A Caltech Library Service

The Neutrino Puzzle: Anomalies, Interactions, and Cosmological Tensions

Kreisch, Christina D. and Cyr-Racine, Francis-Yan and Doré, Olivier (2019) The Neutrino Puzzle: Anomalies, Interactions, and Cosmological Tensions. . (Unpublished)

[img] PDF - Submitted Version
See Usage Policy.


Use this Persistent URL to link to this item:


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 H_0 and σ_8. 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 H_0=72.3±1.4 km/s/Mpc and a lower value of the matter fluctuations σ_8 = 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 non-vanishing sum of neutrino masses. This strongly interacting neutrino cosmology prefers N_(eff) = 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 by shifting the value of other 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. 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.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Kreisch, Christina D.0000-0002-5061-7805
Cyr-Racine, Francis-Yan0000-0002-7939-2988
Doré, Olivier0000-0002-5009-7563
Additional Information:We thank Kris Sigurdson and Roland de Putter for collaboration at early stages of this work. We also thank Jo Dunkley, David Spergel, and Lyman Page for comments on an early version of this manuscript, and Prateek Agrawal and David Pinner for useful conversations. C. D. K. acknowledges the support of the National Science Foundation award number DGE1656466 at Princeton University and of the Minority Undergraduate Research Fellowship at the Jet Propulsion Laboratory. F.-Y. C.-R. acknowledges the support of the National Aeronautical and Space Administration (NASA) ATP grant NNX16AI12G at Harvard University. This work was performed in part at the California Institute of Technology for the Keck Institute for Space Studies, which is funded by the W. M. Keck Foundation. Part of the research described in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. The computations in this paper were run on the Odyssey cluster supported by the FAS Division of Science, Research Computing Group at Harvard University.
Group:Keck Institute for Space Studies
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE-1656466
W. M. Keck FoundationUNSPECIFIED
Classification Code:PACS numbers: 98.80.-k, 14.60.St, 98.70.Vc
Record Number:CaltechAUTHORS:20191001-113947000
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98989
Deposited By: Tony Diaz
Deposited On:01 Oct 2019 19:37
Last Modified:03 Oct 2019 21:46

Repository Staff Only: item control page