The usual inflationary scenario predicts a Gaussian random primordial density fluctuation, different Fourier modes of which do not correlate with each other. In this paper we propose a correlation between these different modes. A simple case is that these different Fourier modes correlate with each other following a Gaussian function. For such a primordial density fluctuation we calculate the CMB angular power spectrum and find that its amplitude decreases but the decrease is different for different $l$. This feature can be used to constrain the the correlation strength from the real data.
We revisit cosmic microwave background (CMB) constraints on primordial black hole dark matter. Spectral distortion limits from COBE/FIRAS do not impose a relevant constraint. Planck CMB anisotropy power spectra imply that primordial black holes with $m_{BH}\gtrsim 5~M_{\odot}$ are disfavored. However, this is susceptible to sizeable uncertainties due to the treatment of the black hole accretion process. These constraints are weaker than those quoted in earlier literature for the same observables.
Scattering of cosmic microwave background (CMB) radiation in galaxy clusters induces polarization signals determined by the quadrupole anisotropy in the photon distribution at the location of clusters. This "remote quadrupole" derived from the measurements of the induced polarization in galaxy clusters provides an opportunity of reconstruction of local CMB temperature anisotropies. In this {\em Letter} we develop an algorithm of the reconstruction through the estimation of the underlying primordial gravitational potential, which is the origin of the CMB temperature and polarization fluctuation…
Next-generation CMB satellite concepts (LiteBIRD, CORE, PIXIE, PICO) are being proposed to detect the primordial CMB B-mode polarization at large angular scales in the sky for tensor-to-scalar ratio values of ${r \lesssim 10^{-3}}$. Yet undetected, primordial CMB B-modes will provide the unique signature of the primordial gravitational waves of quantum origin predicted by inflation. We present recent forecasts on the detection of the primordial CMB B-modes in the presence of astrophysical foregrounds and gravitational lensing effects, in the context of the proposed CMB space mission CORE. We a…
We demonstrate how to obtain optimal constraints on a primordial gravitational wave component in lensed Cosmic Microwave Background (CMB) data under ideal conditions. We first derive an estimator of the tensor-to-scalar ratio, $r$, by using an error-controlled close approximation to the exact posterior, under the assumption of Gaussian primordial CMB and lensing deflection potential. This combines fast internal iterative lensing reconstruction with optimal recovery of the unlensed CMB. We evaluate its performance on simulated low-noise polarization data targeted at the recombination peak. We c…
Unbiased Primordial Gravitational Wave Inference from the CMB with SMICA
Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；CNRS-UCB International Research Laboratory, Centre Pierre Binétruy（法国国家科学研究中心-巴黎第十一大学国际联合实验室，皮埃尔·比内屈中心）
We consider the impact of a stochastic background of primordial magnetic fields with non-vanishing helicity on CMB anisotropies in temperature and polarization. We compute the exact expressions for the scalar, vector and tensor part of the energy-momentum tensor including the helical contribution, by assuming a power-law dependence for the spectra and a comoving cutoff which mimics the damping due to viscosity. We also compute the parity-odd correlator between the helical and non-helical contribution which generate the TB and EB cross-correlation in the CMB pattern. We finally show the impact …
Different inflationary models predict oscillatory features in the primordial power spectrum. These can leave an imprint on both the cosmic microwave background (CMB) and the large-scale structure (LSS) of our Universe, that can be searched for with current data. Inspired by the axion-monodromy model of inflation, we search for primordial oscillations that are logarithmic in wavenumber, using both CMB data from the Planck satellite and LSS data from the WiggleZ galaxy survey. We find that, within our search range for the new oscillation parameters (amplitude, frequency and phase), both CMB-only…
Multi-field inflation models and non-Bunch-Davies vacuum initial conditions both predict sizeable non-Gaussian primordial perturbations and anisotropic $μ$-type spectral distortions of the cosmic microwave background (CMB) blackbody. While CMB anisotropies allow us to probe non-Gaussianity at wavenumbers $k\simeq 0.05\,{\rm Mpc^{-1}}$, $μ$-distortion anisotropies are related to non-Gaussianity of primordial perturbation modes with much larger wavenumbers, $k\simeq 740\,{\rm Mpc^{-1}}$. Through cross-correlations between CMB and $μ$-distortion anisotropies, one can therefore shed light on the a…
