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In dieser Arbeit untersuchen wir die Struktur von Gausschen Prozessen, die durch gewisse lineare Transformationen von zwei Gausschen Martingalen erzeugt werden. Die Klasse dieser Transformationen ist durch nanzmathematische Gleichgewichtsmodelle mit heterogener Information motiviert. In Kapital 2 bestimmen wir für solche Prozesse, die zunächst in einer erweiterten Filtrierung konstruiert werden, die kanonische Zerlegung als Semimartin-gale in ihrer eigenen Filtrierung. Die resultierende Drift wird durch Volterra-Kerne beschrieben. Insbesondere charakterisieren wir diejenigen Prozesse, die in ihrer eigenen Filtrierung eine Brownsche Bewegung bilden. In Kapital 3 konstruieren wir neue orthogonale Zerlegungen der Brownschen Filtrierungen. In den Kapitaln 4 bis 6 wenden wir unsere Resultate zur Charakterisierung Brownscher Bewegungen im Kontext nanzmathematischer Modelle an, in denen es Marktteilnehmer mit zusätzlicher Insider-Information gibt. Wir untersuchen Erweiterungen eines Gleichgewichtsmodells von Kyle [42] und Back [7], in denen die Insider-Information in verschiedener Weise durch Gaussche Martingale spezifiziert wird. Insbesondere klären wir die Struktur von Insider-Strategien, die insofern unaufallig bleiben, als sich die resultierende Gesamtnachfrage wie eine Brownsche Bewegung verhält. / In this thesis, we study Gaussian processes generated by certain linear transformations of two Gaussian martingales. This class of transformations is motivated by nancial equilibrium models with heterogeneous information. In Chapter 2 we derive the canonical decomposition of such processes, which are constructed in an enlarged ltration, as semimartingales in their own ltration. The resulting drift is described in terms of Volterra kernels. In particular we characterize those processes which are Brownian motions in their own ltration. In Chapter 3 we construct new orthogonal decompositions of Brownian ltrations. In Chapters 4 to 6 we are concerned with applications of our characterization results in the context of mathematical models of insider trading. We analyze extensions of the nancial equilibrium model of Kyle [42] and Back [7] where the Gaussian martingale describing the insider information is specified in various ways. In particular we discuss the structure of insider strategies which remain inconspicuous in the sense that the resulting cumulative demand is again a Brownian motion.

Questa tesi è una raccolta di tre articoli riguardanti l’economia dell’informazione. Il primo articolo riguarda i possibili effetti negativi delle elezioni sul benessere degli elettori. Infatti, il controllo ottimo nei confronti di un politico dipende in modo non banale dalla relazione tra effetto disciplinante, effetto di selezione e effetto di riduzione della rendita. Il risultato è che un eccessivo controllo nei confronti di un politico può ridurre il benessere sociale. Il secondo articolo analizza un modello di competizione elettorale nel quale l’abilità del politico è sconosciuta anche al politico stesso oltre che agli elettori. L’analisi è in tempo continuo e sviluppata mediante tecniche di programmazione dinamica e di filtraggio. Le credenze sull’abilità vengono aggiornate secondo la regola di Bayes tramite l’osservazione del processo diffusivo che descrive il valore del settore pubblico. Il politico trae utilità da una rendita che è però inferiore in presenza di una scadenza elettorale. Il terzo articolo descrive una relazione principale-agente in tempo continuo dove l’output è rappresentato da un processo diffusivo il cui drift è determinato dallo sforzo dell’agente, che il principale non osserva, e dall’abilità dell’agente, che non è osservata nemmeno dall’agente stesso. Vengono analizzati sia gli incentivi espliciti dati dal contratto che gli incentivi impliciti legati ai career-concerns. L’analisi è sviluppata in tempo continuo; vengono applicate tecniche di programmazione dinamica e di filtraggio. / This thesis is a collection of three essays about information economics. The first essay studies the possible negative effects of elections on voters’ welfare. In fact, the optimal control of politicians depends on the interplay of disciplining, selection and rent-shrinking effects in a non-trivial way. We show that too much control on the politician may reduce social welfare. The second essay studies an agency model of electoral competition where the incumbent’s ability is unknown to the voters as well as to the politician herself. The analysis is developed in a continuous-time stochastic framework using dynamic programming techniques. Competence is unobservable to everyone and learned over time in a Bayesian fashion through the observation of the value of the public sector. Politicians can divert resources being in office thus reducing the economy wealth but this rent is lower (all other things the same) with an electoral constraint. The third essay describes a continuous-time principal-agent model in which the output is a diffusion process whose drift is determined by the agent’s unobserved effort and by manager’s competence (it is assumed symmetric information about it). We study separately both explicit incentives arising from the contract and implicit incentives arising from career concerns.. All the analysis is developed in a continuous-time stochastic framework; we apply dynamic programming and filtering techniques.

