Question:  Otto Stern is the second most nominated person for a Nobel Prize behind a German theoretical physicist who pioneered developments in what?

Related documents: [0]  [DOC] Otto Stern (17 February 1888 – 17 August 1969) was a German physicist and Nobel laureate in physics. He was the second most nominated person for a Nobel Prize with 82 nominations in the years 1925–1945 (most times nominated is Arnold Sommerfeld with 84 nominations), ultimately winning in 1943. [END] 
[1]  [DOC] 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. He served as PhD supervisor for many Nobel Prize winners in physics and chemistry (only J. J. Thomson's record of mentorship is comparable to his). [END]  
Answer: atomic and quantum physics
atomic and quantum physics