Numerical study of the hard-core Bose-Hubbard Model on an Infinite Square Lattice

We present a study of the hard-core Bose-Hubbard model at zero temperature on an infinite square lattice using the infinite Projected Entangled Pair State algorithm [Jordan et al., Phys. Rev. Lett. 101, 250602 (2008)]. Throughout the whole phase diagram our values for the ground state energy, particle density and condensate fraction accurately reproduce those previously obtained by other methods. We also explore ground state entanglement, compute two-point correlators and conduct a fidelity-based analysis of the phase diagram. Furthermore, for illustrative purposes we simulate the response of the system when a perturbation is suddenly added to the Hamiltonian.Comment: 8 pages, 6 figure

High Accuracy Near-infrared Imaging Polarimetry with NICMOS

The findings of a nine orbit calibration plan carried out during HST Cycle 15, to fully determine the NICMOS camera 2 (2.0 micron) polarization calibration to high accuracy, are reported. Recently Ueta et al. and Batcheldor et al. have suggested that NICMOS possesses a residual instrumental polarization at a level of 1.2-1.5%. This would completely inhibit the data reduction in a number of GO programs, and hamper the ability of the instrument to perform high accuracy polarimetry. We obtained polarimetric calibration observations of three polarimetric standards at three spacecraft roll angles separated by ~60deg. Combined with archival data, these observations were used to characterize the residual instrumental polarization in order for NICMOS to reach its full potential of accurate imaging polarimetry at p~1%. Using these data, we place an 0.6% upper limit on the instrumental polarization and calculate values of the parallel transmission coefficients that reproduce the ground-based results for the polarimetric standards. The uncertainties associated with the parallel transmission coefficients, a result of the photometric repeatability of the observations, are seen to dominate the accuracy of p and theta. However, the updated coefficients do allow imaging polarimetry of targets with p~1.0% at an accuracy of +/-0.6% and +/-15deg. This work enables a new caliber of science with HST.Comment: 13 pages, 9 figures, PASP accepte

High Accuracy Imaging Polarimetry with NICMOS

The ability of NICMOS to perform high accuracy polarimetry is currently hampered by an uncalibrated residual instrumental polarization at a level of 1.2-1.5%. To better quantify and characterize this residual we obtained observations of three polarimetric standard stars at three separate space-craft roll angles. Combined with archival data, these observations were used to characterize the residual instrumental polarization to enable NICMOS to reach its full polarimetric potential. Using these data, we calculate values of the parallel transmission coefficients that reproduce the ground-based results for the polarimetric standards. The uncertainties associated with the parallel transmission coefficients, a result of the photometric repeatability of the observations, dominate the accuracy of p and theta. However, the new coefficients now enable imaging polarimetry of targets with p~1.0% at an accuracy of +/-0.6% and +/-15 degrees.Comment: 5 pages, 2 figures. Contributed talk, "Astronomical Polarimetry 2008. Science from Small to Large Telescopes" La Malbaie, Quebec, Canada, 200

The Effect of Transfer Printing on Pentacene Thin-Film Crystal Structure

The thermal deposition and transfer Printing method had been used to produce pentacene thin-films on SiO2/Si and plastic substrates (PMMA and PVP), respectively. X-ray diffraction patterns of pentacene thin films showed reflections associated with highly ordered polycrystalline films and a coexistence of two polymorph phases classified by their d-spacing, d(001): 14.4 and 15.4 A.The dependence of the c-axis correlation length and the phase fraction on the film thickness and printing temperature were measured. A transition from the 15.4 A phase towards 14.4 A phase was also observed with increasing film thickness. An increase in the c-axis correlation length of approximately 12% ~16% was observed for Pn films transfer printed onto a PMMA coated PET substrate at 100~120 C as compared to as-grown Pn films on SiO2/Si substrates. The transfer printing method is shown to be an attractive for the fabrication of pentacene thin-film transistors on flexible substrates partly because of the resulting improvement in the quality of the pentacene film.Comment: 5 pages, 5 figure

