In this master s thesis, we have studied the possibility of Lorentz invariance violation by considering some terms of the standard-model extesion (SME), specifically, those terms which refer to the quantum electrodynamics extension. We have performed quantum corrections in the fermionic sector of the usual quantum electrodynamics with added terms which violate the Lorentz and CPT symmetries in two different configurations. Firstly, adding operators governed by the coefficient gκλμ and, in a later time, adding operators governed by the coefficient bμ. In the theory with the coefficient gκλμ, we have performed quantum corrections in order to induce, in the bosonic sector of the theory, the conventional Chern-Simons and the higher-derivative terms, and analyze the behavior of both terms in the finite temperature regime, by using the method of derivative expansion and the Matsubara formalism. On the other hand, in the model with the coefficient bμ, we have performed quantum corrections in order to induce, in the bosonic sector, the higher-derivative Chern-Simons term, by using the method of derivative expansion and, subsequently, analyze the behavior of this term in the finite temperatura regime, where we have used the Matsubara formalism again. Thus, for the first case, we have observed that the conventional Chern-Simons term is nonzero only at finite temperature, whereas the higher-derivative term is finite at zero temperature, however, this term goes to zero when the temperature increases infinitely. In the second part of our study, we have shown that the higher-derivative Chern-Simons term is induced at zero temperature, nevertheless, this term goes to zero when the temperature increases too much. / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Nesta dissertação, estudamos a possibilidade de violação da invariância de Lorentz levando em conta alguns termos do modelo padrão estendido, mais especificamente, da parte deste modelo que trata da eletrodinâmica quântica estendida. Realizamos correções quânticas no setor fermiônico da eletrodinâmica quântica usual adicionada de termos que violam as simetrias de Lorentz e CPT em duas configurações diferentes. Primeiramente, adicionando operadores governados pelo coeficiente gκλμ e, em um momento posterior, adicionando operadores governados pelo coeficiente bμ. Para a teoria com o coeficiente gκλμ, realizamos correções quânticas com a intenção de induzir, no setor bosônico da teoria, os termos de Chern-Simons convencional e o de derivada superior, e analisar o comportamento de ambos os termos no regime de temperatura finita, fazendo o uso do método da expansão derivativa e do formalismo de Matsubara. Já para o modelo com o coeficiente bμ, realizamos correções quânticas a fim de induzir, no setor bosônico, o termo de Chern-Simons de derivada superior, usando o método da expansão derivativa e, posteriormente, analisar o comportamento deste termo no regime de temperatura finita, ao utilizarmos novamente o formalismo de Matsubara. Assim, para o primeiro caso, notamos que o termo de Chern-Simons convencional é diferente de zero apenas à temperatura finita, enquanto que, o termo de derivada superior é finito em temperatura zero, porém, tal termo vai a zero quando a temperatura cresce infinitamente. Na segunda parte do nosso estudo, mostramos que o termo de Chern-Simons de derivada superior é induzido no regime de temperatura zero, contudo, tal termo vai a zero quando a temperatura cresce muito.

The effective action of Euler Heisenberg describes the nonlinear dynamics of electromagnetic fields in vacuum. Such action takes into account the polarization in a vacuum for a bond, in addition to describing also the photon propagation through arbitrary electromagnetic fields that vary slowly. So, since its discovery, the effective action of Euler Heisenberg has been studied in various contexts, such as the scattering of light by light, pair production in a vacuum, Division of photons, birefringence in vacuum, effective action in gravity and string theory, among others. In this work we performed a study on the Lorentz transformations of observer and grains, showing that, in the presence of a field, the revolutions and changes of speed (boost) break the equivalence between these two transformations (Observer and particle). We studied also the violation of Lorentz invariance by consideration of some terms related to the extended standard model, with a focus on quantum electrodynamics extended. We carry out a Perturbative calculation in the cμν coefficient, a coefficient of this responsible for violation of Lorentz symmetry of particle, however impose rotational invariance. From the results of this calculation, we can retrieve the Perturbative result to the effect of the Division of photons in a vacuum, as well as the effective action of Euler Heisenberg with Lorentz violation, the linear coefficient c00. / Conselho Nacional de Desenvolvimento Científico e Tecnológico / A ação efetiva de Euler-Heisenberg descreve a dinâmica não linear de campos eletromagnéticos no vácuo. Tal ação leva em conta a polarização no vácuo para um laço, além de descrever também a propagação de fótons através de campos eletromagnéticos arbitrários que variam lentamente. Então, desde a sua descoberta, a ação efetiva de Euler-Heisenberg tem sido estudada em vários contextos, tais como o espalhamento da luz pela luz, produção de pares no vácuo, divisão de fótons, birrefringência no vácuo, ação efetiva em gravidade e teoria de cordas, dentre outros. Neste trabalho realizamos inicialmente um estudo sobre as transformações de Lorentz de observador e de partícula, mostrando que, na presença de um campo de fundo, as rotações e mudanças de velocidade (boost) quebram a equivalência entre essas duas transformações (observador e partícula). Estudamos também a violação da invariância de Lorentz através da consideração de alguns termos referentes ao modelo padrão estendido, com foco na eletrodinâmica quântica estendida. Efetuamos um cálculo não perturbativo no coeficiente cμν , coeficiente este responsável pela violação da simetria de Lorentz de partícula, no entanto impomos invariância rotacional. A partir dos resultados desse cálculo, conseguimos recuperar o resultado perturbativo para o efeito da divisão de fótons no vácuo, assim como a ação efetiva de Euler-Heisenberg com violação de Lorentz, linear no coeficiente c00.

