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The Euro Crisis: Three EssaysSteinkamp, Sven 19 January 2015 (has links)
This dissertation is a collection of three essays dealing with selected problems of the Euro Area during its most recent crisis. It applies empirical, theoretical, and institutional analyses to gain new insights into many of its financial aspects.
The first essay offers an alternative explanation for the surge in government bond spreads. Many researchers attribute this phenomenon to market sentiment and multiple equilibria alone. We show that an often neglected fundamental variable may drive spreads: a decrease in the expected recovery value of private market participants. With an ever-increasing share of crisis countries’ debt held by official creditors, private investors may feel pushed into the position of subordinated creditors.
The other two essays both explain the sharp increase in central bank credit from different perspectives. First, from the national perspective, central banks may be confronted with a classical tragedy-of-the-commons problem, which gives rise to an expansionary bias. Second, from the perspective of the ECB, we argue that the empirical patterns surrounding the liquidity provision in December 2011 are reminiscent of a speculative attack on a fixed exchange rate system.
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[pt] EQUILÍBRIOS DE NASH EM MERCADOS ELÉTRICOS COM FUNÇÕES DE OFERTA QUADRÁTICAS COTADAS / [en] NASH EQUILIBRIA IN POOL-BASED ELECTRICITY MARKETS WITH BOUNDED QUADRATIC SUPPLY FUNCTIONSMARCELO MORAES RESENDE 20 June 2023 (has links)
[pt] Este trabalho analisa um mercado de eletricidade em que os geradores
declaram funções de custo quadráticas para o operador da rede e também
suas disponibilidades máximas de produção. O operador, então, determina as
quantidades a serem produzidas por cada gerador de modo a atender a uma
demanda inelástica, ao menor custo possível. Estabelecem-se alguns resultados
que permitem computar os equilíbrios de Nash deste modelo e descrevem-se
algumas de suas propriedades, tais como condições de existência. / [en] This work analyzes an electricity market in which generators declare
quadratic cost functions for the grid operator and also the maximum capacity
available. The operator then determines the quantities that each generator
must produce to meet an inelastic demand at the lowest possible cost. Some
results are established that allow computing the Nash equilibria of this model
and some of their properties are described, such as existence conditions.
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Phase Stability of Iron Nitride Fe4N at High Pressure—Pressure-Dependent Evolution of Phase Equilibria in the Fe–N SystemWetzel, Marius Holger, Rabending, Tina Trixy, Friák, Martin, Všianská, Monika, Šob, Mojmír, Leineweber, Andreas 10 July 2024 (has links)
Although the general instability of the iron nitride γ′-Fe4N with respect to other phases at high pressure is well established, the actual type of phase transitions and equilibrium conditions of their occurrence are, as of yet, poorly investigated. In the present study, samples of γ′-Fe4N and mixtures of α Fe and γ′-Fe4N powders have been heat-treated at temperatures between 250 and 1000 °C and pressures between 2 and 8 GPa in a multi-anvil press, in order to investigate phase equilibria involving the γ′ phase. Samples heat-treated at high-pressure conditions, were quenched, subsequently decompressed, and then analysed ex situ. Microstructure analysis is used to derive implications on the phase transformations during the heat treatments. Further, it is confirmed that the Fe–N phases in the target composition range are quenchable. Thus, phase proportions and chemical composition of the phases, determined from ex situ X-ray diffraction data, allowed conclusions about the phase equilibria at high-pressure conditions. Further, evidence for the low-temperature eutectoid decomposition γ′→α+ε′ is presented for the first time. From the observed equilibria, a P–T projection of the univariant equilibria in the Fe-rich portion of the Fe–N system is derived, which features a quadruple point at 5 GPa and 375 °C, above which γ′-Fe4N is thermodynamically unstable. The experimental work is supplemented by ab initio calculations in order to discuss the relative phase stability and energy landscape in the Fe–N system, from the ground state to conditions accessible in the multi-anvil experiments. It is concluded that γ′-Fe4N, which is unstable with respect to other phases at 0 K (at any pressure), has to be entropically stabilised in order to occur as stable phase in the system. In view of the frequently reported metastable retention of the γ′ phase during room temperature compression experiments, energetic and kinetic aspects of the polymorphic transition γ′⇌ε′ are discussed.
