1,524 research outputs found
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.
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
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
Petrological and experimental study of CV-CK chondrites and conditions of metamorphism in carbonaceous asteroids
No full textLes chondrites carbonées (CCs) sont des objets primitifs accrétés lors de la formation du Système Solaire. Composées en grande partie de chondres, de matrice et d’inclusions réfractaires, elles ont enregistré les hétérogénéités chimiques, isotopiques et minéralogiques de la nébuleuse solaire. Contrairement aux autres classes de chondrites, la grande majorité des CCs sont primitives (types pétrologiques 1 à 3). Elles n’ont donc pas subi de métamorphisme important sur leur corps parent. Toutefois, un groupe de CCs, les CKs, montre un métamorphisme thermique intense (types pétrologiques 4 à 6). Ces chondrites sont caractérisées par des matrices recristallisées, des olivines équilibrées à ∼Fa31, un degré d’oxydation important (olivines riches en NiO, rapport métal/magnétite proche de zéro), des teneurs en éléments réfractaires lithophiles intermédiaires aux CVs et aux COs, ou encore des compositions isotopiques en oxygène se situant dans le champ défini par les CVs et les COs. Les CKs ont été peu étudiées jusqu’au début des années 90, car peu nombreuses (seulement 210 classifiées au 6 décembre 2011) et de petite taille (masse médiane ∼33,5g). Leurs compositions isotopiques et chimiques laissent supposer l’existence d’un lien génétique avec les CV3. Les découvertes récentes de nouvelles CKs depuis 1990, et notamment de CK3 par le biais de collectes systématiques au Sahara et en Antarctique, permettent l’étude détaillée de l’évolution métamorphique des CKs, notamment à la transition 3–4. Ce travail a pour but de caractériser les conditions dans lesquelles s’est déroulé cet épisode métamorphique, et grâce à l’observation de plusieurs CK3–4, d’étudier la relation CV-CK. La caractérisation détaillée de l’évolution métamorphique de 19 CKs dont 5 CK3 a permis de confirmer que les différences observées entre les divers composants chondritiques (abondance, minéralogie, texture) des CVs et des CKs peuvent être expliquées par un épisode thermique secondaire de HT-BP (∼300–650°C) en conditions oxydantes (∼NNO). De plus, l’analyse de profils de diffusions dans les chondres des CKs indique des durées de métamorphisme intermédiaires à celles communément invoquées pour du choc (de quelques secondes à quelques jours) et pour la désintégration d’éléments à courte durée de vie (plusieurs millions d’années). Une série d’expériences réalisées en four 1 atmosphère avec contrôle de la fugacité d’oxygène nous a permis de reproduire les textures caractéristiques des CKs et d’obtenir une teneur en fer d’équilibre des olivines des CVs, valeur proche de celle mesurée dans les CKs. Cela semble donc confirmer que les CKs sont des CVs rééquilibrées. Par conséquent, la classification actuelle de ces chondrites en deux groupes distincts devrait être modifiée afin de rendre compte de l’existence de cette série métamorphique CV-CK continue. Nous proposons de considérer le chauffage radiatif comme cause possible du métamorphisme des CKs. Un modèle numérique nous a permis de confirmer que des météoroïdes carbonés avec des périhélies situés entre 0,07 et 0,15 UA peuvent être chauffés à des températures pouvant aller jusqu’à 780°C. Les tailles pré-atmosphériques estimées pour les CV-CK (de quelques centimètres à 2,5 mètres) sont compatibles avec ce type de processus. La fragmentation d’un corps parent homogène de type CV (possiblement l’astéroïde à l’origine de la famille d’Eos) pourrait former des météoroïdes qui, sous l’effet de phénomènes de résonances, seraient redirigés vers l’intérieur du Système Solaire et pourraient ainsi être métamorphisés par chauffage radiatif. Ce type de processus thermique secondaire n’étant efficace que pour de petits fragments d’astéroïdes, il ne doit pas être considéré comme un processus corps-parent stricto sensu.Carbonaceous chondrites (CCs) are primitive objects accreted during the earliest stage of the Solar System formation. Mainly composed of chondrules, matrix and refractory inclusions, CCs recorded chemical, isotopic and mineralogical heterogeneities of the solar nebula. Unlike other chondrite classes, most CCs are primitive (petrologic types 1 to 3), i.e., they have not been affected