Made available in DSpace on 2015-05-14T12:14:07Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 735779 bytes, checksum: 2ffa25e5b45beedc0c8f4f31d5f79b06 (MD5) Previous issue date: 2013-06-14 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this thesis, we review some basic concepts related to Lorentz symmetry violation and Horava-Lifshitz-like theories. We present our contribution to the calculation of the effective potential in two frameworks that exhibit Lorentz invariance violation. First, we calculate the effective potential for some HL-like theories. We obtained results for the pure scalar model, for the scalar QED with critical exponent z = 2 and z generic, and for the Yukawa model also with z = 2 and with arbitrary values of z. For the latter model, we show that the effective potential vanishes for even z and has nontrivial values for odd z. The second framework is the Kostelecký-Berger model that implements the Lorentz symmetry breaking in supersymmetry. We develop the theory of superfields for three and four-dimensional space-time based on this model and show how this development leads to a theory of superfields with ether-like Lorentz violation. We also obtained the one loop contributions to the effective action and effective potential in this theory. / Nesta tese, revisamos alguns conceitos básicos relacionados à violação da simetria de Lorentz e a teorias do tipo Horava-Lifshitz. Apresentamos nossa contribuição ao cálculo do potencial efetivo em duas formulações que exibem violação da invariância de Lorentz. Primeiro, calculamos o potencial efetivo para algumas teorias do tipo HL. Obtivemos resultados para o modelo escalar puro, para a QED escalar com expoente crítico z = 2 e z genérico, e para o modelo de Yukawa também com z = 2 e com valores arbitrários de z. Para este último modelo, demonstramos que o potencial efetivo se anula para z par e possui valores não triviais para z ímpar. A segunda formulação é o modelo de Kostelecký-Berger que implementa a quebra da simetria de Lorentz em supersimetria. Desenvolvemos a teoria de supercampos para três e quatro dimensões do espaço-tempo com base neste modelo e mostramos como este desenvolvimento leva a uma teoria de supercampos com violação de Lorentz do tipo-éter. Obtemos também as contribuições de um loop para a ação efetiva e para potencial efetivo nesta teoria.

