1,572 research outputs found
The CMB bispectrum
No full textWe use a separable mode expansion estimator with WMAP7 data to estimate the bispectrum for all the primary families of non-Gaussian models, including non-scaling feature (periodic) models, the flat (trans-Planckian) model, DBI and ghost inflation, as well as previously constrained simple cases. We review the late-time mode expansion estimator methodology which can be applied to any non-separable primordial and CMB bispectrum model, and we demonstrate how the method can be used to reconstruct the CMB bispectrum from an observational map. We extend the previous validation of the general estimator using local map simulations. We apply the estimator to the coadded WMAP 7-year V and W channel maps, reconstructing the WMAP bispectrum using l 150). We find no significant evidence of non-Gaussianity for all cases well-described by the given eigenmodes. In the overall non-Gaussian analysis, we find one anomalous mode n = 33 with a 3.39 sigma amplitude which could give rise to an oscillatory model signal with l* <= 150. We propose a measure (F) over bar (NL) for the total integrated bispectrum and find that the measured value is consistent with the null hypothesis that CMB anisotropies obey Gaussian statistics. We argue that this general bispectrum survey with the WMAP data represents the best test of Gaussianity to date and we discuss future prospects with higher precision and resolution, notably from the Planck satellite
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The instanton liquid and the axion
Get PDFThe ultimate goal of this thesis is to improve our understanding of the cosmology of axions. Axions couple to QCD
instantons and these non-perturbative effects are modeled within the framework of the interacting instanton liquid model (IILM). The thesis describes the significant advances made within the IILM in order to study the quark-gluon plasma in realistic parameter regimes. In particular, a determination of the temperature-dependent axion mass in the IILM lays the foundation for a critical reevaluation and update of present cosmological axion constraints.
We develop grand canonical Monte Carlo routines to study topological fluctuations in the quark-gluon plasma. The model is calibrated against the topological susceptibility at zero temperature, in the chiral regime of physical quark masses. A numerical framework to derive interactions among the pseudo-particles is developed that is in principle exact, and is used to cure a pathology in the presently available finite temperature interactions.
The IILM reduces field theory to a molecular dynamics description, and we show that, quite generically, the dynamics for non-trivial backgrounds in the presence of light quarks is reminiscent of a strongly associating fluid. To deal with the well-known difficulty in simulating ionic fluids, we develop advanced algorithms based on Biased Monte Carlo techniques.
We study the IILM at finite temperature in the quenched and unquenched sector, with due diligence to a consistent thermodynamic limit. Of particular interest is chiral symmetry breaking and the temperature dependence of the topological susceptibility, and we study in detail the effects of instanton--anti-instanton pairs. Our determination of the topological susceptibility provides, for the first time, a well-motivated axion mass for all temperatures.
The misalignment mechanism for axion production is studied in detail, solving the evolution equations exactly in a radiation dominated FRW universe with the full temperature dependence of the effective degrees of freedom taken into account. Improved constraints in the classic and anthropic axion window are derived. We generalise the latter to large angle fine-tuning by including in the isocurvature contribution to the cosmic microwave background radiation the full anharmonic axion potential effects. Finally, we reexamine bounds from axion string radiation in the thermal scenario to complete a comprehensive update of all cosmological axion constraints
General CMB and primordial bispectrum estimation: Mode expansion, map making, and measures of F_{NL}
No full textWe present a detailed implementation of two parallel bispectrum estimation methods which can be applied to general nonseparable primordial and cosmic microwave background (CMB) bispectra. The method exploits bispectrum mode decompositions on the tetrahedral domain of allowed wave number or multipole values, using both separable basis functions and related orthonormal modes. We provide concrete examples of such modes constructed from symmetrized tetrahedral polynomials, demonstrating the rapid convergence of expansions describing nonseparable bispectra. We use these modes to create rapid and robust pipelines for generating simulated CMB maps of high resolution (l>2000) given an arbitrary primordial power spectrum and bispectrum or an arbitrary late-time CMB angular power spectrum and bispectrum. By extracting coefficients for the same separable basis functions from an observational map, we are able to present an efficient fNL estimator for a given theoretical model with a nonseparable bispectrum. The estimator has two manifestations, comparing the theoretical and observed coefficients at either primordial or late times, thus encompassing a wider range of models, including secondary anisotropies and lensing as well as active models, such as cosmic strings. We provide examples and validation of both fNL estimation methods by direct comparison with simulations in a WMAP-realistic context. In addition, we demonstrate how the full primordial and CMB bispectrum can be extracted from observational maps using these mode expansions, irrespective of the theoretical model under study. We also propose a universal definition of the bispectrum parameter FNL, so that the integrated bispectrum on the observational domain can be more consistently compared between theoretical models. We obtain WMAP5 estimates of fNL for the equilateral model from both our primordial and late-time estimators which are consistent with each other, as well as results already published in the literature. These general bispectrum estimation methods should prove useful for non-Gaussianity analysis with the Planck satellite data, as well as in other contexts
Primordial Non-Gaussianity and Bispectrum Measurements in the Cosmic Microwave Background and Large-Scale Structure