Dans nos travaux, nous avons considéré un processus de Lévy X avec une composante brownienne non nulle et dont la partie à sauts est un processus de Poisson composé. Nous avons supposé que la valeur d'une entreprise est modélisée par un processus stochastique de la forme V = Vo exp X et que cette entreprise est mise à défaut dès lors que sa valeur passe sous un certain seuil b déterminé de façon exogène et qui donc, est une donnée du problème. L'instant de défaut T est alors de la forme Tx pour x= ln(Vo) ln((b) où x> 0, Tx = inf{t 2:0: X, 2:x}. Dans un premier temps, nous supposons que des agents observant la valeur V des ac­tifs de la firme souhaitent connaître le comportement de l'instant de défaut. Dans ce modèle, au chapitre 2, nous avons étudié d'une part la régularité de la densité de la loi de l'instant de défaut. D'autre part, nous avons étudié la loi conjointe de l'instant de défaut, de l'overshoot et de l'undershoot. Au chapitre 3, nous avons obtenu une équation à valeurs mesures dont le quadriplet formé par la variable aléatoire X,, le su­ premum du processus X à l'instant t, le supremum du processus X au dernier instant de saut avant l'instant t et le dernier instant de saut à l'instant t est solution au seris faible, puis une équation dont ce quadriplet est une solution forte. Dans un second temps, au chapitre 4, nous avons supposé que des investisseurs souhaitant détenir une part de cette entreprise ne disposent pas de l'information complète. Ils n'observent pas la valeur des actifs de la firme V, mais sa valeur bruitée. Leur information est modélisée par la filtration Ç = (Ç,, t 2: 0) engendrée par cette observation. Dans ce modèle, nous avons montré que la loi conditionnelle de l'instant de défaut sachant la tribu Ç, admet une densité par rapport à la mesure de Lebesgue et obtenu une équation de Volttera dont cette densité est solution. Cette connaissance permet aux investisseurs de prévoir au vu de leur information, quand est-ce que l'instant de défaut va intervenir après l'instant t. Nous avons complété ce travail par des simulations numériques. / In this Ph.D thesis, we consider a jump-diffusion process which the diffusion part is a drifted Brownian motion and the jump part is a compound Poisson process. We assume that a firm value is modelling by a stochastic process V = V0 exp-X. This firm goes to default whenever its value is below a specified tlrreshold b which is exo­ genously determined. For x = ln(Vo) - ln(b) > 0, the default time is of the form Tx = inf{t 2:0: X, 2: x}. First, we suppose that agents observe perfectly the firm value. In this mode, we sho­ wed in chapter 2 that the density of the default time is continuons, then study the joint law of the default time, overshoot an undershoot. We obtained in chapter 3 a valued measure differentia equation which the solution is the quadruplet formed by the random variable X,, the running supremum x; of X at time t, the supremum of X at the last jump time before t and the last jump time before t. Secondly, we assume that investors wishing detain a part of the firm can not observe the firm value. They observe a noisy value of the firm and their information is madel­ ling by the filtration g = (9,,t 2: 0) generated by their observation. In this mode, we have shown that the conditional density of Tx with respect to Ç has a density which is solution of one stochastic integral-differentia equation The knowledge of this density allows investors to predict the default time after time t. This second part is the chapter 4.

