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Licia Verde - One of the best experts on this subject based on the ideXlab platform.
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constraining primordial non gaussianity with Bispectrum and power spectrum from upcoming optical and radio surveys
Monthly Notices of the Royal Astronomical Society, 2018Co-Authors: Dionysios Karagiannis, M Liguori, Andrei Lazanu, Alvise Raccanelli, N Bartolo, Licia VerdeAbstract:We forecast constraints on primordial non-Gaussianity (PNG) and bias parameters from measurements of galaxy power spectrum and Bispectrum in future radio continuum and optical surveys. In the galaxy Bispectrum, we consider a comprehensive list of effects, including the bias expansion for non-Gaussian initial conditions up to second order, redshift space distortions, redshift uncertainties and theoretical errors. These effects are all combined in a single PNG forecast for the first time. Moreover, we improve the Bispectrum modelling over previous forecasts, by accounting for trispectrum contributions. All effects have an impact on final predicted bounds, which varies with the type of survey. We find that the Bispectrum can lead to improvements up to a factor $\sim 5$ over bounds based on the power spectrum alone, leading to significantly better constraints for local-type PNG, with respect to current limits from \textit{Planck}. Future radio and photometric surveys could obtain a measurement error of $\sigma(f_{\mathrm{NL}}^{\mathrm{loc}}) \approx 0.2$. In the case of equilateral PNG, galaxy Bispectrum can improve upon present bounds only if significant improvements in the redshift determinations of future, large volume, photometric or radio surveys could be achieved. For orthogonal non-Gaussianity, expected constraints are generally comparable to current ones.
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relativistic wide angle galaxy Bispectrum on the light cone
Physical Review D, 2018Co-Authors: Daniele Bertacca, M Liguori, Alvise Raccanelli, N Bartolo, Licia Verde, S MatarreseAbstract:Given the important role that the galaxy Bispectrum has recently acquired in cosmology and the scale and precision of forthcoming galaxy clustering observations, it is timely to derive the full expression of the large-scale Bispectrum going beyond approximated treatments which neglect integrated terms or higher-order bias terms or use the Limber approximation. On cosmological scales, relativistic effects that arise from observing on the past light-cone alter the observed galaxy number counts, therefore leaving their imprints on N-point correlators at all orders. In this paper we compute for the first time the Bispectrum including all general relativistic, local and integrated, effects at second order, the tracers' bias at second order, geometric effects as well as the primordial non-Gaussianity contribution. This is timely considering that future surveys will probe scales comparable to the horizon where approximations widely used currently may not hold; neglecting these effects may introduce biases in estimation of cosmological parameters as well as primordial non-Gaussianity.
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signatures of horndeski gravity on the dark matter Bispectrum
Journal of Cosmology and Astroparticle Physics, 2015Co-Authors: Emilio Bellini, Licia Verde, Raul JimenezAbstract:We present a detailed study of second-order matter perturbations for the general Horndeski class of models. Being the most general scalar-tensor theory having second-order equations of motion, it includes many known gravity and dark energy theories and General Relativity with a cosmological constant as a specific case. This enables us to estimate the leading order dark matter Bispectrum generated at late-times by gravitational instability. We parametrize the evolution of the first and second-order equations of motion as proposed by Bellini and Sawicki (2014), where the free functions of the theory are assumed to be proportional to the dark energy density. We show that it is unnatural to have large ∼> 10% (∼> 1%) deviations of the Bispectrum introducing even larger ∼ 30% (∼ 5%) deviations in the linear growth rate. Considering that measurements of the linear growth rate have much higher signal-to-noise than Bispectrum measurements, this indicates that for Horndeski models which reproduce the expansion history and the linear growth rate as predicted by GR the dark matter Bispectrum kernel can be effectively modelled as the standard GR one. On the other hand, an observation of a large Bispectrum deviation that can not be explained in terms of bias would imply either that themore » evolution of perturbations is strongly different than the evolution predicted by GR or that the theory of gravity is exotic (e.g., breaks the weak equivalence principle) and/or fine-tuned.« less
