The cosmic microwave background (CMB) provides unprecedented details about the history of our universe and helps to establish the standard model in modern cosmology. With the ongoing and future CMB observations, higher precision can be achieved and novel windows will be opened for studying different phenomena. Non-Gaussianity is one of the most exciting effects which fascinate many cosmologists. While numerous alternative inflationary models predict detectable primordial non-Gaussianities generated during inflation, the single-field slow-roll inflation of the standard model is known to produce negligible non-Gaussianities. However, post-inflationary processes guarantee the generation of non-Gaussianities through the nonlinear evolution of our universe after inflation, regardless of the underlying inflationary theory. These non-Gaussianities not only may contaminate the potential primordial non-Gaussian signals, but also may offer independent tests for late-time physics (such as General Relativity). Therefore, it is of great interest to study them quantitatively. In this thesis, we will study the post-inflationary non-Gaussianities in two main aspects. First, we calculate the CMB bispectrum imprinted by the 2nd-order perturbations during recombination. We carry out a numerical calculation including all the dominant effects at recombination and separate them consistently from the late-time effects. We find that the recombination bispectrum is subdominant compared to the ISW-lensing bispectrum. Although the effect will not be detectable for the Planck mission, its signal-to-noise is large enough that they present themselves as systematics. Thus, it has to be taken into account in future experiments. Second, we formulate the lensing, redshift and time-delay effects through the Boltzmann equation. The new formalism allows us to explicitly list out all the approximations implied in the canonical remapping approach. In particular, we quantify the correction of the CMB temperature power spectrum from the lens-lens couplings and confirm that the correction is small.

AMANDA-II est un télescope à neutrinos composé d'un réseau tri-dimensionnel de senseurs optiques déployé dans la glace du Pôle Sud.<p>Son principe de détection repose sur la mise en évidence de particules secondaires chargées émises lors de l'interaction d'un neutrino de haute énergie (> 100 GeV) avec la matière environnant le détecteur, sur base de la détection de rayonnement Cerenkov.<p><p>Ce travail est basé sur les données enregistrées par AMANDA-II entre 2000 et 2006, afin de rechercher des sources cosmiques de neutrinos.<p>Le signal recherché est affecté d'un bruit de fond important de muons et de neutrinos issus de l'interaction du rayonnement cosmique primaire dans l'atmosphère. En se limitant à l'observation de l'hémisphère nord, le bruit de fond des muons atmosphériques, absorbés par la Terre, est éliminé.<p>Par contre, les neutrinos atmosphériques forment un bruit de fond irréductible constituant la majorité des 6100 événements sélectionnés pour cette analyse.<p>Il est cependant possible d'identifier une source ponctuelle de neutrinos cosmiques en recherchant un excès local se détachant du bruit de fond isotrope de neutrinos atmosphériques, couplé à une sélection basée sur l'énergie, dont le spectre est différent pour les deux catégories de neutrinos.<p><p>Une approche statistique originale est développée dans le but d'optimiser le pouvoir de détection de sources ponctuelles, tout en contrôlant le taux de fausses découvertes, donc le niveau de confiance d'une observation.<p>Cette méthode repose uniquement sur la connaissance de l'hypothèse de bruit de fond, sans aucune hypothèse sur le modèle de production de neutrinos par les sources recherchées. De plus, elle intègre naturellement la notion de facteur d'essai rencontrée dans le cadre de test d'hypothèses multiples.La procédure a été appliquée sur l'échantillon final d'évènements récoltés par AMANDA-II.<p><p>---------<p><p>MANDA-II is a neutrino telescope which comprises a three dimensional array of optical sensors deployed in the South Pole glacier. <p>Its principle rests on the detection of the Cherenkov radiation emitted by charged secondary particles produced by the interaction of a high energy neutrino (> 100 GeV) with the matter surrounding the detector.<p><p>This work is based on data recorded by the AMANDA-II detector between 2000 and 2006 in order to search for cosmic sources of neutrinos. A potential signal must be extracted from the overwhelming background of muons and neutrinos originating from the interaction of primary cosmic rays within the atmosphere.<p>The observation is limited to the northern hemisphere in order to be free of the atmospheric muon background, which is stopped by the Earth. However, atmospheric neutrinos constitute an irreducible background composing the main part of the 6100 events selected for this analysis.