Browsing by Author "Coelho, Isabel"
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- Extinction or coexistence in periodic Kolmogorov systems of competitive typePublication . Coelho, Isabel; Rebelo, Carlota; Sovrano, ElisaWe study a periodic Kolmogorov system describing two species nonlinear competition. We discuss coexistence and extinction of one or both species, and describe the domain of attraction of nontrivial periodic solutions in the axes, under conditions that generalise Gopalsamy conditions. Finally, we apply our results to a model of microbial growth and to a model of phyto-plankton competition under the e_ect of toxins.
- Positive Solutions of the Dirichlet Problem for the One-dimensional Minkowski-Curvature EquationPublication . Coelho, Isabel; Corsato, Chiara; Obersnel, Franco; Omari, PierpaoloWe discuss existence and multiplicity of positive solutions of the Dirichlet problem for the quasilinear ordinary differential equation-(u' / root 1 - u'(2))' = f(t, u). Depending on the behaviour of f = f(t, s) near s = 0, we prove the existence of either one, or two, or three, or infinitely many positive solutions. In general, the positivity of f is not required. All results are obtained by reduction to an equivalent non-singular problem to which variational or topological methods apply in a classical fashion.