NCube/papyrus huggingface dataset:
Conception d'un environnement de simulation pour le calcul des profils d'élargissement Stark des raies d'hélium neutre

This thesis deals with the study of white dwarf stars of the DB type, whose spectrum is dominated by neutral helium lines. Recent work has revealed that physical parameters — namely the effective temperature and the stellar mass — measured using the so-called spectroscopic technique are problematic for this type of white dwarf. In this study, we re-examine one of the essential ingredients of this method, namely the calculation of Stark broadening profiles of neutral helium lines. This problem was addressed 25 years ago by our research group using the standard Stark broadening theory. Semi-analytical profiles calculated under this theory consider electrons as dynamic and ions as static. With the improvement of computer numerical power, other research groups have significantly improved the treatment of Stark brodening by producing numerical simulations describing in detail the dynamics and interactions of the perturbers (ions and electrons) near the emitter (the helium atom in our case). However, they generated Stark profile tables, applicable to the computation of synthetic spectra for white dwarf stars, for only two lines of the helium atom. In this thesis, we describe the creation of our own simulation environment including some important aspects considered in previous work (unification of ion and electron treatment, correction for ion dynamics, transition of the electron contribution to broadening from the core to the wings of the profile, numerical integration of the quantum operator of the time evolution of helium perturbed by a fluctuating electric field, Debye correction for the correlation of the motion of charged perturbers, local density variation and particle reinjection) in order to better represent the dynamical environment of the helium atom. Intermediate steps, such as the construction of the simulation space and the quasi-static model, allowed us to validate this simulation space and the respect of the system statistics. Once these validation steps were completed, we produced grids of Stark profiles for the two most important lines of the helium atom in the optical, namely He ɪ λ4471 et He ɪ λ4922, for temperatures between 10,000 K and 40,000 K and electronic densities between 1 × 10¹⁴ cm⁻³ and 6 × 10¹⁷ cm⁻³. A comparison with other published results shows that our calculations rival the best profiles obtained in the field of numerical simulations of Stark broadening. The development of this tool paves the way for the creation of a new generation of white dwarf atmosphere models that will allow us to refine the spectroscopic analysis of these objects.

Keyphrases: dense matter, numerical simulation, opacity, quantum physics, white dwarf
Étude de la variabilité photométrique dans le vent des étoiles Wolf-Rayet

We present an analysis of photometric observations of Wolf-Rayet stars in an effort to characterize their ubiquitous short-term stochastic variability and the origin of the periodic variability due to atmospheric eclipses in two specific systems. With data from BRITE-Constellation, we investigated what we initially thought to be atmospheric eclipses in the WR22 and WR48 systems. Both stars’ datasets were first analyzed using an analytical atmospheric eclipse model, and then a fully numerical core and wind eclipse model was used to better characterize the ambiguous case of WR22. The mass-loss rate of the Wolf-Rayet component, the optical depth of the wind and the inclination angle of the system were accurately determined for WR22, whereas for WR48 an upper limit was found for those parameters using an inclination angle from the litterature. The study of the short-term stochastic variability in the winds of 55 Wolf-Rayet stars was obtained with 70 time-series produced by MOST, BRITE and TESS. The amplitude spectra of these stars were analyzed using a semi-Lorentzian function that allowed us to extract characteristic parameters. Comparisons between the values we obtained and those from the litterature were carried out and we discuss the possible contribution to the variability of various physical processes, namely the line de-shadowing instability, the presence of a subsurface iron-group driven convection zone and possibly of internal gravitational waves generated at the boundary between the convective core and the radiative layer to the observed variability.

Keyphrases: Binaries : eclipsing, Techniques : photo-metric
Décharge à courant alternatif (AC) dans l’air et en contact avec l’eau : caractérisation fondamentale et application au traitement des eaux

Gas phase discharges in contact with liquids is a relatively novel research field in plasma physics. Plasma-liquid systems are very promising for various technological applications, such as medicine, solid-state physics, and environmental remediation. However, further development of the applications requires understanding of plasma-liquid interactions. In this thesis, interaction between an air plasma directly coupled in contact with water is studied. This thesis includes three chapters. Chapter 1 presents a general introduction of the plasma-liquid interactions and their applications in water treatment. Chapter 2, an article published in Journal of Physics D: Applied Physics, is an investigation of the spatial and temporal dynamics of an air plasma produced by AC discharge between a pin electrode and water. Chapter 3, an article published in Plasma Chemistry and Plasma Processing, is an investigation of the various modes produced by an AC-driven air discharge in contact with water. The electrical characteristics of each discharge mode are presented in detail, and variations in water properties (namely water acidity and conductivity) are also discussed. The efficiency of each discharge mode on the degradation rate of methylene blue, a standard pollutant, is also reported.