<p>It is nevertheless possible to identify a point source of cosmic neutrinos by looking for a local excess breaking away from the isotropic background of atmospheric neutrinos;<p>This search is coupled with a selection based on the energy, whose spectrum is different from that of the atmospheric neutrino background.<p><p>An original statistical approach has been developed in order to optimize the detection of point sources, whilst controlling the false discovery rate -- hence the confidence level -- of an observation. This method is based solely on the knowledge of the background hypothesis, without any assumption on the production model of neutrinos in sought sources. Moreover, the method naturally accounts for the trial factor inherent in multiple testing.The procedure was applied on the final sample of events collected by AMANDA-II. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Contemporary projects to measure anisotropies in the cosmic microwave background (CMB) are now detecting hundreds to thousands of extragalactic radio sources, most of them blazars. As a member of a group of CMB scientists involved in the construction of catalogues of such sources and their analysis, I wish to point out the potential value of CMB surveys to studies of AGN jets and their polarization. Current CMB projects, for instance, reach mJy sensitivity, offer wide sky coverage, are blind and generally of uniform sensitivity across the sky (hence useful statistically), make essentially simultaneous multi-frequency observations at frequencies from 30 to 857 GHz, routinely offer repeated observations of sources with interesting cadences and now generally provide polarization measurements. The aim here is not to analyze in any depth the AGN science already derived from such projects, but rather to heighten awareness of their promise for the AGN community.

The aim of this thesis is an explanation of the murals of Portico 2 in Tepantitla palace in Teotihuacan on the basis of the scientific literature and the knowledge, that I have gained by studying. Here will be introduced opinions, ideas and theories of diferent scholars about what is depict on the murals, It will be made a try about a critical evaluation and revision, and I will do my best for make out a beneficial conclusion. There is no uniform view of what is depicted on the paintings of the portico 2 of the Tepantitla palace. Alfonso Caso expained the murals like Tlalocan, the paradise dominated by the God of Rain and Storm Tlaloc, Esther Pasztory and Peter T. Furst expained them as an image of the cosmic tree - the axis of the world - that connects the heavens, the earth and the underworld. Annabeth Headrick and María T. Uriart agree that murals represent a ceremony. For Headrick, the top register is the focal point, which is supposed to be the scene of raising of the sacred cosmic tree (the lower register is then a record of the celebrations taking place during the ceremony). For Uriarte, the concept of ball game and the significance of the toponym Teotihuacan, what both is connected with begining of time. Patrizia Granzier interprets the scene as a garden - a place where sacred and profane...

Galactic cosmic rays are the high-energy particles that stream into our solar system from distant corners of our Galaxy. The Earth's atmosphere serves as an ideal detector for the high energy cosmic rays which interact with the air molecule nuclei causing propagation of extensive air showers. The primary cosmic ray particles interact with the molecules in the atmosphere and produce showers of secondary particles (mainly pions) at about 15 km altitude. These pions decay into muons which are the dominant particles of radiation (about 80%) at the surface of the Earth. In recent years, there are growing interests in the applications of the cosmic ray measurements such as space/earth weather monitoring, homeland security activities based on the cosmic ray muon tomography, radiation effects on health via air travel, etc. A simulation program (based on the Geant4 software package developed at CERN) has been developed at Georgia State University for studying cosmic ray showers in the atmosphere. The results of this simulation study will provide unprecedented knowledge of geo-position-dependent cosmic ray shower profiles and will significantly advance cosmic ray applications. Simulation results are critically important for determining the temperature coefficients in every pressure layer in the atmosphere in order to calculate the temperature variations using the cosmic ray data. Using a single particle shower simulation, the weighted particle altitude distributions on a global scale are calculated with geomagnetic field implementation. The results of the simulation can aid the computation of the effective temperature in stratosphere.

