14,368 research outputs found
Topological Susceptibility from Slabs
In quantum field theories with topological sectors, a non-perturbative
quantity of interest is the topological susceptibility chi_t. In principle it
seems straightforward to measure chi_t by means of Monte Carlo simulations.
However, for local update algorithms and fine lattice spacings, this tends to
be difficult, since the Monte Carlo history rarely changes the topological
sector. Here we test a method to measure chi_t even if data from only one
sector are available. It is based on the topological charges in sub-volumes,
which we denote as slabs. Assuming a Gaussian distribution of these charges,
this method enables the evaluation of chi_t, as we demonstrate with numerical
results for non-linear sigma-models.Comment: 23 pages, 8 figures, 6 table
The Slab Method to Measure the Topological Susceptibility
In simulations of a model with topological sectors, algorithms which proceed
in small update steps tend to get stuck in one sector, especially on fine
lattices. This distorts the numerical results; in particular it is not
straightforward to measure the topological susceptibility chi_t. We test a
method to measure chi_t even if configurations from only one sector are
available. It is based on the topological charges in sub-volumes, which we
denote as "slab". This enables the evaluation of chi_t, as we demonstrate with
numerical results for non-linear sigma-models and for 2-flavour QCD. In the
latter case, the gradient flow is applied for the smoothing of the gauge
configurations, and the slab method results for chi_t are stable over a broad
range of flow times.Comment: 7 pages, 7 figures, talk presented at the 34th International
Symposium on Lattice Field Theory, 24-30 July 2016, Southampton, UK. Minor
corrections, references added, Fig. 5 replace
Topology in the 2d Heisenberg Model under Gradient Flow
The 2d Heisenberg model --- or 2d O(3) model --- is popular in condensed
matter physics, and in particle physics as a toy model for QCD. Along with
other analogies, it shares with 4d Yang-Mills theories, and with QCD, the
property that the configurations are divided in topological sectors. In the
lattice regularisation the topological charge can still be defined such
that . It has generally been observed, however, that the
topological susceptibility does not
scale properly in the continuum limit, i.e. that the quantity diverges for (where is the correlation length in
lattice units). Here we address the question whether or not this divergence
persists after the application of the Gradient Flow.Comment: 10 pages, LaTex, 7 figures, 2 tables, talk presented at the XXXI
Reuni\'on Anual de la Divisi\'on de Part\'iculas y Campos de la Sociedad
Mexicana de F\'isica (CINVESTAV, Mexico City
Analysis of marine conflicts
The traffic conflict technique (TCT) is a powerful technique applied in road traffic safety assessment as a surrogate of the traditional accident data analysis. It has subdued the conceptual and implemental weaknesses of the accident statistics. Although this technique has been applied effectively in road traffic, it has not been practised well in marine traffic even though this traffic system has some distinct advantages in terms of having a monitoring system. This monitoring system can provide navigational information as well as other geometric information of the ships for a larger study area over a longer time period. However, for implementing the TCT in the marine traffic system, it should be examined critically to suit the complex nature of the traffic system. This paper examines the suitability of the TCT to be applied to marine traffic and proposes a framework for a follow up comprehensive conflict study
Detection of immunoglobulin (Ig) A antibodies against porcine epidemic diarrhea virus (PEDV) in fecal and serum samples
Many assays for detection of antibodies against porcine epidemic diarrhea virus (PEDV) are based on detection of neutralizing antibodies or immunoglobulin (Ig) G in serum samples. However, due to the particular features of the mucosal immune system, presence of serum antibodies against enteric pathogens, such as PEDV, not always correlates with protection. In contrast, anti-PEDV IgA antibodies correlate with protection against subsequent challenges. An indirect PEDV IgA ELISA was previously developed to monitor IgA levels in colostrum and milk samples. In the present paper we describe an adaptation of the protocol for detection of IgA antibodies in serum and fecal samples.• The adapted protocol will aid in future assessment of protective levels of humoral response against PEDV infection by measuring IgA levels in serum and fecal samples.
• Fecal samples are non-invasive and easy to collect at any time by animal caretakers and therefore offering advantages over the serum sample collection procedure.
• A strong positive correlation between the anti-PEDV levels in fecal and serum samples was identified; however, detection of IgA antibodies was often more successful in serum than in paired fecal samples due to overall lower sample-to-positive (S/P) ratios for the latter sample type
Those Hawaiian melodies
https://digitalcommons.library.umaine.edu/mmb-vp/3740/thumbnail.jp
Gravitational potential of a homogeneous circular torus: new approach
The integral expression for gravitational potential of a homogeneous circular
torus composed of infinitely thin rings is obtained. Approximate expressions
for torus potential in the outer and inner regions are found. In the outer
region a torus potential is shown to be approximately equal to that of an
infinitely thin ring of the same mass; it is valid up to the surface of the
torus. It is shown in a first approximation, that the inner potential of the
torus (inside a torus body) is a quadratic function of coordinates. The method
of sewing together the inner and outer potentials is proposed. This method
provided a continuous approximate solution for the potential and its
derivatives, working throughout the region.Comment: 10 pages, 9 figures, 1 table; some misprints in formulae were
correcte
Sources and modes of action of invasive knotweed allelopathy : the effects of leaf litter and trained soil on the germination and growth of native plants
Invasive knotweeds, native to Eastern Asia, are among the most dominant plant invaders of European and North American temperate ecosystems. Recent studies indicate that one cause of this dominance might be allelopathy, but the possible sources and modes of action of this allelopathy are insufficiently understood. Here, we asked whether the invasive knotweed Fallopia × bohemica can exert allelopathic effects on native plants also through its leaf litter, or through persistent soil contaminants, and whether these affect the germination or growth of native plants. In a germination experiment with nine native species neither litter leachate, an aqueous extract of knotweed leaves added to the soil, nor trained soil with a history of Fallopia pre-cultivation suppressed the germination or early growth of natives. A mesocosm study with experimental native communities showed that the presence of F. × bohemica, although not a dominant in these communities, caused significant shifts of life-history strategy in two dominant natives, and that similar effects could be elicited through litter leachates or trained soil alone. However, there were hardly any effects on the biomass of natives. Our study indicates that knotweed allelopathy acts on the growth rather than germination of natives, and that soil contamination through persistent allelochemicals may not be a significant problem in habitat restoration. It also shows that allelopathic effects can sometimes be subtle changes in life-history and allocation patterns of the affected species
The Economics of Desertification, Land Degradation, and Drought; Toward an Integrated Global Assessment
Land degradation has not been comprehensively addressed at the global level or in developing countries. A suitable economic framework that could guide investments and institutional action is lacking. This study aims to overcome this deficiency and to provide a framework for a global assessment based on a consideration of the costs of action versus inaction regarding desertification, land degradation, and drought (DLDD). Most of the studies on the costs of land degradation (mainly limited to soil erosion) give cost estimates of less than 1 percent up to about 10 percent of the agricultural gross domestic product (GDP) for various countries worldwide. But the indirect costs of DLDD on the economy (national income), as well as their socioeconomic consequences (particularly poverty impacts), must be accounted for, too. Despite the numerous challenges, a global assessment of the costs of action and inaction against DLDD is possible, urgent, and necessary. This study provides a framework for such a global assessment and provides insights from some related country studies.Agricultural Finance, Crop Production/Industries, Environmental Economics and Policy, Land Economics/Use, Resource /Energy Economics and Policy,
The economics of desertification, land degradation, and drought: Toward an integrated global assessment
cost of inaction, desertification, drought, Economics, Land degradation, prevention of land degradation,
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