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Alkyl pipéridine démixantes pour le captage du CO2 : approche thermodynamique / Demixing Alkyl piperidines for CO2 capture : A thermodynamic approachLowe, Alexander Rowland 12 December 2016 (has links)
L'augmentation de la concentration de dioxyde de carbone (CO2) dans l'atmosphère depuis la révolution industrielle a conduit à l'augmentation de la température moyenne du globe. Pour limiter l’accroissement des températures atmosphériques moyennes, la quantité de dioxyde de carbone émise dans l'atmosphère doit être réduite. Une des solutions envisagée sur les sources fixes est le captage et le stockage du CO2. Ce procédé d’absorption/désorption, bien connu dans le traitement du gaz naturel, est onéreux et peu efficace pour le traitement du gaz des sources fixes et doit être optimisé. La solution proposée s’appuie sur l’utilisation de solvants démixants, présentant une séparation de phase équilibre liquide-liquide (LLE) en solution aqueuse en fonction de la température. Ce manuscrit présente une étude réalisée pour la famille des alkyl-pipéridines connues pour ses séparations de phase. Cette étude permettra d’évaluer l’influence de la taille, de la positionet du nombre de substituants sur les propriétés thermodynamiques d’intérêt pour le procédé. Pour étudier les LLE des solutions aqueuses démixantes, en particulier dans le cas des solutions chargées en gaz, deux instruments ont été mis au point. Il a été possible de démontrer que les changements opérés sur les diagrammes de phase des amines sont liés aux réactions chimiques mises en jeu lors de la dissolution du CO2. Pour les alkyl-pipéridines tertiaire on observe la température de démixtion diminue avec l’addition de CO2, allant avec la formation de carbonates. Avec les alkyl-pipéridines secondaires la température de démixtion augmente, ce qui est lié à la présence en solution de carbamates qui stabilisent la solution aqueuse. Le comportement des amines secondaires très encombrées, qui ne peuvent donc pas formées de carbamates, est similaire à celui des amines tertiaires, ce qui est cohérent avec les conclusions précédentes. Une étude approfondies des propriétés thermodynamiques d’excès (VE, CpE et HE) des alkyl-pipéridines en solution aqueuse a également permis de démontrer des relations structure - propriétés. La position du substituant sur le cycle pipéridine a une influence considérable et prévisible sur l’intensité des propriétés d’excès, alors que la nature de l’amine (secondaire ou tertiaire) va influencer la position de l’extremum de cette propriété. Enfin, une modélisation thermodynamique rigoureuses des solubilités et des enthalpies de dissolution du CO2 dans les solutions aqueuses de pipéridines a permis de déterminer les constantes de formation des carbamates dans les solutions aqueuses de 3- et 4-méthylpipéridines. / The increase of carbon dioxide (CO2) concentration in the atmosphere, since the industrial revolution has led to the rise in the average global climate temperature. To prevent the escalation of global climate temperatures the amount of CO2 emitted into the atmosphere must be reduced. One solution is carbon capture and sequestration which removes CO2 from fixed sources. The absorption/desorption cycle is well known for the treatment of acid gas, but is expensive and not as efficient for the treatment of gas from fixed/industrial sources. A solution to this problem is the use of aqueous demixing amine solvents which present a liquid-liquid phase equilibrium (LLE) as a function of temperature. This manuscript presents a study done to measure the LLE and thermodynamic properties of the alkyl piperidine family, which can be used for carbon capture processes. This work evaluates the effect of the size, position and number of alkyl substituents on the thermodynamic properties of interest in the carbon capture process. To study the LLE of aqueous demixing solutions, particularly gas loaded solutions, two novel apparatuses were developed. The results demonstrate that the changes in the amine phase diagrams are related to the chemical reactions involved with dissolution of CO2. The tertiary alkyl piperidines displayed reduced demixing temperature with the addition of CO2 due to the formation of carbonate species. The secondary alkyl piperidines display an increasing demixing temperature which is related to the formation of carbamate species which stabilizes the solution. Secondary alkyl piperidines that are severely sterically hindered, which cannot produce carbamates, behave similarly to the tertiary amine which is coherent with the preceding conclusion. The structure property relationship concerning the excess thermodynamic properties (VE, CpE et HE) of aqueous solutions were studied in depth. This revealed that the position of the substituents on the cyclic ring has a considerable and obvious influence on the intensity of the excess properties, along with the class of the amine, whether secondary or tertiary, will influence the positions of the extrema of the excess property. To conclude, a rigorous thermodynamic model based on the CO2 solubility and the enthalpy of solution for CO2 in aqueous solutions of alkyl piperidine, allowed for the determination of the carbamate formation constants of 3- and 4-methylpiperidine.