Plus d'un siècle après leur découverte, les rayons cosmiques continuent d'intriguer les physiciens. Le flux de ces particules d'origine extraterrestre décroît fortement en fonction de leur énergie. Au-delà de 1 PeV(10¹⁵ eV), le flux devient trop faible pour permettre la détection directe sur des échelles de temps raisonnables. Cependant, les cascades de particules secondaires créées après l'interaction des rayons cosmiques avec les constituants de l'atmosphère sont détectables depuis le sol, c'est la détection indirecte. A partir de 100 PeV, le nombre d'observations est trop faible pour estimer de manière précise la masse des rayons cosmiques et ainsi contraindre les modèles de mécanismes d'accélération, de propagation et de type de sources. La détermination de la composition est effectuée à l'Observatoire Pierre Auger par les télescopes de fluorescence via la mesure de la variable Xmax avec un cycle utile de 14%. Xmax est la profondeur d'atmosphère traversée à laquelle le nombre de particules secondaires atteint sa valeur maximale. Cette observable est fortement corrélée à la masse du rayon cosmique qui a initié la gerbe. Un grand nombre d'observations est requis pour effectuer une détermination précise de la masse car les fluctuations statistiques de Xmax sont importantes. La radio détection apparaît alors comme une excellente alternative à la détection par fluorescence, puisque la technique mesurant ce signal a un cycle utile proche de 100%. Cette thèse propose une méthode d'estimation de la masse des rayons cosmiques d'ultra haute énergie basée seulement sur l'étude des signaux radio et leur simulation, afin de reconstruire de manière systématique l’énergie, le cœur et la profondeur Xmax des gerbes détectées par l’expérience AERA sur le site de l'Observatoire Pierre Auger en Argentine. L'influence de la modélisation de l'atmosphère dans le code de simulation SELFAS sur les valeurs reconstruites est étudiée. Notamment la géométrie des couches atmosphériques, la manière de traiter l'indice de réfraction et la densité de l'air ainsi que leurs variations journalières et saisonnières. / More than a century after their discovery, cosmic-raysare still puzzling physicists. The flux of these particlescoming from extraterrestrial sources strongly decreasesas a function of their energy. Above 1 PeV (10¹⁵ eV), theparticle flux becomes too low to allow a direct detectionon a reasonable time scale. However, the cascades ofsecondary particles produced after the interaction ofcosmic-rays with the constituents of the atmosphere aredetectable at the ground level; it is the indirect detection.Above 100 PeV, the number of observations is too lowto accurately estimate the mass of the cosmic rays andthen to constrain the prediction models of accelerationmechanisms, propagation and type of sources. Thedetermination of their composition is achieved at thePierre Auger Observatory using fluorescencetelescopes from the measurement of the Xmaxobservable with a duty cycle of 14%. Xmax, defined asthe atmosphere depth at which the number ofsecondary particles reaches its maximal value, is highlycorrelated to the mass of the cosmic ray that hascreated the air shower. A large number of observationsis required for a precise estimation of the mass as theXmax statistical fluctuations are important. The radiodetection is a perfect alternative to the fluorescencemethod as the duty cycle of a typical radio detector isclose to 100%. This thesis proposes a method toestimate the mass of ultra-high energy cosmic raysusing only the radio signals and their simulation. Thegoal is to systematically reconstruct the Xmax depth ofeach air shower detected by the AERA experimentwithin the site of the Pierre Auger Observatory inArgentina. The influence of the description of theatmosphere on the reconstructed shower parameters, inthe SELFAS code, has been studied. It includes thegeometry of the atmospheric layers, the way to calculatethe air refractive index and density, as well as their dailyand seasonal fluctuations.

