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Littérature scientifique sur le sujet « Cosmological analysis »

Auteur : Grafiati

Publié le 14 décembre 2024

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Articles de revues sur le sujet "Cosmological analysis"

Brout, Dillon, Dan Scolnic, Brodie Popovic, Adam G. Riess, Anthony Carr, Joe Zuntz, Rick Kessler et al. « The Pantheon+ Analysis : Cosmological Constraints ». Astrophysical Journal 938, n^o 2 (1 octobre 2022) : 110. http://dx.doi.org/10.3847/1538-4357/ac8e04.

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Abstract We present constraints on cosmological parameters from the Pantheon+ analysis of 1701 light curves of 1550 distinct Type Ia supernovae (SNe Ia) ranging in redshift from z = 0.001 to 2.26. This work features an increased sample size from the addition of multiple cross-calibrated photometric systems of SNe covering an increased redshift span, and improved treatments of systematic uncertainties in comparison to the original Pantheon analysis, which together result in a factor of 2 improvement in cosmological constraining power. For a flat ΛCDM model, we find Ω M = 0.334 ± 0.018 from SNe Ia alone. For a flat w 0CDM model, we measure w 0 = −0.90 ± 0.14 from SNe Ia alone, H 0 = 73.5 ± 1.1 km s−1 Mpc−1 when including the Cepheid host distances and covariance (SH0ES), and w 0 = − 0.978 − 0.031 + 0.024 when combining the SN likelihood with Planck constraints from the cosmic microwave background (CMB) and baryon acoustic oscillations (BAO); both w 0 values are consistent with a cosmological constant. We also present the most precise measurements to date on the evolution of dark energy in a flat w 0 w a CDM universe, and measure w a = − 0.1 − 2.0 + 0.9 from Pantheon+ SNe Ia alone, H 0 = 73.3 ± 1.1 km s−1 Mpc−1 when including SH0ES Cepheid distances, and w a = − 0.65 − 0.32 + 0.28 when combining Pantheon+ SNe Ia with CMB and BAO data. Finally, we find that systematic uncertainties in the use of SNe Ia along the distance ladder comprise less than one-third of the total uncertainty in the measurement of H 0 and cannot explain the present “Hubble tension” between local measurements and early universe predictions from the cosmological model.

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Nagasawa, Michiyasu. « Numerical Analysis of Cosmological Defects ». Progress of Theoretical Physics Supplement 138 (2000) : 644–45. http://dx.doi.org/10.1143/ptps.138.644.

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NOUTCHEGUEME, NORBERT, et ALEXIS NANGUE. « GLOBAL EXISTENCE TO THE EINSTEIN-SCALAR FIELD SYSTEM ON THE ROBERTSON–WALKER SPACE-TIMES WITH HYPERBOLIC AND SPHERICAL SYMMETRIES ». Journal of Hyperbolic Differential Equations 07, n^o 01 (mars 2010) : 69–83. http://dx.doi.org/10.1142/s0219891610002074.

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ELLIS, GEORGE F. R. « DYNAMICAL PROPERTIES OF COSMOLOGICAL SOLUTIONS ». Journal of Hyperbolic Differential Equations 02, n^o 02 (juin 2005) : 381–95. http://dx.doi.org/10.1142/s0219891605000464.

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I will consider how there are FOSH formulations and associated results in relativistic cosmology expressed in 1+3 tetrad form. The characteristics of scalar and vector perturbations are timelike, hence the real domains of dependence in cosmology are much smaller than implied by the light cone, associated with gravitational wave perturbations.

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ALLEN, PAUL T., et ALAN D. RENDALL. « ASYMPTOTICS OF LINEARIZED COSMOLOGICAL PERTURBATIONS ». Journal of Hyperbolic Differential Equations 07, n^o 02 (juin 2010) : 255–77. http://dx.doi.org/10.1142/s0219891610002141.

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In cosmology an important role is played by homogeneous and isotropic solutions of the Einstein–Euler equations and linearized perturbations of these. This paper proves results on the asymptotic behavior of scalar perturbations both in the approach to the initial singularity of the background model and at late times. The main equation of interest is a linear hyperbolic equation whose coefficients depend only on time. Expansions for the solutions are obtained in both asymptotic regimes. In both cases, it is shown how general solutions with a linear equation of state can be parametrized by certain functions which are coefficients in the asymptotic expansion. For some nonlinear equations of state, it is found that the late-time asymptotic behavior is qualitatively different from that in the linear case.

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Tiwari, L. K. « MATHEMATICAL ANALYSIS OF COSMOLOGICAL MODELS WITH LINEARLY VARYING DECELERATION PARAMETER ». South East Asian J. of Mathematics and Mathematical Sciences 19, n^o 03 (30 décembre 2023) : 449–58. http://dx.doi.org/10.56827/seajmms.2023.1903.34.

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Bianchi type-V is investigated using a decaying cosmological constant with perfect fluid. The study solves Einstein field equations by assuming that the deceleration parameter q is functionally connected to the Hubble parameter H, which yields the scale factor a. As cosmic time t increases, the cosmological model experiences exponential inflation. The physical characteristics and behavior of the cosmological model are also covered.

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Ove, R. « Analysis of cosmological gravitational wave residue ». Classical and Quantum Gravity 7, n^o 12 (1 décembre 1990) : 2225–36. http://dx.doi.org/10.1088/0264-9381/7/12/007.

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Akbar, M., Tayeb Brahimi et S. M. Qaisar. « Thermodynamic Analysis of Cosmological Black Hole ». Communications in Theoretical Physics 67, n^o 1 (janvier 2017) : 47. http://dx.doi.org/10.1088/0253-6102/67/1/47.

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Méndez, Vicenç, et Josep Triginer. « Qualitative analysis of causal cosmological models ». Journal of Mathematical Physics 37, n^o 6 (juin 1996) : 2906–19. http://dx.doi.org/10.1063/1.531546.

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Abramo, L. Raul, Lucas F. Secco et Arthur Loureiro. « Fourier analysis of multitracer cosmological surveys ». Monthly Notices of the Royal Astronomical Society 455, n^o 4 (3 décembre 2015) : 3871–89. http://dx.doi.org/10.1093/mnras/stv2588.

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Thèses sur le sujet "Cosmological analysis"

Pearson, Russell Charles. « The statistical analysis of cosmological models ». Thesis, Queen Mary, University of London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264659.

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Rivera, Echeverri José David [UNESP]. « Cosmological analysis of optical galaxy clusters ». Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/152493.

