Johannes Kellendonk
Gap labelling and the pressure on the boundary
(283K, pdf-file)

ABSTRACT.  In quantum systems described by families of $1$-particle 
Schr\"odinger operators on half-spaces the pressure on the boundary 
per unit energy is topologically quantised if 
the Fermi energy lies in a gap of the bulk spectrum. 
Its relation with the integrated density of states can be expressed in 
an integrated version of Streda's formula. 
This leads also to a gap labelling 
theorem for systems with constant magnetic field. 
The proof uses non-commutative topology.