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signatures of horndeski gravity on the dark matter Bispectrum
arXiv: Cosmology and Nongalactic Astrophysics, 2015Co-Authors: Emilio Bellini, Raul Jimenez, Licia VerdeAbstract:We present a detailed study of second-order matter perturbations for the general Horn- deski class of models. Being the most general scalar-tensor theory having second-order equations of motion, it includes many known gravity and dark energy theories and General Relativity with a cosmological constant as a specific case. This enables us to estimate the leading order dark matter Bispectrum generated at late-times by gravitational instability. We parametrize the evolution of the first and second-order equations of motion as proposed by Bellini and Sawicki (2014), where the free functions of the theory are assumed to be proportional to the dark energy density. We show that it is unnatural to have large 10% ( 1%) deviations of the Bispectrum introducing even larger ~ 30% (~ 5%) deviations in the linear growth rate. Considering that measurements of the linear growth rate have much higher signal-to-noise than Bispectrum measurements, this indicates that for Horndeski models which reproduce the expansion history and the linear growth rate as predicted by GR the dark matter Bispectrum kernel can be effectively modelled as the standard GR one. On the other hand, an observation of a large Bispectrum deviation that can not be explained in terms of bias would imply either that the evolution of perturbations is strongly different than the evolution predicted by GR or that the theory of gravity is exotic (e.g., breaks the weak equivalence principle) and/or fine-tuned.
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dark matter and halo Bispectrum in redshift space theory and applications
arXiv: Cosmology and Nongalactic Astrophysics, 2014Co-Authors: Hector Gilmarin, Christian Wagner, Licia Verde, Jorge Norena, Will J PercivalAbstract:We present a phenomenological modification of the standard perturbation theory prediction for the Bispectrum in redshift space that allows us to extend the model to mildly non-linear scales over a wide range of redshifts, $z\leq1.5$. We find that we can describe the Bispectrum of dark matter particles with $\sim5%$ accuracy for $k_i\lesssim0.10\,h/{\rm Mpc}$ at $z=0$, for $k_i\lesssim0.15\,h/{\rm Mpc}$ at $z=0.5$, for $k_i\lesssim0.17\,h/{\rm Mpc}$ at $z=1.0$ and for $k_i\lesssim0.20\,h/{\rm Mpc}$ at $z=1.5$. We also test that the fitting formula is able to describe with similar accuracy the Bispectrum of cosmologies with different $\Omega_m$, in the range $0.2\lesssim \Omega_m \lesssim 0.4$, and consequently with different values of the logarithmic grow rate $f$ at $z=0$, $0.4\lesssim f(z=0) \lesssim 0.6$. We apply this new formula to recover the bias parameters, $f$ and $\sigma_8$, by combining the redshift space power spectrum monopole and quadrupole with the Bispectrum monopole for both dark matter particles and haloes. We find that the combination of these three statistics can break the degeneracy between $b_1$, $f$ and $\sigma_8$. For dark matter particles the new model can be used to recover $f$ and $\sigma_8$ with $\sim1%$ accuracy. For dark matter haloes we find that $f$ and $\sigma_8$ present larger systematic shifts, $\sim10%$. The systematic offsets arise because of limitations in the modelling of the interplay between bias and redshift space distortions, and represent a limitation as the statistical errors of forthcoming surveys reach this level. Conveniently, we find that these residual systematics are mitigated for combinations of parameters. The improvement on the modelling of the Bispectrum presented in this paper will be useful for extracting information from current and future galaxy surveys. [abridged]
J Fergusson - One of the best experts on this subject based on the ideXlab platform.