La propagation des rayons Ɣ de très haute énergie (E > 100GeV) dans l'univers est affectée par les propriétés du milieu extragalactique. Ces photons à l'échelle du TeV, issus des processus d'accélération de particules dans les noyaux actifs de galaxies, peuvent en effet interagir avec des photons du fond optique et infrarouge qui baignent l'univers et produire des paires d'électrons et de positrons. Ce processus réduit la transparence de l'univers aux rayons Ɣ de très haute énergie mais permet en revanche de sonder les propriétés du milieu extragalactique de façon unique. Dans cette thèse, les données prises par le réseau de télescopes à imagerie Tcherenkov atmosphérique H.E.S.S. sont analysées et utilisées afin de caractériser la transparence de l'univers aux rayons Ɣ de très haute énergie. Une mesure indépendante de la distribution spectrale en énergie du fond cosmologique optique et infrarouge est réalisée à travers l'ajustement des modulations observées dans les spectres en énergie obtenus avec H.E.S.S. pour un échantillon de noyaux actifs de galaxies brillants dans une gamme en redshift 0.03 < z < 0.28. Les résultats obtenus sont compatibles avec les limites inférieures dérivées par comptages de galaxies et ne suggèrent pas d'anomalie de la transparence de l'univers aux rayons Ɣ vis à vis des modèles actuels du fond de lumière extragalactique. Des processus de second ordre affectant la propagation des rayons Ɣ de très haute énergie sont également explorés. Des limites sur une brisure de la symétrie de Lorentz à l'échelle de Planck sont obtenues à partir de l'analyse spectrale du noyau actif Mrk 501 observé dans un état de flux exceptionnel par H.E.S.S. en 2014, à grand angle zénithal. Enfin, des contraintes sur le champ magnétique extragalactique sont dérivées en considérant l'émission Ɣ secondaire attendue à partir de simulations des cascades électromagnétiques initiées lors du processus d'absorption pour le noyau actif distant PG 1553+113 vu par H.E.S.S. et le télescope spatial Fermi. Cette thèse a également été l'occasion d'une participation aux développements de certains aspects de la calibration et de l'analyse des données de H.E.S.S. / The propagation of very high energy Ɣ rays in the universe depends on the properties of the extragalactic medium. Such TeV-scale photons travelling cosmological distances are -emitted through particle acceleration mechanisms in active galaxy nuclei- can interact with the low-energy photons of the extragalactic background light (EBL) and produce electron-positron pairs. This effect reduces the transparency of the universe to very high energy Ɣ rays but it also provides a unique opportunity to probe the properties of the extragalactic medium. In this thesis, data taken with the H.E.S.S. array of Cherenkov telescopes are analyzed and used to characterize the transparency of the universe to very high energy Ɣ rays. A independent measurement of the spectral energy distribution of the EBL with H.E.S.S. is presented. It is obtained by extracting the EBL absorption signal from the fit of spectral modulations in the high-quality spectra of a sample of bright blazars in the redshift range 0.03 < z < 0.28. The intensity of the EBL obtained in different spectral bands is presented together with the associated Ɣ-ray horizon. The obtained results are consistent with lower limits derived from galaxy counts and do not suggest an anomaly of the transparency of the universe to Ɣ rays with respect to current models of the extragalactic background light. Second-order processes affecting the propagation of very high energy Ɣ rays in the universe are also considered. Limits on Lorentz invariance violation at Planck scale are obtained from the spectral analysis of the active galaxy nucleus Mrk 501 observed during a high-flux state by H.E.S.S. in 2014, at large zenith angle. Finally, constraints on the extragalactic magnetic field properties are derived by considering the secondary Ɣ-ray emission expected from the simulation of electromagnetic cascades initiated by the absorption process for the distant active galaxy nucleus PG 1553+113 seen by H.E.S.S. and the Fermi Ɣ-ray space telescope. In this thesis some developments related to the calibration and analysis of H.E.S.S. data are also presented.

Ein Fortschritt im Verständnis der Naturgesetzte wäre eine quantenphysikalische Beschreibung der Gravitation. Eine gültige Theorie der Quantengravitation (QG) existiert derzeit wegen des fehlenden experimentellen Zugangs des Planck-Skalen-Bereichs nicht. Dennoch können Experimente Hinweise für die Suche nach einer QG liefern. Die Standardmodellerweiterung (SME) bspw. beschreibt mögliche QG-induzierte beobachtbare niederenergetische Planck-Skalen-Effekte. Diesem Ansatz folgend wurde ein modernes Michelson-Morley-Experiment der nächsten Generation entwickelt, das es erstmalig erlaubt, simultan Obergrenzen für niederenergetische Planck-Skalen-Effekte in den Bewegungsgleichungen von Photonen und Fermionen zu bestimmen. Das zugrundeliegende theoretische Modell innerhalb der SME wurde neu betrachtet und Unstimmigkeiten korrigiert. Der Aufbau besteht aus ultra-stabilen kryogenen optischen Resonatoren (COREs) und Mikrowellenresonatoren, die gemeinsam im Raum rotieren. Die durch thermisches Rauschen limitierte vorhergesagte relative Frequenzinstabilität der entwickelten COREs liegt bei Temperaturen von flüssigem Helium im Bereich von 10^-17. Die Mikrowellenresonatoren können eine relative Frequenzinstabilität von 10^-16 erreichen. Um Störeinflüsse zu reduzieren, wurde zudem ein rauscharmer Niedrigtemperatur- sowie Drehtischaufbau konzipiert. Parallel wurde mit den Mikrowellenresonatoren ein einjähriges modernes Michelson-Morley-Experiment