Schwermer's research deals with algebraic groups in number theory, arithmetic geometry, Lie groups, and L-functions. He has written essays on the history of mathematics, for example, about Helmut Hasse, Hermann Minkowski, and Emil Artin.
Kohomologie arithmetisch definierter Gruppen und Eisensteinreihen, Springer, Lectures Notes in Mathematics Bd.988, 1983, ISBN9783540122920, doi:10.1007/BFb0070268
as editor with Jean-Pierre Labesse: Cohomology of arithmetic groups and automorphic forms, Springer, 1990, Lecture Notes in Mathematics (Konferenz Luminy/Marseille 1989), doi:10.1007/BFb0085723
Minkowski, Hensel, and Hasse: On The Beginnings of the Local-Global Principle, in Jeremy Gray, Karen Parshall: Episodes in the history of modern algebra (1800-1950), American Mathematical Society 2007