Abstract
We study the ratio of two different continuous-state branching processes with
immigration whose total mass is forced to be constant at a dense set of times.
These lead to the definition of the $Łambda$- asymmetric frequency process
($Łambda$-AFP) as a solution of to an SDE. We prove that this SDE has a unique
strong solution which is a Feller process. We also calculate a large population
limit when the mass tends to infinity and study the fluctuations of the process
around its deterministic limit. Furthermore, we find conditions for the
$Łambda$-AFP to have a moment dual. The dual can be interpreted in terms of
selection, (coordinated) mutation, pairwise branching (efficiency),
coalescence, and a novel component that comes from the asymmetry between the
reproduction mechanisms. A pair of equally distributed continuous-state
branching processes has an associated $Łambda$-AFP whose dual is a
$Łambda$-coalescent. The map that sends each continuous-state branching
process to its associated $Łambda$-coalescent (according to the former
procedure) is a homeomorphism between metric spaces.
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