Paired composite fermion wavefunctions

We construct a family of BCS paired composite fermion wavefunctions that generalize, but remain in the same topological phase as, the Moore-Read Pfaffian state for the half-filled Landau level. It is shown that for a wide range of experimentally relevant inter-electron interactions the groundstate can be very accurately represented in this form.Comment: 4 pages, 2 figure

The orbital motion, absolute mass, and high-altitude winds of exoplanet HD209458b

For extrasolar planets discovered using the radial velocity method, the spectral characterization of the host star leads to a mass-estimate of the star and subsequently of the orbiting planet. In contrast, if also the orbital velocity of the planet would be known, the masses of both star and planet could be determined directly using Newton's law of gravity, just as in the case of stellar double-line eclipsing binaries. Here we report on the detection of the orbital velocity of extrasolar planet HD209458b. High dispersion ground-based spectroscopy during a transit of this planet reveals absorption lines from carbon monoxide produced in the planet atmosphere, which shift significantly in wavelength due to the change in the radial component of the planet orbital velocity. These observations result in a mass determination of the star and planet of 1.00+-0.22 Msun and 0.64+-0.09 Mjup respectively. A ~2 km/sec blueshift of the carbon monoxide signal with respect to the systemic velocity of the host star suggests the presence of a strong wind flowing from the irradiated dayside to the non-irradiated nightside of the planet within the 0.01-0.1 mbar atmospheric pressure range probed by these observations. The strength of the carbon monoxide signal suggests a CO mixing ratio of 1-3x10-3 in this planet's upper atmosphere.Comment: 11 Pages main article and 6 pages suppl. information: A final, edited version appears in the 24 May 2010 issue of Natur

Paired composite fermion phase of quantum Hall bilayers at \nu = 1/2 + 1/2

We provide numerical evidence for composite fermion pairing in quantum Hall bilayer systems at filling $\nu=1/2 + 1/2$ for intermediate spacing between the layers. We identify the phase as $p_x + i p_y$ pairing, and construct high accuracy trial wavefunctions to describe the groundstate on the sphere. For large distances between the layers, and for finite systems, a competing "Hund's rule" state, or composite fermion liquid, prevails for certain system sizes. We argue that for larger systems, the pairing phase will persist to larger layer spacing.Comment: 4 pages, 2 figures; v2: final version, as published in journa

The Inner Galaxy resolved at IJK using DENIS data

We present the analysis of three colour optical/near-infrared images, in IJK, taken for the DENIS project. The region considered covers 17.4 square deg and lies within |l|<5 deg, |b|<1.5 deg. The adopted methods for deriving photometry and astrometry in these crowded images, together with an analysis of the deficiencies nevertheless remaining, are presented. The numbers of objects extracted in I,J and K are 748000, 851000 and 659000 respectively, to magnitude limits of 17,15 and 13. 80% completeness levels typically fall at magnitudes 16, 13 and 10 respectively, fainter by about 2 magnitudes than the usual DENIS limits due to the crowded nature of these fields. A simple model to describe the disk contribution to the number counts is constructed, and parameters for the dust layer derived. We find that a formal fit of parameters for the dust plane, from these data in limited directions, gives a scalelength and scaleheight of 3.4+-1.0 kpc and 40+-5 pc respectively, and a solar position 14.0+-2.5 pc below the plane. This latter value is likely to be affected by localised dust asymmetries. We convolve a detailed model of the systematic and random errors in the photometry with a simple model of the Galactic disk and dust distribution, to simulate expected colour-magnitude diagrams. These are in good agreement with the observed diagrams, allowing us to isolate those stars from the inner disk and bulge. After correcting for local dust-induced asymmetries, we find evidence for longitude-dependent asymmetries in the distant J and K sources, consistent with the general predictions of some Galactic bar models. We consider complementary L-band observations in a second paper.Comment: 14 pages, 33 figures, LaTeX, MNRAS accepte

Topological and geometric decomposition of nematic textures

Directional media, such as nematic liquid crystals and ferromagnets, are characterized by their topologically stabilized defects in directional order. In nematics, boundary conditions and surface-treated inclusions often create complex structures, which are difficult to classify. Topological charge of point defects in nematics has ambiguously defined sign and its additivity cannot be ensured when defects are observed separately. We demonstrate how the topological charge of complex defect structures can be determined by identifying and counting parts of the texture that satisfy simple geometric rules. We introduce a parameter called the defect rank and show that it corresponds to what is intuitively perceived as a point charge based on the properties of the director field. Finally, we discuss the role of free energy constraints in validity of the classification with the defect rank.Comment: 16 pages, 5 figure

Detection of carbon monoxide in the high-resolution day-side spectrum of the exoplanet HD 189733b

