Cross Correlation of Cosmic Fields: A Powerful Statistical Tool for Astrophysics, Cosmology, and Fundamental Physics

A special issue of Universe (ISSN 2218-1997). This special issue belongs to the section "Universe Letters".

Deadline for manuscript submissions: closed (20 May 2022) | Viewed by 3317

Special Issue Editors

SISSA—Scuola Internazionale Superiore di Studi Avanzati, 34136 Trieste, Italy
Interests: galaxy formation; cosmology; gravitational waves; dark matter
SISSA—Scuola Internazionale Superiore di Studi Avanzati, Trieste, Italy
Interests: cosmology; fundamental physics; dark energy; astrostatistics

Special Issue Information

Dear Colleagues,

Over the past few decades, a wide set of cosmological observations have allowed us to greatly enhance our understanding of the basic properties and evolutionary history of the Universe, firmly establishing the concordance LCDM model. Nevertheless, such a framework has raised some puzzling and still unresolved issues, such as the nature and dynamics of dark matter and dark energy, possible modifications to Einstein’s theory of gravity on large scales, and the existence and characterization of primordial gravitational waves as an ultimate probe of inflation. In these respects, global observational efforts from ground and space are ongoing to: (i) provide a detailed 3D mapping of the large-scale structure of the Universe, as signposted by galaxies, galaxy clusters (e.g., via the Sunyaev–Zeldovich effect), gravitational lenses, 21 cm sources, gravitational waves, multimessenger emissions, and astrophysical backgrounds over the electromagnetic spectrum (e.g., infrared, optical, X rays and gamma); and (ii) attain unprecedented precision measurements of cosmic microwave background (CMB) observables, such as detailed CMB spectral features, CMB lensing, the optical depth for electron scattering (related to cosmic reionization), and especially the curl B-mode polarization signal. The cross-correlation of such datasets has been recently established as a powerful statistical tool to investigate open issues from a new perspective, possibly easing tomographic analysis in redshift slices and relieving the killer impact of diverse systematics. At the forefront of current research, such cross-correlations are being measured with increasing accuracy and will undoubtedly constitute the primary targets of forthcoming cosmological studies. 

This Special Issue of Universe solicits papers regarding cross-correlations of cosmic fields, with focus both on their statistical foundations and on their exploitation for science in astrophysics, cosmology, and fundamental physics.

Only short letters and communications (about 5–10 pages) will be considered for publication in this Special Issue.

Dr. Andrea LAPI
Prof. Dr. Carlo BACCIGALUPI
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Universe is an international peer-reviewed open access monthly journal published by MDPI.

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Keywords

  • Cosmology 
  • Astrophysics 
  • Astrostatistics 
  • Fundamental physics 
  • Cross-correlation 
  • Cosmic microwave background—CMB 
  • Large-scale structure of the universe 
  • Dark matter 
  • Dark energy 
  • Modified gravity 
  • Gravitational waves 
  • Galaxies 
  • Galaxy clusters 
  • 21 cm emission 
  • Multimessenger sources 
  • Gravitational lensing 
  • Cosmic reionization 
  • CMB lensing 
  • CMB polarization 
  • Astrophysical backgrounds

Published Papers (2 papers)

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Research

5 pages, 474 KiB  
Article
The Role of Cross-Correlations in the Multi-Tracer Area
by Alain Blanchard
Universe 2022, 8(9), 479; https://0-doi-org.brum.beds.ac.uk/10.3390/universe8090479 - 13 Sep 2022
Viewed by 1073
Abstract
Mapping the same volume of space with different tracers allows us to obtain information through estimated quantities exploiting the multi-tracer technique. Indeed, the cross-correlation of different probes provides information that cannot be otherwise obtained. In addition, some estimated quantities are not sensitive to [...] Read more.
Mapping the same volume of space with different tracers allows us to obtain information through estimated quantities exploiting the multi-tracer technique. Indeed, the cross-correlation of different probes provides information that cannot be otherwise obtained. In addition, some estimated quantities are not sensitive to the noise produced by the sampling variance but are only limited by the shot (or Poisson) noise, an attractive perspective. A simple example is the ratio between the (cross)-correlations, measuring the ratio of the bias parameters. Multi-tracer approaches can thereby provide additional information that cannot be extracted from independent volumes. Full article
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18 pages, 2918 KiB  
Article
Detectability of the Cross-Correlation between CMB Lensing and Stochastic GW Background from Compact Object Mergers
by Giulia Capurri, Andrea Lapi and Carlo Baccigalupi
Universe 2022, 8(3), 160; https://0-doi-org.brum.beds.ac.uk/10.3390/universe8030160 - 03 Mar 2022
Cited by 4 | Viewed by 1507
Abstract
The anisotropies of the Stochastic Gravitational-Wave Background (SGWB), produced by merging compact binaries, constitute a possible new probe of the Large-Scale Structure (LSS). However, the significant shot noise contribution caused by the discreteness of the GW sources and the poor angular resolution of [...] Read more.
The anisotropies of the Stochastic Gravitational-Wave Background (SGWB), produced by merging compact binaries, constitute a possible new probe of the Large-Scale Structure (LSS). However, the significant shot noise contribution caused by the discreteness of the GW sources and the poor angular resolution of the instruments hampers the detection of the intrinsic anisotropies induced by the LSS. In this work, we investigate the potential of cross-correlating forthcoming high precision measurements of the SGWB energy density and the Cosmic Microwave Background (CMB) lensing convergence to mitigate the effect of shot noise. Combining a detailed model of stellar and galactic astrophysics with a novel framework to distribute the GW emitters in the sky, we compute the auto- and cross-correlation power spectra for the two cosmic fields, evaluate the shot noise contribution and predict the signal-to-noise ratio. The results of our analysis show that the SGWB energy density correlates significantly with the CMB lensing convergence and that the cross-correlation between these two cosmic fields reduces the impact of instrumental and shot noise. Unfortunately, the S/N is not high enough to detect the intrinsic SGWB anisotropies. Nevertheless, a network composed of both present and future generation GW interferometers, operating for at least 10 yrs, should be able to measure the shot noise contribution. Full article
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