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穩定性與多重性-以二部門體系動態調整方式為例 / Stability and indeterminacy --the dynamic adjustment of two-sector economy連科雄, Lian, Ke-Shaw Unknown Date (has links)
本篇論文試圖藉由比較一個產業生產技術為固定規模報酬的經濟體系,如何因外部因素的影響而改變其動態調整方式。在此考慮的外部因素有資本移動的開放與否、生產要素的外部性、及政府對要素報酬的課稅。考慮各種因素後,所得出的結論為在生產函數為Cobb-Douglas型式且產業生產技術為固定規模報酬的情況下:
1.多重均衡路徑在資本帳封閉時期唯有效用函數為特例時才能使其出現,但在資本自由移動時期對於所有的效用函數型態皆會成立。
2.其他條件保持不變之下,單獨存在生產要素外部性或是對要素所得課稅皆可使體系存在多重均衡路徑。
3.其他條件保持不變之下,若生產要素外部性與要素所得稅皆同時存在時,可使體系存在唯一的穩定馬鞍路徑。
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Solid-liquid Phase Equilibria and Crystallization of Disubstituted Benzene DerivativesNordström, Fredrik January 2008 (has links)
The Ph.D. project compiled in this thesis has focused on the role of the solvent in solid-liquid phase equilibria and in nucleation kinetics. Six organic substances have been selected as model compounds, viz. ortho-, meta- and para-hydroxybenzoic acid, salicylamide, meta- and para-aminobenzoic acid. The different types of crystal phases of these compounds have been explored, and their respective solid-state properties have been determined experimentally. The solubility of these crystal phases has been determined in various solvents between 10 and 50 oC. The kinetics of nucleation has been investigated for salicylamide by measuring the metastable zone width, in five different solvents under different experimental conditions. A total of 15 different crystal phases were identified among the six model compounds. Only one crystal form was found for the ortho-substituted compounds, whereas the meta-isomeric compounds crystallized as two unsolvated polymorphs. The para-substituted isomers crystallized as two unsolvated polymorphs and as several solvates in different solvents. It was discovered that the molar solubility of the different crystal phases was linked to the temperature dependence of solubility. In general, a greater molar solubility corresponds to a smaller temperature dependence of solubility. The generality of this relation for organic compounds was investigated using a test set of 41 organic solutes comprising a total of 115 solubility curves. A semi-empirical solubility model was developed based on how thermodynamic properties relate to concentration and temperature. The model was fitted to the 115 solubility curves and used to predict the temperature dependence of solubility. The model allows for entire solubility curves to be constructed in new solvents based on the melting properties of the solute and the solubility in that solvent at a single temperature. Based on the test set comprising the 115 solubility curves it was also found that the melting temperature of the solute can readily be predicted from solubility data in organic solvents. The activity of the solid phase (or ideal solubility) of four of the investigated crystal phases was determined within a rigorous thermodynamic framework, by combining experimental data at the melting temperature and solubility in different solvents and temperatures. The results show that the assumptions normally used in the literature to determine the activity of the solid phase may give rise to errors up to a factor of 12. An extensive variation in the metastable zone width of salicylamide was obtained during repeated experiments performed under identical experimental conditions. Only small or negligible effects on the onset of nucleation were observed by changing the saturation temperature or increasing the solution volume. The onset of nucleation was instead considerably influenced by different cooling rates and different solvents. A correlation was found between the supersaturation ratio at the average onset of nucleation and the viscosity of the solvent divided by the solubility of the solute. The trends suggest that an increased molecular mobility and a higher concentration of the solute reduce the metastable zone width of salicylamide. / QC 20100831
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Darstellung und Charakterisierung ternärer Molybdate in den Systemen M - Mo - O (M = Sn, Pb, Sb)Feja, Steffen 25 October 2004 (has links) (PDF)
