Prof. Lamberto Rondoni (Politecnico di Torino)
The time-reversal properties of charged systems in a constant external magnetic field are reconsidered, showing that the evolution equations are invariant under novel symmetry operations that imply new signature properties for time-correlation functions under time reversal. Such symmetry relations do not require that the magnetic field be reversed, which makes them applicable to material properties of a single system, rather than of two distinct physical situations. This implies, that Onsager-Casimir relations may be replaced by Onsager reciprocal relations even in the presence of a constant magnetic field, or of mechanically analogous situations. These findings determine, for example, null components of the correlation functions of velocities and currents and of the associated transport coefficients. The theory is developed for both classical and quantum systems, in analogy to Kubo's approach, but the quantum mechanical version leads to new intriguing questions. The theoretical predictions are then illustrated by molecular dynamics simulations of superionic AgI.