His early research concerned various properties and structures of algebraic numbers. In 1981 he proved the Fröhlich conjecture relating the symmetries of algebraic integers to the behaviour of certain analytic functions called ArtinL-functions. In recent years his research has led him to study various aspects of arithmetic geometry: in particular, he and his collaborators have demonstrated how geometric properties of zeros of integral polynomials in many variables can be determined by the behaviour of associated L-functions.