M. Arias, J. Campos, R. Ortega,
L.A. Sánchez, P.J. Torres, A.J. Ureña
Publications:
2011 2010 2009 2008 2007 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994
2011
2010
R. Halk, P.J. Torres, On periodic solutions of second-order differential equations with attractive-repulsive singularities, Journal of Differential Equations, 248 (2010) 111-126. pdf-file
R. Ortega, A. Rivera, Global bifurcations from the center of mass in the Sitnikov problem, Discrete and Continuous Dynamical Systems B 14 (2010) 719-732 pdf-file
A. Ruiz-Herrera, Coexistence states for cyclic 3-dimensional systems, Advanced Nonlinear Studies, 10 (2010) 401-412. pdf-file
L.A. Sánchez, Convex cones associated to generalized cones in R^n , Linear Algebra and its Applications, 433 (2010) 2122-2138.pdf-file
A. J. Ureña, Invariant manifolds around equilibria of Newtonian equations: some pathological examples, Journal of Differential Equations 249 (2010) 366-391 pdf-file
2009
M. Arias, J. Campos, C. Marcelli, Fastness and continuous dependence in front propagation in Fisher-KPP equations, Discrete and Continuous Dynamical Systems-B, 11 (2009) 11-30. pdf-file
J. Belmonte-Beitia, V.M. Perez-Garcia, P.J. Torres, Solitary waves for linearly coupled nonlinear Schrödinger equations with inhomogeneous coefficients, Journal of Nonlinear Science, 19 (2009), 437-451. pdf-file
J.A. Cid, P.J. Torres, Solvability for some boundary value problems with $\phi$-Laplacian operators, Discrete and Continuous Dynamical Systems-A, 23 (2009) 727-732. pdf-file
D. Núñez, P.J. Torres, On the motion of an oscillator with a periodically time-varying mass, Nonlinear Analysis Series B: Real World Applications 10 (2009) 1976-1983 .pdf-file
D. Núñez, P.J. Torres, Stabilization by vertical vibrations, Mathematical Methods in the Applied Sciences, 32 (2009) 1118 - 1128. pdf-file
R. Ortega, The pendulum equation: from periodic to almost periodic forcings, Differential and Integral Equations 22 (2009) 801-814. pdf-file
L.A. Sánchez, Global asymptotic stability of the Goodwin system with repression, Nonlinear Analysis: Real World Applications 10 (2009), pp. 2151-2156. pdf-file
L. A. Sánchez, Cones of rank 2 and the Poincaré-Bendixson property for a new class of monotone systems, Journal of Differential Equations 216 (2009), 1170-1190. pdf-file
J.P.P. Veerman, D. Daescu, M.J. Romero-Valles, P.J. Torres, A Single Particle Impact Model for Motion in Avalanches, Physica D: Nonlinear Phenomena 238 (2009) 1897-1908. pdf-file
2008
M. Arias, J. Campos, M. Cuesta, J.-P. Gossez, An asymmetric Neumann problem with weights, Ann. Inst. H. Poincaré Anal. Non Linéaire 25 (2008), 267-280.
J. Belmonte-Beitia, V.M. Pérez-García, V. Vekslerchik, P.J.Torres, Lie Symmetries, qualitative analysis and exact solutions of nonlinear Schrödinger equations with inhomogeneous nonlinearities, Discrete and Continuous Dynamical Systems-B, 9 (2008), 221-233.
J. Campos, Como conectar matrices de determinante positivo por el procedimiento de eliminación de Gauss-Jordan, Gac. R. Soc. Mat. Esp. 11 (2008)
J. Campos, J. Mawhin, R. Ortega, Maximum principles around an eigenvalue with constant eigenfunctions , Comunications in Contemporary Mathematics 10 (2008) 1243-1259. pdf-file
J. Campos and R. Ortega, Location of fixed points and periodic solutions in the plane, Discrete and Continuous Dynamical Systems-B, 9 (2008) 517-523.
D. Franco, P.J. Torres, Periodic solutions of singular systems without the strong force condition, Proc. Amer. Math. Soc. 136 (2008) 1229-1236.