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Os aglomerados de galáxias são os maiores objetos ligados que observamos no universo. Dado que as galáxias são consideradas traçadores de matéria escura, os aglomerados de galáxias nos permitem estudar a formação e a evolução de estruturas em grande escala. As contagens do número de aglomerados de galáxias são sensı́veis ao modelo cosmológico, portanto são usadas como observáveis para restringir os parâmetros cosmológicos. Nesta tese estudamos os aglomerados de galáxias óticos. Iniciamos o trabalho analisando a degradação da precisão e a exatidão no desvio para o vermelho fotométrico estimado através de métodos de aprendizagem de máquina (machine learning) ANNz2 e GPz. Além do valor singular do desvio para o vermelho fotométrico clássico (isto é, valor médio ou máximo da distribuição), implementamos um estimador baseado em uma amostragem de Monte Carlo usando a função de distribuição cumulativa. Mostramos que este estimador para o algoritmo ANNz2 apresenta a melhor concorância com a distribuição do desvio para o vermelho espectroscópico, no entanto, uma maior dispersão. Por outro lado, apresentamos o buscador de aglomerados VT-FOFz, o qual combina as técnicas de Voronoi Tessellation e Friends of Friends. Estimamos seu desempenho através de catálogos simulados. Calculamos a completeza e a pureza usando uma região de cilindrica no espaço 2+1 (ou seja, coordenadas angulares e desvio para o vermelho). Para halos maciços e aglomerados com alta riqueza, obtemos valores elevados de completeza e pureza. Comparamos os grupos de galáxias detectados através do buscador de aglomera- dos VT-FOFz com o catálogo RedMaPPer SDSS DR8. Recuperamos ∼ 90% dos aglomerados de galáxias do catálogo RedMaPPer até o desvio para o vermelho de z ≈ 0.33 considerando galáxias mais brilhantes com r < 20.6. Finalmente, realizamos uma previsão cosmológica usando um método MCMC para um modelo plano de wCDM por meio da abundância de aglomerados de galáxias. O modelo fiducial é um universo ΛCDM plano. Os efeitos devidos à massa observável estimada e aos deslocamentos para o vermelho fotométricos são incluı́dos através de um modelo de auto-calibração. Empregamos a função de massa de Tinker para estimar o número de contagens em uma faixa de massa e um bin de deslocamento para o vermelho. Assumimos que a riqueza e a massa do aglomerado estejam relacionadas através de uma lei de potência. Recuperamos os valores fiduciais com nı́vel de confiança de até 2σ para os testes considerados.
The galaxy clusters are the largest bound objects observed in the universe. Given that the galaxies are considered as tracers of dark matter, the galaxy clusters allow us to study the formation and evolution of large-scale structures. The cluster number counts are sensitive to the cosmological model, hence they are used as probes to constrain the cosmological parameters. In this work we focus on the study of optical galaxy clusters. We start analyzing the degradation of both precision and accuracy in the estimated photometric redshift via ANNz2 and GPz machine learning methods. In addition to the classical singular value for the photometric redshift (i.e., mean value or maximum of the distribution), we implement an estimator based on a Monte Carlo sampling by using the cumulative distribution function. We show that this estimator for the ANNz2 algorithm presents the best agreement with the distribution for spectroscopic redshift, nonetheless a higher scattering. On the other hand, we present the VT-FOFz cluster finder, which combines the techniques Voronoi Tessellation and Friends of Friends. Through mock catalogs, we estimate its performance. We compute the completeness and purity by using a cylindrical region in the 2+1 space (i.e., angular coordinates and redshift). For massive haloes and clusters with high richness, we obtain high values of completeness and purity. We compare the detected galaxy clusters via the VT-FOFz cluster finder with the redMaPPer SDSS DR8 cluster catalog. We recover ∼ 90% of the galaxy clusters of the redMaPPer catalog until the redshift z ≈ 0.33 considering brighter galaxies with r < 20.6. Finally, we perform a cosmological forecasting by using a MCMC method, for a flat wCDM model through galaxy cluster abundance. The fiducial model is a flat ΛCDM Universe. The effects due to the estimated observable mass and the photometric redshifts are included via a self-calibriation model. We employ the Tinker’s mass function to estimate the number counts in a range of mass and a redshift bin. We assume that the richness and the cluster mass are related through a power law. We recover the fiducial values at 2σ confindence level for the considered tests.

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Rivera, Echeverri José David. « Cosmological analysis of optical galaxy clusters / ». São Paulo, 2017. http://hdl.handle.net/11449/152493.

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Orientador: Maria Cristina Batoni Abdalla Ribeiro
Coorientador: Filipe Batoni Abdalla
Banca: Filipe Batoni Abdalla
Banca: Laerte Sodré Júnior
Banca: Marcos Vinícius Borges Teixeira Lima
Banca: Martín Makler
Resumo: Os aglomerados de galáxias são os maiores objetos ligados que observamos no universo. Dado que as galáxias são consideradas traçadores de matéria escura, os aglomerados de galáxias nos permitem estudar a formação e a evolução de estruturas em grande escala. As contagens do número de aglomerados de galáxias são sensı́veis ao modelo cosmológico, portanto são usadas como observáveis para restringir os parâmetros cosmológicos. Nesta tese estudamos os aglomerados de galáxias óticos. Iniciamos o trabalho analisando a degradação da precisão e a exatidão no desvio para o vermelho fotométrico estimado através de métodos de aprendizagem de máquina (machine learning) ANNz2 e GPz. Além do valor singular do desvio para o vermelho fotométrico clássico (isto é, valor médio ou máximo da distribuição), implementamos um estimador baseado em uma amostragem de Monte Carlo usando a função de distribuição cumulativa. Mostramos que este estimador para o algoritmo ANNz2 apresenta a melhor concorância com a distribuição do desvio para o vermelho espectroscópico, no entanto, uma maior dispersão. Por outro lado, apresentamos o buscador de aglomerados VT-FOFz, o qual combina as técnicas de Voronoi Tessellation e Friends of Friends. Estimamos seu desempenho através de catálogos simulados. Calculamos a completeza e a pureza usando uma região de cilindrica no espaço 2+1 (ou seja, coordenadas angulares e desvio para o vermelho). Para halos maciços e aglomerados com alta riqueza, obtemos valores elevados de ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The galaxy clusters are the largest bound objects observed in the universe. Given that the galaxies are considered as tracers of dark matter, the galaxy clusters allow us to study the formation and evolution of large-scale structures. The cluster number counts are sensitive to the cosmological model, hence they are used as probes to constrain the cosmological parameters. In this work we focus on the study of optical galaxy clusters. We start analyzing the degradation of both precision and accuracy in the estimated photometric redshift via ANNz2 and GPz machine learning methods. In addition to the classical singular value for the photometric redshift (i.e., mean value or maximum of the distribution), we implement an estimator based on a Monte Carlo sampling by using the cumulative distribution function. We show that this estimator for the ANNz2 algorithm presents the best agreement with the distribution for spectroscopic redshift, nonetheless a higher scattering. On the other hand, we present the VT-FOFz cluster finder, which combines the techniques Voronoi Tessellation and Friends of Friends. Through mock catalogs, we estimate its performance. We compute the completeness and purity by using a cylindrical region in the 2+1 space (i.e., angular coordinates and redshift). For massive haloes and clusters with high richness, we obtain high values of completeness and purity. We compare the detected galaxy clusters via the VT-FOFz cluster finder with the redMaPPer SDSS DR8 cluster catalog. We recover ∼ 90% of the galaxy clusters of the redMaPPer catalog until the redshift z ≈ 0.33 considering brighter galaxies with r < 20.6. Finally, we perform a cosmological forecasting by using a MCMC method, for a flat wCDM model through galaxy cluster abundance. The fiducial model is a flat ΛCDM Universe. The effects due to the estimated observable mass and (Complete abstract click electronic access below)
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Stadel, Joachim Gerhard. « Cosmological N-body simulations and their analysis / ». Thesis, Connect to this title online ; UW restricted, 2001. http://hdl.handle.net/1773/5449.