Fault-tolerant quantum computation versus Gaussian noise

We study the robustness of a fault-tolerant quantum computer subject to Gaussian non-Markovian quantum noise, and we show that scalable quantum computation is possible if the noise power spectrum satisfies an appropriate "threshold condition." Our condition is less sensitive to very-high-frequency noise than previously derived threshold conditions for non-Markovian noise.Comment: 30 pages, 6 figure

A Large Mass of H2 in the Brightest Cluster Galaxy in Zwicky 3146

We present the Spitzer/IRS mid-infrared spectrum of the infrared-luminous (L_{IR}=4e11 L_sun) brightest cluster galaxy (BCG) in the X-ray-luminous cluster Z3146 (z=0.29). The spectrum shows strong aromatic emission features, indicating that the dominant source of the infrared luminosity is star formation. The most striking feature of the spectrum, however, is the exceptionally strong molecular hydrogen (H2) emission lines, which seem to be shock-excited. The line luminosities and inferred warm H2 gas mass (~1e10 M_sun) are 6 times larger than those of NGC 6240, the most H2-luminous galaxy at z <~ 0.1. Together with the large amount of cold H2 detected previously (~1e11 M_sun), this indicates that the Z3146 BCG contains disproportionately large amounts of both warm and cold H2 gas for its infrared luminosity, which may be related to the intracluster gas cooling process in the cluster core.Comment: 13 pages, 3 figures, 1 table; Accepted for publication in ApJ

Predicion of charge separation in GaAs/AlAs cylindrical Russian Doll nanostructures

We have contrasted the quantum confinement of (i) multiple quantum wells of flat GaAs and AlAs layers, i.e. (\GaAs)_{m}/(\AlAs)_n/(\GaAs)_p/(\AlAs)_q, with (ii) ``cylindrical Russian Dolls'' -- an equivalent sequence of wells and barriers arranged as concentric wires. Using a pseudopotential plane-wave calculation, we identified theoretically a set of numbers ($m,n,p$ and $q$) such that charge separation can exist in ``cylindrical Russian Dolls'': the CBM is localized in the inner GaAs layer, while the VBM is localized in the outer GaAs layer.Comment: latex, 8 page

NICMOS Imaging of the Nuclei of Arp 220

We report high resolution imaging of the ultraluminous infrared galaxy Arp 220 at 1.1, 1.6, and 2.22 microns with NICMOS on the HST. The diffraction-limited images at 0.1--0.2 arcsecond resolution clearly resolve both nuclei of the merging galaxy system and reveal for the first time a number of luminous star clusters in the circumnuclear envelope. The morphologies of both nuclei are strongly affected by dust obscuration, even at 2.2 microns : the primary nucleus (west) presents a crescent shape, concave to the south and the secondary (eastern) nucleus is bifurcated by a dust lane with the southern component being very reddened. In the western nucleus, the morphology of the 2.2 micron emission is most likely the result of obscuration by an opaque disk embedded within the nuclear star cluster. The morphology of the central starburst-cluster in the western nucleus is consistent with either a circumnuclear ring of star formation or a spherical cluster with the bottom half obscured by the embedded dust disk. Comparison of cm-wave radio continuum maps with the near-infrared images suggests that the radio nuclei lie in the dust disk on the west and near the highly reddened southern component of the eastern complex. The radio nuclei are separated by 0.98 arcseconds (corresponding to 364 pc at 77 Mpc) and the half-widths of the infrared nuclei are approximately 0.2-0.5 arcseconds. At least 8, unresolved infrared sources -- probably globular clusters -- are also seen in the circumnuclear envelope at radii 2-7 arcseconds . Their near-infrared colors do not significantly constrain their ages.Comment: LaTex, 15 pages with 1 gif figure and 5 postscript figures. ApJL accepte