# Neutrinos and Other Dark Lights: Cosmological Constraints

SpeakerTalk DateTalk Series
Lloyd Knox (UC Davis)25 April 2012Institute of Astronomy Seminars

#### Abstract

A number of lines of evidence, both laboratory and astrophysical,
suggest that there are extra (sterile) neutrino species, or otherwise
extra light and dark degrees of freedom ('dark lights') than exist in
the standard model of particle physics. I will review the physical
origin of cosmological constraints on $N_{\rm eff}$ which is the
energy density in dark lights expressed in units of the contribution
from one active and massless neutrino species. I will also review the
current constraints from light element abundances, high-resolution
cosmic microwave background data, distance vs. redshift measurements,
and galaxy cluster abundances.

#### Presentation

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