Conversation so far:
Where was Aleksandr Solzhenitsyn born?
Aleksandr Solzhenitsyn was born in Kislovodsk, RSFSR (now in Stavropol Krai, Russia).
What year was Aleksandr Solzhenitsyn born?
Aleksandr Solzhenitsyn was born 11 December 1918.
What did Aleksandr Solzhenitsyn's parents do?
While in Moscow Taisiya Zakharovna met and married Isaakiy Semyonovich Solzhenitsyn, a young officer in the Imperial Russian Army of Cossack origin and fellow native of the Caucasus region.
Where did Aleksandr Solzhenitsyn go to school?
Aleksandr Solzhenitsyn studied mathematics and physics at Rostov State University.

Question: What did he major in?
Self-contained rewrite: What did Aleksandr Solzhenitsyn major in at Rostov State University?