Incompressible Even Denominator Fractional Quantum Hall States in the Zeroth Landau Level of Monolayer Graphene

Incompressible even denominator fractional quantum Hall states at fillings $\nu = \pm \frac{1}{2}$ and $\nu = \pm \frac{1}{4}$ have been recently observed in monolayer graphene. We use a Chern-Simons description of multi-component fractional quantum Hall states in graphene to investigate the properties of these states and suggest variational wavefunctions that may describe them. We find that the experimentally observed even denominator fractions and standard odd fractions (such as $\nu=1/3, 2/5$, etc.) can be accommodated within the same flux attachment scheme and argue that they may arise from sublattice or chiral symmetry breaking orders (such as charge-density-wave and antiferromagnetism) of composite Dirac fermions, a phenomenon unifying integer and fractional quantum Hall physics for relativistic fermions. We also discuss possible experimental probes that can narrow down the candidate broken symmetry phases for the fractional quantum Hall states in the zeroth Landau level of monolayer graphene.Comment: 5 page

Pliocene-Pleistocene radiolarian biostratigraphy and paleoclimatology at DSDP Site 278 on the Antarctic Convergence : [with 3 plates (16+16+12 photos)]

Siliceous-rich sediments of late Pliocene to early Pleistocene age at DSDP Site 278, located on the Antarctic Convergence, contain an excellent radiolarian biostratigraphic and paleoclimatic record. The radiolarian zonation indicates that the middle Pliocene is missing in a diconformity. Three radiolarian zones are recognized above the disconformity, and from comparison with previous piston core studies, indicate a continuous biostratigraphic sequence from the early part of the Brunhes Normal paleomagnetic epoch (0.69 m.y. B.P.) to the earliest part of the Matuyama Reversed Epoch (2.40 m.y. B.P.). Oscillations in the frequency of the cool-water radiolarian Antarctissa strelkovi indicate 9 or 10 warm-water episodes during that part of the Matuyama Reversed Epoch represented, with one warm-water episode inferred to be missing in the disconformity. The most important radiolarian species are illustrated by SEM and LM photographs

Schwinger-Keldysh approach to out of equilibrium dynamics of the Bose Hubbard model with time varying hopping

We study the real time dynamics of the Bose Hubbard model in the presence of time-dependent hopping allowing for a finite temperature initial state. We use the Schwinger-Keldysh technique to find the real-time strong coupling action for the problem at both zero and finite temperature. This action allows for the description of both the superfluid and Mott insulating phases. We use this action to obtain dynamical equations for the superfluid order parameter as hopping is tuned in real time so that the system crosses the superfluid phase boundary. We find that under a quench in the hopping, the system generically enters a metastable state in which the superfluid order parameter has an oscillatory time dependence with a finite magnitude, but disappears when averaged over a period. We relate our results to recent cold atom experiments.Comment: 22 pages, 7 figure