Accretion discs efficiently transport angular momentum by a wide variety of as yet imperfectly understood mechanisms, with profound implications for the disc lifetime and planet formation. We discuss two different methods of angular momentum transport: first, generation of acoustic waves by mixing of inertial waves, and second, the generation of a self-sustaining magnetic field via the magnetorotational instability (MRI) which would be a source of dissipative turbulence. Previous local simulations of the MRI have shown that the dynamo changes character on addition of vertical stratification. We investigate numerically 3D hydrodynamic shearing waves with a conserved Hermitian form in an isothermal disc with vertical gravity, and describe the associated symplectic structure. We continue with a numerical investigation into the linear evolution of the MRI and the undular magnetic buoyancy instability in isolated flux regions and characterise the resultant quasi-linear EMFs as a function of height above the midplane. We combine this with an analytic description of the linear modes under an assumption of a poloidal-toroidal scale separation. Finally, we use RAMSES to perform full MHD simulations in a zero net flux shearing box, followed by spatial and a novel temporal averaging to reveal the essential structure of the dynamo. We find that inertial modes may be efficiently converted into acoustic modes for "bending waves", despite a fundamental ambiguity in the inertial mode structure. With our linear MRI and the undular magnetic buoyancy modes we find the localisation of the instability high in the atmosphere becomes determined by magnetic buoyancy rather than field strength for small enough azimuthal wavenumber, and that the critical Alfven speed below which the dynamo can operate increases with increasing distance from the midplane. We calculate analytically quasi-linear EMFs which predict both a vertical propagation of toroidal field and a method for creation of radial field. From our fully nonlinear calculations we find an electromotive force in phase with the toroidal field, which is itself 3π/2 out of phase with the radial (sheared) field at the midplane, and good agreement with our quasi-linear analytics. We have identified an efficient mechanism for generating acoustic waves in a disc. In our investigation of the accretion disc dynamo, we have reproduced analytically the EMFs calculated in our simulations, given arguments based on the phase of relevant quantities, several correlation integrals and the scalings suggested by our analytic work. Our analysis contributes significantly to an explanation for the dynamo in an accretion disc.

Until recently, obtaining rest-frame optical spectra of galaxies at z > 1 was a time consuming and challenging observation due to the difficult nature of near-infrared (near-IR) spectroscopy. However, with the advent of second generation ground-based near-IR spectrographs (e.g. KMOS, MOSFIRE), and the new low resolution near-IR grisms on the Hubble Space Telescope (HST), we have entered a new era in the study of high redshift galaxies. This thesis explores the physical properties of star-forming galaxies in the redshift range 1 < z < 3 by utilising a custom reduction of the 3D-HST near-IR grism spectroscopic survey. One of the most important observational constraints on the evolution of galaxies is the mass-metallicity relation (MZR), which is sensitive to both the star-formation history and various inflow/outflow processes. I use the 3D-HST spectra to provide a new constraint on the MZR at 2:0 < z < 2:3, and moreover measure the O/H abundance directly from the oxygen and hydrogen emission lines ([OII], [OIII] and Hβ) as opposed to the more common method at high redshift of inferring O/H from the N/H ratio (via [NII] and Hα). I show that the traditional form of the MZR is recovered from the 3D-HST data, with metallicity increasing with the stellar mass of a galaxy. However, the absolute metallicity values I derive are inconsistent with previous N/H-based measurements of metallicity at these redshifts. Moreover, I show that the 3D-HST data is inconsistent with the `fundamental metallicity relation' (FMR), and that, contrary to previous claims, this local Universe relation may not hold out to z & 2. To investigate this metallicity discrepancy further, I measure the evolution of the [OIII]/Hβ nebular emission line ratio in the 3D-HST spectra over the redshift range 1:3 < z < 2:3. I compare this observed line ratio evolution with state-of-the- art theoretical models which take into account the independent evolution of the ionization parameter, electron density and metallicity of star-forming regions with redshift. The homogeneous 3D-HST dataset allows me to perform a consistent analysis of this evolution which takes into account line luminosity selection effects. I show that, according to models, the observed [OIII]/Hβ evolution cannot be accounted for by pure metallicity evolution. Instead I am able to infer that the line ratio evolution is more consistent with, at the very least, an evolution to stronger ionizing conditions at high redshift, and perhaps even denser star-forming regions. I explore how this result can also explain the observed discrepancy between high redshift metallicity measurements. In light of this finding, I revisit the MZR at z >~ 2 and employ a purely theoretical approach to inferring metallicities from nebular lines, which is able to account for an evolution in ionization conditions. I then use a selection of galaxies from the local Universe, which mimic the properties of high redshift galaxies, to derive a more robust ionization sensitive, conversion, between N/H and O/H. With this new conversion which I am able to bring the previous inconsistent metallicity measurements at z >~ 2 back into agreement. Finally, I am able to show that, in this new formalism, the metallicity evolution between z = 2 and z = 3 is perhaps not as large as previously reported. To conclude I discuss ongoing work as part of the KMOS Deep Survey (KDS) being undertaken with the near near-IR Multi-Object Spectrograph KMOS on the VLT. I describe the observations and data reduction that has been completed to date and describe how this instrument will allow me to extend the work presented in this thesis to z > 3. I also introduce FIGS, a new HST near-IR grism survey seeking to spectroscopically identify galaxies at 5:5 < z < 8:5 and work I have begun in exploring this dataset.

