Quantum Hall Phase Diagram of Second Landau-level Half-filled Bilayers: Abelian versus Non-Abelian States

The quantum Hall phase diagram of the half-filled bilayer system in the second Landau level is studied as a function of tunneling and layer separation using exact diagonalization. We make the striking prediction that bilayer structures would manifest two distinct branches of incompressible fractional quantum Hall effect (FQHE) corresponding to the Abelian 331 state (at moderate to low tunneling and large layer separation) and the non-Abelian Pfaffian state (at large tunneling and small layer separation). The observation of these two FQHE branches and the quantum phase transition between them will be compelling evidence supporting the existence of the non-Abelian Pfaffian state in the second Landau level.Comment: 4 pages, 3 figure

Non-Gaussian errors of baryonic acoustic oscillations

We revisit the uncertainty in baryon acoustic oscillation (BAO) forecasts and data analyses. In particular, we study how much the uncertainties on both the measured mean dilation scale and the associated error bar are affected by the non-Gaussianity of the non-linear density field. We examine two possible impacts of non-Gaussian analysis: (1) we derive the distance estimators from Gaussian theory, but use 1000 N-Body simulations to measure the actual errors, and compare this to the Gaussian prediction, and (2) we compute new optimal estimators, which requires the inverse of the non-Gaussian covariance matrix of the matter power spectrum. Obtaining an accurate and precise inversion is challenging, and we opted for a noise reduction technique applied on the covariance matrices. By measuring the bootstrap error on the inverted matrix, this work quantifies for the first time the significance of the non-Gaussian error corrections on the BAO dilation scale. We find that the variance (error squared) on distance measurements can deviate by up to 12% between both estimators, an effect that requires a large number of simulations to be resolved. We next apply a reconstruction algorithm to recover some of the BAO signal that had been smeared by non-linear evolution, and we rerun the analysis. We find that after reconstruction, the rms error on the distance measurement improves by a factor of ~1.7 at low redshift (consistent with previous results), and the variance ({\sigma}^2) shows a change of up to 18% between optimal and sub-optimal cases (note, however, that these discrepancies may depend in detail on the procedure used to isolate the BAO signal). We finally discuss the impact of this work on current data analyses.Comment: 13 pages, 11 figures, MNRAS accepte

Elastic theory of quantum Hall smectics: effects of disorder

We study the effect of disorder on quantum Hall smectics within the framework of an elastic theory. Based on a renormalization group calculation, we derive detailed results for the degrees of translational and orientational order of the stripe pattern at zero temperature and carefully map out the disorder and length-scale regimes in which the system effectively exhibits smectic, nematic, or isotropic behavior. We show that disorder always leads to a finite density of free dislocations and estimate the scale on which they begin to appear.Comment: 4 pages latex with 1 EPS figur

Evidence for a Z < 8 Origin of the Source Subtracted Near Infrared Background

This letter extends our previous fluctuation analysis of the near infrared background at 1.6 microns to the 1.1 micron (F110W) image of the Hubble Ultra Deep field. When all detectable sources are removed the ratio of fluctuation power in the two images is consistent with the ratio expected for faint, z<8, sources, and is inconsistent with the expected ratio for galaxies with z>8. We also use numerically redshifted model galaxy spectral energy distributions for 50 and 10 million year old galaxies to predict the expected fluctuation power at 3.6 microns and 4.5 microns to compare with recent Spitzer observations. The predicted fluctuation power for galaxies at z = 0-12 matches the observed Spitzer fluctuation power while the predicted power for z>13 galaxies is much higher than the observed values. As was found in the 1.6 micron (F160W) analysis the fluctuation power in the source subtracted F110W image is two orders of magnitude below the power in the image with all sources present. This leads to the conclusion that the 0.8--1.8 micron near infrared background is due to resolved galaxies in the redshift range z<8, with the majority of power in the redshift range of 0.5--1.5.Comment: Accepted for publication in the Astrophysical Journa

Finite size effects in the magnetization of periodic mesoscopic systems

We calculate the orbital magnetization of a confined 2DEG as a function of the number of electrons in the system. Size effects are investigated by systematically increasing the area of the confining region. The results for the finite system are compared to an infinite one, where the magnetization is calculated in the thermodynamic limit. In all calculations the electron-electron interaction is included in the Hartree approximation.Comment: LaTeX with 4 PostScript figures included, to appear in EP2DS 13 proceeding

Type 1 fimbriae mutants of Escherichia coli K12: characterization of recognized afimbriate strains and construction of new fim deletion mutants

We have used Southern hybridization analysis to characterize the extent of fim homology in recognized type 1 fimbriae mutants of Escherichia coli K12, including strains HB101, P678-54, and VL584. We have found extensive homology in strain HB101, and confirm that P678-54 lacks the majority of fim DNA. Strain VL584 contains a deletion of the entire fim region. We have used a new allelic exchange procedure to generate novel fim deletion derivatives of strains MG1655, MM294, and YMC9. To increase the utility of the new deletion strains we also isolated recA derivatives of each mutant. These strains facilitate the isolation, characterization, and manipulation of cloned fimbriae genes from diverse sources.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74928/1/j.1365-2958.1991.tb00790.x.pd

Evidence for a Goldstone Mode in a Double Layer Quantum Hall System

The tunneling conductance between two parallel 2D electron systems has been measured in a regime of strong interlayer Coulomb correlations. At total Landau level filling $\nu_T=1$ the tunnel spectrum changes qualitatively when the boundary separating the compressible phase from the ferromagnetic quantized Hall state is crossed. A huge resonant enhancement replaces the strongly suppressed equilibrium tunneling characteristic of weakly coupled layers. The possible relationship of this enhancement to the Goldstone mode of the broken symmetry ground state is discussed.Comment: 4 pages, 3 figures, 2 minor typeos fixe