M. Kunze, R. Ortega, Complete orbits for twist maps on the plane, Ergodic Theory and Dynamical Systems 28 (2008) 1197-1213. pdf-file
J. Llibre, R. Ortega, On the families of periodic orbits of the Sitnikov problem , SIAM J. on applied Dynamical Systems 7 (2008) 561-576.
F. Mañosas, P.J. Torres, Two inverse problems for analytic potential systems, Journal of Differential Equations 245 (2008) 3664-3673. pdf-file
R. Ortega, Retracts, fixed point index and differential equations, Revista de la Academia de Ciencias de Madrid 102 (2008) 89-100. pdf-file
R. Ortega, Trivial dynamics for a class of analytic homeomorphisms of the plane, Discrete and Continuous Dynamical Systems-B 10 (2008) 651-659. pdf-file
R. Ortega, Principios del máximo para la ecuación del telégrafo, Libro-Homenaje a J.M. Fraile Peláez, Universidad Complutense, Madrid 2008, pág. 109-113. pdf-file
P.J. Torres, Periodic oscillations of the relativistic pendulum with friction Physics Letters A 372 (2008) 6386-6387.pdf-file
P.J. Torres and V.V. Konotop, On existence of dark solitons in a cubic-quintic nonlinear Schrödinger equation with a periodic potential , Communications in Mathematical Physics 282 (2008) 1-9. pdf-file
A. J. Ureña, All periodic minimizers are unstable , Archiv der Mathematik 91 (2008) 63-75. pdf-file
2007
J. Belmonte-Beitia, V.M. Pérez-García, V. Vekslerchik, P.J. Torres, Lie symmetries and solitons in nonlinear systems with spatially inhomogeneous nonlinearities, Phys. Rev. Lett. 98 (2007), 064102.
J. Campos, M.J. Romero-Vallés, P.J. Torres, A fractal structure in a bouncing ball model, Int. J. Qualitative Th. Diff. Eqs Appl. Vol. 1(2007), 76-87.
J. Campos, M.J. Romero-Vallés, P.J. Torres, J.J.P. Veerman, Dynamics of a jumping particle on a staircase profile, Chaos, Solitons & Fractals 32-2 (2007), 415-426.
J. Chu, P.J. Torres, Applications of Schauder's Fixed Point Theorem to Singular Differential Equations, Bull. London Math. Soc. 39 (2007), 653-660.
Jifeng Chu, Pedro J. Torres, Meirong Zhang, Periodic solutions of second order non-autonomous singular dynamical systems, J. Differential Equations 239 (2007), 196-212.
W. Dambrosio and R. Ortega, Topological translations and nonlinear resonance, Advanced Nonlinear Studies 7 (2007), 97-106.
D. Franco, E. Liz and P.J. Torres, Existence of periodic solutions for population models with periodic delay, Indian J. Pure Appl. Math. Vol.38 n.3 (2007), 143-152.
R. Martins, A.J. Ureña, The star-shaped condition on Ding's version of the Poincaré-Birkhoff theorem, Bull. London Math. Soc. 39 (2007), 803-810.
D. Nuñez, P.J. Torres, KAM dynamics and stabilization of a particle sliding over a periodically driven curve, Applied Mathematical Letters 20(6) (2007), 610-615.
R. Ortega, Degree theory and almost periodic problems, Progress in Nonlinear Differential Equations and Apps. Vol. 75, Birkhauser (2007), 345-356, pdf-file
V.M. Pérez-García, P.J. Torres, and G.D. Montesinos, The method of moments for Nonlinear Schrodinger Equations: Theory and Applications, SIAM J. Appl. Math. 67(4) (2007), 990-1115.
P.J. Torres, Weak singularities may help periodic solutions to exist, J. Differential Equations 232 (2007), 277-284.
P.J. Torres, Existence of closed solutions for a polynomial first order differential equation, J. Math. Anal. Appl. 328 (2007), 1108-1116.
P.J. Torres, Existence and stability of periodic solutions for second order semilinear differential equations with a singular nonlinearity, Proceedings of the Royal Society of Edinburgh 137A (2007), 195-201.
A.J. Ureña, Nondegeneracy of elliptic problems with periodic nonlinearities in the plane, Z. Angew. Math. Phys. 58 (2007), 391-415.
A.J. Ureña, Invariant manifolds near a minimizer, J. Differential Equations 240 (2007) 172-195.
