Equality characterization for continuous-generator quasi-arithmetic means

Characterize the strictly increasing continuous generators f,g defined on an appropriate domain C in a finite-dimensional Euclidean space for which the corresponding weighted quasi-arithmetic means with fixed weights and a fixed number of variables are equal for every input tuple.

Background

The paper introduces vector-valued weighted quasi-arithmetic means and formulates their equality problem for a fixed number of variables and fixed weights. It notes that the complete equality characterization remains unresolved even in the real-valued setting for non-continuous generators, while the classical continuous scalar case is known.

The stated problem asks specifically for a characterization under the additional assumption that the generators are continuous, and leaves the domain C to be chosen appropriately.

References

Is it possible to solve the equality problem of QAMs assuming that the generators are {\em continuous}? That is, how can we characterize the strictly increasing generators $ f, g : C R $ for which eq-EqualityProblem holds on an appropriate domain $ C \subseteq R $?

Generalized inverses of strictly monotone transformations  (2608.19997 - Tóth, 20 Aug 2026) in Section 5, second Open Problem