scholarly journals Constraints on features in the inflationary potential from future Euclid data

2020 ◽  
Vol 496 (3) ◽  
pp. 3448-3468
Author(s):  
Ivan Debono ◽  
Dhiraj Kumar Hazra ◽  
Arman Shafieloo ◽  
George F Smoot ◽  
Alexei A Starobinsky
Keyword(s):  
Monte Carlo ◽  
Markov Chain ◽  
Large Scale ◽  
Strong Support ◽  
Power Spectra ◽  
Spectral Amplitude ◽  
Microwave Background ◽  
Slow Roll ◽  
Primordial Power Spectrum ◽  
Small Scales

ABSTRACT With Planck cosmic microwave background observations, we established the spectral amplitude and tilt of the primordial power spectrum. Evidence of a red spectral tilt (ns = 0.96) at 8σ provides strong support for the inflationary mechanism, especially the slow roll of the effective scalar field in its nearly flat potential as the generator of scalar primordial perturbations. With the next generation of large-scale structure surveys, we expect to probe primordial physics beyond the overall shape and amplitude of the main, smooth, and slowly changing part of the inflaton potential. Using the specifications for the upcoming Euclid survey, we investigate to what extent we can constrain the inflation potential beyond its established slow-roll behaviour. We provide robust forecasts with Euclid and Planck mock data from nine fiducial power spectra that contain suppression and wiggles at different cosmological scales, using the Wiggly Whipped Inflation (WWI) framework to generate these features in the primordial spectrum. We include both Euclid cosmic shear and galaxy clustering, with a conservative cut-off for non-linear scales. Using Markov chain Monte Carlo simulations, we obtain an improvement in constraints in the WWI potential, as well an improvement for the background cosmology parameters. We find that apart from improving the constraints on the overall scale of the inflationary potential by 40–50 per cent, we can also identify oscillations in the primordial spectrum that are present within intermediate to small scales ($k\sim 0.01\!-\!0.2\, \mathrm{Mpc^{-1}}$).

scholarly journals Inflation story: slow-roll and beyond

2021 ◽  
Vol 2021 (12) ◽  
pp. 038
Author(s):  
Dhiraj Kumar Hazra ◽  
Daniela Paoletti ◽  
Ivan Debono ◽  
Arman Shafieloo ◽  
George F. Smoot ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Large Scale ◽  
Microwave Background ◽  
Angular Power Spectrum ◽  
Slow Roll ◽  
Primordial Power Spectrum ◽  
Cosmic Microwave Background Temperature ◽  
Scale Temperature ◽  
Temperature Polarization ◽  
Background Temperature

Abstract We present constraints on inflationary dynamics and features in the primordial power spectrum of scalar perturbations using the Cosmic Microwave Background temperature, polarization data from Planck 2018 data release and updated likelihoods. We constrain the slow-roll dynamics using Hilltop Quartic Potential and Starobinsky R + R 2 model in the Einstein frame using the Planck 2018 binned Plik likelihood. Using the Hilltop as base potential, we construct Whipped Inflation potential to introduce suppression in the scalar power spectrum at large angular scales. We notice marginal (68% C.L.) preference of suppression from the large scale temperature angular power spectrum. However, large-scale E-mode likelihood based on high frequency instrument cross spectrum, does not support this suppression and in the combined data the preference towards the suppression becomes negligible. Based on the Hilltop and Starobinsky model, we construct the Wiggly Whipped Inflation potentials to introduce oscillatory features along with the suppression. We use unbinned data from the recently released CamSpec v12.5 likelihood which updates Planck 2018 results. We compare the Bayesian evidences of the feature models with their baseline slow-roll potentials. We find that the complete slow-roll baseline potential is moderately preferred against potentials which generate features. Compared to Planck 2015 PlikHM bin1 likelihood, we find that the significance of sharp features has decreased owing to the updates in the data analysis pipeline. We also compute the bispectra for the best fit candidates obtained from our analysis.

COSMOLOGICAL CONSTRAINT ON BRANS-DICKE THEORY

2011 ◽  
Vol 01 ◽  
pp. 195-202
Author(s):  
XUELEI CHEN ◽  
FENGQUAN WU
Keyword(s):  
Monte Carlo ◽  
Perturbation Theory ◽  
Markov Chain ◽  
Large Scale ◽  
Mcmc Method ◽  
Covariant Formalism ◽  
Microwave Background ◽  
Cosmological Perturbation ◽  
Cosmological Perturbation Theory ◽  
Cosmological Constraint

