Constraining scalar dark matter with Big Bang nucleosynthesis and atomic
  spectroscopy
  Scalar dark matter can interact with Standard Model (SM) particles, altering
the fundamental constants of Nature in the process. Changes in the fundamental
constants during and prior to Big Bang nucleosynthesis (BBN) produce changes in
the primordial abundances of the light elements. By comparing the measured and
calculated (within the SM) primordial abundance of $^{4}$He, which is
predominantly determined by the ratio of the neutron-proton mass difference to
freeze-out temperature at the time of weak interaction freeze-out prior to BBN,
we are able to derive stringent constraints on the mass of a scalar dark matter
particle $\phi$ together with its interactions with the photon, light quarks
and massive vector bosons via quadratic couplings in $\phi$, as well as its
interactions with massive vector bosons via linear couplings in $\phi$. We also
derive a stringent constraint on the quadratic interaction of $\phi$ with the
photon from recent atomic dysprosium spectroscopy measurements.
