1,077 research outputs found
The AdS/CFT/Unparticle Correspondence
We examine the correspondence between the anti-de Sitter (AdS) description of
conformal field theories (CFTs) and the unparticle description of CFTs. We show
how unparticle actions are equivalent to holographic boundary actions for
fields in AdS, and how massive unparticles provide a new type of infrared
cutoff that can be simply implemented in AdS by a soft breaking of conformal
symmetry. We also show that processes involving scalar unparticles with
dimensions d_s<2 or fermion unparticles with dimensions d_f<5/2 are insensitive
to ultraviolet cutoff effects. Finally we show that gauge interactions for
unparticles can be described by bulk gauge interactions in AdS and that they
correspond to minimal gauging of the non-local effective action, and we compute
the fermion unparticle production cross-section.Comment: 26 pages, 1 figur
Economics of producing alfalfa
The Oklahoma Cooperative Extension Service periodically issues revisions to its publications. The most current edition is made available. For access to an earlier edition, if available for this title, please contact the Oklahoma State University Library Archives by email at [email protected] or by phone at 405-744-6311
Toric anti-self-dual Einstein metrics via complex geometry
Using the twistor correspondence, we give a classification of toric
anti-self-dual Einstein metrics: each such metric is essentially determined by
an odd holomorphic function. This explains how the Einstein metrics fit into
the classification of general toric anti-self-dual metrics given in an earlier
paper (math.DG/0602423). The results complement the work of Calderbank-Pedersen
(math.DG/0105263), who describe where the Einstein metrics appear amongst the
Joyce spaces, leading to a different classification. Taking the twistor
transform of our result gives a new proof of their theorem.Comment: v2. Published version. Additional references. 14 page
Transition from Townsend to glow discharge: subcritical, mixed or supercritical
The full parameter space of the transition from Townsend to glow discharge is
investigated numerically in one space dimension in the classical model: with
electrons and positive ions drifting in the local electric field, impact
ionization by electrons ( process), secondary electron emission from
the cathode ( process) and space charge effects. We also perform a
systematic analytical small current expansion about the Townsend limit up to
third order in the total current that fits our numerical data very well.
Depending on and system size pd, the transition from Townsend to glow
discharge can show the textbook subcritical behavior, but for smaller values of
pd, we also find supercritical or some intermediate ``mixed'' behavior. The
analysis in particular lays the basis for understanding the complex
spatio-temporal patterns in planar barrier discharge systems.Comment: 12 pages, 10 figures, submitted to Phys. Rev.
The changing trend in nitrate concentrations in major aquifers due to historical nitrate loading from agricultural land across England and Wales from 1925 to 2150
Nitrate is necessary for agricultural productivity, but can cause considerable problems if released into aquatic systems. Agricultural land is the major source of nitrates in UK groundwater. Due to the long time-lag in the groundwater system, it could take decades for leached nitrate from the soil to discharge into freshwaters. However, this nitrate time-lag has rarely been considered in environmental water management. Against this background, this paper presents an approach to modelling groundwater nitrate at the national scale, to simulate the impacts of historical nitrate loading from agricultural land on the evolution of groundwater nitrate concentrations. An additional process-based component was constructed for the saturated zone of significant aquifers in England and Wales. This uses a simple flow model which requires modelled recharge values, together with published aquifer properties and thickness data. A spatially distributed and temporally variable nitrate input function was also introduced. The sensitivity of parameters was analysed using Monte Carlo simulations. The model was calibrated using national nitrate monitoring data. Time series of annual average nitrate concentrations along with annual spatially distributed nitrate concentration maps from 1925 to 2150 were generated for 28 selected aquifer zones. The results show that 16 aquifer zones have an increasing trend in nitrate concentration, while average nitrate concentrations in the remaining 12 are declining. The results are also indicative of the trend in the flux of groundwater nitrate entering rivers through baseflow. The model thus enables the magnitude and timescale of groundwater nitrate response to be factored into source apportionment tools and to be taken into account alongside current planning of land-management options for reducing nitrate losses
