This thesis deals with the personality and life of the Tuscan Renaissance scientist Galileo Galilei, a time in which he lived, and his relationship with the Catholic Church. The aim of the thesis is to acquaint the reader with the life of Galileo Galilei and Renaissance society, and thus capture important moments and influences that shaped Galileo's personality and life orientation. The thesis is divided into three main chapters. The first part deals with the Renaissance period and the related European Reformation. It focuses on the Renaissance in Italy, then education, religious situation and seeing the world. The second chapter is dedicated to Galileo's biography, with regard to his work and then researchers who were with Galileo joint activity. The last part refers to the religious situation of 16th to 17th century, considering the Council of Trent, the Roman Inquisition and the cosmology of how the people regarded it in antiquity and later the Catholic Church and scientists in the early modern period. This part especially illustrates the conflict Galileo and the Church. It describes the reasons of the conflict, the trial of Galileo and the consequences that flowed from it. The thesis is supplemented with events after Galileo's death. The conclusion summarizes the most important influences that...

Late-time cosmic acceleration is one of the most interesting unsolved puzzles in modern cosmology. The explanation most accepted nowadays, dark energy, raises questions about its own nature, e.g. what exactly is dark energy, and implications to the observations, e.g. how to handle fine tuning problem and coincidence problem. Hence, dark energy evolution through cosmic history, together with its equation of state, are subjects of research in many current experiments. In this dissertation, using Markov Chain Monte Carlo sampling, we try to constrain the evolution of the dark energy equation of state in a nearly model-independent approach by combining different datasets coming from observations of baryon acoustic oscillations, cosmic chronometers, cosmic microwave background anisotropies and type Ia supernovae. We found no strong evidence that could indicate deviations from LCDM model, which is the standard model in cosmology accepted today. / A aceleração cósmica atual é um dos mais interessantes enigmas não resolvidos da cosmologia moderna. A explicação mais aceita hoje em dia, a energia escura, levanta questões acerca de sua própria natureza, como o que é exatamente a energia escura, e as implicações para as observações, por exemplo como lidar com o problema do ajuste fino e o problema da coincidência. Por isso, a evolução da energia escura durante a história cósmica, juntamente com sua equação de estado, são objetos de pesquisa em inúmeros experimentos atuais. Nesta dissertação, usando amostragem por cadeias de Markov de Monte Carlo, tentamos restringir a evolução da equação de estado da energia escura em uma abordagem quase independente de modelo ao combinar diferentes conjuntos de dados provenientes de observações de oscilações acústicas de bárions, cronômetros cósmicos, anisotropias da radiação cósmica de fundo e supernovas tipo Ia. Não encontramos evidências fortes que pudessem indicar desvios do modelo LCDM, o qual é o modelo padrão aceito hoje na cosmologia.

In this thesis, Newman-Penrose techniques are used to obtain some new exact solutions to Einstein's field equations of general relativity and to assist in the physical interpretation of some exact radiative space-times. Attention is restricted to algebraically special space-times with a twist-free, repeated principal null congruence. In particular, the Robinson-Trautman type N solutions, which describe expanding gravitational waves, are investigated for all possible values of the cosmological constant A and the Gaussian curvature parameter E. The wave surfaces are always (hemi-)spherical, with successive surfaces displaced along time-like, space-like or null lines, depending on E. Explicit sandwich waves of this class are studied in Minkowski, de Sitter or anti-de Sitter backgrounds and a particular family of such solutions, which can be used to represent snapping or decaying cosmic strings, is considered in detail. The singularity and global structure of the solutions is also presented. In the remaining part of the thesis, the complete family of space-times with a non-expanding, shear-free, twist-free, geodesic principal null congruence (Kundt waves), that are of algebraic type III and for which the cosmological constant (Ac) is non-zero, is presented. The possible presence of an aligned pure radiation field is also assumed. These space-times generalise the known vacuum solutions of type N with arbitrary Ac and type III with Ac = O. It is shown that there are two, one and three distinct classes of solutions when Ac is respectively zero, positive and negative and, in these cases, the wave surfaces are plane, spherical or hyperboloidal in Minkowski, de Sitter or anti-de Sitter backgrounds respectively. The singularities which occur in these space-times are interpreted in terms of envelopes of these wave surfaces. Again, by considering functions of the retarded time which "cross-over" between canonical types, sandwich waves are also studied. The limiting cases of these, giving rise to shock or impulsive waves, are also considered.

