Global ETD Search
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Showing 1 to 20 of 25 for “"Bispectrum"”.
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High-Resolution CMB Bispectrum Estimator
… their subsequent evolution until now. The CMB bispectrum, the Fourier equivalent of the three-point 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 …
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Connecting Inflation to Observations Through the Bispectrum
Numerically calculating the full primordial bispectrum predicted by a model of inflation and comparing it to what we see in the CMB sky is very computationally intensive, necessitating layers of approximations and limiting the models which can be constrained. The inherent separability of the tree …
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Advancing the Matter Bispectrum Estimation in Large-Scale Structure
… like the three-point correlation function or bispectrum in Fourier space, will be indispensable for furthering our understanding of the Universe. While these methodologies have been developed over the years and applied to CMB analyses, similar work on large-scale structure is still in its …
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The power spectrum and bispectrum of inflation and cosmic defects
… Higher order statistics, such as the bispectrum, are required to test and constrain such models. The late-time distribution of matter in the Universe - large-scale structure (LSS) - contains much more information than the CMB that has not yet been used. In this thesis, we look at both …
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Accelerating radio transient detection using the Bispectrum algorithm and GPGPU
… by using a closure quantity known as the "bispectrum": the product of visibilities around a closed loop of antennae. The proposed algorithm has been shown to be easily parallelized and suitable for Graphics processing units (GPUs).Recent advancements in the field of many core technology …
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Estimation of astronomical images from the bispectrum of atmospherically distorted infrared data.
The uses of the bispectrum for recovering the images of one-dimensional infrared astronomical speckle data are examined in detail. An analytic model for the bispectral transfer function, the variance, and the covariance of the bispectrum are developed. The models are evaluated by Monte Carlo …
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Cosmological constraints using 2- and 3-point correlations with meerkat, the ska and other surveys
… (tree-level and one-loop) in redshift space and bispectrum tree-level models. 21-cm emission from neutral hydrogen is a promising tool for probing the matter distribution in the universe post-reionization. The HI signals contain signatures of the primordial universe and the growth of large-scale …
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Probing primordial non-Gaussianity using large scale structure
… 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 configuration as well as the …
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Early Seeds and Cosmic Skies: Quantum Origins of the Universe and Insights from Large-Scale Structure
… Theory. Specifically, we develop the one-loop bispectrum of galaxies in redshift space, addressing key subtleties about its renormalisation. We then analyse BOSS data and demonstrate that the inclusion of the bispectrum significantly reduces error bars in key cosmological parameters compared to …
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Post-inflationary non-Gaussianities on the cosmic microwave background
… in two main aspects. First, we calculate the CMB bispectrum imprinted by the 2nd-order perturbations during recombination. We carry out a numerical calculation including all the dominant effects at recombination and separate them consistently from the late-time effects. We find that the …
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Probing the Cosmological Initial Conditions Using the CMB
… 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, disfavoring canonical single field slow-roll inflation. The signal is robust to variations in lmax , frequency, and …
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Interferometric Methods
… Moving on from this, the closure phase bispectrum is presented as a way of uncovering the cosmological Epoch of Reionisation signal from the H{\sc i} line. This is using the HERA telescope, which consists of a dense core of parabolic antennas in a highly redundant layout. A data …
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Quantification of linear and nonlinear energy transfer processes in a plane wake
… limited cases. Previous measurements of the auto-bispectrum showed that three-wave interaction processes are important in the transitioning wake. However, quantification of these processes can only be obtained from measurement of the nonlinear energy transfer rates resulting from the nonlinear …
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Fundamental physics from observations of the early universe
… order effects may be important. I calculate the bispectrum due to these second order effects and find that they are not an important source of confusion with the primordial non-Gaussianities. 21-cm observations of the era between the recombination and reionization will provide a wealth of data in …
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On characterisation and decomposition of internet traffic dynamics
… order spectral capabilities and particularly the bispectrum, traffic engineering tasks may be beneficially improved. In spite of the advantageous diagnostics offered in several traffic engineering applications such as anomaly diagnosis, the practical capabilities offered by the bispectrum are …
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Higher Order Couplings in the Clustering of Biased Tracers of Large-Scale Structure
… and cubic bias parameters are tree-level bispectrum and trispectrum, respectively. Since these statistics are computationally quite expensive, we use efficient squared and cubic field estimators that contain integrated bispectrum and trispectrum information. We use the constraints to model …
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Projected Angular Statistics for Large-scale Structure Cosmology
… to the calculation of the tree-level angular bispectrum (or three-point function) of galaxy clustering, including redshift-space distortions. We extend the full-sky to flat-sky correspondence and derive approximate formulae for the angular bispectrum, which can be evaluated efficiently. On …
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Practical Aspects of Assessing Nonlinear Ultrasonic Response of Cyclically Load 7075-T6 Aluminum
… analysis techniques such as the power spectrum, bispectrum, and bicoherence spectrum are applied. The ultrasonic nonlinearity parameters by Cantrell and Jhang are introduced and presented as a function of the material fatigue growth, the number of fatigue cycles. This thesis presents the …
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Development of Reduced-Order Models for Lift and Drag on Oscillating Cylinders with Higher-Order Spectral Moments
… Moreover, the amplitude and phase of the cross-bispectrum could be used to establish the lift-drag relation for oscillating cylinders. A forced van der Pol equation is used to represent the lift on a transversely oscillating cylinder, and a parametrically excited van der Pol equation is used to …
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