by thermal parent-body processes. However, CK chondrites suffered an intense metamorphism (petrologic types 4 to 6). The CK group is characterized by recrystallized matrices, equilibrated olivines (∼Fa31), a high level of oxidation (Ni-rich olivines, metal/magnetite ratio close to zero), low contents of refractory inclusions, refractory lithophile abundances intermediate between CV and CO groups, and oxygen isotope compositions overlapping the CV and CO groups. CKs have been poorly studied until the 1990’s, in part due to the small number of classified samples (210 as of December 6th, 2011), and their small masses (median mass∼33.5g). Isotopic and major element compositions support a genetic link with CV3s. Since1990, recent discoveries of CKs, in particular of CK3s recovered by systematic Antarctic and Saharan collects, allow a detailed study of the CK metamorphic evolution, especially at the 3–4 transition. The objective of this study is the characterization of the conditions of metamorphism of CKs, and through analyses of several CK3–4 samples, the study of the CV-CK relationship. The detailed characterization of the metamorphic evolution of 19 CKs, including 5 CK3, confirms that observed differences between chondritic components in CVs and CKs (abundance, mineralogy, texture) can be explained by a secondary HT-BP thermal process (∼300–650°C) under oxidizing conditions (∼NNO). Moreover, durations of metamorphism obtained by the analysis of diffusion profiles in CK chondrules are intermediate between those commonly admitted for shock (few seconds to several days) and for short-lived radionuclides decay (several million years). An experimental study, using a 1-atmosphere furnace with controlled oxygen fugacity, provides additional arguments for the CV-CK relationship. We reproduced characteristic CK textures and obtained olivine iron contents of equilibrated CVs close to those measured in CKs. These experiments confirm that CKs can be considered as reequilibrated CVs. Thus, the current classification of CVs and CKs in two distinct groups should be modified in order to account for the existence of the CV-CK continuous metamorphic series from type 3 to 6. We propose to consider radiative heating as a possible cause of metamorphism for CKs. Numerical thermal modeling indicates that carbonaceous meteoroids with low perihelia (between 0.07 and 0.15 AU) can be heated at temperatures up to 780°C. Pre-atmospheric sizes estimated for CVs and CKs (from a few centimeters to 2.5 meters) support this thermal process. Fragmentation of an homogeneous CV-type parent body (possibly the parent asteroid at the origin of the Eos family) could be the source of meteoroids which, due to resonances, move toward the Sun and thus be metamorphosed by radiative heating. This secondary thermal process, affecting only small asteroid fragments, should not be considered as a parent-body process in the sense that it did not occur on the asteroid before its disruption
Processing of refractory species in the vicinity of rocklines
No full textInternational audienceIn our solar system, meteoritical matter exhibits a variety in bulk compositions that is representative of the processing history of refractory matter in the protosolar nebula (PSN). This history is usually investigated via a thermodynamic approach, where refractory grains condense out from a hot cloud. However, in the innermost regions of the PSN the migration timescale of grains can exceed the evaporation timescale of refractory species.We investigate the role played by rocklines (condensation/sublimation lines of refractory materials) in the innermost regions of the PSN to compute the composition of drifting and evaporating grains. To do so, we compute the evolution of the PSN using a 1D viscous accretion disk model [1]. The disk is initially filled with dust that is a mixture of several refractory species of protosolar composition. This dust exists in the form of refractory grains and their vapors. The radial transport of grains is computed by solving an advection-diffusion equation, and phase transitions are accounted for by computing sublimation and condensation rates for each species. We then compare the composition of the PSN computed by our model with the composition of meteoritical bodies collected on Earth.We find that the compositional gradient in the PSN that is created by rocklines, shown in Figures 1 and 2, matches the composition of cosmic