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observed parity odd cmb temperature Bispectrum
Journal of Cosmology and Astroparticle Physics, 2015Co-Authors: Maresuke Shiraishi, M Liguori, J FergussonAbstract:Parity-odd non-Gaussianities create a variety of temperature bispectra in the cosmic microwave background (CMB), defined in the domain: l{sub 1} + l{sub 2} + l{sub 3} = odd. These models are yet unconstrained in the literature, that so far focused exclusively on the more common parity-even scenarios. In this work, we provide the first experimental constraints on parity-odd Bispectrum signals in WMAP 9-year temperature data, using a separable modal parity-odd estimator. Comparing theoretical Bispectrum templates to the observed Bispectrum, we place constraints on the so-called nonlineality parameters of parity-odd tensor non-Gaussianities predicted by several Early Universe models. Our technique also generates a model-independent, smoothed reconstruction of the Bispectrum of the data for parity-odd configurations.
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observed parity odd cmb temperature Bispectrum
arXiv: Cosmology and Nongalactic Astrophysics, 2014Co-Authors: Maresuke Shiraishi, M Liguori, J FergussonAbstract:Parity-odd non-Gaussianities create a variety of temperature bispectra in the cosmic microwave background (CMB), defined in the domain: $\ell_1 + \ell_2 + \ell_3 = {\rm odd}$. These models are yet unconstrained in the literature, that so far focused exclusively on the more common parity-even scenarios. In this work, we provide the first experimental constraints on parity-odd Bispectrum signals in WMAP 9-year temperature data, using a separable modal parity-odd estimator. Comparing theoretical Bispectrum templates to the observed Bispectrum, we place constraints on the so-called nonlineality parameters of parity-odd tensor non-Gaussianities predicted by several Early Universe models. Our technique also generates a model-independent, smoothed reconstruction of the Bispectrum of the data for parity-odd configurations.
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general parity odd cmb Bispectrum estimation
Journal of Cosmology and Astroparticle Physics, 2014Co-Authors: Maresuke Shiraishi, M Liguori, J FergussonAbstract:We develop a methodology for estimating parity-odd bispectra in the cosmic microwave background (CMB). This is achieved through the extension of the original separable modal methodology to parity-odd Bispectrum domains (l1+l2+l3 = odd). Through numerical tests of the parity-odd modal decomposition with some theoretical Bispectrum templates, we verify that the parity-odd modal methodology can successfully reproduce the CMB Bispectrum, without numerical instabilities. We also present simulated non-Gaussian maps produced by modal-decomposed parity-odd bispectra, and show the consistency with the exact results. Our new methodology is applicable to all types of parity-odd temperature and polarization bispectra.
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general parity odd cmb Bispectrum estimation
arXiv: Cosmology and Nongalactic Astrophysics, 2014Co-Authors: Maresuke Shiraishi, M Liguori, J FergussonAbstract:We develop a methodology for estimating parity-odd bispectra in the cosmic microwave background (CMB). This is achieved through the extension of the original separable modal methodology to parity-odd Bispectrum domains ($\ell_1 + \ell_2 + \ell_3 = {\rm odd}$). Through numerical tests of the parity-odd modal decomposition with some theoretical Bispectrum templates, we verify that the parity-odd modal methodology can successfully reproduce the CMB Bispectrum, without numerical instabilities. We also present simulated non-Gaussian maps produced by modal-decomposed parity-odd bispectra, and show the consistency with the exact results. Our new methodology is applicable to all types of parity-odd temperature and polarization bispectra.
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the cmb Bispectrum
Journal of Cosmology and Astroparticle Physics, 2012Co-Authors: J Fergusson, M Liguori, E P S ShellardAbstract:We 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 3.39σ amplitude which could give rise to an oscillatory model signal with l* ≤ 150. We propose a measure 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.
M Liguori - One of the best experts on this subject based on the ideXlab platform.
