Editing Stanisław Ulam (section)

===Statistics of branching and multiplicative processes===
Even the inherent statistical fluctuations of [[neutron]] multiplication within a [[chain reaction]] have implications with regard to implosion speed and symmetry. In November 1944, [[David Hawkins (philosopher)|David Hawkins]]<ref name='HAWKINS'/> and Ulam addressed this problem in a report entitled "Theory of Multiplicative Processes".<ref name='LA171'/> This report, which invokes [[probability-generating function]]s, is also an early entry in the extensive literature on statistics of [[Branching process|branching]] and multiplicative processes. In 1948, its scope was extended by Ulam and Everett.<ref name='MULT123'/>

Early in the Manhattan project, [[Enrico Fermi]]'s attention was focused on the use of reactors to produce plutonium. In September 1944, he arrived at Los Alamos, shortly after breathing life into the [[Manhattan Project#Hanford reactors|first Hanford reactor]], which had been [[Nuclear poison|poisoned]] by a [[Xenon-135|xenon isotope]].<ref name="HEWLETT"/> Soon after Fermi's arrival, [[Teller's "Super" bomb]] group, of which Ulam was a part, was transferred to a new division headed by Fermi.<ref name="ULAM 152-153"/> Fermi and Ulam formed a relationship that became very fruitful after the war.<ref name="ULAM 162-167"/>