Keyphrases: Plasma-liquid interface, electrical discharge, time resolved imaging, plasma structuration, water treatment
De la théorie des jeux à l’exobiologie : l’émergence de la coopération comme phénomène critique

The emergence of complexity, and of life more speciﬁcally, is still one of the most intractable conundrums for modern science. Recent work emphasized the relevance of statistical physics and critical phenomena theory’s contribution to those questions — especially of self-organized criticality theory — just as much as the role of biochemical cooperation in life’s ﬁrst moments. Moreover, the description of the mechanisms by which life could have appeared is of particular interest for astrophysics, because our comprehension of those mechanisms inﬂuences how biosignatures are analyzed in the context of the search for life elsewhere in the Universe. The analysis presented here concerns a model in game theory that allows to study cooperation phenomena — implemented in spatial context as to emulate the dynamics of a system in which life could have appeared. An analysis of the model’s parameter space reveals that it displays phase transition and self-organization of spatial structures phenomenon, those elements being adjuvants to the emergence of cooperation between a priori egoist players, in a context that is initially not favorable to the emergence of cooperative behavior. The results obtained here thus seem to support the idea that both biochemical cooperation can emerge through phase transition phenomena, and that the underlying lattice iterated prisoner’s dilemma model used here behaves like a self-organized critical system.

Keyphrases: complexity, origin of life, self-organized criticality, statistical physics, critical phenomenon, cooperation, prisoner’s dilemma, phase transition
Suivi photométrique de candidates exoplanètes identifiées par le Transiting Exoplanet Survey Satellite

The majority of the exoplanets known to date have been discovered using the transit method, which indirectly infers the existence of such objects by measuring a temporary and repeated drop in the brightness of a star when, for the right alignement, an exoplanet passes in front of it. The search for biosignatures, thus life, in an exoplanet atmosphere is now the main objective in this field of study, and for several reasons, planets with a radius less than approximately two Earth radii around red dwarfs are particularly targeted. With the goal of finding more such systems in the solar neighbourhood and in all regions of the sky, the Transiting Exoplanet Survey Satellite (TESS) was launched in April 2018. The large image sampling of 21'' per pixel of the cameras on board TESS often results in data contamination of stars showing promising transit signal, by the flux of nearby stars. If one of these contaminating sources happens to be an eclipsing binary, an astrophysical phenomenon able to mimic a transit, the detection is most likely a false positive event. Thus, follow-up observations in photometry and in spectroscopy are generally required to identify the genuine exoplanets. This thesis presents the results of a photometric monitoring campaign at the Observatoire du Mont-Mégantic with the Planètes Extra-Solaires en Transit et Occultations (PESTO) camera of nine exoplanet candidates identified by TESS. A transit curve fitting routine developed during this master’s provides an estimation for certain physical parameters (radius, semi-major axis and inclination) of these candidates. Among them, TOI 1452.01 stands out, because this probable exoplanet has an estimated radius close to two Earth radii, in addition to being located within the habitable zone of its red dwarf host, i.e. at a distance allowing the presence of liquid water on its surface.

Keyphrases: Satellite TESS, Exoplanet, TESS, Photometry, Transit method, Follow-up observations
Contrat racial aux États-Unis : sujet, pouvoir et résistance

Racial Contract is one of the pioneering books that brought critical race theories into political philosophy. In this liberal analysis of racial inequalities, Charles W. Mills proposes to use white supremacy as a conceptual tool to describe and explain race-related problems in the United States. However, the emancipatory potential of this subversive approach among "black" people has not been studied. In this master thesis, after comparing various conceptions of "race", we examine how Mills articulates the concepts of "white supremacy" and "epistemology of ignorance" to explain racial injustices. Finally, we explore Shannon Sullivan's theory of resistance to assess its compatibility with Mills' descriptive theory. In the end, we believe that a philosophy of resistance would benefit from turning to critical theories of race other than that of Mills, such as W.E.B. Du Bois, in order to have a concept of the "black" individual that accounts for his or her agentivity and thus his or her capacity to resist. We also argue that the concept of "white supremacy", as developed by Mills, is a coherent, valid and potentially useful theoretical tool for the development of a philosophy of black resistance. Finally, even if its scope is rather limited, we consider that the contribution of "race traitors" such as Shannon Sullivan to a philosophy of resistance can potentially be positive.