spherules, chondrules, and chondrites. Moreover, our model shows that solid matter is concentrated in the vicinity of these sublimation/condensation fronts. Although our model only focuses on the most abundant refractory species (olivine, represented in our model by its end members forsterite and fayalite; enstatite and ferrosilite pyroxenes; kamacite and taenite metal; and iron sulfide), it suggests that rocklines heavily processed refractory matter in the PSN, which has important consequences for the composition of small and large bodies in the innermost regions of the solar system. The local increase of the iron abundance close to rocklines of iron alloys could have contributed to the high Fe-content in Mercury.Figure 1. Composition profiles of the PSN in a Mg-Fe-Si ternary diagram (expressed in mass fraction) at different times, with composition of glass cosmic spherules (S-V type), barred olivine spherules (S-BO type), porphyritic spherules (S-P type) and C-chondrules. Protosolar and Earth's compositions are represented by Sun's and Earth's symbols, respectively, and Mercury's composition is represented by a red circle. Figure 2. Same as Figure 1, but here the Fe wt% is represented as a function of heliocentric distance. Color boxes correspond to typical compositions of chondrules (0%-10%), glass cosmic spherules (10%-30%), and porphyritic and barred olivine cosmic spherules (30%-60%). [1] Aguichine, A., Mousis, O., Devouard, B., and Ronnet, T. 2020, ApJ, 901, 97
Aqueous alteration of meteorites : a proxy of water circulation on extraterrestrial bodies
No full textLes différentes météorites échantillonnent à la fois les astéroïdes de la ceinture principale et aussi la planète Mars, possédant tous une histoire géologique intense et complexe. Cette thèse tente de décrypter une partie de cette histoire, l’altération aqueuse. En premier lieu, elle étudie les produits formés par l’altération aqueuse sur les astéroïdes primitifs par l’analyse de leurs fragments, les chondrites « primitives ». La comparaison de plusieurs techniques employées pour l’étude des phases secondaires a mis en évidence une méthodologie idéale pour l’étude des météorites peu altérés. Afin d’interpréter les analyses des météorites et de leurs processus secondaires dans le contexte du système solaire, nous proposons de nouveaux liens météorites-astéroïdes grâce à la comparaison de spectres infrarouges de chondrites non groupées et des différentes classes d’astéroïdes. Finalement, l’étude des météorites martiennes, les nakhlites, apporte des contraintes sur la composition des produits d’altération aqueuse martiens et donne accès aux conditions d’altération aqueuse sur la planète MarsThe various meteorites sample both the asteroids of the main belt and also the planet Mars, all showing an intense and complex geological history. This thesis attempts to untangle a part of this story, the aqueous alteration. First, this thesis studies the aqueous alteration products formed on primitive asteroids by analyzing their fragments, the "primitive" chondrites. The comparison of several techniques used for the study of secondary phases revealed an ideal methodology for the study of lightly altered meteorites. In order to interpret the analyzes of meteorites and their secondary processes in the context of the solar system, we propose new meteorite-asteroid links through the comparison of infrared spectra of ungrouped chondrites with different classes of asteroids. Finally, the study of Martian meteorites, the nakhlites, gives constraints on the composition of Martian aqueous alteration products and provides access to the aqueous weathering conditions on the planet Mar
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
Cournot and Bertrand in shipping models with circular markets
No full textWe investigate two shipping (delivered pricing) duopoly models with circular markets, Cournot and Bertrand. In the Cournot model, maximal distance between two firms becomes the unique equilibrium outcome if transport cost is increasing with distance, irrespective of whether the transport cost function is convex or concave. This result is robust in the sense that cost heterogeneity between two firms does not change the result. In contrast to the Cournot model, this location pattern can fail to be an equilibrium in the Bertrand model. Copyright (c) 2006 the author(s). Journal compilation (c) 2006 RSAI.
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