842 research outputs found

    Isomorphism theorem for BSS recursively enumerable sets over real closed fields

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    AbstractThe main result of this paper lies in the framework of BSS computability: it shows roughly that any recursively enumerable set S in RN, N⩽∞, where R is a real closed field, is isomorphic to RdimS by a bijection ϕ which is decidable over S. Moreover the map S↦ϕ is computable. Some related matters are also considered like characterization of the real closed fields with a r.e. set of infinitesimals, and the dimension of r.e. sets

    Forecasting Inflation using Economic Indicators: the Case of France

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    In order to provide short run forecasts of headline and core HICP inflation for France, we assess the forecasting performance of a large set of economic indicators, individually and jointly, as well as using dynamic factor models. We run out-of-sample forecasts implementing the Stock and Watson (1999) methodology. It turns out that, according to usual statistical criteria, the combination of several indicators -in particular those derived from surveys- provides better results than dynamic factor models, even after pre-selection of the variables included in the panel. However, factors included in VAR models exhibit more stable forecasting performance over time. Results for HICP excluding unprocessed food and energy are very encouraging. Moreover, we show that it is possible to use forecasts on this indicator to project overall inflation.Inflation ; Out-of-sample forecast ; Indicator models ; Dynamic factor models ; Phillips curve.

    A model of the physical properties of comet Encke

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    The available observational data on periodic comet Encke were collected and interpreted in order to construct a model of the comet. The model is intended for use in the design of scientific experiments and spacecraft systems to be used on future missions to Encke. Numerical values and ranges of uncertainty are given for all of the important structural, compositional, and photometric parameters with references to the original research from which these were calculated or estimated

    Hot methane line lists for exoplanet and brown dwarf atmospheres

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    We present comprehensive experimental line lists of methane (CH4) at high temperatures obtained by recording Fourier transform infrared emission spectra. Calibrated line lists are presented for the temperatures 300 - 1400 degC at twelve 100 degC intervals spanning the 960 - 5000 cm-1 (2.0 - 10.4 microns) region of the infrared. This range encompasses the dyad, pentad and octad regions, i.e., all fundamental vibrational modes along with a number of combination, overtone and hot bands. Using our CH4 spectra, we have estimated empirical lower state energies (Elow in cm-1) and our values have been incorporated into the line lists along with line positions (cm-1) and calibrated line intensities (S' in cm molecule-1). We expect our hot CH4 line lists to find direct application in the modeling of planetary atmospheres and brown dwarfs.Comment: Supplementary material is provided via the Astrophysical Journal referenc
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