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McEwen, Jason Douglas. « Analysis of cosmological observations on the celestial sphere ». Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612795.

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Porredon, Diez de Tejada Anna Maria. « Multi-probe cosmological analysis with the dark energy survey ». Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/669428.

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Les actuals i futures cartografies de galàxies cobriran un major volum i recolliran imatges de millor qualitat que les obtingudes fins ara, permetent mesures precises de la última etapa de l'Univers i proves potents de la naturalesa de l’energia fosca i la Relativitat General. Aquests cartografiats ens permetran obtenir informació cosmològica a partir de diversos observables, i la combinació d'aquests pot millorar la robustesa i precisió dels resultats de l'anàlisi. Aquesta tesi es centra en la combinació de diferents traçadors de l'estructura a gran escala (LSS) per tal d'obtenir mesures dels paràmetres cosmològics més precises. Primer, combinem la distribució de galàxies de la mostra corresponent al primer any de dades del Dark Energy Survey (DES Y1) amb la distorsió de la radiació còsmica de fons (CMB) deguda a la matèria fosca on viuen aquestes galàxies (CMB lensing) provinent de la combinació òptima entre el South Pole Telescope i Planck. En aquest anàlisi obtenim mesures en el biaix galàctic, la funció de creixement de LSS i paràmetres cosmològics. Els nostres resultats són consistents amb el model estàndard (\LCDM) i altres resultats de DES Y1. La informació que podem obtenir de l'anàlisi està limitada per les restriccions d'escala, però esperem que millori en els futurs anàlisis. A continuació, combinem la distribució de galàxies de dues mostres diferents (en l'anomenat mètode multi-traçador) per analitzar els senyals de distorsió en la distribució de galàxies deguda a les seves velocitats ``peculiars'' (RSD) i de la possible contribució no-Gaussiana a les fluctuacions inicials de la distribució de matèria (PNG). Per a aquest propòsit, considerem un parell de mostres optimistes (amb gran nombre de galàxies i diferències en el biaix) i les mostres de DES del 3r any d'observacions (DES Y3) que actuaran con a lents gravitatòries. Trobem que les mesures en RSD poden millorar un factor cinc a distàncies properes i les mesures en PNG un factor tres o més. També comprovem l'impacte d'incloure CMB lensing en l'anàlisi, en el qual no variem la cosmologia, trobant que majoritàriament millora les mesures en el biaix. Per últim, definim i optimitzem una de galàxies limitada en magnitud que s'utilitzarà per les mesures de la distribució de galàxies en l'anàlisi de DES Y3, actuant com a lent gravitacional respecte a galàxies més llunyanes (lens sample). Per aquest propòsit, ens basem en previsions de Fisher i posem a prova com aquestes canvien al variar el nombre de galàxies i la incertesa en la posició donat un conjunt de talls en magnitud. També caracteritzem l'impacte en els nostres resultats de diferents particions de la mostra en intervals de desplaçament al vermell (redshift), tant per aquesta mostra com per l'altra lens sample (REDMAGIC). Finalment, les nostres previsions mostren que amb aquesta mostra que hem optimitzat podem obtenir mesures un 15\% més precises que amb REDMAGIC.
Ongoing and future photometric surveys will enable detailed measurements of the late-time Universe and powerful tests of the nature of dark energy and General Relativity. These surveys will be able to obtain cosmological constraints from multiple probes, and the combination of these probes can improve their robustness and constraining power. This thesis is focused on the combination of multiple tracers of large-scale structure (LSS) to obtain tighter cosmological constraints. First, we combine the galaxy clustering from the Dark Energy Survey (DES) Year 1 (Y1) data with CMB lensing from the optimal combination of South Pole Telescope (SPT) and Planck, obtaining constraints on the galaxy bias, the growth function and the cosmological parameters. Our results are consistent with \LCDM$ $ and other measurements of DES Y1. However, their constraining power is limited due to conservative scale cuts. We expect an improved signal-to-noise in future analyses. We then combine the galaxy clustering of two different galaxy samples (the so-called multi-tracer approach) to explore the constraints on redshift space distortions (RSD) and primordial non-Gaussianities (PNG). For this purpose, we consider a pair of optimistic samples (with large bias differences and number densities) and the DES Year 3 (Y3) lens samples. We find that the constraints on RSD can be improved a factor of five at low redshift with respect to a single tracer, and the constraints on PNG can be improved more than a factor three. We also test the impact of including CMB lensing cross-correlations in our analysis, in which we keep the cosmology fixed, finding it mainly improves the galaxy bias constraints. Last, we define and optimize a magnitude limited galaxy sample to be used for the galaxy clustering measurements in the DES Y3 analysis, in combination with galaxy-galaxy lensing. We rely on Fisher forecasts, and we test how these change given the variations obtained for the number density and estimated redshift uncertainty for a set of magnitude cuts. We also characterize the impact of redshift binning choices in our cosmological constraints for this sample and the other DES Y3 lens sample: REDMAGIC. Finally, our forecasts show that we can potentially obtain 15\% tighter constraints with this magnitude limited sample, compared to REDMAGIC.

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Lin, Qiufan. « Learning salient information with neural networks for cosmological analysis ». Electronic Thesis or Diss., Aix-Marseille, 2021. http://www.theses.fr/2021AIXM0532.

