Question:  Otto Stern is the second most nominated person for a Nobel Prize behind a German theoretical physicist who pioneered developments in what?
Sentence (from "Arnold Sommerfeld"): Arnold Johannes Wilhelm Sommerfeld, {'1': ", '2': ", '3': 'ForMemRS', '4': "} (] ; 5 December 1868 – 26 April 1951) was a German theoretical physicist who pioneered developments in atomic and quantum physics, and also educated and mentored a large number of students for the new era of theoretical physics.
Relevant evidence: Yes