New light species and the CMB

By Christopher Brust, D. Kaplan, Matthew T. Walters. 2013

135 citations recorded by the source corpus.

A bstractWe consider the effects of new light species on the Cosmic Microwave Background. In the massless limit, these effects can be parameterized in terms of a single number, the relativistic degrees of freedom. We perform a thorough survey of natural, minimal models containing new light species and numerically calculate the precise contribution of each of these models to this number in the framework of effective field theory. After reviewing the relevant details of early universe thermodynamics, we provide a map between the parameters of any particular theory and the predicted effective number of degrees of freedom. We then use this map to interpret the recent results from the Cosmic Microwave Background survey done by the Planck satellite. Using this data, we present new constraints on the parameter space of several models containing new light species. Future measurements of the Cosmic Microwave Background can be used with this map to further constrain the parameter space of all such models.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/c0c5a8f40a39e4685446692ea17124ae7541df76

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Citations in the corpus

CMB-S4 Science Case, Reference Design, and Project Plan (2019, background): “, axions, sterile neutrinos, dark sectors, and beyond [150, 194, 155, 3].”
Neutrino decoupling beyond the Standard Model: CMB constraints on the Dark Matter mass with a fast and precise Neff evaluation (2018, background): “The agreement between the observations of the Cosmic Microwave Background (CMB) [1, 2], and the primordial element abundances [3, 4] with the SM prediction [5–15] of three relativistic neutrino species represents a success of the Standard Model, and constitues a non-trivial test for some of its exte”
The Simons Observatory: science goals and forecasts (2018, background): “…light particles of spin 1/2, 1 and/or 3/2 that were in thermal equilibrium with the particles of the Standard Model at any point back to the time of reheating (see, e.g., Brust et al. 2013; Chacko et al. 2015; Baumann et al. 2016b); these could be measurable by SO if multiple species are involved.”
A 2.4% DETERMINATION OF THE LOCAL VALUE OF THE HUBBLE CONSTANT (2016, background): “A cosmologically constrained value of ΔNeff can be used to diagnose the nature of the new particle and its decoupling temperature (Brust et al. 2013).”
Non-Abelian dark matter and dark radiation (2015, background): “The dark gluons are observable through their contribution to the radiation density in the universe, an effect which is conventionally expressed in terms of an effective number of neutrino species (see [20] for a recent discussion of bounds on new relativistic degrees of freedom from the CMB).”
Hot axions and the H0 tension (2018, methodology): “[22, 25, 27] for previous estimations and [28] for the calculation of the cross sections in the case of quarks.”
Phases of new physics in the CMB (2015, background): “For example, decays of massive fields are abundant in well-motivated extensions of the Standard Model, but were forbidden in [25] on the basis of being non-minimal.”