Ce mémoire de recherche-création explore les différentes modalités de la représentation d’une théorie scientifique—la théorie de la relativité, développée par Albert Einstein au début du XXe siècle—et se concentre sur le voyage dans le temps. Le mémoire est divisé en deux parties : un texte de recherche et un projet de création. Dans le texte de recherche, le premier chapitre rappelle ce qu’est la théorie de la relativité et fait un bref historique des films sur le voyage dans le temps; le second chapitre est une analyse du film Interstellar réalisé par Christopher Nolan en collaboration avec le physicien américain, Kip Thorne. Dans ce film, la théorie de la relativité n’est pas un élément secondaire, mais le coeur même de l’histoire. Ma création, présentée ici dans un document de jeu (Concept narratif d’un jeu vidéo), est un projet de jeu vidéo se déroulant pendant la seconde guerre mondiale, dans lequel le joueur devra voyager dans le temps pour sauver l’humanité du pouvoir nazi. / This research-creation master’s thesis explores the different modalities of the representation of the Theory of Relativity, developed by Albert Einstein in the beginning of the 20th century and focuses on time travel. The dissertation is divided into two parts: a research essay and a creation project. The first chapter of the research explains the basis of the Theory of Relativity and gives a brief history of time-travel in cinema. The second chapter analyses the movie Interstellar, produced by Christopher Nolan in collaboration with the American physicist Kip Thorne. This motion picture is a prime example of the Theory of Relativity in modern cinema. The creation section, presented here in a Video game narrative concept, is a video game project set during the Second World War, in which the player will have to travel through time in order to save humanity from the Nazis.

Un des grand défis de la physique actuelle est la quantification de la gravit é. La théorie d’Einstein est remarquable pour ses prédictions. Malheureusement, elle reste une théorie classique et de ce fait en désaccord avec les progrès actuels en physique des particules qui montrent qu’à faible distance, une théorie physique doit être quantique. Une des pistes pour résoudre ce problème est d’étudier la version classique de la gravité dans l’espoir d’en déduire des propriétés ou même la forme de la théorie quantique.<p><p>Un des outils pour étudier une theorie est la notion de dualité. On dit que deux théories sont duales quand elles décrivent le même système par des moyens différents. La dualité est le dictionnaire permettant de passer d’une description à l’autre. Dans ma thèse, j’ai étudié deux dualités s’appliquant à la gravité en 4 dimensions.<p><p>La première est connue sous le nom de dualité électromagnétique. A l’origine, cette dualité s’applique à l’électromagnétisme où elle échange les rôles du champ & / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

This thesis investigates the correlation between the grammatical gender of generic nouns denoting animals and the perceived biological sex of their referents. Based upon an approach by Imai et al. (2014), a reaction task experiment was conducted in which participants had to make inferences about the biological sex of specific animals. Four languages with differing grammatical gender systems were tested: Spanish, French, German and English. The experiment was conducted with native speakers in their respective languages. The results showed that Spanish, French and German speakers were influenced by grammatical gender when completing the task, while results in the English test group remained unaffected by this factor. In the Spanish and French sample there were several test conditions where gender effects were significant, whereas for the German sample significant effects could only be found in one test condition. Furthermore, in the French and German test groups, significant gender effects were found only when the target words were accompanied by gender-marked definite articles. For Spanish, effects were significant even when the stimuli were presented in the plural form without articles. These results imply that structural features, such as gender marking articles and the transparency of the Spanish gender system, seem to facilitate the projection of sex-specific properties onto grammatical gender. This study can be taken as weak support for linguistic relativity.

Astrophysical observations of the cosmic microwave background point to inconsistencies in the standard model of cosmology, and a primordial accelerated expansion of the universe known as inflation has been suggested as a solution. Unfortunately, observational evidence of inflation is lacking, and there exists hundreds of models that populate the inflationary landscape. In this thesis, we explore three of these and see what constraints are set on them in order to account for observations. We find that two of the models have regimes of trans-planckian nature, while the third leads to a non-invertible equation. / Astronomiska observationer av den kosmiska bakgrundsstrålningen tyder på bristfälligheter i standardkosmologin, vilket har lett till förslaget om en accelererande expansion i de tidigaste skeden av universum känd som inflation. I avsaknaden av observationella bevis finns det numera hundratals inflationsmodeller, och i detta arbete kommer vi att rikta fokuset mot tre av dessa avvilka två visar sig överstiga transplanckianska värden medan den sista leder till en ekvation som inte är inverterbar.

