Metric fluctuations and decoherence

Recently a model of metric fluctuations has been proposed which yields an effective Schr\"odinger equation for a quantum particle with a modified inertial mass, leading to a violation of the weak equivalence principle. The renormalization of the inertial mass tensor results from a local space average over the fluctuations of the metric over a fixed background metric. Here, we demonstrate that the metric fluctuations of this model lead to a further physical effect, namely to an effective decoherence of the quantum particle. We derive a quantum master equation for the particle's density matrix, discuss in detail its dissipation and decoherence properties, and estimate the corresponding decoherence time scales. By contrast to other models discussed in the literature, in the present approach the metric fluctuations give rise to a decay of the coherences in the energy representation, i. e., to a localization in energy space.Comment: 7 page

Cosmic ray short burst observed with the Global Muon Detector Network (GMDN) on June 22, 2015

We analyze the short cosmic ray intensity increase ("cosmic ray burst": CRB) on June 22, 2015 utilizing a global network of muon detectors and derive the global anisotropy of cosmic ray intensity and the density (i.e. the omnidirectional intensity) with 10-minute time resolution. We find that the CRB was caused by a local density maximum and an enhanced anisotropy of cosmic rays both of which appeared in association with Earth's crossing of the heliospheric current sheet (HCS). This enhanced anisotropy was normal to the HCS and consistent with a diamagnetic drift arising from the spatial gradient of cosmic ray density, which indicates that cosmic rays were drifting along the HCS from the north of Earth. We also find a significant anisotropy along the HCS, lasting a few hours after the HCS crossing, indicating that cosmic rays penetrated into the inner heliosphere along the HCS. Based on the latest geomagnetic field model, we quantitatively evaluate the reduction of the geomagnetic cut-off rigidity and the variation of the asymptotic viewing direction of cosmic rays due to a major geomagnetic storm which occurred during the CRB and conclude that the CRB is not caused by the geomagnetic storm, but by a rapid change in the cosmic ray anisotropy and density outside the magnetosphere.Comment: accepted for the publication in the Astrophysical Journa

Weakly forced atmospheric GCMs : lessons from model comparisons

Even when forced with mostly identical physical parametrizations, general circulation models (GCMs) of Venus produce significant dispersion in the simulated zonal wind fields and meridional circulations. Horizontal resolution, lower boundary layer parametrization and initial state are among the most sensitive aspects, and consistent trends are not obtained between models (or even by the same model at varying resolution). When comparing simplified temperature forcing with realistic radiative transfer in the LMD Venus GCM, it is also clear that the description of this forcing is critical to understand the meridional circulation, and therefore the dynamical cycle of angular momentum in this sensitive atmosphere. The role of numerical aspects is also obvious in the case of Titan, another weakly forced atmosphere in superrotation. Modeling Titan’s stratospheric superrotation has proved difficult, and recent GCM successes highlight that our ability to model these processes correctly is highly sensitive to numerical aspects, especially horizontal dissipation. These studies show us that modelers need to keep humble and aware of the difficulty to assess robust behaviour with only one GCM. Intercomparison of different GCMs is a useful way to identify robust interpretations from model-dependent aspects

Nonlinear electrodynamics and the Pioneer 10/11 spacecraft anomaly

The occurrence of the phenomenon known as photon acceleration is a natural prediction of nonlinear electrodynamics (NLED). This would appear as an anomalous frequency shift in any modeling of the electromagnetic field that only takes into account the classical Maxwell theory. Thus, it is tempting to address the unresolved anomalous, steady; but time-dependent, blueshift of the Pioneer 10/11 spacecrafts within the framework of NLED. Here we show that astrophysical data on the strength of the magnetic field in both the Galaxy and the local (super)cluster of galaxies support the view on the major Pioneer anomaly as a consequence of the phenomenon of photon acceleration. If confirmed, through further observations or lab experiments, the reality of this phenomenon should prompt to take it into account in any forthcoming research on both cosmological evolution and origin and dynamical effects of primordial magnetic fields, whose seeds are estimated to be very weak.Comment: Final version accepted for publication in Europhysics Letters, uses EPL style, 7 page

Desempenho de quatro genótipos de soja-hortaliça em dois anos agrícolas.

Made available in DSpace on 2011-04-09T16:16:11Z (GMT). No. of bitstreams: 1 castoldidesempenho.pdf: 436637 bytes, checksum: 2bdeeb03a3d040c3d1f03cc5f16b5eb5 (MD5) Previous issue date: 2009-09-1

Avaliação de espécies leguminosas na formação de cafezais no Estado do Acre.

Leguminosas quando consorciadas com o café e usadas como adubação verde podem contribuir fornecendo nitrogênio e proteção ao solo pela adição de matéria orgânica. Essa pesquisa foi conduzida com o objetivo de avaliar o efeito do uso de leguminosas na fertilidade do solo e no controle de plantas invasoras de cafezais no Estado do Acre. O experimento foi conduzido no período de novembro de 2000 a abril de 2003, em delineamento experimental de blocos ao acaso, com quatro repetições. Os tratamentos utilizados foram as leguminosas Stizolobium atterrimum, Cajanus cajan, Canavalia endiformis e Flemingia congesta e a testemunha (sem leguminosa). Os cafeeiros, cultivar Icatu PR 182039-1 (H4782-7-788), foram plantados em novembro de 2000, no espaçamento de 4,0m entre fileiras e 0,8m entre covas, com uma planta por cova. As leguminosas foram plantadas nas entrelinhas dos cafeeiros. As variáveis analisadas foram: fertilidade do solo e incidência de plantas invasoras nos cafezais. A Flemingia congesta foi a que melhor controlou as plantas invasoras, dado o volume de fitomassa produzida e a possibilidade de 2 cortes durante um período de doze meses, evidenciando o potencial desta leguminosa na formação de novos cafezais no Acre. Os teores de cálcio do solo e a soma de bases aumentaram quando se utilizou a Flemingia congesta. The objective of this work was to evaluate the effect of legume species on the soil fertility of and weed control of coffee plant. The experiment was carried out from November 2000 to April 2003. The experimental delineation was by randomized blocks, utilizing the legumes Stizolobium atterrimum, Cajanus cajan, Canavalia endiformis, Flemingia congesta, and the control (without legumes). The Flemingia congesta provided the best weed control, given the volume of matter produced, the possibility of two cuttings during a twelve months period. These results showed the potential of this legume in the formation of new coffee crops in Acre. The levels of calcium increased with the utilization of Flemingia congesta