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Les réseaux de neurones avec apprentissage profond sont des outils puissants permettant de capturer des informations à partir de données. Cependant, les réseaux de neurones sont enclins à s'adapter à des informations spécifiques qui sont enchevêtrées avec les informations saillantes que vont exploiter certaines tâches, ce qui biaiserait les résultats. Dans le but de développer des outils d'apprentissage profond robustes en préparation des futures sondages cosmologiques, cette thèse se concentre sur l'apprentissage d'informations saillantes à partir d'images multicolores avec des réseaux de neurones. Plus précisément, nous tentons d'établir des représentations informatives des données afin de capturer des informations saillantes à différents niveaux d'abstraction dans quelques tâches : À faible niveau d'abstraction, nous effectuons une traduction bidirectionnelle semi-supervisée d'images de galaxies multicolores entre deux sondages. À un niveau élevé d'abstraction, nous proposons une procédure pour corriger les biais d'estimation des méthodes basées sur les données en utilisant une représentation pré-entraînée. En plus des études astrophysiques, notre travail interdisciplinaire explore l'analyse d'images optiques sous-marines auxquelles les techniques développées en astrophysique peuvent être appliquées. Comme de nouveaux défis ont été rencontrés dans le traitement des données astronomiques, principalement le bruit et la rareté des données, notre travail implique la nécessité de faire progresser les techniques d'apprentissage automatique pour s'adapter aux problèmes réels et optimiser l'exploitation des données
Deep learning neural networks are powerful data-driven tools to capture information from data. However, neural networks are prone to fitting on specific information that is entangled with the salient information concerned for certain tasks, which would bias the output prediction of a model. Aiming at developing robust deep learning tools in preparation for future cosmological surveys, this thesis focuses on learning salient information from multi-color images with neural networks. In specific, we attempt to establish informative representations of data in order to capture salient information at different levels of abstraction in a few tasks: At a low level, we perform semi-supervised two-way translation of multi-color galaxy images between two surveys. At a high level, we propose a procedure to correct estimation biases for data-driven methods using a pre-trained representation. In addition to astrophysical studies, our interdisciplinary work explores the analysis of underwater optical images in which the techniques developed in astrophysics can be applied. As new challenges have been encountered in dealing with astronomical data, predominantly noise and sparsity of data, our work implies the needs for advances of machine learning techniques to fit real problems and optimize the exploitation of data

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Hollowood, Devon. « Cosmological Studies through Large-Scale Distributed Analysis of Chandra Observations ». Thesis, University of California, Santa Cruz, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10973254.

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The formation history of galaxy clusters is a powerful probe of cosmology. In particular, one may place strong constraints on the dark energy equation of state by examining the evolution across redshift of the number density of galaxy clusters as a function of mass. In this thesis, I describe my contributions to cluster cosmology, in particular to the development of the richness optical observable mass proxy.

I introduce redMaPPer, an optical cluster finder which represents an important upstream input for my thesis work. I next introduce the Mass Analysis Tool for Cha ndra (MATCha), a pipeline which uses a parallelized algorithm to analyze archival Chandra data. MATCha simultaneously calculates X-ray temperatures and luminosities and performs centering measurements for hundreds of potential galaxy clusters using archival X-ray exposures. I run MATCha on the redMaPPer SDSS DR8 cluster catalog and use MATCha's output X-ray temperatures and luminosities to analyze the galaxy cluster temperature-richness, luminosity-richness, luminosity-temperature, and temperature-luminosity scaling relations. I investigate the distribution of offsets between the X-ray center and redMaPPer center within 0.1 < z < 0.35 and explore some of the causes of redMaPPer miscentering. I collaborate with members of the Dark Energy Survey in order to repeat this analysis on Dark Energy Survey Year 1 data. I outline the various ways in which MATCha constitutes an important upstream work for a variety of astrophysical applications. These include the calibrations of two separate mass proxies, the study of the AGN fraction of galaxy clusters, and cosmology from cluster number densities and stacked weak lensing masses. Finally, I outline future upgrades and applications for MATCha throughout the lifespan of the Dark Energy Survey and the Large Synoptic Survey Telescope.

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Alfedeel, Alnadhief Hamed Ahmed. « The impact of inhomogeneity on the analysis of cosmological data ». Doctoral thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/4952.

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Includes abstract.
Includes bibliographical references.
We consider the Lemaˆıtre metric, which is the inhomogeneous, spherically symmetric metric, containing a non-static, comoving, perfect fluid with non-zero pressure. We use it to generalise the metric of the cosmos algorithm, first derived for the zero-pressure Lemaˆıtre-Tolman (LT) metric, to the case of non-zero pressure and non-zero cosmological constant. We present a method of integration with respect to the null coordinate w, instead of comoving t, and reduce the Einstein’s Field Equation (EFEs) to a system of differential equations (DEs). We show that the non-zero pressure introduces new functions, and makes several functions depend on time that did not in the case of LT. We present clearly, step by step an algorithmic solution for determining the metric of the cosmos from cosmological data for the Lemaˆıtre model, on which a numerical implementation can be based. In our numerical execution of the algorithm we have shown that there are some regions which need special treatment : the origin and the maximum in the diameter distance. We have coded a set of MATLAB programs for the numerical implementation of this algorithm, for the case of pressure with a barotropic equation of state and non-zero Λ. Initially, the computer code has been successfully tested using artificial and ideal cosmological data on the observer’s past null cone, for homogeneous and non-homogeneous spacetimes. Then the program has also been generalized to handle realistic data, which has statistical fluctuations. A key step is the data smoothing process, which fits a smooth curve to discrete data with statistical fluctuations, so that the integration of the DEs can proceed. Since the algorithm is very sensitive to the second derivative of one of the data functions, this has required some experimentation with methods. Finally, we have successfully extracted the metric functions for the Lemaˆıtre model, and their evolution from the initial data on the past null cone.

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PIETROBON, DAVIDE. « Making the best of cosmological perturbations : theory and data analysis ». Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2010. http://hdl.handle.net/2108/1197.

