4,033 research outputs found
Direct numerical integration for multi-loop integrals
We present a method to construct a suitable contour deformation in loop
momentum space for multi-loop integrals. This contour deformation can be used
to perform the integration for multi-loop integrals numerically. The
integration can be performed directly in loop momentum space without the
introduction of Feynman or Schwinger parameters. The method can be applied to
finite multi-loop integrals and to divergent multi-loop integrals with suitable
subtraction terms. The algorithm extends techniques from the one-loop case to
the multi-loop case. Examples at two and three loops are discussed explicitly.Comment: 20 pages, v2: version to be published, v3: acknowledgement adde
Diagnosing Fractionalization from the Spin Dynamics of Spin Liquids on the Kagome Lattice by Quantum Monte Carlo Simulations
Based on large-scale quantum Monte Carlo simulations, we examine the
dynamical spin structure factor of the Balents-Fisher-Girvin kagome lattice
quantum spin- model, which is known to harbor an extended quantum
spin liquid phase. We use a correlation-matrix sampling scheme combined with a
stochastic analytic continuation method to resolve the spectral functions of
this anisotropic quantum spin model with a three-site unit-cell. Based on this
approach, we monitor the spin dynamics throughout the phase diagram of this
model, from the XY-ferromagnetic region to the quantum spin liquid
regime. In the latter phase, we identify a gapped two-spinon continuum in the
transverse scattering channel, which is faithfully modeled by an effective
spinon tight-binding model. Within the longitudinal channel, we identify gapped
vison excitations and exhibit indications for the translational symmetry
fractionalization of the visons via an enhanced spectral periodicity.Comment: 6 pages, 9 figures, v2: published versio
Direct contour deformation with arbitrary masses in the loop
We present a method, which constructs a suitable deformation vector in loop
momentum space, when the loop integration is done numerically with the help of
the subtraction method. The method presented here extends previously discussed
techniques from the massless case to the general case of arbitrary masses in
the loop.Comment: 18 pages, version to be publishe
Detection and visualisation of climate trends in China
Research on climate trends in China has been carried out within a co-operation of the Justus Liebig Universities Department of Geography and Zentrum fĂĽr internationale Entwicklungs- und Umweltforschung (ZEU) and the Nanjing Institute of Geography and Limnology (CAS). First results were introduced by BECKER et al. 2003 a, b who worked on precipitation trend analyses in the Yangtze River Catchment. In the meanwhile, the National Climatic Centre of China (NCCC) kindly provided climatic data in China within the framework of this co-operation. Financial support from the CAS Key project KZCX3-SW-331 and the NSFC project 40271112 enabled the data acquisition. The analysis of both, precipitation and temperature data for the whole of China from 1951- 2002 can be carried out now. A shorter version of the precipitation trend observation will soon be published in Theoretical and Applied Climatology (GEMMER et al. 2003, accepted for publication/in print). Results of the temperature trend research have not been published yet. They will be submitted to an international Journal when further statistical approaches with regard to daily temperature data are processed. The discussion paper in hand will make the actual results accessible for further research groups in Germany. --
Temporal and spatial heterogeneity in aging colloids: a mesoscopic model
A coarse-grained model of dense hard sphere colloids building on simple
notions of particle mobility and spatial coherence is presented and shown to
reproduce results of experiments and simulations for key quantities such as the
intermediate scattering function, the particle mean-square displacement and the
mobility correlation function. All results are explained by two
emerging and interrelated dynamical properties: i) a rate of intermittent
events, quakes, which decreases as the inverse of the system age t; ii) a
length scale characterizing correlated domains, which increases linearly in log
t. This leads to simple and accurate scaling forms expressed in terms of a
single scaling variable Finally, we propose a method to experimentally extract
the growing length scale of an aging colloid and suggest that a suitable
scaling of the probability density function of particle displacement can
experimentally reveal the rate of quakes.Comment: 5 pages 6 figure
Dynamic Switching State Systems for Visual Tracking
This work addresses the problem of how to capture the dynamics of maneuvering objects for visual tracking. Towards this end, the perspective of recursive Bayesian filters and the perspective of deep learning approaches for state estimation are considered and their functional viewpoints are brought together
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