Keyphrases: critical race theory, race, Racial Contract, social constructionism, Charles W. Mills, philosophy of race, white supremacy, white privilege, Shannon Sullivan, race traitor, constructivisme social
Le rôle constitutif de l'imagination chez Spinoza

This work offers an analysis of the concept of imagination, also called knowledge of the first kind, in order to put forward its constitutive role. For this, we will first discuss the way Spinoza’s philosophy evolved, following Antonio Negri’s interpretation. We will then account for Spinoza’s approach of imagination, making it essentially positive and constitutive, and only accidentally the origin of error. With this, we will explain what causes Spinoza to interrupt his work on the Ethics to write the Theological-Political Treatise, by exposing the need (both socio-political and philosophical) forcing Spinoza to develop imagination’s positivity and power, through which the world constitutes itself without any transcendence whatsoever. We will see, along with Negri, that this positive concept of imagination enables Spinoza to fully embrace immanence. This is how he can go beyond the traditional philosophical horizon which wants the world to be organized by Totality or, in Spinoza’s case, by the Substance, which in this horizon always retains a hint of transcendence. Subsequentially, we will define imagination, mainly from the Ethics, and then we will present the scope of imagination’s constitutive power by presenting the process by which are constituted objects, subjects and time, by means of habit and memory, and then the process by which are constituted all kinds of society and even all types of social life, by means of imitation of the affects. We will conclude our research by looking at the political theory immediately resulting of imagination’s constitutive role. This will also reveal how Spinoza’s positive concept of imagination answers the socio-political need that motivated him, while witnessing religious intolerance and the resurgence of monarchy in Holland, to reorient his work towards these questions and towards the role of imagination.

Keyphrases: Antonio Negri, Imagination, Philosophy, Ontology, Ethics, Thelogical-Political Treatise, Politics
Accès, transmission et circulation du savoir : la proposition d'Eckhart de Hochheim

Anyone interested in the thought of Meister Eckhart is confronted with the glaring difference in style, if not in content, between his Latin academic writings and his Middle-High German predicative writings, which were addressed to two distinct communities. These apparent differences raise the question of the gnoseological model to which Eckhart adheres and require to clarify the type of knowledge he sought to transmit. The present work attempts to shed light on Eckhart's theory of knowledge in order to draw conclusions about Eckhart's transmission of knowledge. This research project concludes that the differences observed in the corpuses stem from an avowed and justified attempt to favour the transmission of knowledge to a non-academic public from a single onto-gnoseological model, giving intelligibility to the differences by understanding them as a matter of the form of discourse. In order to reach these conclusions, this dissertation, first of all, vindicates Eckhart's philosophical quality and importance by clarifying the reasons for his categorization as a “mystic”. Second, once the rationality of Eckhart's thought has been established, I will develop and analyze Eckhart's theory of knowledge as it appears in chosen primary sources. Finally, in a third stage, this dissertation examines the role and importance of the change of language achieved by Eckhart in order to offer an expression to the problem of the accessibility, transmission and circulation of academic knowledge.

Keyphrases: Eckhart von Hochheim, Philosophy, History of philosophy, Middle Ages, Meister Eckhart, Teaching, Knowledge, Scholarly practice
La notion de lǐ 禮, « ritualité », dans la pensée de Xunzi  
(IIIème siècle avant notre ère)

Rituality, whether of a religious or ethical nature, or even as a matter of custom, punctuates the lives of individuals, groups and communities, emphasizes and maintains social ties as well as it anchors the human world in the natural world. Confucian philosophy gives a central place to this notion of lǐ 禮, "rituality", and it is probably, within this school of thought, Xunzi (3rd century BC) who gives it the greatest philosophical role. However, a multitude of tensions animates this concept of "rituality" which lies at the junction of the Natural and the Cultural, the ethical and the sacred, the material and the intangible, the profane and the religious. This master dissertation is based on the exegesis of relevant excerpts from the Xunzi. By the study of the semantic and lexical field of rituality as well as the etymological analysis of the key concepts associated with it, we provide a new vision to the reader concerning the interpretation of lǐ. We restore the cosmic breath – fractals of binary oppositions relating the microcosm to the macrocosm – at work in the thoughts of the scholar and expose the intimate links uniting rituality to inner moral sense. We argue that an approach integrating and differentiating actuality from potentiality in Xunzi's philosophy provides a solution to the problem of human nature – as conceived by the thinker. Our conceptions of representation and cosmology shed a new light on, respectively, ritual symbolism and cosmological order. We uncover the way in which rituality creates the inner moral sense of individuals, integrates man into society and society into the order of the world. We discover a thinker that extirpates the divine from the transcendent religious dimension to make humanity and human morality the custodians of the sacred.