mit einer Sensitivität im Bereich von 10^-18 durchgeführt und erstmalig vollständig entkoppelte Obergrenzen für niederenergetische Planck-Skalen-Effekte im Bereich von 10^-17 bestimmt. Für den Aufbau der nächsten Generation lässt sich basierend auf der Frequenzinstabilität der COREs und der Mikrowellenresonatoren eine Sensitivität für niederenergetische Planck-Skalen-Effekte im Bereich von 10^-20 abschätzen. Zum ersten Mal kann somit der hypothetische Planck-unterdrückte-Bereich mit elektromagnetischen Resonatoren erkundet werden. / The next big leap in understanding the working principles of nature can be expected from a quantum physical description of gravity. None of the quantum gravity (QG) candidate theories can be verified, since observations at the Planck regime have currently been impossible. Still, experiments can help to give insights. For example, standard model extension (SME) describes potential observable low-energy remnant Planck scale effects. With this in mind, a design for a next-generation modern Michelson-Morley experiment has been developed that allows extracting upper bounds on potentially observable remnant Planck scale effects in the equations of motion of photons and fermions simultaneously. The corresponding theoretical model within the framework of the SME has been revisited and discrepancies have been corrected. The experimental setup consists of co-rotating ultra-stable cryogenic optical resonators (COREs) and ultra-stable sapphire loaded cryogenic microwave whispering-gallery resonators. The developed COREs have a theoretical thermal noise limited fractional frequency instability on the order of 10^-17 at liquid helium temperatures. The cryogenic microwave resonators allow in principle a performance on the order of 10^-16. For noise reduction, a suitable low noise cryogenic as well as turntable system has been designed. In parallel, a one-year modern Michelson-Morley measurement campaign with a sensitivity on the order of 10^-18 was carried out using the cryogenic microwave resonators. The experiment has allowed to set new stringent disentangled upper bounds on remnant Planck scale effects on the order of 10^-17. With the frequency performance of the COREs and cryogenic microwave resonators of the next-generation experimental setup, a sensitivity for remnant Planck scale effects on the order of 10^-20 can be estimated. Thus, the designed setup has the potential to explore the hypothetical Planck suppressed regime using electromagnetic resonators for the first time.

Relativity is one of the most important and well tested theories and Lorentz invariance is one of its pillars. Lorentz invariance violation (LIV), however, has been discussed in several quantum gravity and high energy models. For this reason, it is crucial to test it. Several tests, both terrestrial and astrophysical, have been performed in the last years and provide limits on the violation. This work takes part in these efforts and discuss the possibility of testing LIV with ultra-high energy cosmic rays (UHECRs). The effects of LIV in their propagation and the resulting changes in the spectrum of UHECRs are obtained and compared to the experimental data from the Pierre Auger Observatory. An analytical calculation for the inelasticity in the laboratory frame with LIV of any a + b &rarr; c + d interaction is presented and used to obtain the phase space and the energy losses of the pion production for protons, the photodisintegration for nuclei and the pair production for photons with LIV. A parametrization for the threshold energy of the photodisintegration with LIV is also proposed. The main effect seen is a decrease in the phase space and a resulting decrease in the energy loss. These changes have been implemented in Monte Carlo propagation codes and the resulting spectra of protons, nuclei and photons on Earth have been obtained and fitted to the data from the Pierre Auger Observatory. It is shown that upper limits on the photon LIV coefficient can be derived from the upper limits on the photon flux from the Pierre Auger Observatory. / Relatividade é uma das mais importantes e bem testadas teorias e a invariância de Lorentz é um de seus pilares. A violação da invariância de Lorentz (VIL), todavia, tem sido discutida em diversos modelos de gravidade quântica e altas energias. Por tal motivo, é crucial testá-la. Diversos testes, tanto terrestres quanto astrofísicos, foram realizados nos últimos anos e fornecem limites na violação. Este trabalho se insere nesses esforços e discute a possibilidade de testar VIL com raios cósmicos de altíssima energia. Os efeitos da VIL em sua propagação e as consequentes mudanças no espectro de raios cósmicos de altíssima energia são obtidos e comparados com os dados experimentais do Observatório Pierre Auger. Um cálculo analítico para a inelasticidade no referencial do laboratório com VIL para qualquer interação da forma a + b &rarr; c + d é apresentado e usado para obter o espaço de fase e as perdas de energia para a produção de píons para prótons, a fotodesintegração para núcleos e a produção de pares para fótons com VIL. Uma parametrização para o limiar de energia da fotodesintegração com VIL também é proposta. O principal efeito observado é uma diminuição no espaço de fase e uma consequente diminuição nas perdas de energia. Tais mudanças foram implementadas em códigos de Monte Carlo para a propagação e os espectros resultantes para prótons, núcleos e fótons na Terra foram obtidos e ajustados aos dados do Observatório Pierre Auger. É mostrado que limites superiores nos coeficientes de VIL para o fóton podem ser deduzidos dos limites superiores para o fluxo de fótons do Observatório Pierre Auger.

