58 research outputs found
Some Applications of the Overlap Formalism
The massless vector Schwinger model with number of flavors is
studied on the lattice using the overlap formalism. A full Monte Carlo
simulation yields values for the bilinear fermion condensate that are in
agreement with the exact solution of the continuum Schwinger model with an
added Thirring interaction.Comment: 3 pages, uuencoded postscript fil
Visual mining of moving flock patterns in large spatio-temporal data sets using a frequent pattern approach
The popularity of tracking devices continues to contribute to increasing volumes of spatio-temporal data about moving objects. Current approaches in analysing these data are unable to capture collective behaviour and correlations among moving objects. An example of these types of patterns is moving flocks. This article develops an improved algorithm for mining such patterns following a frequent pattern discovery approach, a well-known task in traditional data mining. It uses transaction-based data representation of trajectories to generate a database that facilitates the application of scalable and efficient frequent pattern mining algorithms. Results were compared with an existing method (Basic Flock Evaluation or BFE) and are demonstrated for both synthetic and real data sets with a large number of trajectories. The results illustrate a significant performance increase. Furthermore, the improved algorithm has been embedded into a visual environment that allows manipulation of input parameters and interactive recomputation of the resulting flocks. To illustrate the visual environment a data set containing 30 years of tropical cyclone tracks with 6 hourly observations is used. The example illustrates how the visual environment facilitates exploration and verification of flocks by changing the input parameters and instantly showing the spatio-temporal distribution of the resulting flocks in the Space-Time Cube and interactively selecting
Chiral Symmetry Restoration in the Schwinger Model with Domain Wall Fermions
Domain Wall Fermions utilize an extra space time dimension to provide a
method for restoring the regularization induced chiral symmetry breaking in
lattice vector gauge theories even at finite lattice spacing. The breaking is
restored at an exponential rate as the size of the extra dimension increases.
Before this method can be used in dynamical simulations of lattice QCD, the
dependence of the restoration rate to the other parameters of the theory and,
in particular, the lattice spacing must be investigated. In this paper such an
investigation is carried out in the context of the two flavor lattice Schwinger
model.Comment: LaTeX, 37 pages including 18 figures. Added comments regarding power
law fitting in sect 7. Also, few changes were made to elucidate the content
in sect. 5.1 and 5.3. To appear in Phys. Rev.
Effective actions with fixed points, (error in derivation of coefficient corrected)
The specific form of the constant term in the asymptotic expansion of the
heat-kernel on an axially-symmetric space with a codimension two fixed-point
set of conical singularities is used to determine the associated conformal
change of the effective action in four dimensions. Another derivation of the
relevant coefficient is presented.Comment: 10p,uses JyTeX,MUTP/94/1
Quantum Field Theories on Manifolds with Curved Boundaries: Scalar Fields
A framework allowing for perturbative calculations to be carried out for
quantum field theories with arbitrary smoothly curved boundaries is described.
It is based on an expansion of the heat kernel derived earlier for arbitrary
mixed Dirichlet and Neumann boundary conditions.
The method is applied to a general renormalisable scalar field theory in four
dimensions using dimensional regularisation to two loops and expanding about
arbitrary background fields. Detailed results are also specialised to an
symmetric model with a single coupling constant. Extra boundary terms are
introduced into the action which give rise to either Dirichlet or generalised
Neumann boundary conditions for the quantum fields. For plane boundaries the
resulting renormalisation group functions are in accord with earlier results
but here the additional terms depending on the extrinsic curvature of the
boundary are found. Various consistency relations are also checked and the
implications of conformal invariance at the critical point where the
function vanishes are also derived. The local Scr\"odinger equation for the
wave functional defined by the functional integral under deformations of the
boundary is also verified to two loops. Its consistency with the
renormalisation group to all orders in perturbation theory is discussed.Comment: 50 pages, DAMTP/92-3
Bose-Einstein condensation in arbitrarily shaped cavities
We discuss the phenomenon of Bose-Einstein condensation of an ideal
non-relativistic Bose gas in an arbitrarily shaped cavity. The influence of the
finite extension of the cavity on all thermodynamical quantities, especially on
the critical temperature of the system, is considered. We use two main methods
which are shown to be equivalent. The first deals with the partition function
as a sum over energy levels and uses a Mellin-Barnes integral representation to
extract an asymptotic formula. The second method converts the sum over the
energy levels to an integral with a suitable density of states factor obtained
from spectral analysis. The application to some simple cavities is discussed.Comment: 10 pages, LaTeX, to appear in Physical Review
Integrating omics to characterize ecoâphysiological adaptations: How moose diet and metabolism differ across biogeographic zones
1. With accelerated land conversion and global heating at northern latitudes, it becomes crucial to understand, how life histories of animals in extreme environments adapt to these changes. Animals may either adapt by adjusting foraging behavior or through physiological responses, including adjusting their energy metabolism or both. Until now, it has been difficult to study such adaptations in freeâranging animals due to methodological constraints that prevent extensive spatiotemporal coverage of ecological and physiological data.
