Ortega, Rafael; Schliessauf, Henrik Recurrent motions in a piecewise linear oscillator. (English) Zbl 1515.37042 Ann. Henri Poincaré 24, No. 2, 697-715 (2023). MSC: 37E40 37B20 37C27 34C15 70K40 PDFBibTeX XMLCite \textit{R. Ortega} and \textit{H. Schliessauf}, Ann. Henri Poincaré 24, No. 2, 697--715 (2023; Zbl 1515.37042) Full Text: DOI
Ortega, Rafael Variations on Lyapunov’s stability criterion and periodic prey-predator systems. (English) Zbl 1493.34153 Electron. Res. Arch. 29, No. 6, 3995-4008 (2021). Reviewer: Maite Grau (Lleida) MSC: 34D20 92D25 34A30 37C60 PDFBibTeX XMLCite \textit{R. Ortega}, Electron. Res. Arch. 29, No. 6, 3995--4008 (2021; Zbl 1493.34153) Full Text: DOI
Barutello, Vivina; Ortega, Rafael; Verzini, Gianmaria Regularized variational principles for the perturbed Kepler problem. (English) Zbl 1482.70016 Adv. Math. 383, Article ID 107694, 64 p. (2021). Reviewer: Martha Alvarez-Ramírez (Ciudad de México) MSC: 70F16 34C25 49J35 70F05 PDFBibTeX XMLCite \textit{V. Barutello} et al., Adv. Math. 383, Article ID 107694, 64 p. (2021; Zbl 1482.70016) Full Text: DOI arXiv
Misquero, Mauricio; Ortega, Rafael Some rigorous results on the 1:1 resonance of the spin-orbit problem. (English) Zbl 1476.70051 SIAM J. Appl. Dyn. Syst. 19, No. 4, 2233-2267 (2020). MSC: 70F15 70F40 37N05 34D06 70K28 PDFBibTeX XMLCite \textit{M. Misquero} and \textit{R. Ortega}, SIAM J. Appl. Dyn. Syst. 19, No. 4, 2233--2267 (2020; Zbl 1476.70051) Full Text: DOI
Ortega, Rafael; Rojas, David A proof of Bertrand’s theorem using the theory of isochronous potentials. (English) Zbl 1481.34046 J. Dyn. Differ. Equations 31, No. 4, 2017-2028 (2019). Reviewer: Kwok-wai Chung (Hong Kong) MSC: 34C11 34C25 70K40 PDFBibTeX XMLCite \textit{R. Ortega} and \textit{D. Rojas}, J. Dyn. Differ. Equations 31, No. 4, 2017--2028 (2019; Zbl 1481.34046) Full Text: DOI arXiv Link
Enguiça, Ricardo; Ortega, Rafael Functions with average and bounded motions of a forced discontinuous oscillator. (English) Zbl 1443.34020 J. Dyn. Differ. Equations 31, No. 3, 1185-1198 (2019). Reviewer: Satoshi Tanaka (Sendai) MSC: 34A36 34C11 34C15 37C60 PDFBibTeX XMLCite \textit{R. Enguiça} and \textit{R. Ortega}, J. Dyn. Differ. Equations 31, No. 3, 1185--1198 (2019; Zbl 1443.34020) Full Text: DOI
Ortega, Rafael Periodic differential equations in the plane. A topological perspective. (English) Zbl 1427.34052 De Gruyter Series in Nonlinear Analysis and Applications 29. Berlin: De Gruyter (ISBN 978-3-11-055040-5/hbk; 978-3-11-055116-7/ebook). xi, 185 p. (2019). Reviewer: Alessandro Fonda (Trieste) MSC: 34C25 34-02 34D20 34C11 55M20 PDFBibTeX XMLCite \textit{R. Ortega}, Periodic differential equations in the plane. A topological perspective. Berlin: De Gruyter (2019; Zbl 1427.34052) Full Text: DOI
Ortega, Rafael; Rojas, David Periodic oscillators, isochronous centers and resonance. (English) Zbl 1411.34051 Nonlinearity 32, No. 3, 800-832 (2019). Reviewer: Alessandro Fonda (Trieste) MSC: 34C15 34D05 34D10 34D23 34E10 34C11 PDFBibTeX XMLCite \textit{R. Ortega} and \textit{D. Rojas}, Nonlinearity 32, No. 3, 800--832 (2019; Zbl 1411.34051) Full Text: DOI arXiv Link
