Arithmetic properties of three-dimensional algebraic tori

We compute the Shafarevich-Tate group, the kernel of the weak approximation and the Manin groups of three-dimensional algebraic tori defined over an algebraic number field. A minimal example of a torus with fractional Tamagawa number is constructed. A criterion for the validity of the Hasse norm principle for extensions of degree four of an algebraic number field is given.