We develop the covariant formalism of the cosmological perturbation theory for the Brans-Dicke gravity, and use it to calculate the cosmic microwave background (CMB) anisotropy and large scale structure (LSS) power spectrum. We introduce a new parameter ζ which is related to the Brans-Dicke parameter ζ = ln (1/ω + 1), and use the Markov-Chain Monte Carlo (MCMC) method to explore the parameter space. Using the latest CMB data published by WMAP, ACBAR, CBI, Boomerang teams, and the LSS data from the SDSS survey DR4, we find that the the 2σ (95.5%) bound on ζ is about |ζ| > 10-2, or |ω| > 102, the precise limit depends somewhat on the prior used.

scholarly journals Exact joint likelihood of pseudo-Cℓ estimates from correlated Gaussian cosmological fields

2019 ◽  
Vol 491 (3) ◽  
pp. 3165-3181 ◽  
Author(s):  
Robin E Upham ◽  
Lee Whittaker ◽  
Michael L Brown
Keyword(s):  
Quadratic Form ◽  
Power Spectrum ◽  
Quadratic Forms ◽  
Joint Distribution ◽  
Large Scale ◽  
Power Spectra ◽  
Microwave Background ◽  
Cosmological Constraints ◽  
Statistical Precision ◽  
Joint Likelihood

ABSTRACT We present the exact joint likelihood of pseudo-Cℓ power spectrum estimates measured from an arbitrary number of Gaussian cosmological fields. Our method is applicable to both spin-0 fields and spin-2 fields, including a mixture of the two, and is relevant to cosmic microwave background (CMB), weak lensing, and galaxy clustering analyses. We show that Gaussian cosmological fields are mixed by a mask in such a way that retains their Gaussianity and derive exact expressions for the covariance of the cut-sky spherical harmonic coefficients, the pseudo-aℓms, without making any assumptions about the mask geometry. We then show that each auto or cross-pseudo-Cℓ estimator can be written as a quadratic form, and apply the known joint distribution of quadratic forms to obtain the exact joint likelihood of a set of pseudo-Cℓ estimates in the presence of an arbitrary mask. We show that the same formalism can be applied to obtain the exact joint likelihood of quadratic maximum likelihood power spectrum estimates. Considering the polarization of the CMB as an example, we show using simulations that our likelihood recovers the full, exact multivariate distribution of EE, BB, and EB pseudo-Cℓ power spectra. Our method provides a route to robust cosmological constraints from future CMB and large-scale structure surveys in an era of ever-increasing statistical precision.

scholarly journals Reconstructing the Primordial Power Spectrum

2005 ◽  
Vol 216 ◽  
pp. 28-34
Author(s):  
S. L. Bridle ◽  
A. M. Lewis ◽  
J. Weller ◽  
G. Efstathiou
Keyword(s):  
Power Spectrum ◽  
Spectral Index ◽  
Large Scale ◽  
Cosmological Parameters ◽  
Wilkinson Microwave Anisotropy Probe ◽  
Microwave Background ◽  
Primordial Power Spectrum ◽  
Initial Spectrum ◽  
Redshift Survey ◽  
Cosmic Microwave Background Data

We reconstruct the shape of the primordial power spectrum from the latest cosmic microwave background data, including the new results from the Wilkinson Microwave Anisotropy Probe (WMAP), and large scale structure data from the two degree field galaxy redshift survey (2dFGRS). We discuss two parameterizations taking into account the uncertainties in four cosmological parameters. First we parameterize the initial spectrum by a tilt and a running spectral index, finding marginal evidence for a running spectral index only if the first three WMAP multipoles (ℓ = 2, 3, 4) are included in the analysis. Secondly, to investigate further the low CMB large scale power, we modify the conventional power-law spectrum by introducing a scale above which there is no power. We find a preferred position of the cut at kc ∼ 3 × 10--4 Mpc--1 although kc = 0 (no cut) is not ruled out.

scholarly journals Reconstructing the EFT of inflation from cosmological data

2019 ◽  
Vol 7 (4) ◽  
Author(s):  
Amel Durakovic ◽  
Paul Hunt ◽  
Subodh Patil ◽  
Subir Sarkar
Keyword(s):  
Large Scale ◽  
Effective Theory ◽  
De Sitter ◽  
Microwave Background ◽  
Functional Parameters ◽  
Primordial Power Spectrum ◽  
Cosmological Data ◽  
Cent Level ◽  
Best Fit ◽  
Adiabatic Mode