Relativity is one of the most important and well tested theories and Lorentz invariance is one of its pillars. Lorentz invariance violation (LIV), however, has been discussed in several quantum gravity and high energy models. For this reason, it is crucial to test it. Several tests, both terrestrial and astrophysical, have been performed in the last years and provide limits on the violation. This work takes part in these efforts and discuss the possibility of testing LIV with ultra-high energy cosmic rays (UHECRs). The effects of LIV in their propagation and the resulting changes in the spectrum of UHECRs are obtained and compared to the experimental data from the Pierre Auger Observatory. An analytical calculation for the inelasticity in the laboratory frame with LIV of any a + b &rarr; c + d interaction is presented and used to obtain the phase space and the energy losses of the pion production for protons, the photodisintegration for nuclei and the pair production for photons with LIV. A parametrization for the threshold energy of the photodisintegration with LIV is also proposed. The main effect seen is a decrease in the phase space and a resulting decrease in the energy loss. These changes have been implemented in Monte Carlo propagation codes and the resulting spectra of protons, nuclei and photons on Earth have been obtained and fitted to the data from the Pierre Auger Observatory. It is shown that upper limits on the photon LIV coefficient can be derived from the upper limits on the photon flux from the Pierre Auger Observatory. / Relatividade é uma das mais importantes e bem testadas teorias e a invariância de Lorentz é um de seus pilares. A violação da invariância de Lorentz (VIL), todavia, tem sido discutida em diversos modelos de gravidade quântica e altas energias. Por tal motivo, é crucial testá-la. Diversos testes, tanto terrestres quanto astrofísicos, foram realizados nos últimos anos e fornecem limites na violação. Este trabalho se insere nesses esforços e discute a possibilidade de testar VIL com raios cósmicos de altíssima energia. Os efeitos da VIL em sua propagação e as consequentes mudanças no espectro de raios cósmicos de altíssima energia são obtidos e comparados com os dados experimentais do Observatório Pierre Auger. Um cálculo analítico para a inelasticidade no referencial do laboratório com VIL para qualquer interação da forma a + b &rarr; c + d é apresentado e usado para obter o espaço de fase e as perdas de energia para a produção de píons para prótons, a fotodesintegração para núcleos e a produção de pares para fótons com VIL. Uma parametrização para o limiar de energia da fotodesintegração com VIL também é proposta. O principal efeito observado é uma diminuição no espaço de fase e uma consequente diminuição nas perdas de energia. Tais mudanças foram implementadas em códigos de Monte Carlo para a propagação e os espectros resultantes para prótons, núcleos e fótons na Terra foram obtidos e ajustados aos dados do Observatório Pierre Auger. É mostrado que limites superiores nos coeficientes de VIL para o fóton podem ser deduzidos dos limites superiores para o fluxo de fótons do Observatório Pierre Auger.