Get PDFThe most direct probe of non-Gaussian initial conditions has come from bispectrum measurements of temperature fluctuations in the Cosmic Microwave Background and of the matter and galaxy distribution at large scales. Such bispectrum estimators are expected to continue to provide the best constraints on the non-Gaussian parameters in future observations. We review and compare the theoretical and observational problems, current results, and future prospects for the detection of a nonvanishing primordial component in the bispectrum of the Cosmic Microwave Background and large-scale structure, and the relation to specific predictions from different inflationary models
Simulation of the fluorescence detector of the Pierre Auger Observatory
No full textWe present a description of a simulation program for the fluorescence detector (FD) of the Pierre Auger Observatory. The simulation chain covers in detail all the physical processes involved in the fluorescence technique, from the shower longitudinal profile in the atmosphere to ADC-traces in the data acquisition system of the telescopes. Steps in the simulation include the generation of fluorescence and Cherenkov light in the atmosphere, propagation of this light to the telescope aperture, ray-tracing of photons in the Schmidt optics of the telescopes, and finally, simulation of the response of the electronics and the multi-level trigger. As an example of the simulation's use we show the results of a calculation of the trigger efficiency of the FD as a function of cosmic ray energy. (c) 2005 Elsevier B.V. All rights reserved
Topological events on wave dislocation lines: birth and death of small loops, and reconnection
No full textIn three-dimensional space, a wave dislocation, that is, a quantized (optical) vortex or phase singularity, is a line zero of a complex scalar wavefunction. As a 'time' parameter varies, the topology of the vortex can change by encounter with a line of vanishing vorticity (curl of the current associated with the wavefunction). An isolated critical point of the field intensity, sliding along the zero-vorticity line like a bead on a wire, meets the vortex as it encounters the line, and so participates in the singular event. Local expansio n and gauge and coordinates transformations show that the vortex topology can change generically by the appearance or disappearance of a loop, or by the reconnection of branches of a pair of hyperbolas
SMARANDACHE MULTI-SPACE THEORY, Second Edition
Get PDFWe are used to the idea that our space has three dimensions: length, breadth and height with time providing the fourth dimension of spacetime by Einstein. In the string or superstring theories, we encounter 10 dimensions. However, we do not even know what the right degree of freedom is, as Witten said. Today, we have known two heartening notions for sciences. One is the Smarandache multi-space came into being by purely logic. Another is the mathematical combinatorics motivated by a combinatorial speculation, i.e., a mathematical science can be reconstructed from or made by combinatorialization. Both of them contribute sciences for consistency of research with that human progress in 21st century
The muon content of hybrid events recorded at the Pierre Auger Observatory
Get PDFThe hybrid events of the Pierre Auger Observatory are used to test the leading, LHC-tuned, hadronic interaction models. For each of 411 well-reconstructed hybrid events collected at the Auger Observatory withenergy 10E18.8 − 10E19.2 eV, simulated events with a matching longitudinal profile have been produced using QGSJET-II-04 and EPOS-LHC, for proton, He, N, and Fe primaries. The ground signals of simulated events have a factor 1.3-1.6 deficit of hadronically-produced muons relative to observed showers, depending on which high energy event generator is used, and whether the composition mix is chosen to reproduce the observed Xmax distribution or a pure proton composition is assumed. The analysis allows for a possible overall rescaling of theenergy, which is found to lie within the systematic uncertainties.Fil: Farrar, Glennys R.. Observatorio Pierre Auger. Observatorio Sur - Malargue; Argentina. New York University; Estados UnidosFil: Tueros, Matias Jorge. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; Argentina. Universidad de Santiago de Compostela. Facultad de Física; EspañaFil: The Pierre Auger Collaboration. No especifíca;33rd International Cosmic Ray ConferenceRio de JaneiroBrasilInternational Union of Pure and Applied Physic
Harmony and discord within the English ‘counter-culture’, 1965-1975, with particular reference to the ‘rock operas’ Hair, Godspell, Tommy and Jesus Christ Superstar
No full textPhDThis thesis considers the discrete, historically-specific theatrical and musical sub-genre of ‘Rock Opera’ as a lens through which to examine the cultural, political and social changes that are widely assumed to have characterised ‘The Sixties’ in Britain. The musical and dramatic texts, creation and production of Hair (1967), Tommy (1969), Godspell (1971), Jesus Christ Superstar (1970) and other neglected ‘Rock Operas’ of the period are analysed. Their great popularity with ‘mainstream’ audiences is considered and contrasted with the overwhelmingly negative and often internally contradictory reaction towards them from the English ‘counter-culture’. This examination offers new insights into both the ‘counter-culture’ and the ‘mainstream’ against which it claimed to define and differentiate itself.
The four ‘Rock Operas’, two of which are based upon Christian scriptures, are considered as narratives of spiritual quest. The relationship between the often controversial quests for re-defined forms of faith and the apparently precipitous ‘secularization’ and ‘de-Christianization’ of British society during the 1960s and 1970s is considered.
The thesis therefore analyses the ‘Rock Operas’ as significant, enlightening prisms through which to view many of the profound societal debates – over ‘faith’ and ‘belief’ in the widest senses, sexuality, the Vietnam war, generational conflict, drugs and ‘spiritual enlightenment’, and race – which were, to some considerable extent, elevated onto the national, political agenda by the activities of the broadly-defined ‘counter-culture’. It considers subsequent representations of the ‘counter-culture’ as the root of a contested but enduring popular legacy of ‘The Sixties' as a period of profound cultural change
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