scholarly journals Anomalies in the Cosmic Microwave Background and Their Non-Gaussian Origin in Loop Quantum Cosmology

2021 ◽  
Vol 8 ◽  
Author(s):  
Ivan Agullo ◽  
Dimitrios Kranas ◽  
V. Sreenath
Keyword(s):  
Cosmic Microwave Background ◽  
Quantum Cosmology ◽  
Statistical Significance ◽  
New Physics ◽  
Common Origin ◽  
Loop Quantum Cosmology ◽  
Microwave Background ◽  
Λcdm Model ◽  
Non Gaussian ◽  
Dipolar Modulation

Anomalies in the cosmic microwave background (CMB) refer to features that have been observed, mostly at large angular scales, and which show some tension with the statistical predictions of the standard ΛCDM model. In this work, we focus our attention on power suppression, dipolar modulation, a preference for odd parity, and the tension in the lensing parameter AL. Though the statistical significance of each individual anomaly is inconclusive, collectively they are significant, and could indicate new physics beyond the ΛCDM model. In this article, we present a brief, but pedagogical introduction to CMB anomalies and propose a common origin in the context of loop quantum cosmology.

scholarly journals Cosmic Tango Between the Very Small and the Very Large: Addressing CMB Anomalies Through Loop Quantum Cosmology

2021 ◽  
Vol 8 ◽  
Author(s):  
Abhay Ashtekar ◽  
Brajesh Gupt ◽  
V. Sreenath
Keyword(s):  
Power Spectrum ◽  
Quantum Gravity ◽  
Cosmic Microwave Background ◽  
Quantum Cosmology ◽  
Large Scale ◽  
Loop Quantum Gravity ◽  
Statistical Significance ◽  
Loop Quantum Cosmology ◽  
Microwave Background

While the standard, six-parameter, spatially flat ΛCDM model has been highly successful, certain anomalies in the cosmic microwave background bring out a tension between this model and observations. The statistical significance of any one anomaly is small. However, taken together, the presence of two or more of them imply that according to standard inflationary theories we live in quite an exceptional Universe. We revisit the analysis of the PLANCK collaboration using loop quantum cosmology, where an unforeseen interplay between the ultraviolet and the infrared makes the primordial power spectrum scale dependent at very small k. Consequently, we are led to a somewhat different ΛCDM Universe in which anomalies associated with large scale power suppression and the lensing amplitude are both alleviated. The analysis also leads to new predictions for future observations. This article is addressed both to cosmology and loop quantum gravity communities, and we have attempted to make it self-contained.

scholarly journals Isotropic non-Gaussian gNL-like toy models that reproduce cosmic microwave background anomalies

2019 ◽  
Vol 626 ◽  
pp. A13 ◽  
Author(s):  
F. K. Hansen ◽  
T. Trombetti ◽  
N. Bartolo ◽  
U. Natale ◽  
M. Liguori ◽  
...  
Keyword(s):  
Cosmic Microwave Background ◽  
Large Scale ◽  
Statistical Significance ◽  
Common Mechanism ◽  
Small Scale ◽  
Cold Spot ◽  
Microwave Background ◽  
Significance Level ◽  
Non Gaussian ◽  
Cmb Fluctuations

Context. Based on recent observations of the cosmic microwave background (CMB), claims of statistical anomalies in the properties of the CMB fluctuations have been made. Although the statistical significance of the anomalies remains only at the ∼2−3σ significance level, the fact that there are many different anomalies, several of which support a possible deviation from statistical isotropy, has motivated a search for models that provide a common mechanism to generate them. Aims. The goal of this paper is to investigate whether these anomalies could originate from non-Gaussian cosmological models, and to determine what properties these models should have. Methods. We present a simple isotropic, non-Gaussian class of toy models that can reproduce six of the most extensively studied anomalies. We compare the presence of anomalies found in simulated maps generated from the toy models and from a standard model with Gaussian fluctuations. Results. We show that the following anomalies, as found in the Planck data, commonly occur in the toy model maps: (1) large-scale hemispherical asymmetry (large-scale dipolar modulation), (2) small-scale hemispherical asymmetry (alignment of the spatial distribution of CMB power over all scales ℓ = [2, 1500]), (3) a strongly non-Gaussian hot or cold spot, (4) a low power spectrum amplitude for ℓ <  30, including specifically (5) a low quadrupole and an unusual alignment between the quadrupole and the octopole, and (6) parity asymmetry of the lowest multipoles. We note that this class of toy model resembles models of primordial non-Gaussianity characterised by strongly scale-dependent gNL-like trispectra.