Avec une oeuvre dense et complexe, Sylvie Germain constitue aujourd'hui l'une des figures marquantes du paysage littéraire français. A partir d'un corpus formé d'une dizaine de romans, représentatifs de son oeuvre, cette étude essaie d'explorer son univers romanesque qui trouverait son fondement dans le Cosmos et ses quatre éléments. L'objet de cette thèse est donc l'étude de la place et de la fonction symboliques de l'imagination matérielle dans l'oeuvre romanesque de Sylvie Germain. Cette dernière met l'accent sur l'importance de l'hérédité, de la racine, de la transmission et des éléments qui marquent une mémoire familiale. En adoptant les approches thématique et psychanalytique, cette étude est menée sous l'angle du couple antithétique : enracinement/déracinement que nous nous proposons d'approcher d'abord dans son acception géographique pour l'étendre ensuite à toute forme d'arrachement, qu'il soit psychologique ou métaphysique. Nous nous proposons également de démontrer que ces deux désirs d'enracinement et de déracinement créent une nouvelle typologie humaine qui remplacerait l'ancienne typologie nomades/sédentaires. La volonté de déracinement se traduit souvent par une volonté de faire table rase du passé et de s'arracher à une filiation, tandis que l'enracinement exige un travail de réconciliation avec le passé et une quête de la filiation. Enfin, pour écrire cette oeuvre de mémoire, Germain développe un jeu intertextuel et intratextuel et inscrit son texte dans la filiation des récits de commencements et dans une tradition littéraire auxquels elle ne cesse de se ressourcer. / With a dense and complex work of fiction, Sylvie Germain has become a prominent figure in modern French literature. Refering to a large corpus of works illustrative of her fiction, this study attempts to explore her fictional universe that is based on the cosmos and its four elements. The subject of this thesis is therefore the study of space and the symbolic function of material imagination in Germain's novels. In fact, she puts emphasis on the importance of inheritance, roots, transmission, and the elements that mark a family memory. Germain resurrects the rootedness and uprootedness problematic that appeared in French literature in the beginning of the 20th century. Following the thematic and psychoanalytical approaches, this study is built on the binary opposition: rootedness and uprootedness, first within a geographical framework, which later extends to every form of extraction, be it psychological or metaphysical. This study also attempts to prove that both desires of rootedness and uprootedness create a new human typology that would replace the old nomadic/sedentary typology. The will for uprootedness is often translated by the will to make a tabula rasa of the past and to split from a filiation, whereas rootedness requires reconciliation with the past and implies a quest for filiation. Finally, in order to depict memory, Germain develops a pattern of intertextuality and intratextuality, inscribing her text in the line of genesis narratives and in a literary tradition, which both ceaselessly inspire her work.

The new generation of astronomical instruments are not only in need of the highest sensitivity but require also well-controlled and known instrumental systematic effects. This is particularly relevant for projects dedicated to the study of the Cosmic Microwave background (CMB). Following the success of the Planck mission in providing the most detailed picture of the CMB temperature anisotropy to date, the next generation of CMB projects such as COrE (a potential future mission) and QUBIC (a ground based instrument)will be aiming to study the polarisation anisotropy of the CMB. However, the expectedB mode signal from the CMB is several orders of magnitude weaker than the temperature counterpart. Hence the calibration procedures will have to be more stringent than the ones that have been adopted for Planck, to get a proper detection of the primordialB mode signal. For instance, measurements for the receiver and optical systematic effects must be taken into consideration to get a proper reconstruction of the B modepower spectrum. This thesis is focused on the impact of real individual receiver and optical componentson the observation of the primordial B modes. To achieve this, several receiver and quasioptical components have been measured and modelled for their instrumental systematic effects. An analysis pipeline has also been developed, to assess the impact of such instrumental systematic effects on the observation of the primordial B modes. Using the results from the measurements and the analysis pipeline, the instrumental systematic effects that are of concern to the observation of primordial B modes have been identified. This is assuming that no effort has been made to mitigate such instrumental systematic effects.