Starting From tree and one-loop tachyon amplitudes of open string theory in
the presence of a constant B-field, we explore two problems. First we show
that in the noncommutative field theory limit the amplitudes reduce to tre
e and one-loop diagrams of the noncommutative Phi(3) theory. Next, we check
factorization of the one-loop amplitudes in the long cylinder limit. (C) 2
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