Dynamical Dark Matter and the Positron Excess in Light of AMS
  The AMS-02 experiment has recently released data which confirms a rise in the
cosmic-ray positron fraction as a function of energy up to approximately 350
GeV. Over the past decade, attempts to interpret this positron excess in terms
of dark-matter decays have become increasingly complex and have led to a number
of general expectations about the decaying dark-matter particles: such
particles cannot undergo simple two-body decays to leptons, for example, and
they must have rather heavy TeV-scale masses. In this paper, by contrast, we
show that Dynamical Dark Matter (DDM) can not only match existing AMS-02 data
on the positron excess, but also accomplish this feat with significantly
lighter dark-matter constituents undergoing simple two-body decays to leptons.
Moreover, we demonstrate that this can be done without running afoul of
numerous other competing constraints from FERMI and Planck on decaying dark
matter. Finally, we demonstrate that the Dynamical Dark Matter framework makes
a fairly robust prediction that the positron fraction should level off and then
remain roughly constant out to approximately 1 TeV, without experiencing any
sharp downturns. Indeed, if we interpret the positron excess in terms of
decaying dark matter, we find that the existence of a plateau in the positron
fraction at energies less than 1 TeV may be taken as a "smoking gun" of
Dynamical Dark Matter.