CMB photons travel from the last scattering surface, when the primary CMB has been generated, along the surface of the light cone to us. During their travel, they are affected by many secondary effects such as the integrated Sachs-Wolfe effect and CMB lensing. These CMB secondary effects modify the CMB primary power spectrum adding degeneracies and decreasing the sensibility to primordial parameters. The possibility to reconstruct the primary CMB anisotropies will allow us to have a more direct observable to test the physics of the early universe. We propose to study the imprint of features in…
We present forecasts on the primordial non-Gaussianity parameter $f_\text{NL}$ of feature models for the future Cosmic Microwave Background Stage-4 (CMB-S4) experiments. The Fisher matrix of the bispectrum estimator was computed using noise covariances expected for preliminary CMB-S4 specifications including ones for the Simons Observatory. We introduce a novel method that improves the computation by orthonormalising the covariance matrix. The most sensitive CMB-S4 experiment with 1' beam and 1$μK$-arcmin noise would yield a factor of 1.7-2.2 times more stringent constraints compared to Planck…
Searching for the signal of primordial gravitational waves in the B-modes (BB) power spectrum is one of the key scientific aims of the cosmic microwave background (CMB) polarization experiments. However, this could be easily contaminated by several foreground issues, such as the thermal dust emission. In this paper we study another mechanism, the cosmic birefringence, which can be introduced by a CPT-violating interaction between CMB photons and an external scalar field. Such kind of interaction could give rise to the rotation of the linear polarization state of CMB photons, and consequently i…
We forecast how current ({\planck}) and future ({\prism}) cosmic microwave background (CMB) experiments constrain the adiabatic mode and its admixtures with primordial isocurvature modes, using measurements of the reconstructed CMB lensing potential and lensing-induced CMB B-mode polarization anisotropies in combination with the CMB temperature and E-mode polarization anisotropies. We first study the characteristic features of the CMB temperature, polarization and lensing spectra for adiabatic and isocurvature modes. We then consider how lensing-induced B-mode polarization and lensing potentia…
We study the signatures of local type primordial non-Gaussianity, parametrized by $\fnl$, of scalar perturbations in CMB polarization using the probability distribution functions, Minkowski Functionals and Betti numbers. We show that the lowest order non-Gaussian deviation of the PDF of the total polarization intensity is at order $(\fnlσ)^2$. We calculate the non-Gaussian deviations of Minkowski Functionals and Betti numbers from simulated polarization maps. We find that $E$ mode polarization provides independent and equally strong constraint on $\fnl$ as temperature fluctuations. The non-Gau…
We present new limits on the amplitude of potential primordial magnetic fields (PMFs) using temperature and polarization measurements of the cosmic microwave background (CMB) from Planck, BICEP2/Keck Array, POLARBEAR, and SPTpol. We reduce twofold the 95% CL upper limit on the CMB anisotropy power due to a nearly-scale-invariant PMF, with an allowed B-mode power at $\ell=1500$ of $D_{\ell=1500}^{BB} < 0.071 μK^2$ for Planck versus $D_{\ell=1500}^{BB} < 0.034 μK^2$ for the combined dataset. We also forecast the expected limits from soon-to-deploy CMB experiments (like SPT-3G, Adv. ACTpol, or th…
We consider an inhomogeneous model and independently an anisotropic model of primordial power spectrum in order to describe the observed hemispherical anisotropy in Cosmic Microwave Background Radiation. This anisotropy can be parametrized in terms of the dipole modulation model of the temperature field. Both the models lead to correlations between spherical harmonic coefficients corresponding to multipoles, l and l \pm 1. We obtain the model parameters by making a fit to TT correlations in CMBR data. Using these parameters we predict the signature of our models for correlations among differen…
The cosmic microwave background (CMB) spectrum provides tight constraints on the thermal history of the universe up to $z \sim 2\times 10^6$. At higher redshifts thermalization processes become very efficient so that even large energy releases do not leave visible imprints in the CMB spectrum. In this paper we show that the consistency between the accurate determinations of the specific entropy at primordial nucleosynthesis and at the electron-photon decoupling implies that no more than 7.8% of the present day CMB energy density could have been released in the post-nucleosynthesis era. As poin…