Dans le modèle standard de cosmologie ΛCDM, environ 72% de la densité d'énergie totale de l'Univers se présente sous la forme d'énergie sombre qui causerait la présente accélération de l'Univers. Parmi les sondes cosmologiques couramment utilisées, l'effet de lentille gravitationnel forte dans les amas est une technique prometteuse fournissant des contraintes orthogonales sur les paramètres cosmologiques. Le programme HFF a permis une amélioration significative de l'estimation de la distribution de masse des amas. Cependant, la modélisation de l'effet de lentille forte dans les amas semble ne pas atteindre la résolution angulaire des observations HST. Cette thèse fournit une meilleure compréhension de l'impact des erreurs systématiques dans la modélisation paramétrique de l'effet de lentille forte dans les amas de galaxies et, donc, sur la détermination des paramètres cosmologiques. Premièrement, j'ai analysé deux amas de galaxies simulés, ayant les mêmes caractéristiques que les amas du programme HFF, Ares et Hera. J'ai utilisé plusieurs estimateurs afin d'évaluer la qualité de nos reconstructions obtenues, permettant de quantifier l'impact des erreurs systématiques dues, au choix des profils de densité et configurations et, ensuite, de la disponibilité d'images multiples dans la détermination de paramètres cosmologiques. Deuxièmement, en utilisant deux amas de galaxies, j'ai testé quatre modèles cosmologiques pour lesquels l'équation d'état de l'énergie sombre, w(z), est paramétrisée en fonction du redshift. J'ai réalisé plusieurs modélisations pour quantifier l'impact des erreurs systématiques liées à la position des images multiples sur les paramètres cosmologiques. / In the standard cosmological model ΛCDM, about 70% of the energy density of the Universe is in the form of a dark energy that would cause the current acceleration of the Universe. Among the extensively used cosmological probes, using strong lensing features in galaxy clusters is a promising technique yielding orthogonal constraints on cosmological parameters. The program HFF has led to a significant improvement of cluster mass estimates. However, strong lensing modelling appears to be still unable to match the HST observations angular resolution.This thesis provides a better understanding of how systematic errors impact the retrieval of cosmological parameters in order to use strong lensing clusters as reliable cosmological probes. Firstly, I have analyzed two simulated HFF-like clusters, Ares and Hera, I use several estimators to assess the goodness of our reconstructions by comparing our multiple models, with the input models. This allows to quantify the impact of systematic errors arising from the choice of different density profiles and configurations and, secondly, from the availability of constraints in the parametric modelling of strong lensing clusters and therefore on the retrieval of cosmological parameters. Secondly, I probe four cosmological models in which the equation of state of dark energy, w(z), is parameterized as a function of redshift using strong lensing features in two galaxy clusters. To quantify how the cosmological constraints are biased due to systematic effects in the strong lensing modelling, I carry out several modelling attempts considering different uncertainties for the multiple images positions.

Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-10-16T19:37:30Z No. of bitstreams: 1 GIVAL PORDEUS DA SILVA NETO – DISSERTAÇÃO (PPGFísica) 2015.pdf: 4886479 bytes, checksum: 8589cc7f91d5dab59210f3bf9b9a3d97 (MD5) / Made available in DSpace on 2018-10-16T19:37:30Z (GMT). No. of bitstreams: 1 GIVAL PORDEUS DA SILVA NETO – DISSERTAÇÃO (PPGFísica) 2015.pdf: 4886479 bytes, checksum: 8589cc7f91d5dab59210f3bf9b9a3d97 (MD5) Previous issue date: 2015-05-08 / Capes / A constante de Hubble (H0) é considerada fundamental na cosmologia. Ela é crucial para qualquer modelo cosmológico moderno, pois está relacionada com diversas grandezas cosmológicas, portanto, é de extrema importância a determinação mais restritiva e acurada possível do seu valor. A mais recente estimativa de H0 a partir de métodos locais (z 1), H0 = 73:8 2; 4 kms􀀀1Mpc􀀀1, e a partir de redshifts muito altos (z ' 1070), H0 = 67; 3 1; 2 kms􀀀1Mpc􀀀1, são discrepantes em um nível de con fiança de 2; 4 . Dentro deste contexto, Lima e Cunha (LC), a m de lançar alguma luz sobre este problema, derivou uma nova determinação de H0 utilizando quatro testes cosmológicos em redshifts intermediários (z 1), com base no chamado modelo CDM Plano. Eles obtiveram H0 = 74; 1 2; 2 kms􀀀1Mpc􀀀1, em pleno acordo com as medições locais. Neste trabalho, exploramos a robustez do resultado de LC, procurando por erros sistemáticos e a sua dependência com o modelo cosmológico usado. Nós constatamos que o valor H0 a partir desta análise conjunta é muito fracamente dependente de modelos cosmológico, mas a morfologia adotada para inferir o raio central dos aglomerados de galáxias, altera o resultado, sendo a principal fonte de erros sistemáticos. Concluímos que uma melhor compreensão da morfologia dos aglomerados é fundamental para transformar esse método em um poderoso estimador de H0. / The Hubble constant (H0) is considered a fundamental constant of cosmology. It is crucial for any modern cosmological model, it is related to various cosmological quantities, so it is extremely important a restrictive and accurate determination of its value. The most recent estimate of H0 from local observations (z 1), H0 = 73:8 2; 4 kms􀀀�1Mpc􀀀�1, and from high redshifts (z ' 1070), H0 = 67; 3 1; 2 kms􀀀�1Mpc􀀀�1, are discrepant in a con dence level of 2; 4 . Within this context, Cunha and Lima (LC), in order to shed some light on this problem, derived a new determination of H0 using four cosmological tests at intermediate redshifts (z 1), based on the model called Flat CDM. They obtained H0 = 74; 1 2; 2 kms􀀀�1Mpc􀀀�1, in full agreement with local measurements. In this work, we explore the robustness of the result LC looking for systematic errors and its dependence on the cosmological model used. We found that the H0 value from this combined analysis is very weakly dependent on the underlying cosmological model, but the morphology adopted to infer the core radius of galaxy clusters, changes the estimates being the main source of systematic errors. Hence, we conclude that a better understanding of the morphology of the clusters is essential to transform this method in a powerful cross-check to H0.

Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-10-10T19:33:25Z No. of bitstreams: 1 EDME VALE PEREIRA – DISSERTAÇÃO (PPGFísica) 2016.pdf: 765741 bytes, checksum: 06e478d901631d57a3c3905fb212d89c (MD5) / Made available in DSpace on 2018-10-10T19:33:25Z (GMT). No. of bitstreams: 1 EDME VALE PEREIRA – DISSERTAÇÃO (PPGFísica) 2016.pdf: 765741 bytes, checksum: 06e478d901631d57a3c3905fb212d89c (MD5) Previous issue date: 2016-08-11 / Capes / Neste trabalho, estudamos um escalonamento de Horava-Lifshitz destinado a reescrever uma eletrodinâmica que viola a invariância de Lorentz com operadores derivativos controlados por um quadrivetor constante n . Esse método foi usado inicialmente para escalonar a lagrangiana de Maxwell e depois a lagrangiana de altas ordens derivativas, conhecida como modelo Myers-Pospelov. Após o processo de escalonamento, obtivemos que ambas as lagrangianas são descritas em função de um expoente crítico z, que insere um caráter anisotrópico para ambas as teorias. Foram obtidos os propagadores de Feynman e as relações de dispersão para ambos os modelos. Devido ao caráter irrefringente atribuído ao modelo de altas ordens derivativas, usamos os modos de propagação associados, como as soluções por frequências, e efetuamos os cálculos de polarização para determinar os limites superiores de ocorrências dos efeitos da quebra da invariância de Lorentz. Tais operações estão de acordo com as observações de explosões de raios gama, mais especificamente, o evento GRB051218A. O parâmetro que controla a quebra da invariância de Lorentz, apresenta-se superior em 8 (oito) ordens de magnitude, se comparado com alguns resultados da literatura. O atraso temporal na propagação de dois fótons também foi determinado. / In this work, we study a Horava-Lifshitz scaling which can be used to rewrite an electrodynamics which breaks the Lorentz invariance with derivatives operators controlled by a constant four-vector, n . This method was initially used to scale the Maxwell lagrangian and then the high orders derivatives lagrangian, known as Myers-Pospelov model. After of the process, we obtained that both the lagrangian are described in terms of a critical exponent z, which can be inserted as anisotropic character for both theories. The of Feynman propagators and dispersion relations for both models were obtained. Due to the birefringent character attributed to Myers-Pospelov model, we use the associate propagation modes, as solutions for frequencies, and we perform the polarization calculations to determine the upper limits of occurrences related with e ects of Lorentz invariance breaking. Such operations are consistent with the recent observations of gamma-ray bursts, more speci cally, the GRB 051218A event. The parameter which controls of the Lorentz invariance violation, it presents superior in eight (8) orders of magnitude, compared with some results of literature. The time delay in the propagation of two photons was also determined.