Yield conditions for deformation of amorphous polymer glasses
Shear yielding of glassy polymers is usually described in terms of the
pressure-dependent Tresca or von Mises yield criteria. We test these criteria
against molecular dynamics simulations of deformation in amorphous polymer
glasses under triaxial loading conditions that are difficult to realize in
experiments. Difficulties and ambiguities in extending several standard
definitions of the yield point to triaxial loads are described. Two
definitions, the maximum and offset octahedral stresses, are then used to
evaluate the yield stress for a wide range of model parameters. In all cases,
the onset of shear is consistent with the pressure-modified von Mises
criterion, and the pressure coefficient is nearly independent of many
parameters. Under triaxial tensile loading, the mode of failure changes to
cavitation.Comment: 9 pages, 8 figures, revte
Development and Technical Adequacy of the District Capacity Assessment
The purpose of this article is to describe the methods and results used to establish the district capacity assessment’s (DCA) content validity, response process validity, construct validity, internal consistency, and test–retest reliability. The DCA measures a district’s ability to support school-level implementation of evidence-based practices (EBPs). Assessment results are then used to guide action planning. The DCA is grounded in the understanding that districts must develop knowledge and skills in the use of implementation science methods if they are to support successful use of an innovation. Specifically, three studies were conducted. The first study established the DCA’s content validity, that is, the extent to which the DCA represents constructs comprising district-level implementation capacity. The second study established the DCA’s internal structure, or the relationships among the items compared to the constructs being measured and how well the items measured the same construct. The third and final study assessed how the results of the DCA varied over time, thus establishing the instrument’s test–retest reliability. District Implementation Teams, researchers, or facilitators who use the DCA can be confident that the assessment is founded on research drawing from implementation science practices and methods
Biological anthropology in the Indo-Pacific Region: New approaches to age-old questions
Biological anthropological research, the study of both modern and past humans, is a burgeoning field in the Indo-Pacific region. It is becoming increasingly apparent that the unique environments of the Indo-Pacific have resulted in an archaeological record that does not necessarily align with those in the northern hemisphere. New, regionally-specific archaeological models are being developed, and biological anthropological research has an important role to play in establishing past human experience within these models. In the Indo-Pacific, research using ancient and modern human tissues is adding insight into global processes of prehistoric settlement and migrations, subsistence change and human biosocial adaptation. This review synthesises current themes in biological anthropology in this region. It highlights the diverse methods and approaches used by biological anthropologists to address globally-relevant archaeological questions. In recent decades a collaborative approach between archaeologists, biological anthropologists and local communities has become the norm in the region. The many positive outcomes of this multi-disciplinary approach are highlighted here through the use of regionally-specific case studies. This review ultimately aims to stimulate further collaborations between archaeologists, biological anthropologists and the communities in the region, and demonstrate how the evidence from Indo-Pacific research may be relevant to global archaeological models
The Dynamical Cluster Approximation: Non-Local Dynamics of Correlated Electron Systems
We recently introduced the dynamical cluster approximation(DCA), a new
technique that includes short-ranged dynamical correlations in addition to the
local dynamics of the dynamical mean field approximation while preserving
causality. The technique is based on an iterative self-consistency scheme on a
finite size periodic cluster. The dynamical mean field approximation (exact
result) is obtained by taking the cluster to a single site (the thermodynamic
limit). Here, we provide details of our method, explicitly show that it is
causal, systematic, -derivable, and that it becomes conserving as the
cluster size increases. We demonstrate the DCA by applying it to a Quantum
Monte Carlo and Exact Enumeration study of the two-dimensional Falicov-Kimball
model. The resulting spectral functions preserve causality, and the spectra and
the CDW transition temperature converge quickly and systematically to the
thermodynamic limit as the cluster size increases.Comment: 19 pages, 13 postscript figures, revte
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