2006
J. Cabrerizo and A.M. Robles-Pérez, Maximum principles in a certain hyperbolic equation, "Hyperbolic problems. Theory, numerics and applications, I", 327-334. Yokohama Publishers, Yokohama, 2006. pdf-file
J. Campos and J. Mawhin, Periodic solutions of quaternionic-valued ordinary differential equations , Annali di Matematica Pura ed Applicata 185 (2006), S109-S127.
J. Lei and P.J. Torres, $L^1$ criteria for stability of periodic solutions of a newtonian equation, Math. Proc. Cambridge Philos. Soc. 140-2 (2006), 359-368.
R. Ortega, Unbounded motions in forced Newtonian equations, Annali di Matematica Pura ed Applicata 185 (2006), S245-S257.
R. Ortega, M. Tarallo, Almost periodic linear differential equations with non-separated solutions, Journal of Functional Analysis 237 (2006) 402-426.
V.M. Pérez-García, P.J. Torres, V.V. Konotop, Similarity transformations for nonlinear Schödinger equations with time-dependent coefficients, Physica D 221, n. 1 (2006), 31-36.
L.A. Sánchez, Dynamics of the modified Michaelis-Menten system, J. Math. Anal. Appl. 317 (2006), 71-79.
P.J. Torres, Non-trivial periodic solutions of a non-linear Hill’s equation with positively homogeneous term, Nonlinear Anal. 65 (2006), 841-844.
P.J. Torres, Guided waves in a multi-layered optical structure, Nonlinearity 19 (2006), 2103-2113.
A.J. Ureña, Isolated periodic minima are unstable, Ann. Inst. H. Poincaré Anal. Non Linéaire 23 (2006), 877-889.
2005
J.M. Almira, N. Del-Toro, P.J. Torres, Stability invariance of a periodic linear switched system, Dynamics of Continuous, Discrete and Impulsive Systems Serie A: Mathematical Analysis 12, n.1 (2005), 139-148.
J. Lei, P.J. Torres and M. Zhang, Twist character of the fourth order resonant periodic solution, J. Dynam. Differential Equations 17, n.1 (2005), 21 - 50.
F. Mañosas, P.J. Torres, Isochronicity on a class of piecewise continuous oscillators, Proc. Amer. Math. Soc. 133 (2005), 3027-3035.
J. Mawhin, R. Ortega and A.M. Robles-Pérez, Maximum principles for bounded solutions of the telegraph equation in space dimensions two and three and applications, J. Differential Equations 208 (2005), 42-63.
R. Ortega, Stability and index of periodic solutions of a nonlinear telegraph equation, Communications on Pure and Applied Analysis 4 (2005), 823-837.
R. Ortega, The stability of the equilibrium: a search for the right approximation, "Ten Mathematical Essays on Approximation in Analysis and Topology" (J. Ferrera, J. López-Gómez and F.R. Ruiz del Portal, Eds.), 215-234, Elsevier, 2005. pdf-file
R. Ortega and M. Zhang, Optimal bounds for bifurcation values of a superlinear periodic problem, Proceedings of the Royal Society of Edinburgh 135A (2005), 119-132.
A.M. Robles-Pérez, Almost periodic solutions of forced sine-Gordon equations, "Equadiff 2003. International Conference on Differential Equations", 258-263. World Scientific, Singapore, 2005. pdf-file
L.A. Sánchez, Convergence to equilibria in the Lorenz system via monotone methods, J. Differential Equations 217 (2005), 341-362.
D. Qian, P.J. Torres, Periodic motions of linear impact oscillators via the successor map, SIAM J. Math. Anal. 36, n.6 (2005), 1707-1725.
A.J. Ureña, Using closed orbits to bifurcate many periodic solutions for pendulum-type equations, J. Math. Anal. Appl. 302, n.2 (2005), 318-341.
2004
M. Arias, J. Campos, A.M. Robles-Pérez, L. Sanchez, Fast and heteroclinic solutions for a second order ODE related to Fisher-Kolmogorov's equation, Calc. Var. Partial Differential Equations 21 (2004), 319-334. Erratum, Calc. Var. 40 (2011) 291–292.
J. Campos, A. Margheri, R. Martins, C. Rebelo, A note on a modified version of the Poincaré-Birkhoff theorem, J. Differential Equations 203 (2004), 55-63.
