Continuous versus Discrete Market Games

De Meyer and Moussa Saley [4] provide an endogenous justification for the appearance of Brownian Motion in Finance by modeling the strategic interaction between two asymmetrically informed market makers with a zero-sum repeated game with one-sided information. The crucial point of this justification is the appearance of the normal distribution in the asymptotic behavior of Vn(P)//n. In De Meyer and Moussa Saley’s model [4], agents can fix a price in a continuous space. In the real world however, the market compels the agents to post prices in a discrete set. The previous remark raises the following question: Does the normal density still appear in the asymptotic of Vn//n for the discrete market game? The main topic of this paper is to prove that for all discretization of the price set, Vn(P)//n converges uniformly to 0. Despite of this fact, we do not reject De Meyer, Moussa analysis: when the size of the discretization step is small as compared to n-1/2, the continuous market game is a good approximation of the discrete one.Insider trading, game of incomplete information, Brownian Motion

Duality and optimal strategies in the finitely repeated zero-sum games with incomplete information on both sides

The recursive formula for the value of the zero-sum repeated games with incomplete information on both sides is known for a long time. As it is explained in the paper, the usual proof of this formula is in a sense non constructive : it just claims that the players are unable to guarantee a better payoff than the one prescribed by formula, but it does not indicates how the players can guarantee this amount. In this paper we aim to give a constructive approach to this formula using duality techniques. This will allow us to recursively describe the optimal strategies in those games and to apply these results to games with infinite action spaces.Repeated games, dual games, incomplete information, recurrence formula.

Duality and optimal strategies in the finitely repeated zero-sum games with incomplete information on both sides

URL des Cahiers : https://halshs.archives-ouvertes.fr/CAHIERS-MSECahiers de la MSE 2005.27 - Série Bleue - ISSN : 1624-0340The recursive formula for the value of the zero-sum repeated games with incomplete information on both sides is known for a long time. As it is explained in the paper, the usual proof of this formula is in a sense non constructive: it just claims that the players are unable to guarantee a better payoff than the one prescribed by formula, but it does not indicates how the players can guarantee this amount. In this paper we aim to give a constructive approach to this formula using duality techniques. This will allow us to recursively describe the optimal strategies in those games and to apply these results to games with infinite action spaces.La formule de récurrence pour la valeur d'un jeu répété à somme nulle avec asymétrie bilatérale d'information a été établie depuis longtemps dans la littérature existante. Comme nous le remarquons dans ce papier, la preuve usuelle de cette formule est dans un sens non constructive. Elle démontre en particulier que les joueurs ne peuvent pas se garantir un paiement supérieur à celui décrit par la formule, mais cette analyse n'indique pas comment les joueurs parviennent à garantir cette quantité. Dans cet article, en utilisant des techniques de dualité, nous aborderons une approche constructive de cette formule. Cette analyse nous permettra d'apporter une description récursive des stratégies optimales dans ces jeux et également d'étendre les résultats aux jeux avec des espaces d'actions infinis

Relaxation of dynamically disordered tetragonal platelets in the relaxor ferroelectric 0.964Na1/2Bi1/2TiO3−0.036BaTiO30.964\mathrm{Na}_{1/2}\mathrm{Bi}_{1/2}\mathrm{TiO}_3-0.036\mathrm{BaTiO}_3

The local dynamics of the lead-free relaxor $0.964\mathrm{Na}_{1/2}\mathrm{Bi}_{1/2}\mathrm{TiO}_3-0.036\mathrm{BaTiO}_3$ (NBT-3.6BT) have been investigated by a combination of quasielastic neutron scattering (QENS) and ab initio molecular dynamics simulations. In a previous paper, we were able to show that the tetragonal platelets in the microstructure are crucial for understanding the dielectric properties of NBT-3.6BT [F. Pforr et al., Phys. Rev. B 94, 014105 (2016)]. To investigate their dynamics, ab initio molecular dynamics simulations were carried out using $\mathrm{Na}_{1/2}\mathrm{Bi}_{1/2}\mathrm{TiO}_3$ with 001 cation order as a simple model system for the tetragonal platelets in NBT-3.6BT. Similarly, 111-ordered $\mathrm{Na}_{1/2}\mathrm{Bi}_{1/2}\mathrm{TiO}_3$ was used as a model for the rhombohedral matrix. The measured single crystal QENS spectra could be reproduced by a linear combination of calculated spectra. We find that the relaxational dynamics of NBT-3.6BT are concentrated in the tetragonal platelets. Chaotic stages, during which the local tilt order changes incessantly on the timescale of several picoseconds, cause the most significant contribution to the quasielastic intensity. They can be regarded as an excited state of tetragonal platelets, whose relaxation back into a quasistable state might explain the frequency dependence of the dielectric properties of NBT-3.6BT in the 100 GHz to THz range. This substantiates the assumption that the relaxor properties of NBT-3.6BT originate from the tetragonal platelets.Comment: 27 pages, 9 figure

