1,586 research outputs found
A new TiO line list
No full textA new line list for 9 electronic transitions of TiO (alpha, beta, gamma, gamma', delta, epsilon, phi, a-f, and E-B) is presented and made publicly available. It is the latest and much improved version of a suite of TiO line lists inaugurated in Plez et al</p
Some forgotten equilibria of the Bertrand duopoly!?
No full textThis note analyzes the Bertrand duopoly with constant but asymmetric marginal costs on a market with homogenous products. It is shown that there exist some equilibria that are ignored in the literature on IO. In addition, in this setting (perfectly or nearly perfectly) competitive equilibria exist.
Model atmospheres broad-band colors, bolometric corrections and temperature calibrations for O-M stars
No full textBroad band colors and bolometric corrections in the Johnson-Cousins-Glass system (Bessell, 1990; Bessell & Brett, 1988) have been computed from synthetic spectra from new model atmospheres of Kurucz (1995a), Castelli (1997), Plez, Brett & Nordlund (1992),</p
Heterogeneous Behavioral Rules in the Oligopolistic Case
No full textIn a static symmetric duopoly the set of behavioral rules is extended to different types of markup pricing. Using an equilibrium concept suggested in Pasche (2001), it is shown that dependend on the markup neither pure Cournot nor pure Bertrand behavior is a behavioral equilibrium profile. Instead, there is a rationale for the usage of simple heuristics. The presence of markup rules leads to Stackelberg outcomes. Furthermore, pure markup behavior is more competitive than in Cournot case but less competitive than in Bertrand case. It is shown, that multiple behavioral equilibria and heterogeneous behavior may arise, where at least one player uses price setting strategies.oligopoly, markup rules, heterogeneity, behavioral equilibrium.
A Bertrand-Edgeworth-oligopóliumok (Bertrand-Edgeworth oligopolies – a survey of the literature)
No full textAz irodalomban az olyan oligopolmodellek, amelyekben mind az ár, mind a mennyiség döntési változó, Bertrand-Edgeworth-oligopóliumok néven ismertek. E tanulmányban a Bertrand-Edgeworth-oligopóliumokkal kapcsolatos érdekesebb eredményeket tekintjük át. Tárgyaljuk a Bertrand-Edgeworth-típusú oligopolmodellek specifikációját, a Nash-egyensúly létezését, a Nash-egyensúly meghatározását és a Bertrand-Edgeworth-oligopóliumok alkalmazásait. / === / Oligopoly models in which both price and quantity are decisive variables are known in the literature as Bertrand-Edgeworth oligopolies, the most interesting results with which are surveyed in this paper. The author assumes the existence of the Nash equilibrium, as the specification of Bertrand-Edgeworth-type oligopoly models, the determination of the Nash equilibrium, and the application of Bertrand-Edgeworth oligopolies
Data used for the spatio-temporal analysis of the climatic debt observed in understory plant communities
No full textDetails about the variables' computation and definition are provided in Bertrand 2018 and Bertrand et al. 2016. References: Bertrand, R.et al. (2016) Ecological constraints increase the climatic debt in forests. Nature communications 7: 12643. Bertrand, R. (2018) Unequal contributions of species’ persistence and migration on plant communities’ response to climate warming throughout forests. Ecography. Accepted Author Manuscript
Cool star model atmospheres for Gaia : ATLAS, MARCS, and PHOENIX
No full textInternational audienceI present the widely used model atmosphere codes ATLAS, MARCS, and PHOENIX, and I compare their output model structures and spectra for cool stars of FGKM-types. While model atmosphere stratifications agree closely with each other in the f-D approximation, this is not the case for spectra. Differences between model spectra from different codes are largest in the blue-UV, but smaller differences appear in all regions, especially in the molecular features of cooler model spectra. I recommend the groups to try to solve these discrepancies together. In the meantime, users must be careful when using these spectra in regimes where they differ. I discuss here only comparisons of spectra at solar metallicity, and this should be extended to other metallicities. Detailed comparisons with carefully calibrated spectrophotometric data, and high resolution spectra for stars with well known parameters are also of prime importance. It appears that we still need better line positions for molecules. Finally we should remember that f-D models are only a step towards a better representation of reality, and we should keep developing, and carefully test 3-D, NLTE models
Le origini del liberalsocialismo di Bertrand Russell
No full textIl saggio prende in esame le origini del liberalsocialismo di Bertrand Russell. Afferma che tutte le tesi maggiori dell'autore inglese sono presenti nelle prime opere politiche che pubblica.The essay deals with the origins of the liberal socialism of Bertrand Russell. The thesis is that all major ideas of the english author are present in first political books he publish
