13], [4], [6], [16], etc.). In the rest we show that Greechie logics allow for $2$-additive three-valued states, and in case of Greechie lattices we show that one can even construct many $2$-additive two-valued states. Some open questions are posed, too.

**Keywords:** (weak) state on quantum logic, Greechie paste job, Boolean algebra

**AMS Subject Classification:** 03G12, 46C05, 81P10

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