1,443 research outputs found
Perspectivas da bubalinocultura no Baixo Madeira no estado de Rondonia.
Estudo preliminar visando suprir deficiencia de carne e leite dos moradores das margens do Rio Madeira. Envolve aspectos relativos a bubalinocultura, operacoes que formam o sistema, producao de leite, instalacoes, comercializacao e sugestoes para o fomento da bubalinocultura.bitstream/item/55121/1/Circ.tecn-03-0001.pd
Superconformal Black Hole Quantum Mechanics
In recent work, the superconformal quantum mechanics describing D0 branes in
the AdS_2xS^2xCY_3 attractor geometry of a Calabi-Yau black hole with D4 brane
charges p^A has been constructed and found to contain a large degeneracy of
chiral primary bound states. In this paper it is shown that the asymptotic
growth of chiral primaries for N D0 branes exactly matches the
Bekenstein-Hawking area law for a black hole with D4 brane charge p^A and D0
brane charge N. This large degeneracy arises from D0 branes in lowest Landau
levels which tile the CY_3xS^2 horizon. It is conjectured that such a multi-D0
brane CFT1 is holographically dual to IIA string theory on AdS_2xS^2xCY_3.Comment: 8 page
Consistency Conditions on S-Matrix of Spin 1 Massless Particles
Motivated by new techniques in the computation of scattering amplitudes of
massless particles in four dimensions, like BCFW recursion relations, the
question of how much structure of the S-matrix can be determined from purely
S-matrix arguments has received new attention. The BCFW recursion relations for
massless particles of spin 1 and 2 imply that the whole tree-level S-matrix can
be determined in terms of three-particle amplitudes (evaluated at complex
momenta). However, the known proofs of the validity of the relations rely on
the Lagrangian of the theory, either by using Feynman diagrams explicitly or by
studying the effective theory at large complex momenta. This means that a
purely S-matrix theoretic proof of the relations is still missing. The aim of
this paper is to provide such a proof for spin 1 particles by extending the
four-particle test introduced by P. Benincasa and F. Cachazo in
arXiv:0705.4305[hep-th] to all particles. We show how n-particle tests imply
that the rational function built from the BCFW recursion relations possesses
all the correct factorization channels including holomorphic and
anti-holomorphic collinear limits. This in turn implies that they give the
correct S-matrix of the theory.Comment: 24 pages, 4 figure
On the Numerical Evaluation of One-Loop Amplitudes: the Gluonic Case
We develop an algorithm of polynomial complexity for evaluating one-loop
amplitudes with an arbitrary number of external particles. The algorithm is
implemented in the Rocket program. Starting from particle vertices given by
Feynman rules, tree amplitudes are constructed using recursive relations. The
tree amplitudes are then used to build one-loop amplitudes using an integer
dimension on-shell cut method. As a first application we considered only three
and four gluon vertices calculating the pure gluonic one-loop amplitudes for
arbitrary external helicity or polarization states. We compare our numerical
results to analytical results in the literature, analyze the time behavior of
the algorithm and the accuracy of the results, and give explicit results for
fixed phase space points for up to twenty external gluons.Comment: 22 pages, 9 figures; v2: references added, version accepted for
publicatio
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
A Prestação de Serviços Ambientais pode ser uma alternativa aos sistemas tradicionais da agricultura familiar no município de Pacajá, Amazônia Paraense - Brasil?
Os estabelecimentos familiares, em sua maioria, adotam o sistema tradicional de agricultura, usando a área por um ou dois anos, seguido de pousio. Essa produção, na Amazônia, tem sido identificada, por alguns, como problema social e vilã ecológica. Contraponto a essa visão, compreende-se a agricultura familiar como estratégica na manutenção do emprego, redistribuição da renda, garantia da soberania alimentar do país e a alternativa para o desenvolvimento sustentável, devido à diversificação nos sistemas de produção e características equilibradas na relação homem e natureza. Propõe-se no texto a reflexão sobre Prestação de Serviços Ambientais no município de Pacajá-PA. Adotou-se a ferramenta Eco-Cert. PROAMBIENTE desenvolvida pela Embrapa para identificar as práticas contribuintes com os serviços. Os resultados mostraram que a diversificação é fundamental para prestação de serviços ambientais e as famílias participantes do PROAMBIENTE aumentaram o potencial na prestação de serviços, principalmente por não derrubarem as florestas e reduzirem o uso do fogo
A note on the boundary contribution with bad deformation in gauge theory
Motivated by recently progresses in the study of BCFW recursion relation with
nonzero boundary contributions for theories with scalars and
fermions\cite{Bofeng}, in this short note we continue the study of boundary
contributions of gauge theory with the bad deformation. Unlike cases with
scalars or fermions, it is hard to use Feynman diagrams directly to obtain
boundary contributions, thus we propose another method based on the SYM theory. Using this method, we are able to write down a useful
on-shell recursion relation to calculate boundary contributions from related
theories. Our result shows the cut-constructibility of gauge theory even with
the bad deformation in some generalized sense.Comment: 16 pages, 7 figure
N=1/2 Super Yang-Mills Theory on Euclidean AdS2xS2
We study D-branes in the background of Euclidean AdS2xS2 with a graviphoton
field turned on. As the background is not Ricci flat, the graviphoton field
must have both self-dual and antiself-dual parts. This, in general, will break
all the supersymmetries on the brane. However, we show that there exists a
limit for which one can restore half of the supersymmetries. Further, we show
that in this limit, the N=1/2 SYM Lagrangian on flat space can be lifted on to
the Euclidean AdS2xS2 preserving the same amount of supersymmetries as in the
flat case. We observe that without the C-dependent terms present in the action
this lift is not possible.Comment: 12 pages, latex file; v2: minor corrections, references adde
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
Hepta-Cuts of Two-Loop Scattering Amplitudes
We present a method for the computation of hepta-cuts of two loop scattering
amplitudes. Four dimensional unitarity cuts are used to factorise the integrand
onto the product of six tree-level amplitudes evaluated at complex momentum
values. Using Gram matrix constraints we derive a general parameterisation of
the integrand which can be computed using polynomial fitting techniques. The
resulting expression is further reduced to master integrals using conventional
integration by parts methods. We consider both planar and non-planar topologies
for 2 to 2 scattering processes and apply the method to compute hepta-cut
contributions to gluon-gluon scattering in Yang-Mills theory with adjoint
fermions and scalars.Comment: 37 pages, 6 figures. version 2 : minor updates, published versio
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