J. Campos, M. Tarallo, Large minimal period orbits of periodic autonomous systems, Nonlinearity 17 (2004), 357-370.
G.D. Montesinos, V.M. Pérez-García, P.J. Torres, Stabilization of solitons of the multidimensional nonlinear Schrödinger equation: Matter wave breathers, Physica D 191 (2004), 193-210.
R. Ortega, Instability of periodic solutions obtained by minimization, "The first 60 years of Nonlinear Analysis of Jean Mawhin" (M. Delgado, A. Suárez, J. López-Gómez & R. Ortega, Eds.), 189-197. World Scientific, Singapore, 2004.
M. Kunze, R. Ortega, On the number of solutions to semilinear boundary value problems, Advanced Nonlinear Studies 4 (2004), 237-249.
R. Ortega, G. Verzini, A variational method for the existence of bounded solutions of a sublinear forced oscillator, Proc. London Math. Soc. 88 (2004), 775-795.
D. Qian, P.J. Torres, Bouncing solutions of an equation with attractive singularity, Proceedings of the Royal Society of Edinburgh 134A (2004), 201-213.
L.A. Sánchez, Convergence in a Chua's system with three equilibria, Z. Angew. Math. Phys. 55 (2004), 183-200.
P.J. Torres, Some remarks on a Neumann boundary value problem arising in fluid dynamics, ANZIAM Journal 45, n.3 (2004), 327-332.
P.J. Torres, Non-collision periodic solutions of forced dynamical systems with weak singularities, Discrete and Continuous Dynamical Systems 11 (2004), 693-698.
P.J. Torres, Existence and stability of periodic solutions of a Duffing equation by using a new maximum principle, Mediterranean Journal of Mathematics 1, n.4 (2004), 479-486.
P.J. Torres, M. Zhang, Twist periodic solutions of repulsive singular equations, Nonlinear Anal. 56 (2004), 591-599.
A.J. Ureña, The region of solvability of a parametrized boundary value problem can be disconnected, Commun. Contemp. Math. 6, n.6 (2004), 901-912.
2003
A. Alonso, R. Obaya, R. Ortega, Differential equations with limit-periodic forcings, Proc. Amer. Math. Soc. 131 (2003), 851-857.
M. Arias, J. Campos, M. Cuesta, J.-P. Gossez, The functional Fucik spectrum has empty interior, Proceedings of the Royal Society of Edinburgh 133A (2003), 3-10.
A. Lomtatidze, P.J. Torres, On a two-point boundary value problem for second order singular equations, Czechoslovak Math. J. 53(128) n. 1 (2003) , 19-43.
D. Núñez, P.J. Torres, Stable odd solutions of some periodic equations modeling satellite motion, J. Math. Anal. Appl. 279 (2003), 700-709.
R. Ortega, M. Tarallo, Almost periodic upper and lower solutions, J. Differential Equations 193 (2003), 343-358.
R. Ortega, M. Tarallo, Almost periodic equations and conditions of Ambrosetti-Prodi type, Math. Proc. Cambridge Philos. Soc. 135 (2003), 239-254.
R. Ortega, J.R. Ward, A semilinear elliptic system with vanishing nonlinearities, Discrete and Continuous Dynamical Systems: A Supplement Volume "Dynamical Systems and Differential Equations" (2003), 688-693. (Proceedings of the 4th AIMS Meeting 2002 at Wilmington).
P.J. Torres, Existence of one-signed periodic solutions of some second order differential equations via a Krasnoselskii fixed point theorem, J. Differential Equations 190 (2003), 643-662.
P.J. Torres, M. Zhang, A monotone iterative scheme for a nonlinear second order equation based on a generalized anti-maximum principle, Math. Nachr. 251 (2003), 101-107.
2002
M. Arias, J. Campos, M. Cuesta, J.-P. Gossez, Asymmetric elliptic problems with indefinite weights, Ann. Inst. H. Poincaré Anal. Non Linéaire 19 (2002), 581-616.
J. Campos, Massera's theorem for monotone dynamical systems in three dimensions, J. Math. Anal. Appl. 269 (2002), 607-615.
