Physical phase space of lattice Yang-Mills theory and the moduli space of flat connections on a Riemann surface

It is shown that the physical phase space of \g-deformed Hamiltonian lattice Yang-Mills theory, which was recently proposed in refs.[1,2], coincides as a Poisson manifold with the moduli space of flat connections on a Riemann surface with $(L-V+1)$ handles and therefore with the physical phase space of the corresponding $(2+1)$-dimensional Chern-Simons model, where $L$ and $V$ are correspondingly a total number of links and vertices of the lattice. The deformation parameter \g is identified with $\frac {2\pi}{k}$ and $k$ is an integer entering the Chern-Simons action.Comment: 12 pages, latex, no figure

Nuclear Polarization in Quantum Point Contacts in an In-Plane Magnetic Field

Nuclear spin polarization is typically generated in GaAs quantum point contacts (QPCs) when an out-of-plane magnetic field gives rise to spin-polarized quantum Hall edge states, and a voltage bias drives transitions between the edge states via electron-nuclear flip-flop scattering. Here, we report a similar effect for QPCs in an in-plane magnetic field, where currents are spin polarized but edge states are not formed. The nuclear polarization gives rise to hysteresis in the d.c. transport characteristics, with relaxation timescales around 100 seconds. The dependence of anomalous QPC conductance features on nuclear polarization provides a useful test of their spin-sensitivity.Comment: 5 page

Electrical generation of pure spin currents in a two-dimensional electron gas

Pure spin currents are measured in micron-wide channels of GaAs two-dimensional electron gas (2DEG). Spins are injected and detected using quantum point contacts, which become spin polarized at high magnetic field. High sensitivity to the spin signal is achieved in a nonlocal measurement geometry, which dramatically reduces spurious signals associated with charge currents. Measured spin relaxation lengths range from 30 to 50 microns, much longer than has been reported in GaAs 2DEG's. The technique developed here provides a flexible tool for the study of spin polarization and spin dynamics in mesoscopic structures defined in 2D semiconductor systems

On the canonical quantization of anomalous SU(N) chiral Yang-Mills models

Canonical quantization of anomalous SU(N) Yang-Mills models is considered. It is shown that the gauge invariance of the quantum theory can be saved in spite of degeneracy of the Wess-Zumino action.Comment: 9 pages, LaTe