Suppose H is a Banach space,
D is an open set of H containing 0, and V is a function from D ×D to H satisfying
V (0,x) = V (x,0) = x for each x in D. If n is an integer greater than 1, denote
by xn the product of n − x’s associated as follows whenever the product
exists.
Define x0 = 0 and x1 = x.V is said to be power associative if and only if
V (xn,xm) = xn+m whenever each of n and m is a nonnegative integer and xn+m
exists.
Theorem A. If H and V are as above, V is power associative and continuously
differentiable in the sense of Frechet on D × D then there are positive numbers
a and c such that if x is in H and ∥x∥ < a there is a unique continuous
function Tx from [0,1] to the ball of radius c centered at 0 satisfying
V (Tx(s),Tx(t)) = Tx(s + t) whenever each of s,t, and s + t is in [0,1],Tx(0) = 0, and
Tx(1) = x.
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