Learning-based pose edition for efficient and interactive design

Authoring an appealing animation for a virtual character is a challenging task. In computer-aided keyframe animation artists define the key poses of a character by manipulating its underlying skeletons. To look plausible, a character pose must respect many ill-defined constraints, and so the resulting realism greatly depends on the animator's skill and knowledge. Animation software provide tools to help in this matter, relying on various algorithms to automatically enforce some of these constraints. The increasing availability of motion capture data has raised interest in data-driven approaches to pose design, with the potential of shifting more of the task of assessing realism from the artist to the computer, and to provide easier access to nonexperts. In this article, we propose such a method, relying on neural networks to automatically learn the constraints from the data. We describe an efficient tool for pose design, allowing na{\"i}ve users to intuitively manipulate a pose to create character animations

Is Investment Contributing to Competitiveness in Nautical Tourism in the Atlantic Area?

The blue economy contributes significantly to the creation of the Atlantic Area’s identity. In addition, the search for outdoor experiences after the COVID-19 lockdown suspensions has renewed the popularity of nautical tourism in this area and in the world. Despite the negative effects of the economic crisis on tourism, evidence suggests that some tourist destinations in the Atlantic area are resilient. Thus, whereas some branches of the blue economy face considerable challenges to increasing competitiveness, others offer opportunities for economic growth and employment. In this context, investment is necessary to lay the foundations for the sustainable development of nautical tourism. However, regarding the role of investment in productivity and competitiveness in the context of crisis, there is no consensus among academics. Thus, we investigate whether the investment contributed to competitiveness in nautical tourism in the Atlantic Area in 2016–2020. We collected data from ORBIS for 29 nautical-tourism companies and performed a quantitative and qualitative narrative analysis of competitiveness indicators, enabling comparisons pre and during crisis. The results highlight the multiplicity of ways in which crisis impacts nautical-tourism firms. The research fills a gap in the literature by investigating the dynamic capabilities of nautical-tourism SMEs in periods of recession, with a special focus on restructuring and competitiveness strategies. Some recommendations are outlined to promote the efficiency of resources and stimulate the competitiveness of companies to allow the regional development of nautical tourism in the territory of the Atlantic area.info:eu-repo/semantics/publishedVersio

Une méthode de reconnaissance des expressions du visage basée sur la perception

Session "Atelier VISAGES"National audienceLes humains peuvent reconnaître très facilement les expressions du visage en temps réel. Toutefois, la reconnaissance fiable et rapide des expressions faciales en temps réel est une tâche difficile pour un ordinateur. Nous présentons une nouvelle approche de reconnaissance de trois type d'expressions faciales qui se base sur l'idée de ne considérer que de petites régions du visage bien définies pour en extraire les caractéristiques. Cette proposition est basée sur une étude psycho-visuel expérimental menée avec un eye-tracker. Les mouvements des yeux de quinze sujets ont été enregistrés dans des conditions de visualisation libre d'une collection de 54 vidéos montrant six expressions faciales universelles. Les résultats de cette étude montrent que pour certaines expressions du visage une unique région est perceptuellement plus attractive que les autres. Les autres expressions montrent une attractivité pour deux ou trois régions du visage. Cette connaissance est utilisée pour définir une méthode de reconnaissance se concentrant uniquement sur certaines régions perceptuellement attrayantes du visage et ainsi réduire par un facteur de deux les temps de calcul. Nos résultats montrent une précision de reconnaissance automatique de trois expressions de 99.5% sur la base de données d'expression faciale Cohn-Kanade

Facial Expression Recognition using Entropy and Brightness Features

International audienceThis paper proposes a novel framework for universal facial expression recognition. The framework is based on two sets of features extracted from the face image: entropy and brightness. First, saliency maps are obtained by state-of-the-art saliency detection algorithm i.e. "frequencytuned salient region detection". Then only localized salient facial regions from saliency maps are processed to extract entropy and brightness features. To validate the performance of saliency detection algorithm against human visual system, we have performed a visual experiment. Eye movements of 15 subjects were recorded with an eye-tracker in free viewing conditions as they watch a collection of 54 videos selected from Cohn-Kanade facial expression database. Results of the visual experiment provided the evidence that obtained saliency maps conforms well with human fixations data. Finally, evidence of the proposed framework's performance is exhibited through satisfactory classification results on Cohn-Kanade database

Exploring human visual system: study to aid the development of automatic facial expression recognition framework

International audienceThis paper focus on understanding human visual system when it decodes or recognizes facial expressions. Results presented can be exploited by the computer vision research community for the development of robust descriptor based on human visual system for facial expressions recognition. We have conducted psycho-visual experimental study to find which facial region is perceptually more attractive or salient for a particular expression. Eye movements of 15 observers were recorded with an eye-tracker in free viewing conditions as they watch a collection of 54 videos selected from Cohn-Kanade facial expression database, showing six universal facial expressions. The results of the study shows that for some facial expressions only one facial region is perceptually more attractive than others. Other cases shows the attractiveness of two to three facial regions. This paper also proposes a novel framework for automatic recognition of expressions which is based on psycho-visual study