Ortega, Rafael; Ortega, Víctor; Torres, Pedro J. Point-vortex stability under the influence of an external periodic flow. (English) Zbl 1393.37068 Nonlinearity 31, No. 5, 1849-1867 (2018). Reviewer: Vladimir Răsvan (Craiova) MSC: 37J25 34D20 76B47 PDFBibTeX XMLCite \textit{R. Ortega} et al., Nonlinearity 31, No. 5, 1849--1867 (2018; Zbl 1393.37068) Full Text: DOI
Ortega, Rafael Stability of periodic solutions of Hamiltonian systems with low dimension. (English) Zbl 1440.37059 Rend. Semin. Mat., Univ. Politec. Torino 75, No. 1, 53-78 (2017). MSC: 37J25 34D20 PDFBibTeX XMLCite \textit{R. Ortega}, Rend. Semin. Mat., Univ. Politec. Torino 75, No. 1, 53--78 (2017; Zbl 1440.37059) Full Text: Link
Margheri, Alessandro; Ortega, Rafael; Rebelo, Carlota On a family of Kepler problems with linear dissipation. (English) Zbl 1473.70028 Rend. Ist. Mat. Univ. Trieste 49, 265-286 (2017). MSC: 70F16 37N05 70F40 34A34 34C25 PDFBibTeX XMLCite \textit{A. Margheri} et al., Rend. Ist. Mat. Univ. Trieste 49, 265--286 (2017; Zbl 1473.70028)
Ortega, Rafael Translation arcs and stability in two dimensions. (English) Zbl 1355.39009 Alsedà i Soler, Lluís (ed.) et al., Difference equations, discrete dynamical systems and applications, ICDEA, Barcelona, Spain, July 23–27, 2012. Proceedings of the 18th international conference. Berlin: Springer (ISBN 978-3-662-52926-3/hbk; 978-3-662-52927-0/ebook). Springer Proceedings in Mathematics & Statistics 180, 201-221 (2016). MSC: 39A12 39A10 34A34 37C10 PDFBibTeX XMLCite \textit{R. Ortega}, Springer Proc. Math. Stat. 180, 201--221 (2016; Zbl 1355.39009) Full Text: DOI
Ortega, Rafael Symmetric periodic solutions in the Sitnikov problem. (English) Zbl 1354.34072 Arch. Math. 107, No. 4, 405-412 (2016). Reviewer: Ronald L. Huston (Cincinnati) MSC: 34C25 70F07 PDFBibTeX XMLCite \textit{R. Ortega}, Arch. Math. 107, No. 4, 405--412 (2016; Zbl 1354.34072) Full Text: DOI
Ortega, Rafael A forced pendulum equation without stable periodic solutions of a fixed period. (English) Zbl 1323.34057 Port. Math. (N.S.) 71, No. 3-4, 193-216 (2014). Reviewer: Sergei Kornev (Voronezh) MSC: 34C25 34D20 PDFBibTeX XMLCite \textit{R. Ortega}, Port. Math. (N.S.) 71, No. 3--4, 193--216 (2014; Zbl 1323.34057) Full Text: DOI
Margheri, Alessandro; Ortega, Rafael; Rebelo, Carlota Dynamics of Kepler problem with linear drag. (English) Zbl 1298.70010 Celest. Mech. Dyn. Astron. 120, No. 1, 19-38 (2014). MSC: 70F07 70F16 34A26 70G45 PDFBibTeX XMLCite \textit{A. Margheri} et al., Celest. Mech. Dyn. Astron. 120, No. 1, 19--38 (2014; Zbl 1298.70010) Full Text: DOI
Boscaggin, Alberto; Ortega, Rafael Monotone twist maps and periodic solutions of systems of Duffing type. (English) Zbl 1331.34070 Math. Proc. Camb. Philos. Soc. 157, No. 2, 279-296 (2014). Reviewer: Zdzisław Dzedzej (Gdansk) MSC: 34C25 34C46 37E40 PDFBibTeX XMLCite \textit{A. Boscaggin} and \textit{R. Ortega}, Math. Proc. Camb. Philos. Soc. 157, No. 2, 279--296 (2014; Zbl 1331.34070) Full Text: DOI
Boscaggin, A.; Ortega, R.; Zanolin, F. Subharmonic solutions of the forced pendulum equation: a symplectic approach. (English) Zbl 1303.34028 Arch. Math. 102, No. 5, 459-468 (2014). Reviewer: Alessandro Fonda (Trieste) MSC: 34C25 PDFBibTeX XMLCite \textit{A. Boscaggin} et al., Arch. Math. 102, No. 5, 459--468 (2014; Zbl 1303.34028) Full Text: DOI Link