La gravité d’Horava brise la symétrie de Lorentz avec l’introduction d’une foliation intrinsèque de l’espace-temps, définie par un champ scalaire, le khronon. Cette foliation privilégiée rend les solutions de trous noirs plus compliquées que celles de la relativité générale, due à l’apparition de nouveaux horizons: un horizon de matière pour les champs de matière; l’horizon de spin-0 pour les excitations scalaires du khronon, l’horizon de spin-2 pour les ondes gravitationnelles; finalement un horizon universel pour des modes instantanés apparaissant dans l’ultraviolet. On étudie des trous noirs en mouvement lent par rapport au référentiel privilégié. Ces solutions sont cruciales pour déterminer les susceptibilités des trous noirs et prédire leur émission d’ondes gravitationnelles, en particulier l’émission dipolaire des binaires de trous noirs. On trouve que pour des valeurs arbitraires des constantes de couplage, les trous noirs en mouvement lent souffrent de singularités de courbure à l’horizon universel. Des singularités à l’horizon de spin-0 sont aussi présentes mais peuvent être absorbées si l’on sacrifie les solutions plates à l’infini. Cependant, on a trouvé un sous-ensemble de l’espace de paramètres, de dimension un, où les trous noirs en mouvement lent sont partout réguliers et coincident avec ceux de la relativité générale. En particulier, ils n’émettent pas de radiation dipolaire. Remarquablement, ce sous-ensemble est favorisé par les contraintes récentes de l’événement GW170817 ainsi que les tests dans le système solaire. / Horava gravity breaks Lorentz symmetry by introducing a preferred spacetime foliation, which is defined by a timelike dynamical scalar field, the khronon. The presence of this preferred foliation makes black hole solutions more complicated than in General Relativity, with the appearance of multiple distinct event horizons: a matter horizon for matter fields; a spin-0 horizon for the scalar excitations of the khronon; a spin-2 horizon for tensorial gravitational waves; and even a universal horizon for instantaneously propagating modes appearing in the ultraviolet. We study how black hole solutions in Horava gravity change when the black hole is allowed to move with low velocity relative to the preferred foliation. These slowly moving solutions are a crucial ingredient to compute black hole sensitivities and predict gravitational wave emission (and particularly dipolar radiation) from the inspiral of binary black hole systems. We find that for generic values of the theory's three dimensionless coupling constants, slowly moving black holes present curvature singularities at the universal horizon. Singularities at the spin-0 horizon also arise unless one waives the requirement of asymptotic flatness at spatial infinity. Nevertheless, we find that in a one-dimensional subset of the parameter space of the theory's coupling constants, slowly moving black holes are regular everywhere, even though they coincide with the general relativistic ones (thus implying in particular the absence of dipolar gravitational radiation). Remarkably, this subset of the parameter space essentially coincides with the one selected by the recent constraints from GW170817 and by solar system tests.

Des modèles spécifiques de gravitation quantique suggèrent l’existence d’une Violation de l’Invariance de Lorentz (LIV en anglais) à l’échelle de Planck. Une des signatures de cette violation est la modification de la propagation des photons dans le vide, induisant des décalages temporels dépendant de l’énergie des photons observés sur Terre. De tels décalages dans le temps d’arrivée de rayons γ sont recherchés avec l’expérience H.E.S.S. (High Energy Stereoscopic System), grâce aux émissions de très hautes énergies en provenance de sources lointaines telles que les blazars. Néanmoins, l’origine du décalage temporel doit être comprise en détails. En effet, un décalage intrinsèque à la source pourrait venir biaiser les contraintes sur les modèles de gravitation quantique. Cette thèse propose dans un premier temps de s’intéresser à la modélisation temporelle des éruptions de blazars, pour étudier les possibles décalages intrinsèques liés aux processus d’émissions de ces éruptions. Grâce à l’élaboration d’un modèle simple, cette étude met en relief les différentes caractéristiques de ces décalages intrinsèques sur les scénarios d’éruptions de blazar afin d’essayer de les distinguer des décalages potentiellement dus à un effet de LIV et aussi de proposer de nouvelles contraintes basées sur ces décalages temporels. Dans un deuxième temps, la méthode de recherche de décalages temporels dépendant de l’énergie avec H.E.S.S. est présentée ainsi qu’une application sur l’éruption du blazar Markarian 501 ayant eu lieu en juillet 2014. Cette analyse a permis d’établir la meilleure limite obtenue sur le terme quadratique de la signature de la LIV avec l’utilisation d’éruption de blazars. / Specific models of quantum gravity suggest the existence of a Lorentz Invariance Violation (LIV) at the Planck scale. One signature of that violation is a modification the propagation of photons in vacuum which induces energy dependent delays in the arrival time of photons on Earth. The H.E.S.S. (High Energy Stereoscopic System) experiment can search for such delays in the arrival time of gamma rays, thanks to the very high energy emission coming from distant blazars. However, the time delay origin have to be fully understood. Indeed, an intrinsic time delay coming from the source can bias the constraints made on quantum gravity models. In the first part of this thesis, a time dependent blazar flare model is considered to search for the presence of intrinsic time delays related to the emission mechanisms of flares. With the elaboration of a simple scenario, this study highlights the different characteristics of intrinsic time delays in order to investigate how to disentangle them from delays due to LIV as well as to provide new constraints on blazar modeling. In the second part of this thesis, the method used to search for LIV signatures in blazar light curves at very high energy is presented as well as an application to the flare of Markarian 501 which occurred in July 2014. This analysis provides in particular the best upper limit on the quadratic term of LIV signature.