Abstract

Abstract A properly scaled critical Galton–Watson process converges to a continuous state critical branching process ξ ⁢ ( ⋅ ) \xi(\,{\cdot}\,) as the number of initial individuals tends to infinity. We extend this classical result by allowing for overlapping generations and considering a wide class of population counts. The main result of the paper establishes a convergence of the finite-dimensional distributions for a scaled vector of multiple population counts. The set of the limiting distributions is conveniently represented in terms of integrals ( ∫ 0 y ξ ⁢ ( y - u ) ⁢ d u γ \int_{0}^{y}\xi(y-u)\,du^{\gamma} , y ≥ 0 y\geq 0 ) with a pertinent γ ≥ 0 \gamma\geq 0 .

Highlights

  • One of the basic stochastic population models of a self-reproducing system is built upon the following two assumptions: (A) different individuals live independently from each other according to the same individual life law described in (B); (B) an individual dies at age one and at the moment of death gives birth to a random number N of offspring

  • We study {Z(t), t ≥ 0}, a Galton–Watson process with overlapping generations, or GWOprocess for short, where Z(t) is the number of individuals alive at time t in a reproduction system satisfying the following two assumptions: (A*) different individuals live independently from each other according to the same individual life law described in (B*); (B*) an individual lives L units of time and gives N births at random ages τ1, . . . , τN, satisfying

  • The aim of this chapter is to establish an fdd-convergence result for the vector (X1( ⋅ ), . . . , Xq( ⋅ )) composed of the population counts corresponding to different individual scores χ1( ⋅ ), . . . , χq( ⋅ ), which may depend on each other

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Summary

Introduction

One of the basic stochastic population models of a self-reproducing system is built upon the following two assumptions: (A) different individuals live independently from each other according to the same individual life law described in (B); (B) an individual dies at age one and at the moment of death gives birth to a random number N of offspring. We study {Z(t), t ≥ 0}, a Galton–Watson process with overlapping generations, or GWOprocess for short, where Z(t) is the number of individuals alive at time t in a reproduction system satisfying the following two assumptions: (A*) different individuals live independently from each other according to the same individual life law described in (B*); (B*) an individual lives L units of time and gives N births at random ages τ1, . The following three statements are straightforward corollaries of Theorems 1, 2, and 3 respectively In these theorems, it is always assumed that the GWO-process stems from a large number Z0 = n of progenitors born at time zero. (5) In different formulas, the symbols C, C1, C2, c, c1, c2 represent different positive constants

Population Counts
The Litter Sizes
Associated Renewal Process
Expected Population Counts
Branching Renewal Equations
Derivation of the Branching Renewal Equation
Laplace Transform of the Reproduction Law
Basic Convergence Result
Continuous State Critical Branching Process
Riccati Integral Equations
Limit Theorems
Proof of Theorem 1
Proof of Theorem 2
Proof of Theorem 3
Proof of Theorem 4
Full Text
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