Ortega, Rafael Stable periodic solutions in the forced pendulum equation. (English) Zbl 1303.34031 Regul. Chaotic Dyn. 18, No. 6, 585-599 (2013). Reviewer: Sergei Yu. Pilyugin (St. Petersburg) MSC: 34C25 34D20 PDFBibTeX XMLCite \textit{R. Ortega}, Regul. Chaotic Dyn. 18, No. 6, 585--599 (2013; Zbl 1303.34031) Full Text: DOI
Kunze, Markus; Ortega, Rafael Long-time stability estimates for the non-periodic Littlewood boundedness problem. (English) Zbl 1272.34043 Proc. Lond. Math. Soc. (3) 107, No. 1, 39-75 (2013). MSC: 34C11 34D20 37E40 37B55 34C20 PDFBibTeX XMLCite \textit{M. Kunze} and \textit{R. Ortega}, Proc. Lond. Math. Soc. (3) 107, No. 1, 39--75 (2013; Zbl 1272.34043) Full Text: DOI
Ortega, Rafael Prevalence of non-degenerate periodic solutions in the forced pendulum equation. (English) Zbl 1278.34042 Adv. Nonlinear Stud. 13, No. 1, 219-229 (2013). Reviewer: Alessandro Fonda (Trieste) MSC: 34C25 28C10 PDFBibTeX XMLCite \textit{R. Ortega}, Adv. Nonlinear Stud. 13, No. 1, 219--229 (2013; Zbl 1278.34042) Full Text: DOI
Ortega, Rafael The complex periodic problem for a Riccati equation. (English) Zbl 1274.34128 Ann. Univ. Buchar., Math. Ser. 3(61), No. 2, 219-226 (2012). MSC: 34C25 34B30 34C10 34D20 34A30 34A34 PDFBibTeX XMLCite \textit{R. Ortega}, Ann. Univ. Buchar., Math. Ser. 3(61), No. 2, 219--226 (2012; Zbl 1274.34128)
Buică, Adriana; Ortega, Rafael Persistence of equilibria as periodic solutions of forced systems. (English) Zbl 1237.34077 J. Differ. Equations 252, No. 3, 2210-2221 (2012). Reviewer: Alessandro Fonda (Trieste) MSC: 34C25 34D05 34D10 PDFBibTeX XMLCite \textit{A. Buică} and \textit{R. Ortega}, J. Differ. Equations 252, No. 3, 2210--2221 (2012; Zbl 1237.34077) Full Text: DOI
Amster, Pablo; Haddad, Julián; Ortega, Rafael; Ureña, Antonio J. Periodic motions in forced problems of Kepler type. (English) Zbl 1246.34035 NoDEA, Nonlinear Differ. Equ. Appl. 18, No. 6, 649-657 (2011). Reviewer: Anna Capietto (Torino) MSC: 34C25 34C29 70K40 74N20 PDFBibTeX XMLCite \textit{P. Amster} et al., NoDEA, Nonlinear Differ. Equ. Appl. 18, No. 6, 649--657 (2011; Zbl 1246.34035) Full Text: DOI
Ortega, Rafael Linear motions in a periodically forced Kepler problem. (English) Zbl 1235.34136 Port. Math. (N.S.) 68, No. 2, 149-176 (2011). Reviewer: Pedro J. Torres (Granada) MSC: 34C25 34C15 37E40 70K40 PDFBibTeX XMLCite \textit{R. Ortega}, Port. Math. (N.S.) 68, No. 2, 149--176 (2011; Zbl 1235.34136) Full Text: DOI
Makarenkov, Oleg; Ortega, Rafael Asymptotic stability of forced oscillations emanating from a limit cycle. (English) Zbl 1213.34060 J. Differ. Equations 250, No. 1, 39-52 (2011). Reviewer: Alessandro Fonda (Trieste) MSC: 34C23 34C25 34D20 PDFBibTeX XMLCite \textit{O. Makarenkov} and \textit{R. Ortega}, J. Differ. Equations 250, No. 1, 39--52 (2011; Zbl 1213.34060) Full Text: DOI arXiv
Ortega, Rafael The pendulum equation: from periodic to almost periodic forcings. (English) Zbl 1240.34222 Differ. Integral Equ. 22, No. 9-10, 801-814 (2009). Reviewer: Irena Rachůnková (Olomouc) MSC: 34C27 34C15 70K40 58E50 PDFBibTeX XMLCite \textit{R. Ortega}, Differ. Integral Equ. 22, No. 9--10, 801--814 (2009; Zbl 1240.34222)
