Coping with dating errors in causality estimation

We consider the problem of estimating causal influences between observed processes from time series possibly corrupted by errors in the time variable (dating errors) which are typical in palaeoclimatology, planetary science and astrophysics. "Causality ratio" based on the Wiener-Granger causality is proposed and studied for a paradigmatic class of model systems to reveal conditions under which it correctly indicates directionality of unidirectional coupling. It is argued that in the case of a priori known directionality, the causality ratio allows a characterization of dating errors and observational noise. Finally, we apply the developed approach to palaeoclimatic data and quantify the influence of solar activity on tropical Atlantic climate dynamics over the last two millennia. A stronger solar influence in the first millennium A.D. is inferred. The results also suggest a dating error of about 20 years in the solar proxy time series over the same period

Introduction to special issue: Aesthetics in mathematics

Mathematicians often appreciate the beauty and elegance of particular theorems, proofs, and definitions, attaching importance not only to the truth but also to the aesthetic merit of their work. As Henri Poincaré [1930, p. 59] put it, mathematical beauty is a ‘real aesthetic feeling that all true mathematicians recognise’. Others went further, regarding mathematical beauty as a key motivation driving the formulation of mathematical proofs and even as a criterion for choosing one proof over another. As Hermann Weyl famously and provocatively declared, ‘My work always tried to unite the true with the beautiful, but when I had to choose one or the other, I usually chose the beautiful’ (cited [Chandrasekhar, 1987, p. 52])....Talk of the beauty of mathematical theorems, proofs, and definitions may thus be commonplace

Broadband detection of squeezed vacuum: A spectrum of quantum states

We demonstrate the simultaneous quantum state reconstruction of the spectral modes of the light field emitted by a continuous wave degenerate optical parametric amplifier. The scheme is based on broadband measurement of the quantum fluctuations of the electric field quadratures and subsequent Fourier decomposition into spectral intervals. Applying the standard reconstruction algorithms to each bandwidth-limited quantum trajectory, a "spectrum" of density matrices and Wigner functions is obtained. The recorded states show a smooth transition from the squeezed vacuum to a vacuum state. In the time domain we evaluated the first order correlation function of the squeezed output field, showing good agreement with the theory.Comment: 11 pages, 5 figure

O RURAL DE ECONOMIA NÃO-AGRÍCOLA: ASPECTOS ANTROPOLÓGICOS DE MINAS DO CAMAQUÃ

Os projetos de intervenção buscam alavancar alternativas que tenham como ponto de partida alocar os recursos das unidades produtivas em prol do desenvolvimento das localidades rurais. Para a formulação desses projetos, os técnicos precisam conhecer exaustivamente o local a ser trabalhado, para isso, é imprescindível que seja lançado também um olhar antropológico acerca da população que compõem a localidade estudada. Nesse sentido, o presente trabalho teve como objetivo identificar, por meio de uma pesquisa de campo, os aspectos antropológicos (o homem e sua história, ciclos de ocupação, crenças, tradições, mitos, religião) da população de Minas do Camaquã, distrito de Caçapava do Sul no estado do Rio Grande do Sul. A metodologia empregada na pesquisa constituiu-se basicamente de entrevistas semi-estruturadas com moradores locais. A escolha do local para a realização do trabalho deu-se, especialmente, pela peculiaridade da região, visto que se trata de um espaço no meio rural onde a economia predominante decorre das atividades de mineração, não tendo qualquer relação determinante no âmbito econômico com práticas agrícolas. Dentre os resultados obtidos com a pesquisa, destaca-se o sentimento de paternalismo da população local que não se sente responsável pelo local que vive, não existe um sentimento de pertença por parte dessas pessoas. Em seguida, formulou-se recomendações com a pretensão de contribuir para o desenvolvimento rural da localidade como um todo, na perspectiva da participação da população enquanto agentes de desenvolvimento.---------------------------------------------The projects of intervention search to lever alternatives that have as starting point to place the resources of the productive unities on behalf of rural localities development. For the formulation of these projects, the technician has to know thoroughly the place to be worked, for this, it is indispensable to be also cast an anthropological look concerning to the population that consists the studied locality. In this way, the present work had as objective to identify, through a field research, the anthropological aspects ( man and his history, cycles of occupation, beliefs, traditions, myths, religion) of the population from Minas do Camaquã, district of Caçapava do Sul in the state of Rio Grande do Sul. The methodology used in the research constitute basically a semi-structured interview with local residents. The choice of the place for the work carrying out was done, specially, because of the peculiarity of the region, since it is concerned to a space in the rural circle where the predominant economy comes from mining activities, having no determiner relation in economic scope with agricultural practices. Among the results obtained by the research, stands out the paternalism feeling of the local population that don’t feel themselves responsible of the place that they live, there is no feeling of belonging concerned to these people. Next, there were formulated recommendations with the pretension of contributing for the rural development as a whole, in the perspective of the population participation while agents of development.Desenvolvimento rural, aspectos antropológicos, mineração, Rural development, anthropological aspects, mining, Crop Production/Industries,

