2,128 research outputs found
Quantum Structure of Space Near a Black Hole Horizon
We describe a midi-superspace quantization scheme for generic single horizon
black holes in which only the spatial diffeomorphisms are fixed. The remaining
Hamiltonian constraint yields an infinite set of decoupled eigenvalue
equations: one at each spatial point. The corresponding operator at each point
is the product of the outgoing and ingoing null convergences, and describes the
scale invariant quantum mechanics of a particle moving in an attractive
potential. The variable that is analoguous to particle position is the
square root of the conformal mode of the metric. We quantize the theory via
Bohr quantization, which by construction turns the Hamiltonian constraint
eigenvalue equation into a finite difference equation. The resulting spectrum
gives rise to a discrete spatial topology exterior to the horizon. The spectrum
approaches the continuum in the asymptotic region.Comment: References added and typos corrected. 21 pages, 1 figur
On Lie-algebraic solutions of the type IIB matrix model
A systematic search for Lie algebra solutions of the type IIB matrix model is
performed. Our survey is based on the classification of all Lie algebras for
dimensions up to five and of all nilpotent Lie algebras of dimension six. It is
shown that Lie-type solutions of the equations of motion of the type IIB matrix
model exist and they correspond to certain nilpotent and solvable Lie algebras.
Their representation in terms of Hermitian matrices is discussed in detail.
These algebras give rise to certain non-commutative spaces for which the
corresponding star-products are provided. Finally the issue of constructing
quantized compact nilmanifolds and solvmanifolds based on the above algebras is
addressed.Comment: 22 page
Danos provocados por Amblycerus dispar Sharp, 1885 (Coleoptera: Bruchidae) a semente de imbuzeiro (Spondias tuberosa Arruda).
O objetivo deste foi identificar o inseto que estava atacando as sementes de plantas nativas de imbuzeiro, como também avaliar os danos causados as sementes e a existência de plantas jovens na área de estudo
Variabilidade genetica e melhoramento da mandioca (Manihot esculenta Crantz).
A cultura da mandioca constitui uma das mais importantes fontes de carboidratos nos trópicos, empregada na alimentação humana, animal e na indústria de processamento por cerca de 500 milhões de pessoas em todo o mundo. É cultivada em todo o território brasileir
Exact Solutions of the Klein-Gordon Equation in the Presence of a Dyon, Magnetic Flux and Scalar Potential in the Specetime of Gravitational Defects
In this paper we analyse the relativistic quantum motion of a charged spin-0
particle in the presence of a dyon, Aharonov-Bohm magnetic field and scalar
potential, in the spacetimes produced by an idealized cosmic string and global
monopole. In order to develop this analysis, we assume that the dyon and the
Aharonov-Bohm magnetic field are superposed to both gravitational defects. Two
distinct configurations for the scalar potential, , are considered:
the potential proportional to the inverse of the radial distance, i.e.,
, and the potential proportional to this distance, i.e.,
. For both cases the center of the potentials coincide with the
dyon's position. In the case of the cosmic string the Aharonov-Bohm magnetic
field is considered along the defect, and for the global monopole this magnetic
field pierces the defect. The energy spectra are computed for both cases and
explicitly shown their dependence on the electrostatic and scalar coupling
constants. Also we analyse scattering states of the Klein-Gordon equations, and
show how the phase shifts depend on the geometry of the spacetime and on the
coupling constants parameter.Comment: To be published in CQG. Minor comments adde
A post-selection algorithm for improving dynamic ensemble selection methods
Dynamic Ensemble Selection (DES) is a Multiple Classifier Systems (MCS)
approach that aims to select an ensemble for each query sample during the
selection phase. Even with the proposal of several DES approaches, no
particular DES technique is the best choice for different problems. Thus, we
hypothesize that selecting the best DES approach per query instance can lead to
better accuracy. To evaluate this idea, we introduce the Post-Selection Dynamic
Ensemble Selection (PS-DES) approach, a post-selection scheme that evaluates
ensembles selected by several DES techniques using different metrics.
Experimental results show that using accuracy as a metric to select the
ensembles, PS-DES performs better than individual DES techniques. PS-DES source
code is available in a GitHub repositor
Low cost satellite data for monthly irrigation performance monitoring: benchmarks from Nilo Coelho, Brazil.