Das Phasendiagramm Sn - Mo - O wurde für 500°C und 1000°C experimentell abgeleitet. Als ternäre Phasen konnten SnMo2O8 und Sn1-xMo4-yO6-2y dargestellt werden. Die Phasen SnMo5O8 und Sn4,4Mo24O38 konnten unterhalb von 1000°C nicht dargestellt werden. Die Phase SnMo2O8 wurde über Festkörper - Gasphasenreaktion einkristallin dargestellt und auf ihr thermisches Verhalten untersucht. Anhand dieser Untersuchungen konnte das Phasendiagramm SnO2 - MoO3 abgeleitet werden. An dieser Phase wurden Einkristall-untersuchungen durchgeführt. Die Struktur der Phase SnMo2O8 wurde in der Raumgruppe Pa (a = 8,967 Å) gelöst. Die Zinnatome besetzen die Flächen - und Kantenmitten der Elementarzelle. Die Lage der Molybdän - und Sauerstoffpositionen kann über ein Fehlordnungsmodell beschrieben werden. Die Phase Sn1-xMo4-yO6-2y konnte über chemischen Transport mit Wasser einkristallin hergestellt werden. Einkristalluntersuchungen bestätigten eine Überstruktur zur NaMo4O6 - Struktur. Die Phase weist mit hoher Wahrscheinlichkeit eine Unterstöchiometrie im Zinngehalt, sowie im Molybdän - bzw. Sauerstoffgehalt auf. Diese Tatsache konnte durch Mößbaueruntersuchungen am Pulver von Sn1-xMo4-yO6-2y bestätigt werden. Eine Lösung der Struktur von Sn1-xMo4-yO6-2y war bisher nicht möglich. Die thermodynamischen Daten der Phasen SnMo2O8 und SnMo4O6 (vereinfacht für Sn1-xMo4-yO6-2y) konnten theoretisch abgeleitet werden. Das Zustandsdiagramm Sn - Mo - O wurde berechnet. Die Überprüfung der Daten erfolgte durch die Berechnung der Bodenkörper - Gasphasengleichgewichte mit dem Programm TRAGMIN. Mit den abgeleiteten Daten wurden Berechnungen zum chemischen Transportverhalten durchgeführt. Dabei wurde gefunden, dass sich die Phase Sn1-xMo4-yO6-2y über chemischen Transport abscheiden lässt. Das Phasendiagramm Pb - Mo - O wurde bis 1000°C experimentell abgeleitet. Die Phasen PbMoO4 und Pb2MoO5 konnten als einphasige Pulver hergestellt werden. Die Phase Pb0,75Mo4O6 konnte über chemischen Transport einkristallin abgeschieden werden. Beim Erhitzen auf 1250°C wurde die Zersetzung dieser Phase in die Phase PbMo5O8 und Mo beobachtet. Die thermodynamischen Daten der Phasen PbMoO4, Pb2MoO5, Pb5MoO8 und Pb0,75Mo4O6 konnten theoretisch abgeleitet werden. Das Zustandsdiagramm Pb - Mo - O wurde berechnet. Im Verlauf der Rechnungen wurde das Zustandsdiagramm PbO - MoO3 mit dem Programm CHEMSAGE berechnet und mit den Literaturdaten verglichen. Die Überprüfung der Daten erfolgte durch die Berechnung der Bodenkörper - Gasphasengleichgewichte mit dem Programm TRAGMIN. Mit den abgeleiteten Daten wurden Berechnungen zum chemischen Transportverhalten durchgeführt. Dabei wurde gefunden, dass sich die Phase Pb0,75Mo4O6 über chemischen Transport abscheiden lässt. Das Phasendiagramm Sb - Mo - O wurde bei 500°C bzw. 700°C experimentell abgeleitet. Im System existieren die Phasen Sb2MoO6 und Sb2Mo10O31. Sb2Mo10O31 konnte einphasig als Pulver hergestellt werden. Die Existenz einer Phase mit der Zusammensetzung Sb4Mo10O31 konnte nicht bestätigt werden. Es wurden Hinweise auf eine dritte ternäre Phase im System Sb - Mo - O gefunden. Die Phasen Sb2MoO6 und Sb2Mo10O31 konnten über chemischen Transport einkristallin dargestellt werden. Mößbaueruntersuchungen an Sb2Mo10O31 ergaben, dass in der Verbindung ausschliesslich dreiwertiges Sb vorliegt und somit Mo gemischtvalent sein muss. Die thermodynamischen Daten der Phasen Sb2MoO6 und Sb2Mo10O31 konnten theoretisch abgeleitet werden. Das Zustandsdiagramm Sb - Mo - O wurde berechnet. Die Überprüfung der Daten erfolgte durch die Berechnung der Bodenkörper - Gasphasengleichgewichte mit dem Programm TRAGMIN. Mit den abgeleiteten Daten wurden Berechnungen zum chemischen Transportverhalten durchgeführt. Dabei wurde gefunden, dass sich beide ternäre Phasen über chemischen Transport abscheiden lassen.
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Structural, Kinetic and Thermodynamic Aspects of the Crystal Polymorphism of Substituted Monocyclic Aromatic CompoundsSvärd, Michael January 2011 (has links)
