1,122 research outputs found
Integrand reduction of one-loop scattering amplitudes through Laurent series expansion
We present a semi-analytic method for the integrand reduction of one-loop
amplitudes, based on the systematic application of the Laurent expansions to
the integrand-decomposition. In the asymptotic limit, the coefficients of the
master integrals are the solutions of a diagonal system of equations, properly
corrected by counterterms whose parametric form is konwn a priori. The Laurent
expansion of the integrand is implemented through polynomial division. The
extension of the integrand-reduction to the case of numerators with rank larger
than the number of propagators is discussed as well.Comment: v2: Published version: references and two appendices added. v3:
Eq.(6.11) corrected, Appendix B updated accordingl
Single Cut Integration
We present an analytic technique for evaluating single cuts for one-loop
integrands, where exactly one propagator is taken to be on shell. Our method
extends the double-cut integration formalism of one-loop amplitudes to the
single-cut case. We argue that single cuts give meaningful information about
amplitudes when taken at the integrand level. We discuss applications to the
computation of tadpole coefficients.Comment: v2: corrected typo in abstrac
Uso de metodologia simples por análise de imagens para acompanhamento da proliferação de fungos em frutos fatiados.
bitstream/CNPDIA-2009-09/11851/1/BPD17_2006.pd
Optimizing the Reduction of One-Loop Amplitudes
We present an optimization of the reduction algorithm of one-loop amplitudes
in terms of master integrals. It is based on the exploitation of the polynomial
structure of the integrand when evaluated at values of the loop-momentum
fulfilling multiple cut-conditions, as emerged in the OPP-method. The
reconstruction of the polynomials, needed for the complete reduction, is rended
very versatile by using a projection-technique based on the Discrete Fourier
Transform. The novel implementation is applied in the context of the NLO QCD
corrections to u d-bar --> W+ W- W+
Scalar diagrammatic rules for Born amplitudes in QCD
We show that all Born amplitudes in QCD can be calculated from scalar
propagators and a set of three- and four-valent vertices. In particular, our
approach includes amplitudes with any number of quark pairs. The quarks may be
massless or massive. The proof of the formalism is given entirely within
quantum field theory.Comment: 20 pages, references adde
From lightcone actions to maximally supersymmetric amplitudes
In this article actions for N=4 SYM and N=8 supergravity are formulated in
terms of a chiral superfield, which contains only the physical degrees of
freedom of either theory. In these new actions, which originate from the
lightcone superspace, the supergravity cubic vertex is the square of the gauge
theory one (omitting the color structures). Amplitude calculations using the
corresponding Feynman supergraph rules are tedious, but can be simplified by
choosing a preferred superframe. Recursive calculations of all MHV amplitudes
in N=4 SYM and the four-point N=8 supergravity amplitude are shown to agree
with the known results and connections to the BCFW recursion relations are
pointed out. Finally, the new path integrals are discussed in the context of
the double-copy property relating N=4 SYM theory to N=8 supergravity.Comment: 29 pages, 2 figures, v2: title modified, published versio
Características de diferentes quitosanas empregadas como revestimentos protetores de maçãs fatiadas.
Linear and non-linear regression analysis for the sorption kinetics of Rhodamine dye from aqueous solution using Chitosan-Jackfruit nanocomposite
This paper presents experimental results such as the adsorbate-adsorbent chemical properties and chemical interaction as well as adsorption conditions. The experimental results were fitted to batch kinetic studies to obtain the characteristic parameters of each model. According to the evaluation using the Kinetic equation, the maximum sorption capacity at dye concentration was 19.6 (mg g-1), pH 11.6 (mg g-1) and temperature 24.2 (mg g-1) Rhodamine dye were investigated. For all of the systems studied, the pseudo-first-order and pseudo-second-order model provided the best correlation of the kinetic experimental data. The results revealed that with increasing temperature and decreasing pH, ionic strength, and adsorbate concentration, dye removal efficiency has increased. Chitosan-Jackfruit nanocomposite could remove 90.2% dye from the solution containing 40 mg/L dye at 100 min. The results indicated that dye removal followed pseudo-second-order kinetic (R2>0.99). According to the findings, Chitosan-Jackfruit nanocomposites an effective adsorbent for direct dye removal from wastewater
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