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Grazie a esperimenti estremamente raffinati, la cosmologia moderna si trova oggi in quella che puo' essere defi nita l' epoca della precisione. I cosmologi dispongono di una grande quatita' di strumenti per testare il cosiddetto modello cosmologico di concordanza e vincolarne i principali parametri. In particolare, la radiazione cosmica di fondo (CMB) ha svolto, e svolge tutt'oggi, un ruolo chiave in questo ambito. Numerose domande rimangono tuttavia ancora in attesa di una risposta, in particolare quelle che riguardano la fisica dell'inflazione, che ha governato l'Universo nelle prime fasi di evoluzione, e la natura dell' accelerazione dell' espansione dell'Universo, che e' stata osservata negli ultimi anni. La mia attivita' di ricerca ha contribuito ad approfondire lo studio e la conoscenza su entrambe le tematiche, che sono state accomunate dallo sviluppo e dall'utilizzo delle needlets - una nuova "frame" sulla sfera - per analizzare la CMB. Con questo strumento, abbiamo misurato l'effetto Sachs-Wolfe integrato, correlando i dati di WMAP e NVSS, e caratterizzato le proprieta' della dark energy, seguendo un approccio fenomenologico che si basa sull'approssimazione di fl uido perfetto. Stimolati dai risultati ottenuti, abbiamo studiato in dettaglio un modello unifi cato per le componenti di dark energy e dark matter, che fa uso di un'equazione di stato affi ne, e investigato i vincoli sui parametri di questo modello provenienti da WMAP e SDSS. Abbiamo quindi applicato le needlets ai dati di WMAP 5-anni allo scopo di studiare la gaussianita' della distribuzione delle perturbazioni della CMB. Ci siamo dapprima concentrati sulle mappe, rilevando la presenza di regioni anomale, localizzate nell' emisfero meridionale, e studiando l'effetto che queste regioni hanno sullo spettro di potenza angolare. Successivamente, abbiamo misurato la funzione di correlazione a tre punti (bispettro) delle needlets caratterizzandola in termini della sua ampiezza complessiva, descritta dal parametro fNL, e secondo la geometria delle configurazioni triangolari che contribuiscono al segnale totale. Abbiamo misurato una significativa anomalia nelle confi gurazioni isosceli, nuovamente presente nell'emisfero meridionale. Infine, ci siamo concentrati sulla costruzione di un estimatore per il bispettro delle needlets, includendo l'effetto spurio che puo' essere introdotto dalla presenza di eventuale segnale residuo, proveniente da sorgenti di natura prevalentemente Galattica.
Cosmology has entered the precision epoch thanks to several very accurate experiments. Cosmologists now have access to an array of tools to test the cosmological concordance model and constrain its parameters; the Cosmic Microwave Background radiation (CMB), in particular, has been playing a crucial role in this ambition. Many questions remain nonetheless unanswered, especially concerning the physics of the early Universe, the infl ationary mechanism which set the initial conditions for the Universe expansion, and the nature of the late time acceleration of the Universe expansion. My research contributes to both of these sub jects, the common ground being the development of a statistical tool - needlets, a new "frame" on the sphere - to analyse the CMB. By means of needlets, we measure the Integrated Sachs Wolfe effect by cross-correlating WMAP and NVSS datasets and characterise dark energy properties using a phenomenological fluid model. Motivated by our findings, we study in detail a parameterisation of the dark components, dark matter and dark energy, which makes use of an affine equation of state, constraining the parameters of the model by combining WMAP and SDSS datasets. We apply needlets to the WMAP 5-year data release testing the Gaussianity of the CMB perturbations. Our approach is twofold: we first focus on the maps, detecting anomalous spots located in the southern hemisphere and check their effect on the angular power spectrum. We next measure the needlet three-point correlation function (bispectrum) and characterise it in terms of its overall amplitude, constraining the primordial fNL parameter, and considering its properties according to the geometry of the triangle configurations which contribute to the total power. We find a significant anomaly in the isosceles confi gurations, again in the southern hemisphere. Finally we focus on the construction of an optimal estimator for the (needlets) bispectrum, taking into account foreground residuals due mainly to Galactic emission.

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Livres sur le sujet "Cosmological analysis"

Higdon, Dave, Katrin Heitmann, Charles Nakhleh et Salman Habib. Combining simulations and physical observations to estimate cosmological parameters. Sous la direction de Anthony O'Hagan et Mike West. Oxford University Press, 2018. http://dx.doi.org/10.1093/oxfordhb/9780198703174.013.26.

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This article focuses on the use of a Bayesian approach that combines simulations and physical observations to estimate cosmological parameters. It begins with an overview of the Λ-cold dark matter (CDM) model, the simplest cosmological model in agreement with the cosmic microwave background (CMB) and largescale structure analysis. The CDM model is determined by a small number of parameters which control the composition, expansion and fluctuations of the universe. The present study aims to learn about the values of these parameters using measurements from the Sloan Digital Sky Survey (SDSS). Computationally intensive simulation results are combined with measurements from the SDSS to infer about a subset of the parameters that control the CDM model. The article also describes a statistical framework used to determine a posterior distribution for these cosmological parameters and concludes by showing how it can be extended to include data from diverse data sources.

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Beisbart, Claus. Philosophy and Cosmology. Sous la direction de Paul Humphreys. Oxford University Press, 2015. http://dx.doi.org/10.1093/oxfordhb/9780199368815.013.36.

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Cosmological questions (e.g., how far the world extends and how it all began) have occupied humans for ages and given rise to numerous conjectures, both within and outside philosophy. To put to rest fruitless speculation, Kant argued that these questions move beyond the limits of human knowledge. This article begins with Kant’s doubts about cosmology and shows that his arguments presuppose unreasonably high standards on knowledge and unwarranted assumptions about space-time. As an analysis of the foundations of twentieth-century cosmology reveals, other worries about the discipline can be avoided too if the universe is modeled using Einstein’s general theory of relativity. There is now strong observational support for one particular model. However, due to underdetermination problems, the big cosmological questions cannot be fully answered using this model either. This opens the space for more speculative proposals again (e.g., that the universe is only part of a huge multiverse).

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Maggiore, Michele. Evolution of cosmological perturbations. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198570899.003.0010.

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Evolutions equations for cosmological perturbations. Single-component and multi-component fluids. Super-horizon and sub-horizon limits. Adiabatic and isocurvature initial conditions. Analytic and numerical solutions. Power spectra and transfer functions for scalar and tensor perturbations. GW damping from neutrino free-streaming.

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Earman, John. Sharpening the Electromagnetic Arrow(s) of Time. Sous la direction de Craig Callender. Oxford University Press, 2011. http://dx.doi.org/10.1093/oxfordhb/9780199298204.003.0017.

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Time in electromagnetism shares many features with time in other physical theories. But there is one aspect of electromagnetism's relationship with time that has always been controversial, yet has not always attracted the limelight it deserves: the electromagnetic arrow of time. Beginning with a re-analysis of a famous argument between Ritz and Einstein over the origins of the radiation arrow, this chapter frames the debate between modern Einsteinians and neo-Ritzians. It tries to find a clean statement of what the arrow is and then explains how it relates to the cosmological and thermodynamic arrows, representing the most developed and sophisticated attack yet, in either the physics or philosophy literature, on the electromagnetic arrow of time.

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Davidson, Sacha, Paolo Gambino, Mikko Laine, Matthias Neubert et Christophe Salomon, dir. Effective Field Theory in Particle Physics and Cosmology. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198855743.001.0001.