Irrigation performance indicators can help water managers to understand how an irrigation scheme operates under actual circumstances. The new contribution of remote sensing data, is the opportunity to study the crop growing conditions at scales ranging from individual fields to scheme level. Public domain internet satellite data have been used to calculate actual and potential crop evapotranspiration, soil moisture and biomass growth on a monthly basis in the Nilo Coelho irrigation scheme, Pernambuco (Brazil). Satellite interpreted raster maps were merged with vector maps of the irrigation water delivery system. Monthly values of a minimum list of irrigation performance indicators for the various service units in the pressurized Nilo Coelho scheme were determined. Nilo Coelho is a good performing scheme. The performance can be improved further if 25% irrigation water is saved from February to July. The benchmark figures from this modern irrigation system are presented for comparitive analysis with other systems. The acceptable ranges in space and time are presented. On average, 65% of the lateral pumping units on a monthly basis fall within the acceptable limits of irrigation performance. Low cost irrigation performance data based on low resolution satellite images (US$ 1/ha) will help the management team to focus on specific pumping units, and discuss alternative irrigation and farm management strategies with the stakeholders
Reply to the Comment on "Resonant Spectra and the Time Evolution of the Survival and Nonescape Probabilities"
In our paper [Phys. Rev. Lett. 74, 337 (1995)], we derived an exact
expression for the survival and nonescape probabilities as an expansion in
terms of resonant states. It was shown that these quantities exhibit at long
times a different behavior. Although both decay as a power law, they have
different exponents. In this paper we show that, contrary to the claim in the
Comment of R. M. Cavalcanti (quant-ph/9704023), the nonescape probability decay
for long times as an inverse power law.Comment: 1 page, RevTex file, to appear in Phys. Rev. Let
Object-oriented Programming Laws for Annotated Java Programs
Object-oriented programming laws have been proposed in the context of
languages that are not combined with a behavioral interface specification
language (BISL). The strong dependence between source-code and interface
specifications may cause a number of difficulties when transforming programs.
In this paper we introduce a set of programming laws for object-oriented
languages like Java combined with the Java Modeling Language (JML). The set of
laws deals with object-oriented features taking into account their
specifications. Some laws deal only with features of the specification
language. These laws constitute a set of small transformations for the
development of more elaborate ones like refactorings
Induction of resistance to Xanthomonas campestris pv. viticola in grapevine plants.
The objective of this work was to evaluate the effect of Saccharomyces cerevisiae (SC), Acibenzolar-S-Methyl (ASM), organic acids and polyphenols (OAP) and potassium silicate (SiK) on protecting grapevine plants (cv. Redglobe) from Xanthomonas campestris pv. viticola. Four application rates for each product (SC at 2.0, 2.50, 3.0, 3.50 and 4.0 mL 100 L-1; ASM and OAP at 2.50, 3.00, 3.50, 4.50 and 6.00 mL 100 L-1 and SiK at 5.00, 6.50, 7.50 and 8.50 mL 100 L-1) in different application times (0, 5, 10, and 15 days before inoculation), and the enzymatic activity of peroxidases, phenylalanine ammonia-lyase and ?-1,3 glucanases were evaluated. Plants were inoculated with a bacterial suspension of 5 x 108 CFU mL-1 by rubbing with gauze. The epidemiological variables incidence (INC), severity (SEV) and area under the disease progress curve (AUDPC) were assessed. The treatment with ASM had the lowest averages of INC (38%) and SEV (1.52%) from 3 g 100 L-1. The application of 4.5 mL 100 L-1 of OAP reduced the plant disease in 52% of INC and 2.45% of SEV. SiK and SC presented no significant reduction in these variables compared to control. The ASM applied 15 days before the inoculation (DBI) reduced the disease in 91.31% and the APO in 73.34%, while SC and SiK reduced the disease in 67.49 and 60.11%, respectively, with applications at 5 DBI. There was no increase of peroxidase activity in any of the treatments. There was a significant increase in activity of ?-1,3 glucanases and phenylalanine ammonia-lyase in plants treated with ASM at 15 DBI, indicating an influence on the induction of resistance of plants to this disease
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