ON BOREL SUMMABILITY AND ANALYTIC FUNCTIONALS

We show that a formal power series has positive radius of convergence if and only if it is uniformly Borel summable over a circle with center at the origin. Consequently, we obtain that an entire function f is of exponential type if and only if the formal power series Sigma(infinity)(n=0) f((n))(0)z(n) uniformly Borel summable over a circle centered at the origin. We apply these results to obtain a characterization of those Silva tempered ultradistributions which are analytic functionals. We also use Borel summability to represent analytic functionals as Borel sums of their moment Taylor series over the Borel polygon.