Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 25 for “"Non-Gaussianity"”.
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Probing primordial non-Gaussianity using large scale structure
… satellite has lead to a tentative detection of non-Gaussianity. Using the bispectrum statistic applied to the MegaZ catalogue of over 600,000 luminous red galaxies we find new bounds on the large-scale nonGaussianity. We constrain the fNL parameter using a particular type of triangular …
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Multifield inflation in random potentials and the rapid-turn limit
… by looking at what future measurements of local non-Gaussianity will tell us. Local non-Gaussianity has been proposed as a key observable for distinguishing between single- and multifield inflation, as a large value of this parameter would rule out the former. However, a small value would not …
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Reconstructing the Sky with CMB Lensing methods
… provide powerful tests for parameter tensions, non-Gaussianity, neutrino mass, and modifications to Λ−CDM and gravity. However, such cross-correlations are sensitive to CMB foreground contamination, and the resulting biases represent an important challenge for cosmological analyses. In this …
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High-Resolution CMB Bispectrum Estimator
… correlation function, allows us to study weak non-Gaussian signatures of the primordial fluctuations. Primordial non-Gaussianity is a key prediction of many physically well-motivated inflation models, and measuring its shape and amplitude allows us to constrain various models of the early …
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Higher Order Couplings in the Clustering of Biased Tracers of Large-Scale Structure
… In order to extract this information, the non-linearities present in late-time observables provided by LSS surveys must be understood well. In general, there are three main sources of non-linearities: (1) non-linear matter clustering due to gravity; (2) non-linear biasing, i.e. the relation …
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Probing the Cosmological Initial Conditions Using the CMB
… (Yadav and Wandelt 2008) evidence for primordial non-Gaussianity of the local type (fNL) in the temperature anisotropy of the Cosmic Microwave Background. Analyzing the bispectrum of the WMAP 3-year data up to lmax=750 we find 27< fNL<147 (95% CL). This amounts to a rejection of fNL=0 at 2.8sigma, …
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Instrumental Effects in 21 cm Cosmology: One-point Statistics and Power Spectrum with the HERA Interferometer
… X-ray heating. The third moment, which captures non-Gaussianity features of the signals, is significantly diminished by the instrument response and further reduced by the foreground removal process, making it challenging to probe non-Gaussianity. However, there remains the potential to detect …
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Integration of Hidden Markov Modelling and Bayesian Networks for fault analysis of complex systems. Development of a hybrid diagnostics methodology based on the integration of hidden Markov modelling and Bayesian networks for fault detection, prediction and isolation of complex automotive systems
… Characteristics of complex systems such as nonlinearity, dynamicity, non-stationarity, and non-Gaussianity make diagnostics and prognostics more challenging tasks and decrease the application of classic reliability methods remarkably – as they cannot address the dynamic behaviour of these …
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Integration of Hidden Markov Modelling and Bayesian Networks for fault analysis of complex systems. Development of a hybrid diagnostics methodology based on the integration of hidden Markov modelling and Bayesian networks for fault detection, prediction and isolation of complex automotive systems
… Characteristics of complex systems such as nonlinearity, dynamicity, non-stationarity, and non-Gaussianity make diagnostics and prognostics more challenging tasks and decrease the application of classic reliability methods remarkably – as they cannot address the dynamic behaviour of these …
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Fundamental physics from observations of the early universe
… in particular be important in constraining the non-Gaussianity in the initial conditions of the Universe. Inhomogeneities in recombination and reionization amplify the perturbations in the underlying matter density and the resulting second order effects may be important. I calculate the …
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Gravitational waves and gauge fields in the early Universe
… lead to the resonant production of Abelian and non-Abelian gauge bosons. We subsequently demonstrate that gravitational wave emission constrains a similar model invoked to resolve the discrepancy in measurements of the present-day expansion rate. Finally, we study gravitational waves induced by …
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Connecting Inflation to Observations Through the Bispectrum
… fast convergence is the effect of dominant non-physical k-configurations. A secondary difficulty encountered is accurately including the early-time contributions to the higher-order coefficients (which are necessary to capture feature effects, such as resonance non-Gaussianity). In this …
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Stochastic Sea Ice Modeling with the Dynamically Orthogonal Equations
… types and scales of sea ice and the complex nonlinear mechanics and high dimensionality of differential equations, efficient ocean and sea ice probabilistic modeling, Bayesian inversion, and machine learning are challenging. In this work, we implement a deterministic 2D viscoplastic sea ice …
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Robust non-Gaussian semantic simultaneous localization and mapping
… We consider the problem of semantic SLAM under non-Gaussian uncertainty. The most prominent case in which this arises is from data association uncertainty, where we do not know with certainty what objects in the environment caused the measurement made by our sensor. The semantic class of an …
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Post-inflationary non-Gaussianities on the cosmic microwave background
… will be opened for studying different phenomena. Non-Gaussianity is one of the most exciting effects which fascinate many cosmologists. While numerous alternative inflationary models predict detectable primordial non-Gaussianities generated during inflation, the single-field slow-roll inflation of …
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Stochastic Computer Model Calibration and Uncertainty Quantification
… of input. For a simulation where marginal gaussianity assumption is not appropriate, it does not suffice to emulate only the mean and/or variance. We present two different approaches addressing the non-gaussianity behavior of an emulator, by (1) incorporating quantile regression in GP for …
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The cosmic microwave background: gaussianity and polarization
… we can interpret these as either a detection of non-Gaussianity, or some foreground or other overlooked detail in our model of the experiment. The second tool provides a statistically sound and relatively rapid technique for estimating the polarized power spectrum of the CMB. This is the Gibbs …
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Continuous reservoir model updating by ensemble Kalman filter on Grid computing architectures
… truncation can correct negative effects of nonlinearity and non-Gaussianity as effectively as more complex and expensive reparameterization methods.
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High-Energy Aspects of Inflationary Cosmology
… of primordial density perturbations (non-Gaussianity) and primordial gravitational waves (tensor modes). In the first part of the thesis, we explore novel signatures of high-energy physics in higher- order correlation functions of inflationary perturbations. First, we use causality and …
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Uncertainty and sensitivity analysis methods for improving design robustness and reliability
… distributions such as intrinsic extent and non-Gaussianity. Furthermore, uncertainty and sensitivity information are combined to identify specfic strategies for uncertainty mitigation and visualize tradeoffs between available options. These approaches are integrated with design budgets to …
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