This work concerns the interrelationship between thermodynamic, kinetic and structural aspects of crystal polymorphism. It is both experimental and theoretical, and limited with respect to compounds to substituted monocyclic aromatics. Two polymorphs of the compound m-aminobenzoic acid have been experimentally isolated and characterized by ATR-FTIR spectroscopy, X-ray powder diffraction and optical microscopy. In addition, two polymorphs of the compound m-hydroxybenzoic acid have been isolated and characterized by ATR-FTIR spectroscopy, high-temperature XRPD, confocal Raman, hot-stage and scanning electron microscopy. For all polymorphs, melting properties and specific heat capacity have been determined calorimetrically, and the solubility in several pure solvents measured at different temperatures with a gravimetric method. The solid-state activity (ideal solubility), and the free energy, enthalpy and entropy of fusion have been determined as functions of temperature for all solid phases through a thermodynamic analysis of multiple experimental data. It is shown that m-aminobenzoic acid is an enantiotropic system, with a stability transition point determined to be located at approximately 156°C, and that the difference in free energy at room temperature between the polymorphs is considerable. It is further shown that m-hydroxybenzoic acid is a monotropic system, with minor differences in free energy, enthalpy and entropy. 1393 primary nucleation experiments have been carried out for both compounds in different series of repeatability experiments, differing with respect to solvent, cooling rate, saturation temperature and solution preparation and pre-treatment. It is found that in the vast majority of experiments, either the stable or the metastable polymorph is obtained in the pure form, and only for a few evaluated experimental conditions does one polymorph crystallize in all experiments. The fact that the polymorphic outcome of a crystallization is the result of the interplay between relative thermodynamic stability and nucleation kinetics, and that it is vital to perform multiple experiments under identical conditions when studying nucleation of polymorphic compounds, is strongly emphasized by the results of this work. The main experimental variable which in this work has been found to affect which polymorph will preferentially crystallize is the solvent. For m-aminobenzoic acid, it is shown how a significantly metastable polymorph can be obtained by choosing a solvent in which nucleation of the stable form is sufficiently obstructed. For m-hydroxybenzoic acid, nucleation of the stable polymorph is promoted in solvents where the solubility is high. It is shown how this partly can be rationalized by analysing solubility data with respect to temperature dependence. By crystallizing solutions differing only with respect to pre-treatment and which polymorph was dissolved, it is found that the immediate thermal and structural history of a solution can have a significant effect on nucleation, affecting the predisposition for overall nucleation as well as which polymorph will preferentially crystallize. A set of polymorphic crystal structures has been compiled from the Cambridge Structural Database. It is found that statistically, about 50% crystallize in the crystallographic space group P21/c. Furthermore, it is found that crystal structures of polymorphs tend to differ significantly with respect to either hydrogen bond network or molecular conformation. Molecular mechanics based Monte Carlo simulated annealing has been used to sample different potential crystal structures corresponding to minima in potential energy with respect to structural degrees of freedom, restricted to one space group, for each of the polymorphic compounds. It is found that all simulations result in very large numbers of predicted structures. About 15% of the predicted structures have excess relative lattice energies of <=10% compared to the most stable predicted structure; a limit verified to reflect maximum lattice energy differences between experimentally observed polymorphs of similar compounds. The number of predicted structures is found to correlate to molecular weight