We extend previous work (2020Class. Quantum Grav. 37 075001)to the case of Maxwell’s equations with a source. Our work shows how to construct a vector potential for the Maxwell field on the Kerr–Newman background in a radiation gauge. The vector potential has a ‘reconstructed’ term obtained from a Hertz potential solving Teukolsky’s equation with a source, and a ‘correction’ term which is obtainable by a simple integration along outgoing principal null rays. The singularity structure of our vector potential is discussed in the case of a point particle source

<p dir="ltr">Neutron star mergers generate powerful gravitational waves and various types of electromagnetic signals, including gamma-ray bursts (GRB), kilonovae, and their afterglows. Observing and modeling these signals help us understand the physical processes of the merger events. Radiation from mergers can also serve as probes to study nuclear physics and cosmology. In this report, I focus on two types of signals: the GRB afterglow and the kilonova. GRB afterglows are non-thermal radiation produced by the interaction of relativistic jets and circumburst material, where the jets are launched perpendicular to the merger plane. Kilonovae are the thermal radiation emitted from the hot materials ejected during the merger. Besides the modeling of these objects, I also investigate their application in multimessenger astrophysics, especially the constraint on the expansion rate of the Universe. </p><p dir="ltr">First, I developed a GRB afterglow model to account for the off-axis observation of a structured jet. Using a jet structure derived from a three-dimensional general relativistic magnetohydrodynamic simulation, we performed a joint analysis of the multimessenger data of the neutron star merger event GW170817, including the gravitational wave data and GRB afterglow data in the radio band. We have tightly constrained the observing angle of GW170817 and broken the degeneracy between the inclination angle and luminosity distance measured in gravitational waves. With a better constrained distance, we improved the standard siren measurement of the Hubble constant to $H_0 = 69.5\pm 4\ \mathrm{km\ s^{-1}\ Mpc^{-1}}$. The error bar has been reduced by a factor of 2. This work demonstrates that the modeling of off-axis GRB afterglow can significantly improve the standard siren method, provided that we have a reliable jet structure.</p><p dir="ltr">Second, I upgrade the GRB afterglow model in the first work, extending it to the late time where lateral spreading of the GRB jet becomes important. In this model, the ultra-relativistic blastwave is approximated by an infinitely thin two-dimensional surface. With this approximation, the hydrodynamic equations can be analytically integrated over the radius. Further assuming axial symmetry, the three-dimensional hydrodynamic simulation can be reduced to one dimension, which significantly increases the computational efficiency. We have compared our method to full numerical simulations and existing GRB afterglow modeling tools. The comparison shows good agreement and verifies our approach. Compared to these tools, our model has better flexibility and is applicable in a broader context. This method has been developed into a numerical code, \texttt{jetsimpy}, which we have provided to the community. It will serve as a powerful tool in the era of multimessenger astrophysics.</p><p dir="ltr">Finally, I investigate the possibility of long-lived massive neutron stars as neutron star merger remnants. A long-lived massive neutron star can inject a significant amount of energy into the merger ejecta, boosting the luminosity of kilonova by several orders of magnitude. However, this type of event has not yet been observed in optical sky surveys. We developed a boosted kilonova model with a detailed calculation of the photoionization process to better describe the efficiency of energy injection from spin down power to the ejecta. Our study found that boosted kilonovae, if commonly occurring, they should have already been observed given the accumulated time in sky surveys. As a result, the absence of detection implies that long-lived massive neutron stars as neutron star merger remnants are likely to be rare in the Universe.</p>

