We show that the non-superstability (non-stability) of a theory T is equivalent to the condition that for every elementary chain of length u; (un) of saturated models Mi of T with ||M,+i|| > ||M;|| for all s < UJ(U/I), the union of the chain is not saturated. The cardinality of T is immaterial.

We will investigate the superstability of the hyperbolic trigonometric functional equation from the following functional equations: fx y ± gx − y λfxgy andfx y ± gx − y λgxfy, which can be considered the mixed functional equations of the sine function and cosine function, the hyperbolic sine function and hyperbolic cosine function, and the exponential functions, respectively.

In the present paper, the Hyers-Ulam stability and also the superstability of double centralizers and multipliers on Banach algebras are established by using a fixed point method. With this method, the condition of without order on Banach algebras is no longer necessary.

ELEMENTARY CLASSES RAMI GROSSBERG AND SEBASTIEN VASEY Abstract. In the context of abstract elementary classes (AECs) with a monster model, several possible definitions of superstability have appeared in the literature. Among them are no long splitting chains, uniqueness of limit models, and solvability. Under the assumption that the class is tame and stable, we show that (asymptotically) no lon...

abstract. let x be a vector space over a field k of real or complex numbers.we will prove the superstability of the following golab-schinzel type equationf(x + g(x)y) = f(x)f(y); x; y 2 x;where f; g are unknown functions (satisfying some assumptions). then we generalize the superstability result for this equation with values in the field of complex numbers to the case of an arbitrary hilbert spac...