Sidney Dancoff

Who was Sidney Dancoff?

Sidney Michael Dancoff was an American theoretical physicist best known for the Tamm–Dancoff approximation method and for nearly developing a renormalization method for solving quantum electrodynamics.

Dancoff was raised in the Squirrel Hill neighborhood of Pittsburgh. He attended Carnegie Tech on a private scholarship and received his B.S. in physics in 1934, followed by a master's degree from the University of Pittsburgh in 1936. He then went to the University of California at Berkeley where he earned his PhD in 1939 under Robert Oppenheimer.

While Dancoff was at Berkeley, Oppenheimer suggested that he work on the calculation of the scattering of a relativistic electron by an electric field. Such QED calculations typically gave infinite answers. Following earlier perturbation-theory work by Oppenheimer and Felix Bloch, he found that he could deal in various ways with the infinities that arose, sometimes by canceling a positive infinity with a negative one. However, some infinities remained uncanceled and the method did not give finite results. He published a general description of this work in 1939.