Nitrous oxide water column distribution during the transition from anoxic to oxic conditions in the Baltic Sea

International audienceIn January 2003, a major inflow of cold and oxygen-rich North Sea Water in the Baltic Sea terminated an ongoing stagnation period in parts of the central Baltic Sea. In order to investigate the role of North Sea Water inflow to the Baltic Sea with regard to the production of nitrous oxide (N2O), we measured dissolved and atmospheric N2O at 26 stations in the southern and central Baltic Sea in October 2003. At the time of our cruise, water renewal had proceeded to the eastern Gotland Basin, whereas the western Gotland Basin was still unaffected by the inflow. The deep water renewal was detectable in the distributions of temperature, salinity, and oxygen concentrations as well as in the distribution of the N2O concentrations: Shallow stations in the Kiel Bight and Pomeranian Bight were well-ventilated with uniform N2O concentrations near equilibrium throughout the water column. In contrast, stations in the deep basins, such as the Bornholm and the Gotland Deep, showed a clear stratification with deep water affected by North Sea Water. Inflowing North Sea Water led to changed environmental conditions, especially enhanced oxygen (O2) or declining hydrogen sulfide (H2S) concentrations, thus, affecting the conditions for the production of N2O. Pattern of N2O profiles and correlations with parameters like oxygen and nitrate differed between the basins. The dominant production pathway seems to be nitrification rather than denitrification. No indications for advection of N2O by North Sea Water were found. A rough budget revealed a significant surplus of in situ produced N2O after the inflow. However, due to the permanent halocline, it can be assumed that the formed N2O does not reach the atmosphere. Hydrographic aspects therefore are decisive factors determining the final release of produced N2O to the atmosphere

Nitrous oxide in the North Atlantic Ocean

In order to get a comprehensive picture of the distribution of nitrous oxide (N2O) in the North Atlantic Ocean, measurements of dissolved nitrous oxide were made during three cruises in the tropical, subtropical and cold-temperate North Atlantic Ocean in October/November 2002, March/April 2004, and May 2002, respectively. To account for the history of atmospheric N2O, we suggest a new depth-dependent calculation of excess N2O (ΔN2O). N2O depth profiles showed supersaturation throughout the water column with a distinct increasing trend from the cold-temperate to the tropical region. Lowest nitrous oxide concentrations, near equilibrium and with an average of 11.0±1.7 nmol L−1, were found in the cold-temperate North Atlantic where the profiles showed no clear maxima. Highest values up to 37.3 nmol L−1 occurred in the tropical North Atlantic with clear maxima at approximately 400 m. A positive correlation of nitrous oxide with nitrate, as well as excess nitrous oxide with the apparent oxygen utilization (AOU), was only observed in the subtropical and tropical regions. Therefore, we conclude that the formation of nitrous oxide via nitrification occurs in the tropical region rather than in the cold-temperate region of the North Atlantic Ocea

Distribution of N₂O in the Baltic Sea during transition from anoxic to oxic conditions

In January 2003, a major inflow of cold and oxygen-rich North Sea Water terminated an ongoing stagnation period in parts of the central Baltic Sea. In order to investigate the role of North Sea Water inflow in the production of nitrous oxide (N2O), we measured dissolved and atmospheric N<2O at 26 stations in the southern and central Baltic Sea in October 2003. At the time of our cruise, water renewal had proceeded to the eastern Gotland Basin, whereas the western Gotland Basin was still unaffected by the inflow. The deep water renewal was detectable in the distributions of temperature, salinity, and oxygen concentrations as well as in the distribution of the N2O concentrations: Shallow stations in the Kiel Bight and Pomeranian Bight were well-ventilated with uniform N2O concentrations near equilibrium throughout the water column. In contrast, stations in the deep basins, such as the Bornholm and the Gotland Deep, showed a clear stratification with deep water affected by North Sea Water. Inflowing North Sea Water led to changed environmental conditions, especially enhanced oxygen (O2) or declining hydrogen sulphide (H2S) concentrations, thus, affecting the conditions for the production of N2O. Pattern of N2O profiles and correlations with parameters like oxygen and nitrate differed between the basins. Because of the positive correlation between ΔN2O and AOU in oxic waters the dominant production pathway seems to be nitrification rather than denitrification. Advection of N2O by North Sea Water was found to be of minor importance. A rough budget revealed a significant surplus of in situ produced N2O after the inflow. However, due to the permanent halocline, it can be assumed that the N2O produced does not reach the atmosphere. Hydrographic aspects therefore are decisive factors determining the final release of N2O produced to the atmosphere

Measuring quantum optical Hamiltonians

We show how recent state-reconstruction techniques can be used to determine the Hamiltonian of an optical device that evolves the quantum state of radiation. A simple experimental setup is proposed for measuring the Liouvillian of phase-insensitive devices. The feasibility of the method with current technology is demonstrated on the basis of Monte Carlo simulated experiments.Comment: Accepted for publication on Phys. Rev. Lett. 8 eps figures, 4 two-column pages in REVTE