International politics (or international relations) is one of the subfields of the Political Science Department. A number of Columbia scholars are quite well-known in international relations and related fields, including Robert Jervis, Kenneth Waltz, and Richard K. Betts.
Its major schools of thought, as you will find out in any intro to international relations class, include (neo-)realism, liberalism, and constructivism. In general, neo-realism is viewed as being the most dominant at Columbia.
Barack Obama concentrated in international politics during his Columbia years.