J. Campos, E.N. Dancer, R. Ortega, Dynamics in the neighbourhood of a continuum of fixed points, Annali di Matematica Pura ed Applicata 180 (2002), 483-492.
A. Cañada, A.J. Ureña, Solvability of some pendulum-type equations with linear damping and homogeneus Dirichlet conditions, Nonlinear Anal. 49 (2002), 1149-1165.
A. Fonda, P.J. Torres, Multiple solutions of positively homogeneous equations, Nonlinear Anal. 49 (2002), 1137-1147.
J. Mawhin, R. Ortega and A.M. Robles-Pérez, A maximun principle for bounded solutions of the telegraph equation in space dimension three, C. R. Acad. Sci. Paris, Ser. I 334 (2002), 1089-1094.
J. Mawhin, A.J. Ureña, A Hartman-Nagumo inequality for the vector ordinary p-Laplacian and applications to nonlinear boundary value problems, J. Inequal. Appl. 7(5) (2002), 701-725.
D. Nuñez, The method of lower and upper solutions and the stability of periodic oscillations, Nonlinear Anal. 51 (2002), 1207-1222.
R. Ortega, Periodic pertubations of an isochronous center, Qualitative Theory of Dynamical Systems 3 (2002), 83-91.
R. Ortega, L.A. Sánchez, Periodic solutions of forced oscillators with several degrees of freedom, Bull. London Math. Soc. 34 (2002), 308-318.
R. Ortega, M. Tarallo, Massera's theorem for quasi-periodic differential equations, Topological Methods in Nonlinear Anal. 19 (2002), 39-62.
L.A. Sánchez, An application of the theory of monotone system to an electrical circuit, Proceedings of the Royal Society of Edinburgh 132A (2002), 711-728.
P.J. Torres, Periodic solutions of some differential equations with nonlinear damping, Differential Integral Equations 15 (2002), 17-32.
P.J. Torres, Twist solutions of a Hill's equation with singular term , Advanced Nonlinear Studies 2 (2002), 279-287.
2001
J.M. Almira, P.J. Torres, Invariance of the stability of Meissner's equation under a perturbation of its intervals, Annali di Matematica Pura ed Applicata 180, n.2 (2001), 245-253.
M. Arias, J.Campos, M. Cuesta, J.-P. Gossez, Sur certains problèmes elliptiques asymétriques avec poids indéfinis, C. R. Acad. Sci. Paris, Ser. I 332 (2001), 215-218.
J. Campos, E.N. Dancer, On the resonance set in a fourth order equation with jumping nonlinearity, Differential Integral Equations 14 (2001), 257-272.
A. Cañada, A.J. Ureña, Asymptotic behaviour of the solvability set for pendulum-type equations with linear damping and homogeneus Dirichlet conditions, Electron. Journal Differential Equations Conf. 6 (2001), 55-64.
A. Cañada, A.J. Ureña, Some new qualitative properties on the solvability set of pendulum-type equations, Discrete and Continuous Dynamical Systems: A Supplement Volume "Dynamical Systems and Differential Equations" (2001), 66-73. (Proceedings of the 3rd AIMS Meeting 2000 at Kennesaw).
P. Habets, P.J. Torres, Some multiplicity results for periodic solutions of a Rayleigh differential equation, Dynamics of Continuous, Discrete and Impulsive Systems Serie A: Mathematical Analysis 8, n.3 (2001), 335-347.
D. Núñez, P.J. Torres, Periodic solutions of twist type of an earth satellite equation, Discrete and Continuous Dynamical Systems 7 (2001), 303-306.
R. Ortega, Dynamics of a forced oscillator having an obstacle, "Variational and Topological methods in the study of nonlinear phenomena" (V. Benci, G. Cerami, M. Degiovanni, D. Fortunato, Eds.), 75-87. Progress in Nonlinear Differential Equations 49. Birkhauser Boston, Boston MA, 2001. pdf-file
R. Ortega, Invariant curves of mappings with averaged small twist, Advanced Nonlinear Studies 1 (2001), 14-39.
R. Ortega and A.M. Robles-Pérez, A duality theorem for periodic solutions of a class of second order evolutions equations, J. Differential Equations 172 (2001), 409-444.
L.A. Sánchez, The torus principle for three-dimensional analytic autonomous systems having negative divergence, Nonlinear Anal. 44 (2001), 943-956.