Anisotropies in distortions to the frequency spectrum of the cosmic microwave background (CMB) can be created through spatially varying heating processes in the early Universe. For instance, the dissipation of small-scale acoustic modes does create distortion anisotropies, in particular for non-Gaussian primordial perturbations. In this work, we derive approximations that allow describing the associated distortion field. We provide a systematic formulation of the problem using Fourier-space window functions, clarifying and generalizing previous approximations. Our expressions highlight the fac…
We discuss whether an unaccounted contribution to the Cosmic Microwave Background polarization $B$-mode by primordial magnetic fields (PMFs) can bias future constraints on inflationary gravitational waves. As a case-study, we consider a scale-invariant PMF spectrum with amplitude of $\approx{1}\,{\mathrm{nG}}$ on $1\,\mathrm{Mpc}$ scales, compatible with current cosmological bounds. We find a degeneracy in the $B$-mode spectra between PMFs and inflationary gravitational waves. If PMFs of this amplitude are not accounted for, future CMB experiments could claim a false detection of a tensor-to-s…
Galaxy-CMB and galaxy-galaxy lensing on large scales: sensitivity to primordial non-Gaussianity
一个令人信服的检测原始非高斯的局部形式的双谱，其幅度是由fNL参数，提供了一个强大的测试膨胀。本文计算了由fNL引起的弱透镜-星系-星系透镜和星系-宇宙微波背景（CMB）互相关的两点互相关统计量的修正。推导并计算了包含宇宙方差项的星系-星系透镜效应协方差矩阵。我们专注于大尺度（l<100）的剪切测量的形状噪声变得无关紧要，宇宙方差占主导地位的误差预算。对于适度的非高斯性，fNL=+/-50，在R~300 Mpc的尺度上可以看到星系-星系透镜信号在10%水平上的变化，并且随着\propto R ^2的增大而迅速增长。我们还看到了在~150 Mpc的物质功率谱中重子声学振荡特征的清晰特征，这可以通过下一代透镜实验来测量。此外，我们可以探测本地形式的原始非高斯性的星系CMB透镜信号通过关联的高z星系的CMB重建的透镜势。例如，对于fNL=+/-50，我们发现星系-CMB透镜互功率谱在l~40处被修改了~10%，在l~10处被修改了2倍，对于z=2的星系群，偏差为2。对于z值较大的高度偏置的星系群，这种影响更大;因此，与CMB交叉相关的高z星系巡天提供了另一种原始非高斯性的探测。
The Cosmic Microwave Background (CMB) radiation B mode polarization signal contains the unique signature of primordial metric perturbations produced during the inflation. The separation of the weak CMB B-mode signal from strong foreground contamination in observed maps is a complex task, and proposed new generation low noise satellite missions compete with the weak signal level of this gravitational background. In this article, for the first time, we employ a foreground model-independent internal linear combination (ILC) method to reconstruct the CMB B mode signal using simulated observations …
Next-generation galaxy surveys will be able to measure perturbations on scales beyond the equality scale. On these ultra-large scales, primordial non-Gaussianity leaves signatures that can shed light on the mechanism by which perturbations in the early Universe are generated. We perform a forecast analysis for constraining local type non-Gaussianity and its two-parameter extension with a simple scale-dependence. We combine different clustering measurements from future galaxy surveys -- a 21cm intensity mapping survey and two photometric galaxy surveys -- via the multi-tracer approach. Furtherm…
The search for primordial gravitational waves in the Cosmic Microwave Background (CMB) will soon be limited by our ability to remove the lensing contamination to $B$-mode polarization. The often-used quadratic estimator for lensing is known to be suboptimal for surveys that are currently operating and will continue to become less and less efficient as instrumental noise decreases. While foregrounds can in principle be mitigated by observing in more frequency bands, progress in delensing hinges entirely on algorithmic advances. We demonstrate here a new inference method that solves this problem…
Inspired by the study of mild transient reductions in the speed of sound of the adiabatic mode during inflation, we search for a primordial localized feature imprinted in cosmic microwave background and large-scale structure formation observables. We find some common oscillatory patterns both in the Planck CMB temperature-temperature power spectrum and the WiggleZ galaxy spectrum. By performing independent searches with these two data sets, we find a coincidence in the most significant mode previously found by Achúcarro et al. 2013 by using only Planck data. Furthermore, the joint data analysi…
We use the binned bispectrum estimator to determine the bispectra of the dust, free-free, synchrotron, and AME galactic foregrounds using maps produced by the Commander component separation method from Planck 2015 data. We find that all of these peak in the squeezed configuration, allowing for potential confusion with in particular the local primordial shape. Applying an additional functionality implemented in the binned bispectrum estimator code, we then use these galactic bispectra as templates in an $f_\mathrm{NL}$ analysis of other maps. After testing and validating the method and code wit…
We study the degree to which the cosmic microwave background (CMB) can be used to constrain primordial non-Gaussianity involving one tensor and two scalar fluctuations, focusing on the correlation of one polarization $B$ mode with two temperature modes. In the simplest models of inflation, the tensor-scalar-scalar primordial bispectrum is non-vanishing and is of the same order in slow-roll parameters as the scalar-scalar-scalar bispectrum. We calculate the $\langle BTT\rangle$ correlation arising from a primordial tensor-scalar-scalar bispectrum, and show that constraints from an experiment li…