Campos, J.; Mawhin, J.; Ortega, R. Maximum principles around an eigenvalue with constant eigenfunctions. (English) Zbl 1170.35029 Commun. Contemp. Math. 10, No. 6, 1243-1259 (2008). MSC: 35B50 34C25 35J40 35L20 47B60 PDFBibTeX XMLCite \textit{J. Campos} et al., Commun. Contemp. Math. 10, No. 6, 1243--1259 (2008; Zbl 1170.35029) Full Text: DOI
Ortega, Rafael Trivial dynamics for a class of analytic homeomorphisms of the plane. (English) Zbl 1153.37378 Discrete Contin. Dyn. Syst., Ser. B 10, No. 2-3, 651-659 (2008). MSC: 37E30 39A11 34C15 PDFBibTeX XMLCite \textit{R. Ortega}, Discrete Contin. Dyn. Syst., Ser. B 10, No. 2--3, 651--659 (2008; Zbl 1153.37378) Full Text: DOI
Ortega, Rafael Degree theory and almost periodic problems. (English) Zbl 1204.34054 Staicu, Vasile (ed.), Differential equations, chaos and variational problems. Papers from the conference “Views on ODE’s”, Aveiro, Portugal, June 2006. Basel: Birkhäuser (ISBN 978-3-7643-8481-4/hbk). Progress in Nonlinear Differential Equations and Their Applications 75, 345-356 (2008). Reviewer: Jacobo Pejsachowicz (MR2409115) MSC: 34C27 47H11 47N20 PDFBibTeX XMLCite \textit{R. Ortega}, Prog. Nonlinear Differ. Equ. Appl. 75, 345--356 (2008; Zbl 1204.34054) Full Text: DOI
Ortega, Rafael Retracts, fixed point index and differential equations. (English) Zbl 1160.34049 RACSAM, Rev. R. Acad. Cienc. Exactas Fís. Nat., Ser. A Mat. 102, No. 1, 89-100 (2008). Reviewer: Jan Andres (Olomouc) MSC: 34D05 34C37 34C25 37E20 37J45 47N20 PDFBibTeX XMLCite \textit{R. Ortega}, RACSAM, Rev. R. Acad. Cienc. Exactas Fís. Nat., Ser. A Mat. 102, No. 1, 89--100 (2008; Zbl 1160.34049) Full Text: DOI EuDML
Campos, Juan; Ortega, Rafael Location of fixed points and periodic solutions in the plane. (English) Zbl 1360.34090 Discrete Contin. Dyn. Syst., Ser. B 9, No. 3-4, 517-523 (2008). MSC: 34C25 37C25 37C60 PDFBibTeX XMLCite \textit{J. Campos} and \textit{R. Ortega}, Discrete Contin. Dyn. Syst., Ser. B 9, No. 3--4, 517--523 (2008; Zbl 1360.34090) Full Text: DOI
Dambrosio, Walter; Ortega, Rafael Topological translations and nonlinear resonance. (English) Zbl 1120.37025 Adv. Nonlinear Stud. 7, No. 1, 97-106 (2007). MSC: 37E30 34C15 57N05 PDFBibTeX XMLCite \textit{W. Dambrosio} and \textit{R. Ortega}, Adv. Nonlinear Stud. 7, No. 1, 97--106 (2007; Zbl 1120.37025) Full Text: DOI
Ortega, Rafael Unbounded motions in forced Newtonian equations. (English) Zbl 1103.34042 Ann. Mat. Pura Appl. (4) 185, Suppl. 5, S245-S257 (2006). Reviewer: Pavel Rehak (Brno) MSC: 34D10 37J40 70F10 PDFBibTeX XMLCite \textit{R. Ortega}, Ann. Mat. Pura Appl. (4) 185, S245--S257 (2006; Zbl 1103.34042) Full Text: DOI
Ortega, Rafael; Tarallo, Massimo Almost periodic linear differential equations with non-separated solutions. (English) Zbl 1108.34008 J. Funct. Anal. 237, No. 2, 402-426 (2006). Reviewer: Sergei Kornev (Voronezh) MSC: 34A30 34C27 34C37 PDFBibTeX XMLCite \textit{R. Ortega} and \textit{M. Tarallo}, J. Funct. Anal. 237, No. 2, 402--426 (2006; Zbl 1108.34008) Full Text: DOI
Ortega, Rafael Competitive systems with three species and periodic coefficients. (English) Zbl 1107.34331 Dumortier, Freddy (ed.) et al., EQUADIFF 2003. Proceedings of the international conference on differential equations, Hasselt, Belgium, July 22–26, 2003. Hackensack, NJ: World Scientific (ISBN 981-256-169-2/hbk). 90-98 (2005). MSC: 34D05 92D25 37E30 PDFBibTeX XMLCite \textit{R. Ortega}, in: EQUADIFF 2003. Proceedings of the international conference on differential equations, Hasselt, Belgium, July 22--26, 2003. Hackensack, NJ: World Scientific. 90--98 (2005; Zbl 1107.34331) Full Text: DOI