P.J. Torres, Necessary and sufficient conditions for existence of periodic motions of forced systems of particles, Z. Angew. Math. Phys. 52 (2001), 535-540.
2000
M. Arias, J. Campos, J.-P. Gossez, On the antimaximun principle and the Fucik spectrum for the Neumann p-Laplacian, Differential Integral Equations 13 (2000), 217-226.
A. Fonda, R. Ortega, Positively homogeneous equations in the plane, Discrete and Continuous Dynamical Systems 6 (2000), 475-482.
J. Mawhin, R. Ortega and A.M. Robles-Pérez, A maximun principle for bounded solutions of the telegraph equations and applications to nonlinear forcings, J. Math. Anal. Appl. 251 (2000), 695-709.
D. Núñez and R. Ortega, Parabolic fixed points and stability criteria for nonlinear Hill's equation, Z. Angew. Math. Phys. 51 (2000), 890-911.
R. Ortega, Counting periodic solutions of the forced pendulum equation, Nonlinear Anal. 42 (2000), 1055-1062.
R. Ortega, L.A. Sánchez, Abstract competitive systems and orbital stability in R^3, Proc. Amer. Math. Soc. 128 (2000), 2911-2919.
R. Ortega, E. Serra, M. Tarallo, Non-continuation of the periodic oscillations of a forced pendulum in the presence of friction, Proc. Amer. Math. Soc. 128 (2000), 2659-2665.
R. Ortega, M. Tarallo, Degenerate equations of pendulum-type, Communications in Contemporary Mathematics 2 (2000), 127-149.
V.M. Pérez-García, P. Torres, J.J. García-Ripoll, H. Michinel, Moment analysis of paraxial propagation in a nonlinear graded index fibre, J. Opt. B: Quantum Semiclass. Opt. 2 (2000), 353-358.
P.J. Torres, Existence and uniqueness of elliptic periodic solutions of the Brillouin electron beam focusing system, Math. Methods Appl. Sci. 23 (2000), 1139-1143.
P.J. Torres, Periodic motions of forced infinite lattices with nearest neighbor interaction, Z. Angew. Math. Phys. 51 (2000), 333-345.
P.J. Torres, F. Zanolin, Periodic motion of a system of two or three charged particles, J. Math. Anal. Appl. 250 (2000), 375-386.
1999
J.M. Alonso, J. Mawhin, R. Ortega, Bounded solutions of second order semilinear evolution equations and applications to the telegraph equation, Journal de Mathématiques Pures et Apliquées 78 (1999), 49-63.
J. Campos, P. Torres, On the structure of the set of bounded solutions on a periodic Lienard equation, Proc. Amer. Math. Soc. 127 (1999), 1453-1462.
J.J. Garcia-Ripoll, V.M. Pérez-García, P.Torres, Extended parametric resonances in nonlinear Schrödinger systems, Physical Review Letters 83 (9) (1999), 1715-1718.
R. Ortega, Boundedness in a piecewise linear oscillator and a variant of the small twist theorem, Proc. London Math. Soc. 79 (1999), 381-413.
1998
J.M. Alonso, J. Campos, The index and the asymptotic stability of fixed points in two dimensions: a counterexample, Nonlinear Anal. 32 (1998), 719-725.
J.M. Alonso, R. Ortega, Roots of unity and unbounded motions of an asymmetric oscillator, J. Differential Equations 143 (1998), 201-220.
R. Ortega, The number of stable periodic solutions of time-dependent hamiltonian systems with one degree of freedom, Ergodic Theory and Dynamical Systems, 18 (1998), 1007-1018.
R. Ortega, On Littlewood's problem for the asymmetric oscillator, Rendiconti del Seminario Matematico e Fisico di Milano LXVII (1998), 153-164.
R. Ortega and A.M. Robles-Pérez, A maximum principle for periodic solutions of the telegraph equation, J. Math. Anal. Appl. 221 (1998), 625-651.
R. Ortega, A. Tineo, An exclusion principle for periodic competitive systems in three dimensions, Nonlinear Anaysis 31 (1998), 883-893.
P.J. Torres, Bounded solutions in singular equations of repulsive type, Nonlinear Anal. 32 (1998),117-125.
