Information about the interaction of a many-electron quantum system with its environment, we show, is encoded within the one-electron density matrix (1-RDM). While the 1-RDM from an ensemble many-electron quantum system must obey the Pauli exclusion principle, the 1-RDM must obey additional constraints known as generalized Pauli conditions when it corresponds to a closed system describable by a single wave function. By examining the 1-RDM's violation of these generalized Pauli conditions, we obtain a sufficient condition at the level of a single electron for a many-electron quantum system's openness. In an application to exciton dynamics in photosynthetic light harvesting we show that the interaction of the system with the environment (quantum noise) relaxes significant constraints imposed on the exciton dynamics by the generalized Pauli conditions. This relaxation provides a geometric (kinematic) interpretation for the role of noise in enhancing exciton transport in quantum systems.
We proposed a Quaternionic mechanical system motivated by the Foucault pendulum as a classical model for the dynamics of the spin 1/2 system. We showed that this mechanical system contains the dynamics of the spin state of the electron under a uniform magnetic field as it is given by the Schrodinger-Pauli-Equation (SPE). We closed with a characterization of the dynamics of this generalized classical system by showing that it is equivalent with the dynamics of the Schrodinger Pauli Equation as long as the solutions to the generalized classical system are roots of the Lagrangian, that is the condition L = 0 holds.
In the framework of recently developed description of the non-relativistic
constrained quantum mechanics of systems of
N-Coulombically interacting
electrons [Phys. Rev. {\bf A} 78, 032503 (2008)], we study the relation between
spin and statistics in two-electron systems. We find that that the Fermi-Dirac
statistics implies lowering of the spatial SO(3) symmetry of the wave-functions
of electronic states to Abelian SO(2) rotational subgroup, which is accompanied
by reduction of the number of spatial degrees-of-freedom from 6 to 5. We find
that the relation between spin and statistics is necessarily related to the
anti-symmetry of the relative phase of the spatial part of the two-electron
wave-function. We find that it leads to distinct classification of the
electronic states according to their relative orbital parity
(−1)m and total
spin
S={0,1}. We also find that the Pauli exclusion principle is realized
dynamically due to Coulombic interaction between the particles. We find that
the broken rotation symmetry of the wave-functions of the electronic states can
be restored dynamically, due to conservation of the Laplace-Runge-Lenz vector.
We demonstrate that the proposed theoretical description is internally
consistent and predictive, and we find the non-equivalence of the above mention
representation to the conventional Schr\{o}dinger picture for the description
of the quantum dynamics in Coulombic systems with more than one electron.