In this $\textit{Letter}$, we search for the signal of the primordial black holes (PBHs) by correlating the $γ$-ray emissions in the MeV energy band produced by the Hawking evaporation and the lensing effect of the cosmic microwave background (CMB). We use the conservative case of the astrophysical model as much as possible in the calculations, since the potential astrophysical origins dominate the observed emission in the MeV energy band. By carefully discussing the appropriate energy bands corresponding to different PBHs masses, it is worth expecting a tight constraint on the fraction of the…
The origin of large-scale magnetic fields in the Universe is still unknown. Observations suggest the presence of nGauss primordial magnetic fields at the last scattering surface. The presence of such fields will affect the evolution of cosmological perturbations and potentially leave an imprint on the CMB anisotropies. Here, we show that the B-mode power spectrum carries a clear signature of the stochastic primordial magnetic fields up to a few nGauss. Specifically, the presence of nGauss primordial magnetic fields changes the BB power spectrum at all scales. At large scales, the tensor modes …
We use Minkowski Functionals to explore the presence of non-Gaussian signatures in simulated cosmic microwave background (CMB) maps. Precisely, we analyse the non-Gaussianities produced from the angular power spectra emerging from a class of inflationary models with a primordial step-like potential. This class of models are able to perform the best-fit of the low-$\ell$ `features', revealed first in the CMB angular power spectrum by the WMAP experiment and then confirmed by the Planck collaboration maps. Indeed, such models generate oscillatory features in the primordial power spectrum of scal…
The primordial B-modes component of the cosmic microwave background (CMB) polarization is a promising experimental dataset to probe the inflationary paradigm. B-modes are indeed a direct consequence of the presence of gravitational waves in the early universe. However, several secondary effects in the low redshift universe will produce \textit{non-primordial} B-modes. In particular, the gravitational interactions of CMB photons with large-scale structures will distort the primordial E-modes, adding a lensing B-mode component to the primordial signal. Removing the lensing component ("delensing"…
Blind mitigation of foreground-induced biases on primordial $B$ modes for ground-based CMB experiments
International School for Advanced Studies (SISSA)（国际高等研究院）；Università di Trento（特伦托大学）；INFN Sezione di Trieste（的里雅斯特INFN分部）；IFPU（前沿物理研究所）；Dipartimento di Fisica, Università di Roma “Tor Vergata”（罗马“托维加塔”大学物理系）；INFN Sezione di Roma2（罗马第二INFN分部）
We present a minimally parametric, model independent reconstruction of the shape of the primordial power spectrum. Our smoothing spline technique is well-suited to search for smooth features such as deviations from scale invariance, and deviations from a power law such as running of the spectral index or small-scale power suppression. We use a comprehensive set of the state-of the art cosmological data: {\it Planck} observations of the temperature and polarisation anisotropies of the cosmic microwave background, WiggleZ and Sloan Digital Sky Survey Data Release 7 galaxy power spectra and the C…
The Cosmic Microwave Background (CMB) radiation lensing is a promising tool to study the physics of early universe. In this work we probe the imprints of deviations from isotropy and scale invariance of primordial curvature perturbation power spectrum on CMB lensing potential and convergence. Specifically, we consider a scale-dependent hemispherical asymmetry in primordial power spectrum. We show that the CMB lensing potential and convergence and also the cross-correlation of the CMB lensing and late time galaxy convergence can probe the amplitude and the scale dependence of the dipole modulat…
The scattering of cosmic microwave background (CMB) radiation in galaxy clusters induces polarization signals according to the quadrupole anisotropy in the photon distribution at the cluster location. This `remote quadrupole' derived from the measurements of the induced polarization provides an opportunity for reconstructing primordial fluctuations on large scales. We discuss that comparing the local CMB quadrupoles predicted by these reconstructed primordial fluctuations and the direct measurements done by CMB satellites may enable us to test the dark energy beyond cosmic variance limits.
Constraining Primordial Black Holes via p-wave annihilation in light of CMB Spectral Distortion and 21-cm global signal
National Institute of Technology, Meghalaya（梅加拉亚国立技术学院）；Hangzhou Institute for Advanced Study, UCAS（杭州高等研究院）；University of Chinese Academy of Sciences（中国科学院大学）