P.J. Torres, Solving a paradox about discontinuous damping, Austral. Math. Soc. Gaz. 25 (1998), 190-191.
1997
M. Arias, J. Campos, Exact number of solutions of a one-dimensional Dirichlet problem with jumping nonlinearities, Differential Equations and Dynamical Systems 5 (1997), 139-161.
J. Campos, Möbius transformations and periodic solutions of complex Riccati equations, Bull. London Math. Soc. 29 (1997), 205-215.
J. Campos, R. Ortega, A. Tineo, Homeomorphisms of the disk with trivial dynamics and extinction of competitive systems, J. Differential Equations. 138 (1997), 157-170.
R. Ortega, Nonexistence of invariant curves of mappings with small twist, Nonlinearity 10 (1997), 195-197.
R. Ortega, A forced pendulum equation with many periodic solutions, Rocky Mountain J. Math. 27 (1997), 861-876.
1996
J.M. Alonso, R. Ortega, Unbounded solutions of semilinear equations at resonance, Nonlinearity 9 (1996), 1099-1111.
M. Arias, J. Campos, Fucik spectrum of a singular Sturm-Liouville problem, Nonlinear Anal. 27 (1996), 679-697.
J. Campos, R. Ortega, Nonexistence of periodic solutions of a complex Riccati equation, Differential Integral Equations 9 (1996), 247-249.
J. López-Gómez, R. Ortega, A. Tineo, The periodic predator-prey Lotka-Volterra model, Adv. Differential Equations 1 (1996), 403-423.
P. Martínez-Amores, P.J. Torres, Dynamics of a periodic differential equation with a singular nonlinearity of attractive type, J. Math. Anal. Appl. 202 (1996), 1027-1039.
R. Ortega, Asymmetric oscillators and twist mappings, J. London Math. Soc. 53 (1996), 325-342
R. Ortega, Periodic solutions of a newtonian equation: stability by the third approximation, J. Differential Equations 128 (1996), 491-518.
R. Ortega, A criterion for asymptotic stability based on topological degree. Proceedings of the first World Congress of Nonlinear Analysts, Walter de Gruyter, 1996, pp 383-394 pdf-file
R. Ortega, A. Tineo, Resonance and non-resonance in a problem of boundedness, Proc. Amer. Math. Soc. 124 (1996), 2089-2096.
1995
J.M. Alonso, R. Ortega, Boundedness and global asymptotic stability of a forced oscillator, Nonlinear Anal. 25 (1995), 297-309.
J. Alonso, R. Ortega, Global asymptotic stability of a forced Newtonian system with dissipation, J. Math. Anal. Appl. 196 (1995), 965-986.
M. Arias, J. Campos, Radial Fucik spectrum of the Laplace operator, J. Math. Anal. Appl. 190 (1995), 654-666.
E.N. Dancer, J. López-Gómez, R. Ortega, On the spectrum of some linear noncooperative elliptic systems with radial symmetry, Differential Integral Equations 8 (1995), 515-523.
R. Ortega, A boundedness result of Landesman-Lazer type, Differential Integral Equations 8 (1995), 729-734.
R. Ortega, Some applications of the topological degree to stability theory, "Topological Methods in Differential Equations and Inclusions" (A. Granas and M. Frigon, Eds.), 377-409. Kluwer Academic Pub., Dordrecht, 1995. pdf-file
R. Ortega, A. Tineo, On the number of positive periodic solutions for planar competing Lotka-Volterra systems, J. Math. Anal. Appl. 193 (1995), 975-978.
R. Ortega, A. Tineo, Global existence of positive solutions of Lotka-Volterra systems, Nonlinear World 2 (1995), 1-12.
1994
Z. Amine, R. Ortega, Existence of asymptotically stable periodic solutions of a forced equation of Lienard type, Nonlinear Anal. 22 (1994), 993-1003.
Z. Amine, R. Ortega, A periodic prey-predator system, J. Math. Anal. Appl. 185 (1994), 477-489.
E.N. Dancer, R. Ortega, The index of Lyapunov stable fixed points in two dimensions, J. Dynam. Differential Equations 6 (1994), 631-637.
R. Ortega, The stability of the equilibrium of a nonlinear Hill's equation, SIAM J. Math. Anal. 25 (1994), 1393-1401.