Abstract. We give short proofs of two descriptions given by Šemrl of order automorphisms of the effect algebra. This sheds new light on both formulas that look quite complicated. Our proofs rely on Molnár's characterization of order automorphisms of the cone of all positive operators.

DOI: 10.14232/actasm-018-008-7

AMS Subject Classification (1991): 47B49

Keyword(s): self-adjoint operator, operator interval, effect algebra, order isomorphism, operator monotone function

Received November 15, 2017, and in revised form January 13, 2018. (Registered under 8/2018.)