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Effective field theory (EFT) is a general method for describing quantum systems with multiple-length scales in a tractable fashion. It allows us to perform precise calculations in established models (such as the standard models of particle physics and cosmology), as well as to concisely parametrize possible effects from physics beyond the standard models. EFTs have become key tools in the theoretical analysis of particle physics experiments and cosmological observations, despite being absent from many textbooks. This volume aims to provide a comprehensive introduction to many of the EFTs in use today, and covers topics that include large-scale structure, WIMPs, dark matter, heavy quark effective theory, flavour physics, soft-collinear effective theory, and more.

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Adamson, Peter. Abū Bakr al-Rāzī (d. 925),. Sous la direction de Khaled El-Rouayheb et Sabine Schmidtke. Oxford University Press, 2016. http://dx.doi.org/10.1093/oxfordhb/9780199917389.013.3.

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This chapter offers an overview and analysis of an important ethical work by the early thinker Abū Bakr Muḥammad ibn Zakariyyāʾ al-Rāzī (251/865–313/925). In keeping with his main occupation as a medical doctor, this work approaches ethics as “spiritual medicine,” echoing the ancient idea of ethical improvement as a kind of regime the soul. The chapter shows how al-Rāzī drew on Galen in developing this idea, and explores the central idea of the treatise (taken ultimately from Plato, by way of Galen), which is that reason must rule the lower parts of the soul. Consideration is also given to whether the teaching of The Spiritual Medicine can be reconciled with another work of al-Rāzī’s, The Philosophical Life, and with his infamous cosmological theory.

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Lloyd, Howell A. Law and History. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198800149.003.0004.

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An assessment of France’s condition in the late 1550s prefaces an account of why Bodin left Toulouse for Paris, how he embarked on an avocat’s role in the Parlement, and his taking an oath of religious conformity. The chapter’s second section examines Bodin’s attempt at an analysis of ‘universal law’, the Juris universi distributio, comparing the two versions which he published in very different formats. The third section seeks to interpret the arguments on religious issues expressed in his Lettre to Jean Bautru de Matras. Fourthly, Bodin’s first major work is considered: the Methodus for examining histories, viewed as a means of enquiry in three modes, human, natural, and divine, each with legal and ethical connotations. Bodin’s treatment of the first of these embraced multiple social, constitutional, cosmological, and other phenomena, including his theories of ‘climate’ and universal time, and furnished also an agenda for his entire writing career.

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Harding, Dennis. Iron Age Hillforts in Britain and Beyond. Oxford University Press, 2012. http://dx.doi.org/10.1093/oso/9780199695249.001.0001.

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Widely regarded as major visible field monuments of the Iron Age, hillforts are central to an understanding of later prehistoric communities in Britain and Europe from the later Bronze Age. With such a range of variants represented, no single explanation of their function or social significance could satisfy all possible interpretations of their role. While they are conventionally viewed as defence settlements or regional centres controlled by a social elite, this role has been challenged in recent years, and instead hillforts are being considered primarily as expressions of social identity with strong ritual and cosmological associations. Current hillfort interpretations are in danger of reflecting contemporary social sensitivities more strongly than any recognizable Iron Age priorities, and the need for critical analysis of basic archaeological evidence is paramount. Critically reviewing the evidence of hillforts in Britain, in the wider context of Ireland and continental Europe, the volume focuses on their structural features, chronology, landscape context, and their social, economic and symbolic functions, and is well illustrated throughout with site plans, reconstruction drawings, and photographs. Harding reviews the changing perceptions of hillforts and the future prospects for hillfort research, highlighting aspects of contemporary investigation and interpretation.

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Zago, Silvia. A Journey through the Beyond. Lockwood Press, 2022. http://dx.doi.org/10.5913/2022532.

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This volume offers the first comprehensive overview of the evolution over time of a foundational concept of the Egyptian afterlife beliefs, the Duat, or netherworld. The Duat is a complicated, multifaceted notion, which was never canonized into a single version of the beyond, but offered instead a variety of alternatives attempting to describe the metaphysical realms beyond the visible world, and beyond life. Theological speculations gave rise to a rich textual and visual repertoire, which underwent a process of evolution over thousands of years, during which newer ideas and images were constantly introduced. Through the analysis of royal and non-royal funerary texts from the late Old Kingdom to the end of the New Kingdom, this book traces the development of the conceptualization of the notion of Duat, outlining what it encompassed and where it was imagined to be located. In addition to the translation and discussion of the most significant passages of the texts analyzed, each chapter also provides an overview of the individual compositions and of the relevant theological, cosmological, and astronomical notions complementing the conceptual framework, of which the Duat formed but a part. Additionally, discussions of concurrent changes in Egyptian culture, society, and ideology are included in order to clarify the context in which afterlife beliefs and related texts evolved. An analysis of the correlation between funerary compositions and their material supports complements the study, emphasizing the Egyptians' belief in a magical synergy between texts, images, and their contexts in the activation of a suitable, effective afterlife for the recipients of the texts.

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Glausser, Wayne. The Rhetoric of New Atheism. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780190864170.003.0002.

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New atheists face an old problem that entangles them with their theist opponents. The fundamental cosmological question—why does the world exist?—cannot be answered in scientific terms. As questions of cause slip into infinite regress, new atheists, like the theists they resist, must posit that something simply exists: something must be granted exemption from causal reasoning. This chapter first examines new atheists’ responses to the aporia described above, then analyzes several rhetorical tropes they deploy to supplement science proper. These tropes include paralepsis, a sarcasm cluster (apodioxis, tapinosis, diasyrmus), pathopoeia, and the linked tropes of catachresis and metalepsis. Especially with the last three tropes, new atheists find themselves entangled with the religious discourse they mean to supplant.

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Chapitres de livres sur le sujet "Cosmological analysis"

Gambera, M., A. Pagliaro et V. Antonuccio-Delogu. « A Wavelet Analysis of the Coma Cluster ». Dans Generation of Cosmological Large-Scale Structure, 261–66. Dordrecht : Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-009-0053-0_16.

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Blanco, S., O. A. Rosso et A. Costa. « Nonlinear Analysis of a Classical Cosmological Model ». Dans Chaos in Gravitational N-Body Systems, 233–38. Dordrecht : Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-009-0307-4_23.

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Gómez-Flechoso, M. A., L. Benjouali et R. Domínguez Tenreiro. « Cosmological Analysis of the Satellite Galaxy Distribution ». Dans Astrophysics and Space Science Proceedings, 295. Berlin, Heidelberg : Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-11250-8_47.

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Melchiorri, A., C. Odman et P. Serra. « Determination of Cosmological Parameters from Cosmic Microwave Background Anisotropies ». Dans Data Analysis in Cosmology, 237–59. Berlin, Heidelberg : Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-44767-2_8.

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Yess, Capp. « A Two-Dimensional Percolation Analysis of the Las Campanas Redshift Survey ». Dans Generation of Cosmological Large-Scale Structure, 251–54. Dordrecht : Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-009-0053-0_14.

