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Neutrino puzzle: Anomalies, interactions, and cosmological tensions

Christina D. Kreisch, Francis-Yan Cyr-Racine, and Olivier Doré
Phys. Rev. D 101, 123505 – Published 8 June 2020
Physics logo See synopsis: Neutrinos Might Rescue Hubble

Abstract

New physics in the neutrino sector might be necessary to address anomalies between different neutrino oscillation experiments. Intriguingly, it also offers a possible solution to the discrepant cosmological measurements of H0 and σ8. We show here that delaying the onset of neutrino free streaming until close to the epoch of matter-radiation equality can naturally accommodate a larger value for the Hubble constant H0=72.3±1.4kms1Mpc1 and a lower value of the matter fluctuations σ8=0.786±0.020, while not degrading the fit to the cosmic microwave background (CMB) damping tail. We achieve this by introducing neutrino self-interactions in the presence of a nonvanishing sum of neutrino masses. Without explicitly incorporating additional neutrino species, this strongly interacting neutrino cosmology prefers Neff=4.02±0.29, which has interesting implications for particle model building and neutrino oscillation anomalies. We show that the absence of the neutrino free-streaming phase shift on the CMB can be compensated for by shifting the values of several cosmological parameters, hence providing an important caveat to the detections made in the literature. Due to their impact on the evolution of the gravitational potential at early times, self-interacting neutrinos and their subsequent decoupling leave a rich structure on the matter power spectrum. In particular, we point out the existence of a novel localized feature appearing on scales entering the horizon at the onset of neutrino free streaming. While the interacting neutrino cosmology provides a better global fit to current cosmological data, we find that traditional Bayesian analyses penalize the model as compared to the standard cosmological scenario due to the relatively narrow range of neutrino interaction strengths that is favored by the data. The model we present illustrates desirable cosmological impacts to simultaneously resolve the Hubble constant and matter clustering tensions rather than proposing a viable particle model. Our analysis shows that it is possible to find radically different cosmological models that nonetheless provide excellent fits to the data, hence providing an impetus to thoroughly explore alternate cosmological scenarios.

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  • Received 4 April 2019
  • Accepted 13 April 2020

DOI:https://doi.org/10.1103/PhysRevD.101.123505

© 2020 American Physical Society

Physics Subject Headings (PhySH)

Gravitation, Cosmology & Astrophysics

synopsis

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Neutrinos Might Rescue Hubble

Published 8 June 2020

A proposed interaction between neutrinos might explain a discrepancy in measurements of the Universe’s expansion rate.  

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Authors & Affiliations

Christina D. Kreisch1,*, Francis-Yan Cyr-Racine2,3,†, and Olivier Doré4

  • 1Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08544, USA
  • 2Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
  • 3Department of Physics and Astronomy, University of New Mexico, 1919 Lomas Blvd NE, Albuquerque, New Mexico 87131, USA
  • 4Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA

  • *ckreisch@astro.princeton.edu
  • fycr@unm.edu

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Issue

Vol. 101, Iss. 12 — 15 June 2020

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