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constraining primordial non gaussianity with Bispectrum and power spectrum from upcoming optical and radio surveys
Monthly Notices of the Royal Astronomical Society, 2018Co-Authors: Dionysios Karagiannis, M Liguori, Andrei Lazanu, Alvise Raccanelli, N Bartolo, Licia VerdeAbstract:We forecast constraints on primordial non-Gaussianity (PNG) and bias parameters from measurements of galaxy power spectrum and Bispectrum in future radio continuum and optical surveys. In the galaxy Bispectrum, we consider a comprehensive list of effects, including the bias expansion for non-Gaussian initial conditions up to second order, redshift space distortions, redshift uncertainties and theoretical errors. These effects are all combined in a single PNG forecast for the first time. Moreover, we improve the Bispectrum modelling over previous forecasts, by accounting for trispectrum contributions. All effects have an impact on final predicted bounds, which varies with the type of survey. We find that the Bispectrum can lead to improvements up to a factor $\sim 5$ over bounds based on the power spectrum alone, leading to significantly better constraints for local-type PNG, with respect to current limits from \textit{Planck}. Future radio and photometric surveys could obtain a measurement error of $\sigma(f_{\mathrm{NL}}^{\mathrm{loc}}) \approx 0.2$. In the case of equilateral PNG, galaxy Bispectrum can improve upon present bounds only if significant improvements in the redshift determinations of future, large volume, photometric or radio surveys could be achieved. For orthogonal non-Gaussianity, expected constraints are generally comparable to current ones.
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relativistic wide angle galaxy Bispectrum on the light cone
Physical Review D, 2018Co-Authors: Daniele Bertacca, M Liguori, Alvise Raccanelli, N Bartolo, Licia Verde, S MatarreseAbstract:Given the important role that the galaxy Bispectrum has recently acquired in cosmology and the scale and precision of forthcoming galaxy clustering observations, it is timely to derive the full expression of the large-scale Bispectrum going beyond approximated treatments which neglect integrated terms or higher-order bias terms or use the Limber approximation. On cosmological scales, relativistic effects that arise from observing on the past light-cone alter the observed galaxy number counts, therefore leaving their imprints on N-point correlators at all orders. In this paper we compute for the first time the Bispectrum including all general relativistic, local and integrated, effects at second order, the tracers' bias at second order, geometric effects as well as the primordial non-Gaussianity contribution. This is timely considering that future surveys will probe scales comparable to the horizon where approximations widely used currently may not hold; neglecting these effects may introduce biases in estimation of cosmological parameters as well as primordial non-Gaussianity.
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observed parity odd cmb temperature Bispectrum
Journal of Cosmology and Astroparticle Physics, 2015Co-Authors: Maresuke Shiraishi, M Liguori, J FergussonAbstract:Parity-odd non-Gaussianities create a variety of temperature bispectra in the cosmic microwave background (CMB), defined in the domain: l{sub 1} + l{sub 2} + l{sub 3} = odd. These models are yet unconstrained in the literature, that so far focused exclusively on the more common parity-even scenarios. In this work, we provide the first experimental constraints on parity-odd Bispectrum signals in WMAP 9-year temperature data, using a separable modal parity-odd estimator. Comparing theoretical Bispectrum templates to the observed Bispectrum, we place constraints on the so-called nonlineality parameters of parity-odd tensor non-Gaussianities predicted by several Early Universe models. Our technique also generates a model-independent, smoothed reconstruction of the Bispectrum of the data for parity-odd configurations.
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observed parity odd cmb temperature Bispectrum
arXiv: Cosmology and Nongalactic Astrophysics, 2014Co-Authors: Maresuke Shiraishi, M Liguori, J FergussonAbstract:Parity-odd non-Gaussianities create a variety of temperature bispectra in the cosmic microwave background (CMB), defined in the domain: $\ell_1 + \ell_2 + \ell_3 = {\rm odd}$. These models are yet unconstrained in the literature, that so far focused exclusively on the more common parity-even scenarios. In this work, we provide the first experimental constraints on parity-odd Bispectrum signals in WMAP 9-year temperature data, using a separable modal parity-odd estimator. Comparing theoretical Bispectrum templates to the observed Bispectrum, we place constraints on the so-called nonlineality parameters of parity-odd tensor non-Gaussianities predicted by several Early Universe models. Our technique also generates a model-independent, smoothed reconstruction of the Bispectrum of the data for parity-odd configurations.
