Resumen de Wigner's theorem revisited

Gyula Maksa, Zsolt Páles

• In this paper, we give the general solution of the functional equation { �af(x) + f(y)�a; �af(x) . f(y)�a } = { �ax + y�a; �ax . y�a } (x; y �¸ X) where f : X �¨ Y and X; Y are inner product spaces. Related equations are also considered. Our main tool is a real version of Wigner's unitary-antiunitary theorem.