and to the number of rotatable covalent bonds. A close study of two compounds has shown that predicted structures tend to belong to different groups defined by unique hydrogen bond networks, located in well-defined regions in energy/packing space according to the close-packing principle. It is hypothesized that kinetic effects in combination with this structural segregation might affect the number of potential structures that can be realized experimentally. The experimentally determined crystal structures of several compounds have been geometry-optimized (relaxed) to the nearest potential energy minimum using ten different combinations of common potential energy functions (force fields) and techniques for assigning nucleus-centred point charges used in the electrostatic description of the energy. Changes in structural coordinates upon relaxation have been quantified, crystal lattice energies calculated and compared with experimentally determined enthalpies of sublimation, and the energy difference before and after relaxation computed and analysed. It is found that certain combinations of force fields and charge assignment techniques work reasonably well for modelling crystal structures of small aromatics, provided that proper attention is paid to electrostatic description and to how the force field was parameterized. A comparison of energy differences for randomly packed as well as experimentally determined crystal structures before and after relaxation suggests that the potential energy function for the solid state of a small organic molecule is highly undulating with many deep, narrow and steep minima. / QC 20110527
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In situ studies of uranium-plutonium mixed oxides : Influence of composition on phase equilibria and thermodynamic properties / Etudes in situ des oxydes mixtes d'uranium et de plutonium : Influence de la composition sur les équilibres de phase et les propriétés thermodynamiquesStrach, Michal 29 September 2015 (has links)
En raison de leurs propriétés chimiques et physiques, les oxydes mixtes d'uranium et de plutonium sont considérés comme combustibles pour les réacteurs nucléaires de quatrième génération. Dans ce cadre, des études expérimentales complémentaires sont nécessaire, notamment pour mieux comprendre les phénomènes mis en jeu lors de la fabrication ou sous irradiation. L'objet de ce travail est d'étudier le diagramme de phase U-Pu-O dans une large gamme de composition et de températures afin d'améliorer notre connaissance de ce système. La plupart des expériences ont été réalisées par diffraction des rayons X en fonction de la température. La contrôle in situ de la pression partielle en oxygène a permis de faire varier la stœchiométrie en oxygène dans le matériau. L'approche expérimentale a été couplée avec la modélisation thermodynamique par la méthode CALPHAD afin de mieux dimensionner les expériences et interpréter les résultats. Cette méthodologie a permis d'améliorer notre connaissance des équilibres de phase dans le système U-Pu-O. / Due to their physical and chemical properties, mixed uranium-plutonium oxides are considered for fuel in 4th generation nuclear reactors. In this frame, complementary experimental studies are necessary to develop a better understanding of the phenomena that take place during fabrication and operation in the reactor. The focus of this work was to study the U Pu–O phase diagram in a wide range of compositions and temperatures to ameliorate our knowledge of the phase equilibria in this system. Most of experiments were done using in situ X-ray diffraction at elevated temperatures. The control of the oxygen partial pressure during the treatments made it possible to change the oxygen stoichiometry of the sample, which gave us an opportunity to study rapidly different compositions and the processes involved. The experimental approach was coupled with thermodynamic modeling using the CALPHAD method, to precisely plan the experiments and interpret the obtained results. This approach enabled us to enhance the knowledge of phase equilibria in the U–Pu–O system.