Submitted by Vasti Diniz (vastijpa@hotmail.com) on 2017-09-19T14:08:42Z No. of bitstreams: 1 arquivototal.pdf: 1473125 bytes, checksum: e441ef90c05c6d3302f32c912e7eb363 (MD5) / Made available in DSpace on 2017-09-19T14:08:42Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1473125 bytes, checksum: e441ef90c05c6d3302f32c912e7eb363 (MD5) Previous issue date: 2016-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / We have investigated cosmological models governed by a geometrical scalar-tensor theory in the framework of the Weyl integrable manifolds. Such as theory corresponds to the general relativity, minimally coupled to a massless scalar field, in the frame where the geometry is riemannian. We present the fundamental elements of the Weyl geometry and we extend the hamiltonian formalism of the general relativity to this geometry. We propose a foliation invariant by Weyl transformations, in which the Weyl scalar field plays the role of a clock to measure the evolution of the foliation. Cosmological singularities are verified in the clas­sical solutions of the FLRW model and avoided in the quantum cosmology approach. The Weyl transformations provides a canonical transformations between two related frames and a unitary operator is defined to map these two frame in the quantum regime. The physical equivalence in the quantum level is discussed. / Investigamos a cosmologia de modelos regidos por uma teoria escalar-tensorial geometrica, construida numa geometria de Weyl integravel. Tal teoria corresponde a teoria da Relati­vidade Geral, minimamente acoplada a urn campo escalar sem massa, no referencial onde a geometria é Riemanniana. Apresentamos os elementos fundamentais da geometria de Weyl e estendemos o formalismo hamiltoniano da Relatividade Geral para esta geometria, prepa­rando assim o formalismo para descrever teorias ambientadas na geometria de Weyl. Propo­mos uma folheagao invariante por transformagoes de Weyl, a qual emprega o campo escalar de Weyl, oriundo da geometria, como urn relOgio natural para a evolugao do universo. Singu­laridades cosmolOgicas sao verificadas nas predigoes das solugoes classicas do modelo FLRW e removidas quando tratamos a cosmologia quantica deste modelo. As transformagoes de Weyl sao investigadas no espago de fase, onde induzem transformagoes canonicas que viabilizam a equivalencia fisica entre os referenciais de Riemann e Weyl tanto no regime classic° como no quantico.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-26T18:18:25Z No. of bitstreams: 1 monalisasilvadeoliveira.pdf: 473060 bytes, checksum: 1e394ef35b65c023c130f0dbca9a9d12 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-13T12:04:23Z (GMT) No. of bitstreams: 1 monalisasilvadeoliveira.pdf: 473060 bytes, checksum: 1e394ef35b65c023c130f0dbca9a9d12 (MD5) / Made available in DSpace on 2017-05-13T12:04:23Z (GMT). No. of bitstreams: 1 monalisasilvadeoliveira.pdf: 473060 bytes, checksum: 1e394ef35b65c023c130f0dbca9a9d12 (MD5) Previous issue date: 2013-02-28 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho, fazemos uma pequena revisão sobre tensores e sua utilização na Relatividade Geral, apresentamos o método de transformação conforme e o teorema da fatorização e discutimos as soluções de Schwarzschild com e sem constante cosmológica. Então, a solução de Schwarzschild com constante cosmológica é derivada, a partir das equações de campo de Einstein, utilizando-se os conceitos abordados. / In this work, we make a brief review of tensors and their use in General Relativity, we present the local conformal transformation method and the factorization theorem and we discuss Schwarzschild's solutions with and without cosmological constant. Then, the Schwarzschild's solution with cosmological constant is derived, from the Einstein's field equations, using the concepts addressed.

