Affiliation: | Faculty of Mathematics, University of Waterloo, Waterloo, Ontario, Canada ~N2L 3G1 ; Institute of Mathematics, Silesian University, Bankowa 14, PL-40-007 Katowice, Poland ; Universität GH Paderborn, FB 17, D-33095 Paderborn, Germany |
Abstract: | The problem of determining all utility measures over binary gambles that are both separable and additive leads to the functional equation ![begin{equation*}f(v) = f(vw) + f[vQ(w)], qquad v, vQ(w) in [0,k),quad w in [0,1],. end{equation*}](http://www.ams.org/proc/1999-127-10/S0002-9939-99-04863-7/gif-abstract/img1.gif)
The following conditions are more or less natural to the problem: strictly increasing, strictly decreasing; both map their domains onto intervals ( onto a , onto ); thus both are continuous, , , , , . We determine, however, the general solution without any of these conditions (except , , both into). If we exclude two trivial solutions, then we get as general solution ( , ; for ), which satisfies all the above conditions. The paper concludes with a remark on the case where the equation is satisfied only almost everywhere. |