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Slezak, E., Florence Durret et D. Gerbal. « Substructure in ABCG 2256 : Wavelet Analysis of ROSAT Image ». Dans Cosmological Aspects of X-Ray Clusters of Galaxies, 93–94. Dordrecht : Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-1022-8_10.

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Cole, Alex, et Gary Shiu. « Towards the “Shape” of Cosmological Observables and the String Theory Landscape with Topological Data Analysis ». Dans Signals and Communication Technology, 219–44. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-65459-7_9.

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Henneaux, Marc. « Kac-Moody algebras and the structure of cosmological singularities : a new light on the Belinskii-Khalatnikov-Lifshitz analysis ». Dans Quantum Mechanics of Fundamental Systems : The Quest for Beauty and Simplicity, 1–11. New York, NY : Springer New York, 2009. http://dx.doi.org/10.1007/978-0-387-87499-9_11.

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Elder, Jamee. « Theory Testing in Gravitational-Wave Astrophysics ». Dans Synthese Library, 57–79. Cham : Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-26618-8_4.

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AbstractThe LIGO-Virgo Collaboration achieved the first ‘direct detection’ of gravitational waves in 2015, opening a new “window” for observing the universe. Since this first detection (‘GW150914’), dozens of detections have followed, mostly produced by binary black hole mergers. However, the theory-ladenness of the LIGO-Virgo methods for observing these events leads to a potentially-vicious circularity, where general relativistic assumptions may serve to mask phenomena that are inconsistent with general relativity (GR). Under such circumstances, the fact that GR can ‘save the phenomena’ may be an artifact of theory-laden methodology.This paper examines several ways that the LIGO-Virgo observations are used in theory and hypothesis testing, despite this circularity problem. First, despite the threat of vicious circularity, these experiments succeed in testing GR. Indeed, early tests of GR using GW150914 are best understood as a response to the threat of theory-ladenness and circularity. Each test searches for evidence that LIGO-Virgo’s theory-laden methods are biasing their overall conclusions. The failure to find evidence of this places constraints on deviations from the predictions of GR. Second, these observations provide a basis for studying astrophysical and cosmological processes, especially through analyses of populations of events. As gravitational-wave astrophysics transitions into mature science, constraints from early tests of GR provide a scaffolding for these population-based studies. I further characterize this transition in terms of its increasing connectedness to other parts of astrophysics and the prominence of reasoning about selection effects and other systematics in drawing inferences from observations.Overall, this paper analyses the ways that theory and hypothesis testing operate in gravitational-wave astrophysics as it gains maturity. In particular, I show how these tests build on one another in order to mitigate a circularity problem at the heart of the observations.

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Geller, Pamela L. « Maya Mortuary Spaces as Cosmological Metaphors ». Dans Space and Spatial Analysis in Archaeology, 37–45. University of Calgary Press, 2006. http://dx.doi.org/10.1515/9781552384534-007.

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Actes de conférences sur le sujet "Cosmological analysis"

Feithen, William, Daniel Suson et Alex Drlica-Wagner. « Comparative Analysis of Cosmological Simulations via Angular Power Spectra ». Dans Comparative Analysis of Cosmological Simulations via Angular Power Spectra. US DOE, 2024. http://dx.doi.org/10.2172/2426435.

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Kindratenko, Volodymyr V., et Robert J. Brunner. « Accelerating Cosmological Data Analysis with FPGAs ». Dans 2009 17th IEEE Symposium on Field Programmable Custom Computing Machines. IEEE, 2009. http://dx.doi.org/10.1109/fccm.2009.12.

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Padmanabhan, Nikhil, et Ben Albrecht. « Cosmological Particle-Mesh Simulations in Chapel ». Dans SC '17 : The International Conference for High Performance Computing, Networking, Storage and Analysis. New York, NY, USA : ACM, 2017. http://dx.doi.org/10.1145/3144779.3169105.

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Zeyen, Max, James Ahrens, Hans Hagen, Katrin Heitmann et Salman Habib. « Cosmological Particle Data Compression in Practice ». Dans SC '17 : The International Conference for High Performance Computing, Networking, Storage and Analysis. New York, NY, USA : ACM, 2017. http://dx.doi.org/10.1145/3144769.3144776.

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Mahata, Nilanjana, et Subenoy Chakraborty. « Dynamical system analysis of three fluid cosmological model ». Dans INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS ICNAAM 2019. AIP Publishing, 2020. http://dx.doi.org/10.1063/5.0028049.

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Peterka, Tom, Juliana Kwan, Adrian Pope, Hal Finkel, Katrin Heitmann, Salman Habib, Jingyuan Wang et George Zagaris. « Meshing the Universe : Integrating Analysis in Cosmological Simulations ». Dans 2012 SC Companion : High Performance Computing, Networking, Storage and Analysis (SCC). IEEE, 2012. http://dx.doi.org/10.1109/sc.companion.2012.34.

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Roeh, Dylan W., Volodymyr V. Kindratenko et Robert J. Brunner. « Accelerating cosmological data analysis with graphics processors ». Dans 2nd Workshop. New York, New York, USA : ACM Press, 2009. http://dx.doi.org/10.1145/1513895.1513896.

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Santilli, Ruggero Maria, Theodore E. Simos, George Psihoyios et Ch Tsitouras. « Experimental Verification of Isoredshift and its Cosmological Implications ». Dans ICNAAM 2010 : International Conference of Numerical Analysis and Applied Mathematics 2010. AIP, 2010. http://dx.doi.org/10.1063/1.3498629.

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Balakina, E. A., et M. V. Pruzhinskaya. « Peculiar velocities of supernovae Ia in clusters of galaxies ». Dans Всероссийская с международным участием научная конференция студентов и молодых ученых, посвященная памяти Полины Евгеньевны Захаровой «Астрономия и исследование космического пространства». Ural University Press, 2021. http://dx.doi.org/10.15826/b978-5-7996-3229-8.03.

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Observations of supernovae Ia make it possible to estimate the values of cosmological parameters using the Hubble diagram. First of all, such observations give us a value of the Hubble constant, which is one of the most important cosmological parameters. Improving the accuracy of measurements of this parameter is a priority for modern cosmological analysis. Therefore, it is necessary to take into account the influence of the peculiar velocities of supernovae Ia on the measurement of the redshift, which is used in constructing the Hubble diagram. We study the contribution of peculiar velocities due to the motion of host galaxies in the gravitational field of galaxy clusters for a cosmological sample of supernovae Pantheon.