Les vitesses particulières de galaxies fournissent des informations importantes sur notre mouvement par rapport aux grandes structures observées et peuvent être utilisées afin de contraindre la distribution de matière noire sous-jacente. En ce basant sur cette approche, la technique des réalisations contraintes permet de calculer des simulations numériques qui ressemblent à l'Univers Local observé. Ceci fourni un laboratoire numérique puissant pour étudier la dynamique, la formation et l' évolution des structures bien connues de l'Univers Local. L' étape cruciale est de générer, à partir des données observationnelles, des conditions initiales appropriées. Nous présentons ici des améliorations de la technique des simulations contraintes, accompagnées d'un code numérique nouvellement développé et hautement optimisé, qui peut ingérer les énormes ensemble de données observationnelles. Les galaxies évoluent à partir du collapse gravitationnel des surdensités primordiales de l'univers très jeune; leurs mouvements créent un champ de déplacement à grande échelle. Une source majeure d'erreurs systématiques dans les simulations contraintes est produite si l'on ne tient pas compte de cet effet. Afin de dépasser cette limitation, nous avons développé la méthode de reconstruction par approximation inverse de Zeldovich (RZA). La RZA permet de reconstruire les déplacements et les positions initiales des galaxies observées et de générer une estimation significativement meilleure des conditions initiales de l'Univers Local. Cette méthode est intensivement testée sur des données de simulations. Nous étudions aussi l'influence de la qualité des données et de diverses erreurs observationnelles et/ou systématiques. Nous démontrons qu'avec la technique RZA, la qualité de la reconstruction des champs de densité et de vitesse est drastiquement améliorée. La position des objets dans les simulations contraintes évoluées sont retrouvées plus précisément et sur un plus grand intervalle de masses / Galaxy peculiar velocities provide valuable information about our motion with respect to theobserved large-scale structure and can be used to constrain the underlying dark matter distribution.Based on this approach, the technique of constrained realisations allows us to run numericalsimulations that resemble the observed Local Universe. This provides a powerful numerical laboratoryto study the dynamics, formation and evolution of structure in the Local Universe. Thecrucial step is to generate appropriate initial conditions from the observational data.We present here improvements on the technique of constrained simulations, along with anewly developed highly optimised numerical code that can handle the upcoming large observationaldatasets. Galaxies evolve from the gravitational collapse of primordial overdensities in theearly Universe; their motion leads to a large-scale displacement field. A major source of systematicerrors in constrained simulations arises by not accounting for this effect. To overcome thislimitation, we develop the Reverse Zeldovich Approximation (RZA) reconstruction method. TheRZA allows to reconstruct displacements and initial positions of observed galaxies and generatea significantly better estimate of the initial conditions of the Local Universe. This method isextensively tested on simulation data. We also study the influence of data quality and variousobservational and systematic errors. We show that with the RZA technique, the reconstructionquality of the density and velocity fields improves significantly. The positions of objects in theevolved constrained simulations are recovered more accurately and over a wider range of masses. / Die Pekuliargeschwindigkeiten von Galaxien liefern wertvolle Informationen über ihre Bewegungrelativ zu den beobachteten großräumigen Strukturen und können verwendet werden, um diezugrundeliegende Verteilung der dunklen Materie abzuschätzen. Auf dieser Grundlage könnenmit der Methode der “Constrained Realisations” numerische Simulationen durchgeführt werden,die die Materieverteilung im Lokalen Universum widerspiegeln und somit leistungsfähige numerischeExperimente ermoeglichen, um die Dynamik, Entstehung und Evolution von Strukturenim lokalen Universum zu untersuchen. Eine wichtige Voraussetzung für diese Experimente ist es,korrekte Anfangsbedingungen aus den Beobachtungsdaten abzuleiten.In dieser Arbeit werden Verbesserungen der “Constrained Simulations”-Technik sowie ein fürdiesen Zweck neu entwickelter, hochgradig