In this paper a control problem for a controlled linear stochastic equation in a Hilbert space and an exponential quadratic cost functional of the state and the control is formulated and solved. The stochastic equation can model a variety of stochastic partial differential equations with the control restricted to the boundary or to discrete points in the domain. The solution method does not req...

A generalized trigonometric-quadratic functional equation of the form F(x+ y) + G(x− y) = 2H(x)K(y) + L(x) +M(y) over the domain of an abelian group and the range of the complex field is considered. Its stability is established based on the assumption that the function K is unbounded. Subject to certain natural conditions, explicit shapes of the functions H and K are determined. Several existin...