2,524 research outputs found
Higgs transitions of spin ice
Frustrated magnets such as spin ice exhibit Coulomb phases, where
correlations have power-law forms at long distances. Applied perturbations can
cause ordering transitions which cannot be described by the usual Landau
paradigm, and are instead naturally viewed as Higgs transitions of an emergent
gauge theory. Starting from a classical statistical model of spin ice, it is
shown that a variety of possible phases and transitions can be described by
this approach. Certain cases are identified where continuous transitions are
argued to be likely; the predicted critical behavior may be tested in
experiments or numerical simulations.Comment: 23 pages, 10 figures; v2: published version with minor changes;
ancillary file "Figures3D.nb" is a Mathematica (v7) notebook containing
figures as rotatable 3D graphics (see http://www.wolfram.com/cdf-player/ for
a free viewer
Real-time video correlator
Device provides two-dimensional correlation of video data. Operation is reliable, accurate, and predictable
History, College of Medicine: 1959-1968. Chapter 16: Department of Physiological Chemistry
Prepared for the Centennial of The Ohio State University
A gravity survey on the southern and central parts of the Isle of man
The Bouguer anomalies on the Isle of Man have been calculated from a network of 365 stations. The results ofrock density measurements made in the laboratory are stated. The main features shown by the gravity survey of the southern and central parts of the island are two elongated negative anomalies, centered at Foxdale and Dhoon. They are shown to be shallow in origin and it is suggested that they are due to the prensence of two large granite bodies lower in density than the surrounding Manx Slates and only represented at the surface by small outcrops. These two granites are apparently steep sided and lie on a north-east to south-west 'axis' but are not connected. The negative anomaly seen in part in the extreme South-west of the island is probably due to arise on the Poxdale granite. The elongated shape of the granites revealed by the survey can be correlated with the zones of metamorphism, the distribution of the mineral veins and the "anticline of cleavage". Comparing the mass of land above sea level with the mass deficiency due to the granites the southern and central parts of the Isle of Man are found to be under-compensated. A residual gravity map of the Peel area was prepared and it revealed a negative anomaly which is probably due to the baain of lower density Peel Sandstones. The louguer anomalies are found generally to be high on the Isle of Man. This emphasises the fact that the Irish Sea seems to be an area of large positive anomalies for gradients have also been observed on the mainland. No definite conclusion has been reached as to the cause of this Irish Sea anomaly or, indeed, that it has only one cause
An Empirical Study of Factors Associated with Physical Fitness of Sixth Grade Students
The purpose of this study is to determine if there was a relationship between the scores achieved on the Elementary School Fitness Test and the following factors: (1) the economic level of the neighborhood in which the schools were located; (2) family size; (3) achievement scores on the Iowa Basic Skills Test; (4) absenteeism of the students; and (5) health history of students
Optimal Image Reconstruction in Radio Interferometry
We introduce a method for analyzing radio interferometry data which produces
maps which are optimal in the Bayesian sense of maximum posterior probability
density, given certain prior assumptions. It is similar to maximum entropy
techniques, but with an exact accounting of the multiplicity instead of the
usual approximation involving Stirling's formula. It also incorporates an Occam
factor, automatically limiting the effective amount of detail in the map to
that justified by the data. We use Gibbs sampling to determine, to any desired
degree of accuracy, the multi-dimensional posterior density distribution. From
this we can construct a mean posterior map and other measures of the posterior
density, including confidence limits on any well-defined function of the
posterior map.Comment: 41 pages, 11 figures. High resolution figures 8 and 9 available at
http://www.astro.uiuc.edu/~bwandelt/SuttonWandelt200
High Dynamic-Range Radio-Interferometric Images at 327 MHz
Radio astronomical imaging using aperture synthesis telescopes requires
deconvolution of the point spread function as well as calibration of the
instrumental characteristics (primary beam) and foreground
(ionospheric/atmospheric) effects. These effects vary in time and also across
the field of view, resulting in directionally-dependent (DD), time-varying
gains. The primary beam will deviate from the theoretical estimate in real
cases at levels that will limit the dynamic range of images if left
uncorrected. Ionospheric electron density variations cause time and position
variable refraction of sources. At low frequencies and sufficiently high
dynamic range this will also defocus the images producing error patterns that
vary with position and also with frequency due to the chromatic aberration of
synthesis telescopes. Superposition of such residual sidelobes can lead to
spurious spectral signals. Field-based ionospheric calibration as well as
"peeling" calibration of strong sources leads to images with higher dynamic
range and lower spurious signals but will be limited by sensitivity on the
necessary short-time scales. The results are improved images although some
artifacts remain.Comment: to appear in Comptes Rendus Physique (2011
Hidden unity in the quantum description of matter
We introduce an algebraic framework for interacting quantum systems that
enables studying complex phenomena, characterized by the coexistence and
competition of various broken symmetry states of matter. The approach unveils
the hidden unity behind seemingly unrelated physical phenomena, thus
establishing exact connections between them. This leads to the fundamental
concept of {\it universality} of physical phenomena, a general concept not
restricted to the domain of critical behavior. Key to our framework is the
concept of {\it languages} and the construction of {\it dictionaries} relating
them.Comment: 10 pages 2 psfigures. Appeared in Recent Progress in Many-Body
Theorie
Tensor network states and algorithms in the presence of a global SU(2) symmetry
The benefits of exploiting the presence of symmetries in tensor network
algorithms have been extensively demonstrated in the context of matrix product
states (MPSs). These include the ability to select a specific symmetry sector
(e.g. with a given particle number or spin), to ensure the exact preservation
of total charge, and to significantly reduce computational costs. Compared to
the case of a generic tensor network, the practical implementation of
symmetries in the MPS is simplified by the fact that tensors only have three
indices (they are trivalent, just as the Clebsch-Gordan coefficients of the
symmetry group) and are organized as a one-dimensional array of tensors,
without closed loops. Instead, a more complex tensor network, one where tensors
have a larger number of indices and/or a more elaborate network structure,
requires a more general treatment. In two recent papers, namely (i) [Phys. Rev.
A 82, 050301 (2010)] and (ii) [Phys. Rev. B 83, 115125 (2011)], we described
how to incorporate a global internal symmetry into a generic tensor network
algorithm based on decomposing and manipulating tensors that are invariant
under the symmetry. In (i) we considered a generic symmetry group G that is
compact, completely reducible and multiplicity free, acting as a global
internal symmetry. Then in (ii) we described the practical implementation of
Abelian group symmetries. In this paper we describe the implementation of
non-Abelian group symmetries in great detail and for concreteness consider an
SU(2) symmetry. Our formalism can be readily extended to more exotic symmetries
associated with conservation of total fermionic or anyonic charge. As a
practical demonstration, we describe the SU(2)-invariant version of the
multi-scale entanglement renormalization ansatz and apply it to study the low
energy spectrum of a quantum spin chain with a global SU(2) symmetry.Comment: 32 pages, 37 figure
Explicit Construction of the Massive Supersymmetry Multiplets on Spacetime
A systematic method of constructing supersymmetry multiples of second quantized fields is given for the massive case and for any spin, starting from the irreducible representations of the Poincaré Lie superalgebra. This allows a full understanding of the nature of the auxiliary fields
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