Non-LTE iron abundance determination in cool stars : the role of hydrogen collisions
No full textLa détermination d'abondances stellaires très précises a toujours été et reste un point clé de toute analyse spectroscopique.Cependant, de nombreuses études ont montré que l'hypothèse de l'équilibre thermodynamique local (ETL), largement utilisée dans les analyses spectroscopiques est inadéquate pour déterminer les abondances et les paramètres stellaires des étoiles géantes et pauvres en métaux où les effets hors-ETL dominent. C'est pourquoi, une modélisation hors-ETL des spectres stellaires est cruciale afin de reproduire les observations et ainsi déterminer avec précision les paramètres stellaires.Cette modélisation hors-ETL nécessite l'utilisation d'un grand jeu de données atomiques, qui ne sont pas toujours connues avec certitude. Dans les étoiles froides, les taux de collisions de l'atome d'hydrogène sont une des principales sources d'incertitudes. Ces taux sont souvent calculés en considérant une approche classique (l'approximation de Drawin) pour les transitions permises lié-lié et les transitions d'ionisations. Cette approche classique tend à surestimer les taux de collisions et ne reproduit pas correctement le comportement avec les énergies.Dans cette thèse, nous démontrons que l'approximation de Drawin ne peut pas décrire les taux de collisions dans le cas de l'atome d'hydrogène. Nous présentons une nouvelle méthode pour estimer ces taux, par le biais d'ajustement sur des taux quantiques existant pour d'autres éléments.Nous montrons que cette méthode d'ajustement quantique (MAQ) est satisfaisante pour les modélisations hors-ETL lorsque les taux quantiques dédiés ne sont pas effectivement disponibles.Nous testons cette nouvelle méthode, avec le modèle d'atome de Fer que nous avons développé, sur des étoiles de référence issues « du Gaia-ESO survey ».En partant de paramètres photosphériques non-spectroscopiques connus, nous déterminons les abondances (1D) en fer de ces étoiles de référence dans les cas ETL et hors-ETL .Nos résultats dans le cas hors ETL conduisent à un excellent accord entre les abondances de FeI et FeII avec de faibles écarts types de raies à raies, particulièrement dans le cas des étoiles pauvres en métaux.Notre méthode est validée par comparaison avec de nouveaux calculs quantiques préliminaires sur l'atome de Fe I et d'hydrogène, dont les ajustements sont en excellent accord avec les nôtres.Determination of high precision abundances has and will always be an important goal of all spectroscopic studies. The use of LTE assumption in spectroscopic analyses has been extensively shown in the literature to badly affect the determined abundances and stellar parameters, especially in metal-poor and giant stars which can be subject to large non-LTE effects. Non-LTE modeling of stellar spectra is therefore essential to accurately reproduce the observations and derive stellar abundances. Non-LTE calculations require the inputof a bulk of atomic data, which may be subject to uncertainties. In cool stars, hydrogen collisional rates are a major source of uncertainty, which are often approximated using a classical recipe (the Drawin approximation) for allowed bound-bound, and ionization transitions only. This approximation has been shown to overestimate the collisional rates, and does not reproduce the correct behavior with energies. We demonstrate in this dissertation the inability of the Drawin approximation to describe the hydrogen collisional rates.We introduce a new method to estimate these rates based on fitting the existing quantum rates of other elements. We show that this quantum fitting method (QFM) performs well in non-LTE calculations when detailed quantum rates are not available. We test the newly proposed method, with a complete iron model atom that we developed, on a reference set of stars from the Gaia-ESO survey. Starting from well determined non-spectroscopic atmospheric parameters, we determine 1D, non-LTE, and LTE iron abundances for this set ofstars. Our non-LTE results show excellent agreement between Fe I and Fe II abundances and small line-by-line dispersions, especially for the metal-poor stars. Our method is validated upon comparison with new preliminary Fe I+H quantum calculations, whose fits show an excellent agreement with ours
Bertrand Russell y el pragmatismo
No full textThis paper analyzes the two stages of the relationship of the British philosopher Bertrand Russell withpragmatism. The first section reviews the criticisms that the author made to American pragmatists.The second exposes Russell’s pragmatic turn, exposing the causes of this turn and its consequences. This paper argues that both stages should be understood in the context of the discussions about truth that were observed in philosophy in the first decades of the 20th century
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