Quadratic curvature terms are commonly introduced in the action as first-order corrections of General Relativity, and, in this thesis, we investigated their impact on the most simple isolated objects, that are the static and spherically symmetric ones. Most of the work has been done in the context of Stelle's theory of gravity, in which the most general quadratic contractions of curvature tensors are added to the action of General Relativity without a cosmological constant. We studied this theory's possible static, spherically symmetric and asymptotically flat solutions with both analytical approximations and numerical methods. We found black holes with Schwarzschild and non-Schwarzschild nature, naked singularities which can have either an attractive or repulsive gravitational potential in the origin, non-symmetric wormholes which connects an asymptotically flat spacetime with an asymptotically singular one, and non-vacuum solutions modeled by perfect fluids with different equations of state. We described the general geometrical properties of these solutions and linked these short-scale behaviors to the values of the parameters which characterize the gravitational field at large distances. We studied linear perturbations of these solutions, finding that most are unstable, and presented a first attempt to picture the parameter space of stable solutions. We also studied the Thermodynamics of black holes and described their evaporation process: we found that either evaporation leads black holes to unstable configurations, or the predictions of quadratic gravity are unphysical. We also considered the possibility of generalizing Stelle's theory by removing the dependence from the only mass-scale present by including a new dynamical scalar field, making the theory scale invariant. Having a more complex theory, we did not investigate exotic solutions but limited ourselves to the impact of the new additional degrees of freedom on known analytical solutions. It was already known that in a cosmological setting this theory admits a transition between two de Sitter configurations; we analyzed the same problem in the context of static and spherically symmetric solutions and found a transition between two Schwarzschild-de Sitter configurations. In order to do that, we studied both linear perturbations and the semiclassical approximation of the path integral formulation of Euclidean quantum gravity. At last, we tried to extract some phenomenological signatures of the exotic solutions. In particular, we investigated the shadow of an object on background free-falling light, and a possible way of determining the behavior close to the origin using mass measurements that rely on different physical processes. We show that, whenever these measurements are applied to the case of compact stars, in principle it could be possible to distinguish solutions where different equations of state describe the fluid.

No description available.

If most scholars tend to agree that the native language of a speaker does influence the way they will understand the reality around them, the question becomes ambiguous when it comes to bilingual speakers’ cognition. How is their reality affected by the combination of their languages? This study aimed at exploring this question under the angle of grammatical gender. Adult simultaneous early bilingualsin French and Swedish were asked, in an innovative experiment, to match a culturally neutral item to a voice. In a second experiment, the same participants were asked to match a culturally loaded item to a voice. In both experiments, items were carefully chosen according to their grammatical gender. Results indicate that grammatical gender was not a predictor of voice assignment. However, the perceived cultural stereotypes of the items used in the second experiment appeared to be a robust predictor of voice assignment. Findings suggest thus that grammatical gender does not affect how simultaneous early bilingualism French and Swedish would conceptualise artifacts, but cultural gender would.

Notre thèse étudie la relation entre les mécaniques classique et relativiste. Il est généralement supposé, à partir de l’hypothèse des petites vitesses, que la mécanique classique correspond à la mécanique relativiste dans les cas où la vitesse des objets est petite par rapport à la vitesse de la lumière. Cette position nous semble inadéquate pour la simple raison que la mécanique classique ne peut être restreinte au seule domaine des petites vitesses. Nous proposons l’hypothèse que les deux mécaniques ont une structure commune et que chacune se distingue sous certaines conditions. Pour appuyer cette hypothèse, nous proposons une axiomatisation de la mécanique suffisamment générale pour servir de structure commune aux mécaniques classique et relativiste. Cette axiomatisation comporte une théorie de la relativité qui précise comment les quantités relatives sont reliées entre elles lorsque déterminées par rapport à différents référentiels, et les lois du mouvement qui précisent comment les forces exercées sur un objet détermine son mouvement. Cette mécanique générale est déterminée à deux constantes près et c’est en déterminant la valeur de ces constantes qu’apparaît le bris de la structure commune qui génère la mécanique classique d’une part et la mécanique relativiste d’autre part. / Our thesis studies the relationship between classical and relativistic mechanics. It is generally assumed, based on the assumption of small velocities, that classical mechanics corresponds to relativistic mechanics in cases where the speed of objects is small compared to the speed of light. This position seems inadequate to us, for the simple reason that classical mechanics cannot be restricted to the realm of small velocities alone. We propose the hypothesis that the two mechanics have a common structure, and that each can be distinguished under certain conditions. To support this hypothesis, we propose an axiomatization of mechanics that is sufficiently general to serve as a common structure for both classical and relativistic mechanics. This axiomatization includes a theory of relativity that specifies how relative quantities are related to each other when determined with respect to different reference frames, and laws of motion that specify how forces exerted on an object determine its motion. This general mechanics is determined to within two constants, and it is by determining the value of these constants that the common structure that generates classical mechanics on the one hand and relativistic mechanics on the other is broken down.