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general parity odd cmb Bispectrum estimation
Journal of Cosmology and Astroparticle Physics, 2014Co-Authors: Maresuke Shiraishi, M Liguori, J FergussonAbstract:We develop a methodology for estimating parity-odd bispectra in the cosmic microwave background (CMB). This is achieved through the extension of the original separable modal methodology to parity-odd Bispectrum domains (l1+l2+l3 = odd). Through numerical tests of the parity-odd modal decomposition with some theoretical Bispectrum templates, we verify that the parity-odd modal methodology can successfully reproduce the CMB Bispectrum, without numerical instabilities. We also present simulated non-Gaussian maps produced by modal-decomposed parity-odd bispectra, and show the consistency with the exact results. Our new methodology is applicable to all types of parity-odd temperature and polarization bispectra.
Eiichiro Komatsu - One of the best experts on this subject based on the ideXlab platform.
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tensor non gaussianity from axion gauge fields dynamics parameter search
arXiv: Cosmology and Nongalactic Astrophysics, 2018Co-Authors: Aniket Agrawal, Tomohiro Fujita, Eiichiro KomatsuAbstract:We calculate the Bispectrum of scale-invariant tensor modes sourced by spectator SU(2) gauge fields during inflation in a model containing a scalar inflaton, a pseudoscalar axion and SU(2) gauge fields. A large Bispectrum is generated in this model at tree-level as the gauge fields contain a tensor degree of freedom, and its production is dominated by self-coupling of the gauge fields. This is a unique feature of non-Abelian gauge theory. The shape of the tensor Bispectrum is approximately an equilateral shape for $3\lesssim m_Q\lesssim 4$, where $m_Q$ is an effective dimensionless mass of the SU(2) field normalised by the Hubble expansion rate during inflation. The amplitude of non-Gaussianity of the tensor modes, characterised by the ratio $B_h/P^2_h$, is inversely proportional to the energy density fraction of the gauge field. This ratio can be much greater than unity, whereas the ratio from the vacuum fluctuation of the metric is of order unity. The Bispectrum is effective at constraining large $m_Q$ regions of the parameter space, whereas the power spectrum constrains small $m_Q$ regions.
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position dependent power spectrum of the large scale structure a novel method to measure the squeezed limit Bispectrum
Journal of Cosmology and Astroparticle Physics, 2014Co-Authors: Chiting Chiang, Christian Wagner, Fabian Schmidt, Eiichiro KomatsuAbstract:The influence of large-scale density fluctuations on structure formation on small scales is described by the three-point correlation function (Bispectrum) in the so-called ``squeezed configurations,'' in which one wavenumber, say k3, is much smaller than the other two, i.e., k3 << k1 ≈ k2. This Bispectrum is generated by non-linear gravitational evolution and possibly also by inflationary physics. In this paper, we use this fact to show that the Bispectrum in the squeezed configurations can be measured without employing three-point function estimators. Specifically, we use the ``position-dependent power spectrum,'' i.e., the power spectrum measured in smaller subvolumes of the survey (or simulation box), and correlate it with the mean overdensity of the corresponding subvolume. This correlation directly measures an integral of the Bispectrum dominated by the squeezed configurations. Measuring this correlation is only slightly more complex than measuring the power spectrum itself, and sidesteps the considerable complexity of the full Bispectrum estimation. We use cosmological N-body simulations of collisionless particles with Gaussian initial conditions to show that the measured correlation between the position-dependent power spectrum and the long-wavelength overdensity agrees with the theoretical expectation. The position-dependent power spectrum thus provides a new, efficient, and promising way to measure the squeezed-limit Bispectrum from large-scale structure observations such as galaxy redshift surveys.