scholarly journals Hybrid loop quantum cosmology and predictions for the cosmic microwave background

2017 ◽  
Vol 96 (10) ◽  
Author(s):  
Laura Castelló Gomar ◽  
Guillermo A. Mena Marugán ◽  
Daniel Martín de Blas ◽  
Javier Olmedo
Keyword(s):  
Cosmic Microwave Background ◽  
Quantum Cosmology ◽  
Loop Quantum Cosmology ◽  
Microwave Background

scholarly journals Cosmic Tangle: Loop Quantum Cosmology and CMB Anomalies

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 186
Author(s):  
Martin Bojowald
Keyword(s):  
Cosmic Microwave Background ◽  
Quantum Cosmology ◽  
Loop Quantum Cosmology ◽  
Microwave Background ◽  
Recent Claim

Loop quantum cosmology is a conflicted field in which exuberant claims of observability coexist with serious objections against the conceptual and physical viability of its current formulations. This contribution presents a non-technical case study of the recent claim that loop quantum cosmology might alleviate anomalies in the observations of the cosmic microwave background.

scholarly journals Room for New Physics in the Rayleigh-Jeans Tail of the Cosmic Microwave Background

2018 ◽  
Vol 121 (3) ◽  
Author(s):  
Maxim Pospelov ◽  
Josef Pradler ◽  
Joshua T. Ruderman ◽  
Alfredo Urbano
Keyword(s):  
Cosmic Microwave Background ◽  
New Physics ◽  
Microwave Background

scholarly journals THE TOPOLOGY OF THE COSMIC MICROWAVE BACKGROUND ANISOTROPY ON THE SCALE ~1°

1996 ◽  
Vol 05 (04) ◽  
pp. 319-362 ◽  
Author(s):  
D.I. NOVIKOV ◽  
H.E. JØRGENSEN
Keyword(s):  
Cosmic Microwave Background ◽  
Random Field ◽  
Gaussian Noise ◽  
Gaussian Random Field ◽  
Cosmological Models ◽  
Topological Method ◽  
Microwave Background ◽  
Cosmic Microwave Background Anisotropy ◽  
Non Gaussian

In this paper we develop the theory of clusterization of peaks in a Gaussian random field. We have obtained new mathematical results from this theory and the theory of percolation and have proposed a topological method of analysis of sky maps based on these results. We have simulated 10°×10° sky maps of the cosmic microwave background anisotropy expected from different cosmological models with 0.5°–1° resolution in order to demonstrate how this method can be used for detection of non-Gaussian noise in the maps and detection of the Doppler-peak in the spectrum of perturbation of ΔT/T.

scholarly journals PHYSICS WITH COSMIC NEUTRINOS, PEV TO ZEV

2003 ◽  
Vol 18 (22) ◽  
pp. 4065-4083 ◽  
Author(s):  
THOMAS J. WEILER
Keyword(s):  
Cross Section ◽  
Particle Physics ◽  
Statistical Significance ◽  
Cosmic Ray ◽  
New Physics ◽  
Microwave Background ◽  
Radiation Fields ◽  
Cosmic Neutrino ◽  
Long Lifetime ◽  
The Impact

Neutrinos offer a particularly promising eye on the extreme Universe. Neutrinos are not attenuated by intervening radiation fields such as the Cosmic Microwave Background, and so they are messengers from the very distant and very young phase of the universe. Also, neutrinos are not deflected by cosmic magnetic fields, and so they should point to their sources. In addition, there are particle physics aspects of neutrinos which can be tested only with cosmic neutrino beams. After a brief overview of highest-energy cosmic ray data, and the present and proposed experiments which will perform neutrino astronomy, we discuss two particle physics aspects of neutrinos. They are possible long-lifetime decay of the neutrino, and a measurement of the neutrino-nucleon cross-section at a CMS energy orders of magnitude beyond what can be achieved with terrestrial accelerators. Measurement of an anomalously large neutrino cross-section would indicate new physics (e.g. low string-scale, extra dimensions, precocious unification), while a smaller than expected cross-section would reveal an aspect of QCD evolution. We then discuss aspects of neutrino-primary models for the extreme-energy (EE) cosmic ray data. Primary neutrinos in extant data are motivated by the directional clustering at EE reported by the AGASA experiment. We discuss the impact of the strongly-interacting neutrino hypothesis on lower-energy physics via dispersion relations, the statistical significance of AGASA directional clustering, and the possible relevance of the Z-burst mechanism for existing EE cosmic ray data.

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