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  1. Ángel Blasco, Luis Sanz, Pierre Auger & Rafael Bravo de la Parra (2002). Linear Discrete Population Models with Two Time Scales in Fast Changing Environments II: Non-Autonomous Case. Acta Biotheoretica 50 (1).
    As the result of the complexity inherent in nature, mathematical models employed in ecology are often governed by a large number of variables. For instance, in the study of population dynamics we often deal with models for structured populations in which individuals are classified regarding their age, size, activity or location, and this structuring of the population leads to high dimensional systems. In many instances, the dynamics of the system is controlled by processes whose time scales are very different from (...)
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  2. Luis Sanz & Rafael Bravo de la Parra (2002). The Reliability of Approximate Reduction Techniques in Population Models with Two Time Scales. Acta Biotheoretica 50 (4).
    As a result of the complexity inherent in some natural systems, mathematical models employed in ecology are often governed by a large number of variables. For instance, in the study of population dynamics we often find multiregional models for structured populations in which individuals are classified regarding their age and their spatial location. Dealing with such structured populations leads to high dimensional models. Moreover, in many instances the dynamics of the system is controlled by processes whose time scales are very (...)
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  3. Ángel Blasco, Luis Sanz, Pierre Auger & Rafael Bravo de la Parra (2001). Linear Discrete Population Models with Two Time Scales in Fast Changing Environments I: Autonomous Case. Acta Biotheoretica 49 (4).
    In this work we consider a structured population with groups and subgroups of individuals. The intra-group dynamics is assumed to be fast in comparison with the inter-group dynamics. We study linear discrete models where the slow dynamics is represented by a single matrix and the fast dynamics is described by means of the first k terms of a converging sequence of different matrices. The number k can be interpreted as the ratio between the two time scales.The aim of this work (...)
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  4. Luis Sanz & Rafael Bravo de la Parra (1998). Variables Aggregation in Time Varying Discrete Systems. Acta Biotheoretica 46 (3).
    In this work we extend approximate aggregation methods in time discrete linear models to the case of time varying environments. Approximate aggregation consists in describing some features of the dynamics of a general system involving many coupled variables in terms of the dynamics of a reduced system with a few number of variables. We present a time discrete time varying model in which we distinguish two time scales. By using perturbation methods we transform the system to make the global variables (...)
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  5. Eva Sanchez, Pierre Auger & Rafael Bravo de la Parra (1997). Influence of Individual Aggressiveness on the Dynamics of Competitive Populations. Acta Biotheoretica 45 (3-4).
    Two populations are subdivided into two categories of individuals (hawks and doves). Individuals fight to have access to a resource which is necessary for their survival. Conflicts occur between individuals belonging to the same population and to different populations. We investigate the long term effects of the conflicts on the stability of the community. The modelis a set of ODE's with four variables corresponding to hawk and dove individuals of the two populations. Two time scales are considered. A fast time (...)
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