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in in and δn calculations of the Bispectrum from non attractor single field inflation
Journal of Cosmology and Astroparticle Physics, 2013Co-Authors: Eiichiro Komatsu, Xingang Chen, Hassan Firouzjahi, Mohammad Hossein Namjoo, Misao SasakiAbstract:In non-attractor single-field inflation models producing a scale-invariant power spectrum, the curvature perturbation on super-horizon scales grows as ∝a3. This is so far the only known class of self-consistent single-field models with a Bunch-Davies initial state that can produce a large squeezed-limit Bispectrum violating Maldacena's consistency relation. Given the importance of this result, we calculate the Bispectrum with three different methods: using quantum field theory calculations in two different gauges, and classical calculations (the δN formalism). All the results agree, giving the local-form Bispectrum parameter of flocalNL = 5(1+cs2)/(4cs2). This result is valid for arbitrary values of the speed of sound parameter, cs, for a particular non-attractor model we consider in this paper.
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primordial non gaussianity scale dependent bias and the Bispectrum of galaxies
arXiv: Cosmology and Nongalactic Astrophysics, 2009Co-Authors: Donghui Jeong, Eiichiro KomatsuAbstract:We calculate the Bispectrum, B_g(k_1,k_2,k_3), Fourier transform of the three-point function of density peaks (e.g., galaxies), using two different methods: the Matarrese-Lucchin-Bonometto formula and the locality of galaxy bias. The Bispectrum of peaks is not only sensitive to that of the underlying matter density fluctuations, but also to the four-point function. For a physically-motivated, local form of primordial non-Gaussianity in the curvature perturbation, we show that the galaxy Bispectrum contains five physically distinct pieces: (i) non-linear gravitational evolution, (ii) non-linear galaxy bias, (iii) f_nl, (iv) f_nl^2, and (v) \gnl. While (i), (ii), and a part of (iii) have been derived in the literature, (iv) and (v) are derived in this paper for the first time. Our finding suggests that the galaxy Bispectrum is more sensitive to f_nl than previously recognized, and is also sensitive to a new term, g_nl. For a more general form of local-type non-Gaussianity, the coefficient \fnl^2 can be interpreted as \tau_nl, which allows us to test multi-field inflation models. The usual terms from Gaussian initial conditions, have the smallest signals in the squeezed configurations, while the others have the largest signals; thus, we can distinguish them easily. We cannot interpret the effects of f_nl on B_g(k_1,k_2,k_3) as a scale-dependent bias, and thus replacing the linear bias in the galaxy Bispectrum with the scale-dependent bias known for the power spectrum results in an incorrect prediction. As the importance of primordial non-Gaussianity relative to the non-linear gravity evolution and galaxy bias increases toward higher redshifts, galaxy surveys probing a high-redshift universe are particularly useful for probing the primordial non-Gaussianity.
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measuring primordial non gaussianity in the cosmic microwave background
The Astrophysical Journal, 2005Co-Authors: Eiichiro Komatsu, David N Spergel, Benjamin D WandeltAbstract:We derive a fast way for measuring primordial non-Gaussianity in a nearly full-sky map of the cosmic microwave background. We find a cubic combination of sky maps combining Bispectrum configurations to capture a quadratic term in primordial fluctuations. Our method takes only N3/2 operations rather than N5/2, as taken by the Bispectrum analysis (1000 times faster for l = 512), retaining the same sensitivity. A key component is a map of the underlying primordial fluctuations, which can be more sensitive to the primordial non-Gaussianity than a temperature map. We also derive a fast and accurate statistic for measuring non-Gaussian signals from foreground point sources. The statistic is 106 times faster than the full Bispectrum analysis and can be used to estimate contamination from the sources. Our algorithm has been successfully applied to the Wilkinson Microwave Anisotropy Probe sky maps by Komatsu and coworkers.