Reconstructions of the primordial power spectrum (PPS) of curvature perturbations from cosmic microwave background anisotropies and large-scale structure data suggest that the usually assumed power-law PPS has localised features (up to \sim 10\%∼10% in amplitude), although of only marginal significance in the framework of \LambdaΛCDM cosmology. On the other hand if the cosmology is taken to be Einstein-de Sitter, larger features in the PPS (up to \sim 20\%∼20% in amplitude) are required to accurately fit the observed acoustic peaks. Within the context of single clock inflation, we show that any given reconstruction of the PPS can be mapped on to functional parameters of the underlying effective theory of the adiabatic mode within a 2nd-order formalism, provided the best fit fractional change of the PPS, \Delta{P}_{R}/{P}_{R}ΔPR/PR is such that (\Delta{P}_{R}/{P}_{R})^3(ΔPR/PR)3 falls within the 1\,\sigma1σ confidence interval of the reconstruction for features induced by variations of either the sound speed c_\mathrm{s}cs or the slow-roll parameter \epsilonϵ. Although there is a degeneracy amongst these functional parameters (and the models that project onto them), we can identify simple representative inflationary models that yield such features in the PPS. Thus we provide a dictionary (more accurately, a thesaurus) to go from observational data, via the reconstructed PPS, to models that reproduce them to per cent level precision.

scholarly journals S–PASS view of polarized Galactic synchrotron at 2.3 GHz as a contaminant to CMB observations

2018 ◽  
Vol 618 ◽  
pp. A166 ◽  
Author(s):  
N. Krachmalnicoff ◽  
E. Carretti ◽  
C. Baccigalupi ◽  
G. Bernardi ◽  
S. Brown ◽  
...  
Keyword(s):  
Power Law ◽  
Spectral Energy Distribution ◽  
Power Spectra ◽  
Low Frequency ◽  
Spectral Amplitude ◽  
Spectral Energy ◽  
Harmonic Space ◽  
Microwave Background ◽  
Angular Power Spectrum ◽  
Sky Survey

We have analyzed the southern sky emission in linear polarization at 2.3 GHz as observed by the S -band Polarization All Sky Survey (S-PASS). Our purpose is to study the properties of the diffuse Galactic polarized synchrotron as a contaminant to B-mode observations of the cosmic microwave background (CMB) polarization. We studied the angular distribution of the S-PASS signal at intermediate and high Galactic latitudes by means of the polarization angular power spectra. The power spectra, computed in the multipole interval 20 ≤ ℓ ≤ 1000, show a decay of the spectral amplitude as a function of multipole for ℓ ≲ 200, typical of the diffuse emission. At smaller angular scales, power spectra are dominated by the radio point source radiation. We find that, at low multipoles, spectra can be approximated by a power law CℓEE,BB ∝ ℓα, with α ≃ −3, and characterized by a B-to-E ratio of about 0.5. We measured the polarized synchrotron spectral energy distribution (SED) in harmonic space, by combining S-PASS power spectra with low frequency WMAP and Planck ones, and by fitting their frequency dependence in six multipole bins, in the range 20 ≤ ℓ ≤ 140. Results show that the recovered SED, in the frequency range 2.3–33 GHz, is compatible with a power law with βs = −3.22 ± 0.08, which appears to be constant over the considered multipole range and in the different Galactic cuts. Combining the S-PASS total polarized intensity maps with those coming from WMAP and Planck we derived a map of the synchrotron spectral index βs at angular resolution of 2° on about 30% of the sky. The recovered βs distribution peaks at the value around −3.2. It exibits an angular power spectrum which can be approximated with a power law Cℓ ∝ ℓγ with γ ≃ −2.6. We also measured a significant spatial correlation between synchrotron and thermal dust signals, as traced by the Planck 353 GHz channel. This correlation reaches about 40% on the larger angular scales, decaying considerably at the degree scales. Finally, we used the S-PASS maps to assess the polarized synchrotron contamination to CMB observations of the B-modes at higher frequencies. We divided the sky in small patches (with fsky ≃ 1%) and find that, at 90 GHz, the minimal contamination, in the cleanest regions of the sky, is at the level of an equivalent tensor-to-scalar ratio rsynch ≃ 10−3. Moreover, by combining S-PASS data with Planck 353 GHz observations, we recover a map of the minimum level of total polarized foreground contamination to B-modes, finding that there is no region of the sky, at any frequency, where this contamination lies below equivalent tenor-to-scalar ratio rFG ≃ 10−3. This result confirms the importance of observing both high and low frequency foregrounds in CMB B-mode measurements.

scholarly journals CONSTRAINTS ON THE SOUND SPEED OF DYNAMICAL DARK ENERGY

2008 ◽  
Vol 17 (08) ◽  
pp. 1229-1243 ◽  
Author(s):  
JUN-QING XIA ◽  
YI-FU CAI ◽  
TAO-TAO QIU ◽  
GONG-BO ZHAO ◽  
XINMIN ZHANG
Keyword(s):  
Monte Carlo ◽  
Markov Chain ◽  
Dark Energy ◽  
Sound Speed ◽  
Global Analysis ◽  
Precision Measurements ◽  
Microwave Background ◽  
Angular Scale ◽  
Type Ia ◽  
Dynamical Dark Energy