Keyphrases: Xunzi, Religion, Philosophy, Rituality, Ethics, Cosmology, Sacred, Confucianism, Order
L’application des mathématiques aux phénomènes naturels chez Leibniz

This thesis explores Leibniz’s solution to the problem of how mathematics are useful to our understanding of the world, i.e., to our understanding of corporeal phenomena and their relations. In the first chapter, it focuses on how abstract mathematical notions enter in our most immediate understanding of the world. Here, the aim is connecting the pervasiveness of mathematics to the peculiar way by which the individuality of phenomena manifests itself to us. After some metaphysical remarks on Leibniz’s conception of individuation, we study spatial position in the light of the new leibnizian geometrical analysis : Analysis Situs. Spatial position provides us with a way to further distinguish between individual phenomena whose qualities relevant to their real individuation remain ignored. In the sole light of spatial individuation, phenomena are ideal and indeterminate. This situation renders them susceptible to mathematical treatment without further elaboration. In the second chapter, we turn our attention to the question of why mathematical methods in philosophy of nature are epistemologically superior in Leibniz’s eyes. We explore Leibniz’s reason to espouse a mechanical philosophy which comprise indispensable mathematical notions. Leibniz believes that mechanical philosophy is the most intelligible explanation of nature and we mean to assess how mathematics enter this picture. We try to show that the mathematical aspects of mechanical philosophy make it more intelligible by virtue of mathematics’ peculiar mode of reasoning. This mode of reasoning is valid as well as most suited for our finite minds. It provides necessary arguments through incomplete notions. It also encourages the discovery by assisting the imagination with controlled and sensible support that makes knowledge more evident.

Keyphrases: Leibniz, Philosophy, Modern philosophy, Philosophy of mathematics, Mechanical philosophy, Principle of individuation
La justification épistémique chez Husserl : une approche phénoménologique du débat entre fondationnalisme et cohérentisme

The opposition between foundationalism and coherentism is a classical debate in contemporary epistemology. The two conceptions oppose on the justificatory structure of knowledge. From a phenomenological standpoint, this dilemma is mostly apparent. The aim of this thesis is to prove just this. We will procede by focusing on the phenomenology of Edmund Husserl, whose work shows that an alternative conception of epistemic justification is quite possible. Taking our cues in Husserl’s theory of intentionality and his analysis of lived experiences (Erlebnisse), we will explain in what sense perception should be considered as an experience of evidence. To the extent that the intuitive aspect of perceptual experience serves as the foundation for knowledge, Husserl's theory comes close to foundationalism. Perception, however, is not limited to its intuitive moment. It is inscribed in a context where the cohesion of lived experiences plays a crucial role in the epistemic function of experience, which suggests that Husserl's position also incorporates coherentist elements in his theory. Since both foundationalist and coherentist aspects are "intrinsic" to perceptual experience, it seems that, from a phenomenological point of view at least, the classical opposition between the foundational and coherentist structures of justification is too rigid and can be overcome in a shared unified framework.

Keyphrases: Perception, Edmund Husserl, Phenomenology, Epistemology, knowledge, Foundationalism, Coherentism
L'énactivisme autopoïétique : une réponse au problème difficile?

The “hard problem” of consciousness is one of the central problems of philosophy of the mind. Echoing Descartes’s mind-body problem, the hard problem highlights the epistemological and ontological difficulties of physicalism in its attempt to reduce subjective experience to a physical and functional character. This thesis proposes a potential answer to the hard problem of consciousness by the enactive approach, more specifically a variant of the enactive approach that we sometimes call autopoietic enactivism. Autopoietic enactivism presents itself as an alternative approach to “brain-bound” approaches in cognitive science. In contrast to the cognitivist trend, autopoietic enactivism presents a conception of the mind centred around the embodied activity of an organism. At the heart of this embodied conception of the mind lies the concept of autopoiesis, a theory of organic life and biological autonomy defined by the sense-making activity of living organisms. This concept is central to autopoietic enactivism’s solution to the hard problem, as it reveals the deep similarities between both life and mind.

Keyphrases: Autopoietic enactivism, Enactive movement, Hard problem, Consciousness, Embodied cognition, Phenomenology
Le rôle de l'intuition en épistémologie morale

This memoir is about the epistemic value of moral intuitions. Does having an intuition that something is morally right or wrong gives us good reasons to believe that the thing we have the intuition about is right or wrong? To answer this question, I’ll start by explaining what an intuition is. Then, I’ll look into the two biggest theories in moral epistemology: foundationalism and coherentism and how intuition can have a role in both of them. I’ll come to the conclusion that foundationalist theories are preferable to coherentist theories. The rest of the memoir will be a discussion of foundationalist theories in moral epistemology in which moral intuitions are what can justify some foundational beliefs. Those theories are called ‘’intuitionist’’. Following a distinction made by 19th century philosopher Henry Sidgwick, I’ll identify three ways in which intuitionism can be defended: perceptual intuitionism, dogmatic intuitionism and philosophical intuitionism. I’ll explain in details what are those theories and see if they are good theories in moral epistemology. Then, I’ll consider some general objections directed toward intuitionism and see if intuitionism can resist those objections. I come to the conclusion that philosophical intuitionism can resist most of the best objections addressed toward it and that it’s a very plausible theory in moral epistemology.

Keyphrases: Intuition, Henry Sidgwick, Moral epistemology, Self evidence, Foundationalism, Coherentism, Metaethics