optimierter numerischer Code vorgestellt, welcheres ermöglicht, die kommenden, sehr umfangreichen Beobachtungsdaten zu verarbeiten. Galaxienentwickeln sich aus dem Gravitationskollaps von primordialen Überdichten im frühen Universum.Deren Bewegung führt zu einer großräumigen Dislokation, deren Vernachlässigung die größtesystematische Fehlerquelle für “Constrained Simulations” darstellt. An dieser Stelle knüpft dieReverse-Zeldovich-Näherung (RZA) an, die hier vorgestellt wird. Mithilfe der RZA können wirdiese Dislokation abschätzen und somit die ursprünglichen Positionen der beobachteten Galaxienrekonstruieren. Dadurch erhält man wesentlich genauere Anfangsbedingungen fuer die Entwicklungdes Lokalen Universums. Diese Methode wird ausführlich an Simulationsdaten getestet.Der Einfluß der Datenqualität und verschiedener Beobachtungs- und systematischer Fehler wirdeingehend untersucht. Die Rekonstruktionsgenauigkeit der Dichte- und Geschwindigkeitsfelderkann durch den Einsatz der RZA signifikant erhöht werden. In unseren Tests stimmen die Positionenvon Objekten in den mit RZA erzeugten “Constrained Simulations” wesentlich besser mitden ursprünglichen überein, als ohne die RZA, und das für einen deutlich größeren Bereich vonMassen

Le rayonnement fossile, ou CMB, est un sujet d’étude clé pour la cosmologie car il indique l’état de l’univers à une époque primordiale. Le CMB est observable dans le ciel dans la bande de fréquences des micro-ondes. Cependant, il existe des processus astrophysiques, les avant-plans, qui émettent dans les micro-ondes, et rendent indispensable le traitement des données avec des méthodes de séparation de composantes. J'utilisé la méthode aveugle SMICA pour obtenir une estimation directe du spectre de puissance angulaire du CMB. La détermination des petites échelles de ce spectre est limité par les avant-plans comme les galaxies lointaines, et par le biais du bruit. Dans cette analyse, ces deux limitations sont abordées. En ajoutant des hypothèses sur la physique des galaxies lointaines, il est possible de guider l’algorithme pour estimer leur loi d'émission. Un spectre de puissance angulaire obtenu d'une carte du ciel a un biais dû au bruit à petites échelles. Toutefois, les spectres obtenus en croisant différentes cartes n'ont pas ce biais. J'ai donc adapté la méthode SMICA pour qu'elle n'utilise que ces derniers, diminuant l'incertitude due au bruit dans l'estimation du CMB. Cette méthode a été étudiée sur des nombreuses simulations et sur les données Planck 2015, afin d'estimer des paramètres cosmologiques. Les résultats montrent que la contamination résiduelle des avant-plans présente dans le spectre CMB, même si fortement réduite, peut introduire des biais dans l'estimation des paramètres si la forme des résiduels n'est pas bien connue. Dans cette thèse, je montre les résultats obtenus en étudiant un modèle de gravité modifiée. / The Planck satellite observed the whole sky at various frequencies in the microwave range. These data are of high value to cosmology, since they help understanding the primordial universe through the observation of the cosmic microwave background (CMB) signal. To extract the CMB information, astrophysical foreground emissions need to be removed via component separation techniques. In this work I use the blind component separation method SMICA to estimate the CMB angular power spectrum with the aim of using it for the estimation of cosmological parameters. In order to do so, small scales limitations as the residual contamination of unresolved point sources and the noise need to be addressed. In particular, the point sources are modelled as two independent populations with a flat angular power spectrum: by adding this information, the SMICA method is able to recover the joint emission law of point sources. Auto-spectra deriving from one sky map have a noise bias at small scales, while cross-spectra show no such bias. This is particularly true in the case of cross-spectra between data-splits, corresponding to sky maps with the same astrophysical content but different noise properties. I thus adapt SMICA to use data-split cross-spectra only. The obtained CMB spectra from simulations and Planck 2015 data are used to estimate cosmological parameters. Results show that this estimation can be biased if the shape of the (weak) foreground residuals in the angular power spectrum is not well known. In the end, I also present results of the study of a Modified Gravity model called Induced Gravity.