26,301 research outputs found
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
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
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
INTEGRAL discovery of unusually long broad-band X-ray activity from the Supergiant Fast X-ray Transient IGR J18483-0311
We report on a broad-band X-ray study (0.5-250 keV) of the Supergiant Fast
X-ray Transient IGR J18483-0311 using archival INTEGRAL data and a new targeted
XMM-Newton observation. Our INTEGRAL investigation discovered for the first
time an unusually long X-ray activity (3-60 keV) which continuously lasted for
at least 11 days, i.e. a significant fraction (about 60%) of the entire orbital
period, and spanned orbital phases corresponding to both periastron and
apastron passages. This prolongated X-ray activity is at odds with the much
shorter durations marking outbursts from classical SFXTs especially above 20
keV, as such it represents a departure from their nominal behavior and it adds
a further extreme characteristic to the already extreme SFXT IGR J18483-0311.
Our IBIS/ISGRI high energy investigation (100-250 keV) of archival outbursts
activity from the source showed that the recently reported hint of a possible
hard X-ray tail is not real and it is likely due to noisy background. The new
XMM-Newton targeted observation did not detect any sign of strong X-ray
outburst activity from the source despite being performed close to its
periastron passage, on the contrary IGR J18483-0311 was caught during the
common intermediate X-ray state with a low luminosity value of 3x10^33 erg s^-1
(0.5-10 keV). We discuss all the reported results in the framework of both
spherically symmetric clumpy wind scenario and quasi-spherical settling
accretion model.Comment: Accepted for publication on MNRAS. 10 pages, 7 figures, 1 tabl
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
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
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