A natural extension of age structured Leslie matrix models is to replace age classes with stage classes and to assume that, in each time period, the transition from one stage class to the next is incomplete; that is, diagonal terms appear in the transition matrix. This approach is particularly useful in resource systems where size is more easily measured than age. In this linear setting, the pr...

In this invited talk I show how the reddest and rarest galaxies at high redshift (z ≃ 1.5) can be used to set the stellar evolution clock. I argue that one can confidently compute the collapse redshift of these objects. This yields to a high collapse redshift (z > 6) and therefore their age is well constrained (in all cosmologies) between 3 and 4 Gyr. I also show that this is, indeed, the age d...

In this paper, we present a technique for generating Leslie transition matrices from simple age and sex population counts, using an implementation of "Wood's Method" [Wood, 1997]; these matrices can forecast population by age and sex (the "cohort component" method) using simple matrix multiplication and a starting population. Our approach improves on previous methods for creating Leslie matrice...

This paper derives a Lotka–Volterra equation with a certain symmetry from a coupled nonlinear Leslie matrix model for interacting semelparous species. The global analysis focuses on the special case where the system is composed of two species, one species having two age-classes and the other species having a single age-class. This analysis almost completely describes its global dynamics and pro...

The Beverton-Holt theory of harvesting a multicohort fishery subject to constant recruitment, and the Leslie matrix harvesting model modified to include a nonlinear stock-recruitment relationship, are extended and shown to be related through the ultimate-sustainable-yield problem for an age-structured population. The well-known result that the optimal harvesting policy for the Leslie matrix mod...

In [13] Prüß investigated a very general nonlinear age-structured model consisting of n species. He proved the principle of linearized stability, which means that the asymptotic behavior of stationary solutions of the nonlinear system is determined by the spectrum of the linearized operator. In other words the stability is determined by the roots of a complex valued characteristic function as i...

In this paper we have investigated the spectrophotometric properties of the Asymptotic Giant Branch (AGB) stars and their contribution to the integrated infrared emission in simple stellar populations (SSP). Adopting analytical relations describing the evolution of these stars in the HR diagram and empirical relations for the mass-loss rate and the wind terminal velocity, we were able to model ...

A discrete deterministic model is described for the growth of an age-structured population of yeast, Saccharomyces cerevisiae, incorporating recent information on the asymmetry of cell division and control of the cell cycle in this species. Solutions are obtained for the age structure of the population at equilibrium, and for the equilibrium distribution of relative frequency of cells through t...

Context. Colors are usually not used for constraining stellar populations because they are thought to have the well-known agemetallicity degeneracy. But some recent works show that colors can also be used. The simple stellar population (SSP) synthesis model of Bruzual & Charlot (2003) (BC03) is widely used but there is no analysis for its colors. Aims. We try to find colors which can potentiall...

Whereas expectation of life at birth invariably is greater in more privileged populations, the respective survival patterns at middle age canbe entirely different. Comparisons have been made between South African and other populations, using, as a survival index, the number who are 70 years or more at present, as a percentage of the number who were 50 years or more 19 years earlier (data for th...