No / A novel multi-standard dual-wide band filter with a compact size of only 8.8 mm by 16.8mm is designed and developed for transceiver devices. The proposed filter has a fundamental bandwidth of 1.6GHz with fractional bandwidth (FBW) of 29.7% centered at the 5.4GHz band, and second bandwidth of 300.0MHz with FBW of 3.6% centered at the 8.15GHz band. The basic dual-wide bandwidth is attributed to the interaction of the novel modified polygon pair and upper stub loaded stepped impedance resonator. Moreover, the added down stub loaded stepped impedance resonator (SLSIR) further enhances the pass band performance by widening the bandwidth and optimizing reflection coefficient performance considerably. To validate the proposed ideas, the multi-standard filter is designed and simulated by Ansoft HFSS software. The simulated results agree well with the theory predictions. The featured broad bandwidths over two frequency bands and the miniaturized size of the proposed filter make it very promising for applications in future multi-standard wireless communication.

Le processus d’urbanisation conduit à un ensemble de transformations et perturbations qui peuvent avoir des conséquences sur la flore spontanée. Ce travail de thèse porte sur les communautés végétales des espaces herbacés ordinaires distribués au sein 3 aires urbaines de l’ouest de la France : Angers, Nantes et la Roche-sur-Yon. A travers deux approches, taxonomique et fonctionnelle, l’objectif est d’analyser les variations de diversités et de composition floristiques le long de gradients paysagers (notamment d’urbanisation et de connectivité des habitats). Ces milieux apparaissent diversifiés, tout en ne présentant qu’un faible nombre d’espèces exotiques. Le gradient urbain-rural structure les communautés, établissant notamment de fortes distinctions dans leurs compositions spécifiques, et ce, malgré l’absence de variations en terme de richesse et d’homogénéisation. Ces distinctions sont en lien avec des traits relatifs à leurs exigences écologiques (habitat, pH, humidité, lumière)et au niveau de perturbation plus élevé en ville. Ces relations varient malgré tout selon que l’on considère l’abondance locale ou régionale des espèces suggérant que d’autres mécanismes viennent s’ajouter à ces processus de filtre. La mesure in situ de trois traits fonctionnels (hauteur, SLA et phénologie) montre également l’importance de ce processus de filtre sur les espèces à un niveau intraspécifique. L’ensemble des résultats montre la façon dont ces espèces communes s’assemblent au regard des processus écologiques à l’oeuvre dans des environnements urbains, et permet d’ouvrir des perspect / The process of urbanisation leads to a series of transformations and disturbances that may have consequences for wild plant communities. This thesis presents a study of the plant communities of ordinary grasslands distributed among three cities of western France: Angers, Nantes and La Roche-sur-Yon. Using both taxonomical and functional approaches, the aim is to analyse the variation in plant diversity and composition along landscape gradients, in particular those of urbanisation and habitat connectivity. Such grassland habitats appear to be diverse, despite a low number of exotic species. The urban-rural gradient structures such communities, in particular by strongly modifying species composition; and this despite an absence of variation in species richness or of homogenisation. These modifications in community structure are linked to traits for ecological requirements (for habitat, pH, humidity or light)or for adaptation to higher levels of disturbance in towns. These relationships vary according to species’ local or regional abundance, suggesting that other mecanisms accompany the filtering process. Taking into account three functional traits (height, SLA and phenology) measured in situ shows that the filtering process also has consequences at intraspecific level. Taken together, the results show how common species are assembled in response to ecological processes operating in urban environments and open up new perspectives and applications for the integration of grassland plant communities into biodiversity conservation objectives in urban areas

<p>Diss. Stockholm : Handelshögskolan, 2013. Sammanfattning jämte 3 uppsatser.</p>