Exact solution of Riemann--Hilbert problem for a correlation function of the XY spin chain

A correlation function of the XY spin chain is studied at zero temperature. This is called the Emptiness Formation Probability (EFP) and is expressed by the Fredholm determinant in the thermodynamic limit. We formulate the associated Riemann--Hilbert problem and solve it exactly. The EFP is shown to decay in Gaussian.Comment: 7 pages, to be published in J. Phys. Soc. Jp

Liquid acrobatics

We experiment with injecting a continuous stream of gas into a shallow liquid, similar to how one might blow into a straw placed at the bottom of a near-empty drink. By varying the angle of the straw (here a metal needle), we observe a variety of dynamics, which we film using a high-speed camera. Most noteworthy is an intermediate regime in which cyclical jets erupt from the air-liquid interface and breakup into air-born droplets. These droplets trace out a parabolic trajectory and bounce on the air-liquid interface before eventually coalescing. The shape of each jet, as well as the time between jets, is remarkably similar and leads to droplets with nearly identical trajectories. The following article accompanies the linked fluid dynamics video submitted to the Gallery of Fluid Motion in 2008.Comment: Accompanies video submission to APS DFD 2008 Gallery of Fluid Motion, low http://ecommons.library.cornell.edu/bitstream/1813/11469/3/Bird_DFD2008_mpeg1.mpg , and high resolution http://ecommons.library.cornell.edu/bitstream/1813/11469/2/Bird_DFD2008_mpeg2.mp

Competing Quantum Orderings in Cuprate Superconductors: A Minimal Model

We present a minimal model for cuprate superconductors. At the unrestricted mean-field level, the model produces homogeneous superconductivity at large doping, striped superconductivity in the underdoped regime and various antiferromagnetic phases at low doping and for high temperatures. On the underdoped side, the superconductor is intrinsically inhomogeneous and global phase coherence is achieved through Josephson-like coupling of the superconducting stripes. The model is applied to calculate experimentally measurable ARPES spectra.Comment: 5 pages, 4 eps included figure

Infrared radiometer

Radiometer may be used either with an f/16 telescope to measure thermal radiation from the surface of the dark moon or with a short-range optical system to measure thermal radiation from laboratory samples

Low level radiation altimeter system study

Low level radiation altimeter for measuring altitude 50 feet above lunar surfac

The effects of organic farming on the soil physical environment

The aim of this research was to investigate the effects of organic farming practices on the development of soil physical properties, and in particular, soil structure in comparison with conventional agricultural management. The soil structure of organically and conventionally managed soils at one site was compared in a quantitative manner at different scales of observations using image analysis. Key soil physical and chemical properties were measured as well as the pore fractal geometry to characterise pore roughness. Organically managed soils had higher organic matter content and provided a more stable soil structure than conventionally managed soils. The higher porosity (%) at the macroscale in soil under conventional management was due to fewer larger pores while mesoand microscale porosity was found to be greater under organic management. Organically managed soils typically provided spatially well distributed pores of all sizes and of greater roughness compared to those under conventional management. These variations in the soil physical environment are likely to impact significantly on the performance of these soils for a number of key processes such as crop establishment and water availabilit

Microrheological Characterisation of Anisotropic Materials

We describe the measurement of anisotropic viscoelastic moduli in complex soft materials, such as biopolymer gels, via video particle tracking microrheology of colloid tracer particles. The use of a correlation tensor to find the axes of maximum anisotropy, and hence the mechanical director, is described. The moduli of an aligned DNA gel are reported, as a test of the technique; this may have implications for high DNA concentrations in vivo. We also discuss the errors in microrheological measurement, and describe the use of frequency space filtering to improve displacement resolution, and hence probe these typically high modulus materials.Comment: 5 pages, 5 figures. Replaced after refereeing/ improvement. Main results are the same. The final, published version of the paper is here http://link.aps.org/abstract/PRE/v73/e03190

Evidence from Rb–Sr mineral ages for multiple orogenic events in the Caledonides of Shetland, Scotland

Shetland occupies a unique central location within the North Atlantic Caledonides. Thirty-three new high-precision Rb–Sr mineral ages indicate a polyorogenic history. Ages of 723–702 Ma obtained from the vicinity of the Wester Keolka Shear Zone indicate a Neoproterozoic (Knoydartian) age and preclude its correlation with the Silurian Moine Thrust. Ordovician ages of c. 480–443 Ma obtained from the Yell Sound Group and the East Mainland Succession constrain deformation fabrics and metamorphic assemblages to have formed during Grampian accretionary orogenic events, broadly contemporaneously with orogenesis of the Dalradian Supergroup in Ireland and mainland Scotland. The relative paucity of Silurian ages is attributed to a likely location at a high structural level in the Scandian nappe pile relative to mainland Scotland. Ages of c. 416 and c. 411 Ma for the Uyea Shear Zone suggest a late orogenic evolution that has more in common with East Greenland and Norway than with northern mainland Scotland

Infrared identification of IGR J09026-4812 as a Seyfert 1 galaxy

IGR J09026-4812 was discovered by INTEGRAL in 2006 as a new hard X-ray source. Thereafter, an observation with Chandra pinpointed a single X-ray source within the ISGRI error circle, showing a hard spectrum, and improving its high-energy localisation to a subarcsecond accuracy. Thus, the X-ray source was associated to the infrared counterpart 2MASS J09023731-4813339 whose JHKs photometry indicated a highly reddened source. The high-energy properties and the counterpart photometry suggested a high-mass X-ray binary with a main sequence companion star located 6.3-8.1 kpc away and with a 0.3-10 keV luminosity of 8e34 erg/s. New optical and infrared observations were needed to confirm the counterpart and to reveal the nature of IGR J09026-4812. We performed optical and near infrared observations on the counterpart 2MASS J09023731-4813339 with the ESO/NTT telescope on March 2007. We achieved photometry and spectroscopy in near infrared wavelengths and photometry in optical wavelengths. The accurate astrometry at both optical and near infrared wavelengths confirmed 2MASS J09023731-4813339 to be the counterpart of IGR J09026-4812. However, the near infrared images show that the source is extended, thus excluding any Galactic compact source possibility. The source spectrum shows three main emission lines identified as the HeI lambda 1.0830 micron line, and the HI Pa_beta and Pa_alpha lines, typical in galaxies with an active galactic nucleus. The broadness of these lines reached values as large as 4000 km/s pointing towards a type 1 Seyfert galaxy. The redshift of the source is z=0.0391(4). Thus, the near infrared photometry and spectroscopy allowed us to classify IGR J09026-4812 as a Seyfert galaxy of type 1.Comment: 4 pages, 3 figures, Astronomy and Astrophysics in pres