Wenju Liu - One of the best experts on this subject based on the ideXlab platform.
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noise robust direction of arrival estimation for speech source with weighted Bispectrum spatial correlation matrix
IEEE Journal of Selected Topics in Signal Processing, 2015Co-Authors: Wei Xue, Wenju Liu, Shan LiangAbstract:One big challenge to the robust direction of arrival (DOA) estimation for the speech source is the environmental noise. In practical conditions, the noise can be undirected or emitted from a pointed source. In order to improve the reliability of DOA estimation in various adverse noisy conditions, we propose a novel DOA estimation method in this paper, and what lies in the core in the method is the “Weighted Bispectrum Spatial Correlation Matrix (WBSCM).” The Bispectrum is a kind of higher order statistics (HOS) of a signal, and the WBSCM reflects the spatial correlation of the Bispectrum phase differences (BPD) between different microphones. As the HOS of the Gaussian signal is theoretically zero, by formulating in the Bispectrum domain, the proposed method has an inherent advantage against the Gaussian noise. Moreover, the BPD, which is embedded in the WBSCM, contains the redundant information related to the DOA of the speech source. This redundancy helps to improve the robustness in non-Gaussian noise conditions, especially for the directional interference scenarios. In addition, the WBSCM enables Bispectrum weighting to select the speech units in the Bispectrum, in order to highlight the effect of these units in the DOA estimation. Similar to the signal-to-noise estimation, a decision-directed method is proposed to compute the Bispectrum weights. Finally, a new DOA estimator is proposed, which is based on the eigenvalue analysis of the WBSCM. We conduct experiments under various kinds of noisy environments, and the experimental results demonstrate the effectiveness of proposed method.
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doa estimation of speech source in noisy environments with weighted spatial Bispectrum correlation matrix
International Conference on Acoustics Speech and Signal Processing, 2014Co-Authors: Wei Xue, Shan Liang, Wenju LiuAbstract:Although the high order statistics (HOS) has promising property against the Gaussian noise, there still lack effective ways to apply the HOS to DOA estimation of the speech source. In this paper, we propose a novel HOS based DOA estimation method for speech source in strong noise conditions. A “weighted spatial Bispectrum correlation matrix (WSBCM)” is formulated, which contains the spatial correlation information of Bispectrum phase differences. We then propose a new DOA estimator based on the eigenvalue analysis of the WSBCM. Besides the theoretical advantage of the Bispectrum against Gaussian noises, the redundant information in the Bispectrum domain is also exploited to make the WSBCM noise robust. The WSBCM enables Bispectrum weighting to select the speech units in the Bispectrum, which further helps to improve the performance. Experimental results demonstrate that the proposed method outperforms existing algorithms in different kinds of noisy environments.
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weighted spatial Bispectrum correlation matrix for doa estimation in the presence of interferences
Conference of the International Speech Communication Association, 2014Co-Authors: Wei Xue, Shan Liang, Wenju LiuAbstract:Besides the undirected environmental noise, the surrounding interference also brings great challenges to the robust DOA estimation of the speech source. As conventional DOA estimation methods always assume an undirected noise model, they usually cannot perform reliably when the strong inference exists. In this paper, we propose a novel interference robust DOA estimation method, which is based on the “weighted spatial Bispectrum correlation matrix (WSBCM)”. The WSBCM contains the spatial correlation information of Bispectrum phase difference (BPD), and a new DOA estimator is further derived based on the eigenvalue analysis of the WSBCM. By formulating with WSBCM, the proposed method benefits from the redundant DOA-related information provided by the BPD. In addition, the WSBCM enables Bispectrum weighting to highlight the pure speech units in the Bispectrum, which further helps to improve the performance. In order to compute the Bispectrum weights, a decision-directed approach is derived. The effectiveness of the proposed method is demonstrated by experiments conducted under various kinds of interference-existing scenarios.