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Prix d'actifs, bulles et fluctuations macroéconomiques / Asset prices, bubbles and macroeconomic fluctuationsClain-Chamosset-Yvrard, Lise 13 October 2015 (has links)
Cette thèse traite des interactions entre les sphères financière et réelle de l'économie. Elle se compose de quatre chapitres. Dans les deux premiers chapitres, nous étudions l'existence et les fluctuations d'une bulle spéculative rationnelle, comme source de la volatilité des prix d'actifs, en prenant en compte les imperfections financières dans la modélisation des choix des ménages. L'existence d'un choix de portefeuille et de frictions financières favorisent l'émergence des fluctuations d'une bulle et des cycles économiques endogènes. Dans un tel contexte, nous analysons le rôle stabilisateur des politiques fiscales et/ou monétaires. Dans le chapitre 1, nous montrons qu'une politique monétaire répondant aux prix des actifs permet de stabiliser l'économie dans son ensemble. Dans le chapitre 2, nous comparons les vertus stabilisatrices d'un impôt progressif sur le revenu de capital à celles d'une politique monétaire régie par une règle de Taylor. Nous montrons qu'un impôt progressif sur le capital permet de stabiliser l'économie en réduisant la probabilité d'apparition des fluctuations endogènes, alors qu'une règle de Taylor a des vertus stabilisatrices mitigées. Nous étudions, dans le chapitre 3, l'existence de bulles rationnelles dans une économie ouverte à deux pays et la transmission internationale de leur éclatement. L'éclatement de la bulle dans un pays se transmet nécessairement à l'autre pays. L'effet de l'éclatement peut être positif ou négatif sur l'autre pays. Dans le chapitre 4, nous analysons le rôle de l'hétérogénéité sur la dynamique des prix d'actifs et les inégalités lorsque les agents ont des préférences pour la richesse. / This thesis deals with the interplay between the financial and real sectors of the economy. This thesis consists of four chapters. In the first two chapters, we study the existence and endogenous fluctuations of rational speculative bubbles, as a source of volatility in asset prices, taking into account the financial imperfections at the household level. We argue that the existence of a portfolio choice and financial frictions promote the emergence of bubble fluctuations and endogenous business cycles. In this context, we analyze the stabilizing role of fiscal and/or monetary policies. In Chapter 1, we show that a monetary policy responding to asset prices can stabilize the economy as a whole. In Chapter 2, we compare the stabilizing virtues of a progressive taxation on capital income with those of a monetary policy managed by a Taylor rule. We show that a progressive taxation on capital may rule out endogenous fluctuations, whereas a monetary policy under a Taylor rule has a mitigated stabilizing role. In Chapter 3, we study, the existence of rational bubbles in a two-country economy, and the international transmission of their bursting. A bubble bursting in a country necessarily transmits to the othercountry. The effect of a bubble crash in one country onthe bubble issued by the other country can be positive or negative. In Chapter 4, we analyze the role of heterogeneity on the dynamics of asset prices and inequalities when economic agents have preferences for wealth. Heterogeneity in preferences, but also in income, can heighten social inequalities and increase the asset price in the long run, but also promote asset price volatility in the short run.
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