[Abridged] After many attempts over more than a decade, high-resolution spectroscopy has recently delivered its first detections of molecular absorption in exoplanet atmospheres, both in transmission and thermal emission spectra. Targeting the combined signal from individual lines in molecular bands, these measurements use variations in the planet radial velocity to disentangle the planet signal from telluric and stellar contaminants. In this paper we apply high resolution spectroscopy to probe molecular absorption in the day-side spectrum of the bright transiting hot Jupiter HD 189733b. We observed HD 189733b with the CRIRES high-resolution near-infrared spectograph on the Very Large Telescope during three nights. We detect a 5-sigma absorption signal from CO at a contrast level of ~4.5e-4 with respect to the stellar continuum, revealing the planet orbital radial velocity at 154+4/-3 km s-1. This allows us to solve for the planet and stellar mass in a similar way as for stellar eclipsing binaries, resulting in Ms= 0.846+0.068/-0.049 Msun and Mp= 1.162+0.058/-0.039 MJup. No significant absorption is detected from H2O, CO2 or CH4 and we determined upper limits on their line contrasts here. The detection of CO in the day-side spectrum of HD 189733b can be made consistent with the haze layer proposed to explain the optical to near-infrared transmission spectrum if the layer is optically thin at the normal incidence angles probed by our observations, or if the CO abundance is high enough for the CO absorption to originate from above the haze. Our non-detection of CO2 at 2.0 micron is not inconsistent with the deep CO2 absorption from low resolution NICMOS secondary eclipse data in the same wavelength range. If genuine, the absorption would be so strong that it blanks out any planet light completely in this wavelength range, leaving no high-resolution signal to be measured.Comment: A&A, accepted for publication. Fig.1 reduced in qualit

Testing for Majorana Zero Modes in a Px+iPy Superconductor at High Temperature by Tunneling Spectroscopy

Directly observing a zero energy Majorana state in the vortex core of a chiral superconductor by tunneling spectroscopy requires energy resolution better than the spacing between core states $\Delta^2/eF$. We show that nevertheless, its existence can be decisively tested by comparing the temperature broadened tunneling conductance of a vortex with that of an antivortex even at temperatures $T >> \Delta^2/eF$.Comment: 5 pages, 4 figure

Reliability and validity of a domain-specific last 7-d sedentary time questionnaire

Purpose: The objective of this study is to examine test-retest reliability, criterion validity, and absolute agreement of a self-report, last 7-d sedentary behavior questionnaire (SIT-Q-7d), which assesses total daily sedentary time as an aggregate of sitting/lying down in five domains (meals, transportation, occupation, nonoccupational screen time, and other sedentary time). Dutch (DQ) and English (EQ) versions of the questionnaire were examined. Methods: Fifty-one Flemish adults (ages 39.4 +/- 11.1 yr) wore a thigh accelerometer (activPAL3 (TM)) and simultaneously kept a domain log for 7 d. The DQ was subsequently completed twice (median test-retest interval: 3.3 wk). Thigh-acceleration sedentary time was log annotated to create comparable domain-specific and total sedentary time variables. Four hundred two English adults (ages 49.6 +/- 7.3 yr) wore a combined accelerometer and HR monitor (Actiheart (R)) for 6 d to objectively measure total sedentary time. The EQ was subsequently completed twice (median test-retest interval: 3.4 wk). In both samples, the questionnaire reference frame overlapped with the criterion measure administration period. All participants had five or more valid days of criterion data, including one or more weekend day. Results: Test-retest reliability (intraclass correlation coefficient (95% CI)) was fair to good for total sedentary time (DQ: 0.68 (0.50-0.81); EQ: 0.53 (0.44-0.62)) and poor to excellent for domain-specific sedentary time (DQ: from 0.36 (0.10-0.57) (meals) to 0.66 (0.46-0.79) (occupation); EQ: from 0.45 (0.35-0.54) (other sedentary time) to 0.76 (0.71-0.81) (meals)). For criterion validity (Spearman rho), significant correlations were found for total sedentary time (DQ: 0.52; EQ: 0.22; all P <0.001). Compared with domain-specific criterion variables (DQ), modest-to-strong correlations were found for domain-specific sedentary time (from 0.21 (meals) to 0.76 (P < 0.001) (screen time)). The questionnaire generally overestimated sedentary time compared with criterion measures. Conclusion: The SIT-Q-7d appears to be a useful tool for ranking individuals in large-scale observational studies examining total and domain-specific sitting

Mechanisms of vision in the fruit fly

Vision is essential to maximize the efficiency of daily tasks such as feeding, avoiding predators or finding mating partners. An advantageous model is Drosophila melanogaster, since it offers tools that allow genetic and neuronal manipulation with high spatial and temporal resolution, which can be combined with behavioral, anatomical and physiological assays. Recent advances have expanded our knowledge on the neural circuitry underlying such important behaviors as color vision (role of reciprocal inhibition to enhance color signal at the level of the ommatidia); motion vision (motion-detection neurones receive both excitatory and inhibitory input), and sensory processing (role of the central complex in spatial navigation, and in orchestrating the information from other senses and the inner state). Research on synergies between pathways is shaping the field