Efeito de adubação verde no crescimento e produtividade do cafeeiro.

As condições edafoclimáticas do Acre, caracterizadas por altas temperaturas, grande precipitação pluviométrica e solos de baixa fertilidade natural, somada ao manejo agrícola com baixo nível de insumos, podem reduzir a produtividade e longevidade dos cafezais na região. Diante desse quadro tornam-se necessários estudos mais adequados com relação às práticas de cultivo, entre elas o consórcio de leguminosas nas entrelinhas dos cafeeiros como cobertura do solo, controle de invasoras e adubação verde. O objetivo desse trabalho foi avaliar o efeito do uso de leguminosas no crescimento e produtividade de cafeeiros no Estado do Acre. O experimento foi conduzido no período de novembro de 2000 a abril de 2003, em delineamento experimental de blocos ao acaso em esquema de parcelas subdivididas, com quatro repetições. Os tratamentos utilizados nas parcelas foram às leguminosas (Stizolobium atterrimum, Cajanus cajan, Canavalia endiformis e Flemingia congesta) e a testemunha (sem leguminosa) e, nas subparcelas, duas doses de N (0 e 22 g de N por cova). Os cafeeiros, cultivar Icatu PR 182039-1 (H4782-7-788), foram plantados em novembro de 2000, no espaçamento de 4,0m entre fileiras e 0,8m entre covas, com uma planta por cova. As leguminosas foram plantadas nas entrelinhas dos cafeeiros. As variáveis analisadas foram: altura e diâmetro da copa dos cafeeiros e produtividade, em sua primeira colheita economicamente significativa (2 anos e 5 meses após o plantio). A Flemingia congesta e a Mucuna aterrima foram as leguminosas que mais influenciaram positivamente a produtividade dos cafeeiros, independente da adubação nitrogenada. Em relação à testemunha, o aumento em produção foi de 109% quando se utilizou a Flemingia congesta e 52% com a Mucuna aterrima. A altura e diâmetro da copa dos cafeeiros foi afetada negativamente quando utilizou-se a Canavalia endiformis. The objective of this work was to evaluate the effect of legume species on the growth and yield of coffee plant. The experiment was carried out from November 2000 to April 2003. The experimental delineation was by randomized blocks in subdivided plot, utilizing the legumes Stizolobium atterrimum, Cajanus cajan, Canavalia endiformis, Flemingia congesta, and the control (without legumes) in plots, 0 and 22 g of N for each hole in the subplots. The Flemingia congesta and the Stizolobium atterrimum were the species that influenced the productivity of the coffee plants most, independently of the nitrogen fertilization. In relation to the control; this productivity was 109% greater when Flemingia congesta was used and 52% for Stizolobium atterrimum. The Flemingia congesta provided the best weed control, given the volume of matter produced, the possibility of two cuttings during a twelve months period. These results showed the potential of this legume in the formation of new coffee crops in Acre. Contradicting the practice of using Canavalia endiformis legume in the coffee crops in Acre and in other areas, this legume negatively influenced height, crown diameter and growth of the coffee plant

AVERAGE SPATIAL DISTRIBUTION OF COSMIC RAYS BEHIND THE INTERPLANETARY SHOCK-GLOBAL MUON DETECTOR NETWORK OBSERVATIONS

We analyze the galactic cosmic ray (GCR) density and its spatial gradient in Forbush Decreases (FDs) observed with the Global Muon Detector Network (GMDN) and neutron monitors (NMs). By superposing the GCR density and density gradient observed in FDs following 45 interplanetary shocks (IP-shocks), each associated with an identified eruption on the Sun, we infer the average spatial distribution of GCRs behind IP-shocks. We find two distinct modulations of GCR density in FDs, one in the magnetic sheath and the other in the coronal mass ejection (CME) behind the sheath. The density modulation in the sheath is dominant in the western flank of the shock, while the modulation in the CME ejecta stands out in the eastern flank. This east-west asymmetry is more prominent in GMDN data responding to similar to 60 GV GCRs than in NM data responding to similar to 10 GV GCRs, because of the softer rigidity spectrum of the modulation in the CME ejecta than in the sheath. The geocentric solar ecliptic-y component of the density gradient, G(y), shows a negative (positive) enhancement in FDs caused by the eastern (western) eruptions, while G(z) shows a negative (positive) enhancement in FDs caused by the northern (southern) eruptions. This implies that the GCR density minimum is located behind the central flank of IP-shocks and propagating radially outward from the location of the solar eruption. We also confirmed that the average Gz changes its sign above and below the heliospheric current sheet, in accord with the prediction of the drift model for the large-scale GCR transport in the heliosphere.ArticleASTROPHYSICAL JOURNAL. 825(2):100 (2016)journal articl