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Solís-Sánchez, Hugo, Manuel Ortega-Rodríguez, Luis A. Álvarez, Esteban Dodero, E. Gabriela Barrantes et José M. Gamboa. « Cosmographic analysis as framework to evaluate cosmological models ». Dans Proceedings of the MG15 Meeting on General Relativity. WORLD SCIENTIFIC, 2022. http://dx.doi.org/10.1142/9789811258251_0173.

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Rapports d'organisations sur le sujet "Cosmological analysis"

Okumura, Teppei. Cosmological analysis from large-scale anisotropic correlation function of the Sloan Digital Sky Survey. Office of Scientific and Technical Information (OSTI), mars 2008. http://dx.doi.org/10.2172/936341.

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Lynch, James F. A Higgs Universe and the flow of time. Woods Hole Oceanographic Institution, avril 2024. http://dx.doi.org/10.1575/1912/69338.

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Theoretically considering velocities greater than c implies considering an observer’s past and extends the overall analysis into the complex plane. By using a series of rotations by i in the complex plane, one can create a four-lobed structure of “instants of time,” which together with considering matter and antimatter in the lobes and the +/- sense of the rotation, leads to a Higgs field representation of space and time. A 10x10 metric is developed for this system as well as a generalized spacetime interval. It is also shown that the Friedmann Equations are consistent with our “Higgs Cosmology” if generalized to a set of coupled equations that connect the forward and backward going solutions. Simple solutions for the forward and backward going universes are presented, and are shown to be consistent with the backward solution providing both inflation and a “cosmological constant” type of dark energy, Dark matter is also discussed and is hypothesized to be due to the mass of the four “Higgs sectors” as seen through the lens of relativity by an observer in our universe. A PowerPoint presentation on this work is presented at the end of the report as a supplement.

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Lynch, James F. A digital Higgs universe and the flow of time. Woods Hole Oceanographic Institution, octobre 2024. http://dx.doi.org/10.1575/1912/70830.

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Theoretically considering velocities greater than c implies considering an observer’s past and extends the overall analysis into the complex plane. By using a series of rotations by i in the complex plane at the Planck scale, one can create a four-lobed structure of “instants of time,” which together with considering matter and antimatter in the lobes and the +/- sense of the rotation, leads to a Higgs field representation of spacetime. A metric is developed for this system as well as a generalized spacetime interval. It is shown that the Friedmann Equations are consistent with our “Higgs Cosmology” if generalized to a set of gravitationally coupled equations that connect the forward and backward going solutions. Simple solutions for the forward and backward going universes are presented and are shown to be consistent with the backward solution providing both inflation and a “cosmological constant” type of dark energy. Dark matter is discussed and is separately hypothesized to be due to the mass of the four “Higgs sectors” as seen by an observer in our universe. A digital, stroboscopic and holographic universe picture emerges which can also be viewed as a beginning theory of quantum gravity at the Planck scale.

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HEFNER, Robert. IHSAN ETHICS AND POLITICAL REVITALIZATION Appreciating Muqtedar Khan’s Islam and Good Governance. IIIT, octobre 2020. http://dx.doi.org/10.47816/01.001.20.

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Ours is an age of pervasive political turbulence, and the scale of the challenge requires new thinking on politics as well as public ethics for our world. In Western countries, the specter of Islamophobia, alt-right populism, along with racialized violence has shaken public confidence in long-secure assumptions rooted in democracy, diversity, and citizenship. The tragic denouement of so many of the Arab uprisings together with the ascendance of apocalyptic extremists like Daesh and Boko Haram have caused an even greater sense of alarm in large parts of the Muslim-majority world. It is against this backdrop that M.A. Muqtedar Khan has written a book of breathtaking range and ethical beauty. The author explores the history and sociology of the Muslim world, both classic and contemporary. He does so, however, not merely to chronicle the phases of its development, but to explore just why the message of compassion, mercy, and ethical beauty so prominent in the Quran and Sunna of the Prophet came over time to be displaced by a narrow legalism that emphasized jurisprudence, punishment, and social control. In the modern era, Western Orientalists and Islamists alike have pushed the juridification and interpretive reification of Islamic ethical traditions even further. Each group has asserted that the essence of Islam lies in jurisprudence (fiqh), and both have tended to imagine this legal heritage on the model of Western positive law, according to which law is authorized, codified, and enforced by a leviathan state. “Reification of Shariah and equating of Islam and Shariah has a rather emaciating effect on Islam,” Khan rightly argues. It leads its proponents to overlook “the depth and heights of Islamic faith, mysticism, philosophy or even emotions such as divine love (Muhabba)” (13). As the sociologist of Islamic law, Sami Zubaida, has similarly observed, in all these developments one sees evidence, not of a traditionalist reassertion of Muslim values, but a “triumph of Western models” of religion and state (Zubaida 2003:135). To counteract these impoverishing trends, Khan presents a far-reaching analysis that “seeks to move away from the now failed vision of Islamic states without demanding radical secularization” (2). He does so by positioning himself squarely within the ethical and mystical legacy of the Qur’an and traditions of the Prophet. As the book’s title makes clear, the key to this effort of religious recovery is “the cosmology of Ihsan and the worldview of Al-Tasawwuf, the science of Islamic mysticism” (1-2). For Islamist activists whose models of Islam have more to do with contemporary identity politics than a deep reading of Islamic traditions, Khan’s foregrounding of Ihsan may seem unfamiliar or baffling. But one of the many achievements of this book is the skill with which it plumbs the depth of scripture, classical commentaries, and tasawwuf practices to recover and confirm the ethic that lies at their heart. “The Quran promises that God is with those who do beautiful things,” the author reminds us (Khan 2019:1). The concept of Ihsan appears 191 times in 175 verses in the Quran (110). The concept is given its richest elaboration, Khan explains, in the famous hadith of the Angel Gabriel. This tradition recounts that when Gabriel appeared before the Prophet he asked, “What is Ihsan?” Both Gabriel’s question and the Prophet’s response make clear that Ihsan is an ideal at the center of the Qur’an and Sunna of the Prophet, and that it enjoins “perfection, goodness, to better, to do beautiful things and to do righteous deeds” (3). It is this cosmological ethic that Khan argues must be restored and implemented “to develop a political philosophy … that emphasizes love over law” (2). In its expansive exploration of Islamic ethics and civilization, Khan’s Islam and Good Governance will remind some readers of the late Shahab Ahmed’s remarkable book, What is Islam? The Importance of Being Islamic (Ahmed 2016). Both are works of impressive range and spiritual depth. But whereas Ahmed stood in the humanities wing of Islamic studies, Khan is an intellectual polymath who moves easily across the Islamic sciences, social theory, and comparative politics. He brings the full weight of his effort to conclusion with policy recommendations for how “to combine Sufism with political theory” (6), and to do so in a way that recommends specific “Islamic principles that encourage good governance, and politics in pursuit of goodness” (8).

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