2. Through a novel approach of combining DNAâmetabarcoding and nuclear magnetic resonance (NMR)âbased metabolomics, we aim to elucidate the links between diets and metabolism in Scandinavian moose Alces alces over three biogeographic zones using a unique dataset of 265 marked individuals.
3. Based on 17 diet items, we identified four different classes of diet types that match browse species availability in respective ecoregions in northern Sweden. Individuals in the boreal zone consumed predominantly pine and had the least diverse diets, while individuals with highest diet diversity occurred in the coastal areas. Males exhibited lower average diet diversity than females.
4. We identified several molecular markers indicating metabolic constraints linked to diet constraints in terms of food availability during winter. While animals consuming pine had higher lipid, phospocholine, and glycerophosphocholine concentrations in their serum than other diet types, birchâ and willow/aspenârich diets exhibit elevated concentrations of several amino acids. The individuals with highest diet diversity had increased levels of ketone bodies, indicating extensive periods of starvation for these individuals.
5. Our results show how the adaptive capacity of moose at the ecoâphysiological level varies over a large ecoâgeographic scale and how it responds to land use pressures. In light of extensive ongoing climate and land use changes, these findings pave the way for future scenario building for animal adaptive capacity
Free and self-interacting scalar fields in the presence of conical singularities
Free and self-interacting scalar fields in the presence of conical
singularities are analized in some detail. The role of such a kind of
singularities on free and vacuum energy and also on the one-loop effective
action is pointed out using -function regularization and heat-kernel
techniques.Comment: 20 Pages, RevTex, UTF30
Effective Lagrangian for self-interacting scalar field theories in curved spacetime
We consider a self-interacting scalar field theory in a slowly varying
gravitational background field. Using zeta-function regularization and
heat-kernel techniques, we derive the one-loop effective Lagrangian up to
second order in the variation of the background field and up to quadratic terms
in the curvature tensors. Specializing to different spacetimes of physical
interest, the influence of the curvature on the phase transition is considered.Comment: 14 pages, LaTex, UTF 29
A standardisation framework for bioâlogging data to advance ecological research and conservation
Bioâlogging data obtained by tagging animals are key to addressing global conservation challenges. However, the many thousands of existing bioâlogging datasets are not easily discoverable, universally comparable, nor readily accessible through existing repositories and across platforms, slowing down ecological research and effective management. A set of universal standards is needed to ensure discoverability, interoperability and effective translation of bioâlogging data into research and management recommendations.
We propose a standardisation framework adhering to existing data principles (FAIR: Findable, Accessible, Interoperable and Reusable; and TRUST: Transparency, Responsibility, User focus, Sustainability and Technology) and involving the use of simple templates to create a data flow from manufacturers and researchers to compliant repositories, where automated procedures should be in place to prepare data availability into four standardised levels: (a) decoded raw data, (b) curated data, (c) interpolated data and (d) gridded data. Our framework allows for integration of simple tabular arrays (e.g. csv files) and creation of sharable and interoperable network Common Data Form (netCDF) files containing all the needed information for accuracyâofâuse, rightful attribution (ensuring data providers keep ownership through the entire process) and data preservation security.
We show the standardisation benefits for all stakeholders involved, and illustrate the application of our framework by focusing on marine animals and by providing examples of the workflow across all data levels, including filled templates and code to process data between levels, as well as templates to prepare netCDF files ready for sharing.
Adoption of our framework will facilitate collection of Essential Ocean Variables (EOVs) in support of the Global Ocean Observing System (GOOS) and interâgovernmental assessments (e.g. the World Ocean Assessment), and will provide a starting point for broader efforts to establish interoperable bioâlogging data formats across all fields in animal ecology
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