In this paper we study in detail the sound speed — [Formula: see text], which is directly related to the classical perturbations — of dynamical dark energy (DE). We consider especially the case with an equation of state crossing the cosmological constant boundary, and show its implications for cosmic microwave background (CMB) anisotropy. With the present observational data on the CMB, the Type Ia supernova (SNIa) and galaxy clustering, we perform a global analysis to constrain the sound speed of DE, using the Markov chain Monte Carlo method. We find that the sound speed of DE is weakly constrained by current observations, and thus futuristic precision measurements of the CMB on a very large angular scale (low multipoles) are necessary.

scholarly journals White Hole Cosmology - One Best Alternative for Standard Cosmology

2021 ◽  
Author(s):  
U V Satya Seshavatharam ◽  
S Lakshminarayana
Keyword(s):  
Large Scale ◽  
Positive Curvature ◽  
Power Spectra ◽  
Closed Universe ◽  
Theory Of Relativity ◽  
Microwave Background ◽  
White Hole ◽  
Standard Cosmology ◽  
Definition Of ◽  
Large Scale Universe

By modifying the basic definition of cosmic red shift, considering ‘speed of light’ as an absolute cosmic expansion rate and adopting ‘Planck mass’ as the basic seed of the observed large scale universe, it is certainly possible to review and revise the basic picture of ‘standard cosmology’ and in near future, a perfect model of ‘white hole cosmology’ can be developed. In this context we have developed five assumptions. First three assumptions are based on ‘time reversed’ black holes and seem to be well connected with General theory of relativity as well as Quantum mechanics. 4th and 5th assumptions are helpful in understanding current galactic dark matter and flat rotation speeds. It may be noted that, considering our first three assumptions and considering the Planck Legacy 2018 data’s enhanced lensing amplitude in cosmic microwave background power spectra - conceptually, a closed universe having a positive curvature seems to be a best fit for the observed universe. With reference to our recent publication [26], for clarity on the subject, in this short communication, we make an attempt to review and explain our proposed assumptions at fundamental level. Our aim is to see that, professional and non-professional cosmologists must understand the basics of workable quantum cosmology.

scholarly journals Multi-rate Poisson Tree Processes for single-locus species delimitation under Maximum Likelihood and Markov Chain Monte Carlo

2016 ◽  
Author(s):  
P. Kapli ◽  
S. Lutteropp ◽  
J. Zhang ◽  
K. Kobert ◽  
P. Pavlidis ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Markov Chain ◽  
Markov Chain Monte Carlo ◽  
Species Delimitation ◽  
Large Scale ◽  
Dynamic Programming Algorithm ◽  
Large Datasets ◽  
Programming Algorithm ◽  
Link Type ◽  
Similarity Threshold

ABSTRACTMotivationIn recent years, molecular species delimitation has become a routine approach for quantifying and classifying biodiversity. Barcoding methods are of particular importance in large-scale surveys as they promote fast species discovery and biodiversity estimates. Among those, distance-based methods are the most common choice as they scale well with large datasets; however, they are sensitive to similarity threshold parameters and they ignore evolutionary relationships. The recently introduced “Poisson Tree Processes” (PTP) method is a phylogeny-aware approach that does not rely on such thresholds. Yet, two weaknesses of PTP impact its accuracy and practicality when applied to large datasets; it does not account for divergent intraspecific variation and is slow for a large number of sequences.ResultsWe introduce the multi-rate PTP (mPTP), an improved method that alleviates the theoretical and technical shortcomings of PTP. It incorporates different levels of intraspecific genetic diversity deriving from differences in either the evolutionary history or sampling of each species. Results on empirical data suggest that mPTP is superior to PTP and popular distance-based methods as it, consistently, yields more accurate delimitations with respect to the taxonomy (i.e., identifies more taxonomic species, infers species numbers closer to the taxonomy). Moreover, mPTP does not require any similarity threshold as input. The novel dynamic programming algorithm attains a speedup of at least five orders of magnitude compared to PTP, allowing it to delimit species in large (meta-) barcoding data. In addition, Markov Chain Monte Carlo sampling provides a comprehensive evaluation of the inferred delimitation in just a few seconds for millions of steps, independently of tree size.AvailabilitymPTP is implemented in C and is available for download at http://github.com/Pas-Kapli/mptp under the GNU Affero 3 license. A web-service is available at http://[email protected], [email protected], [email protected]

Sign in / Sign up

Export Citation Format

Share Document