Ortega, Rafael; Zhang, Meirong Optimal bounds for bifurcation values of a superlinear periodic problem. (English) Zbl 1088.34036 Proc. R. Soc. Edinb., Sect. A, Math. 135, No. 1, 119-132 (2005). Reviewer: Francisco Balibrea (Murcia) MSC: 34C23 34C25 PDFBibTeX XMLCite \textit{R. Ortega} and \textit{M. Zhang}, Proc. R. Soc. Edinb., Sect. A, Math. 135, No. 1, 119--132 (2005; Zbl 1088.34036) Full Text: DOI
Ortega, Rafael Instability of periodic solutions obtained by minimization. (English) Zbl 1210.37042 Delgado, M. (ed.) et al., The first 60 years of nonlinear analysis of Jean Mawhin. Papers from the conference, Sevilla, Spain, April 2003. River Edge, NJ: World Scientific (ISBN 981-238-765-X/hbk ). 189-197 (2004). MSC: 37J45 34C25 47J30 58E05 PDFBibTeX XMLCite \textit{R. Ortega}, in: The first 60 years of nonlinear analysis of Jean Mawhin. Papers from the conference, Sevilla, Spain, April 2003. River Edge, NJ: World Scientific. 189--197 (2004; Zbl 1210.37042)
Ortega, Rafael; Verzini, Gianmaria A variational method for the existence of bounded solutions of a sublinear forced oscillator. (English) Zbl 1072.34038 Proc. Lond. Math. Soc., III. Ser. 88, No. 3, 775-795 (2004). Reviewer: Vojislav Marić (Novi Sad) MSC: 34C11 49J35 34B15 PDFBibTeX XMLCite \textit{R. Ortega} and \textit{G. Verzini}, Proc. Lond. Math. Soc. (3) 88, No. 3, 775--795 (2004; Zbl 1072.34038) Full Text: DOI
Ortega, Rafael; Tarallo, Massimo Almost periodic equations and conditions of Ambrosetti-Prodi type. (English) Zbl 1055.34085 Math. Proc. Camb. Philos. Soc. 135, No. 2, 239-254 (2003). Reviewer: Hans F. Günzler (Kiel) MSC: 34C27 34C11 34A34 PDFBibTeX XMLCite \textit{R. Ortega} and \textit{M. Tarallo}, Math. Proc. Camb. Philos. Soc. 135, No. 2, 239--254 (2003; Zbl 1055.34085) Full Text: DOI
Ortega, Rafael; Tarallo, Massimo Almost periodic upper and lower solutions. (English) Zbl 1043.34046 J. Differ. Equations 193, No. 2, 343-358 (2003). Reviewer: Klaus R. Schneider (Berlin) MSC: 34C29 PDFBibTeX XMLCite \textit{R. Ortega} and \textit{M. Tarallo}, J. Differ. Equations 193, No. 2, 343--358 (2003; Zbl 1043.34046) Full Text: DOI
Alonso, Ana I.; Obaya, Rafael; Ortega, Rafael Differential equations with limit-periodic forcings. (English) Zbl 1021.34015 Proc. Am. Math. Soc. 131, No. 3, 851-857 (2003). Reviewer: Laura-Iulia Aniţa (Iaşi) MSC: 34B15 34C25 34C11 PDFBibTeX XMLCite \textit{A. I. Alonso} et al., Proc. Am. Math. Soc. 131, No. 3, 851--857 (2003; Zbl 1021.34015) Full Text: DOI
Dancer, E. N.; Campos, J.; Ortega, R. Dynamics in the neighbourhood of a continuum of fixed points. (English) Zbl 1223.49019 Ann. Mat. Pura Appl. (4) 180, No. 4, 483-492 (2002). MSC: 49J45 34A34 PDFBibTeX XMLCite \textit{E. N. Dancer} et al., Ann. Mat. Pura Appl. (4) 180, No. 4, 483--492 (2002; Zbl 1223.49019) Full Text: DOI
Ortega, Rafael Periodic perturbations of an isochronous center. (English) Zbl 1043.34049 Qual. Theory Dyn. Syst. 3, No. 1, 83-91 (2002). Reviewer: Valery A. Gaiko (Minsk) MSC: 34C99 PDFBibTeX XMLCite \textit{R. Ortega}, Qual. Theory Dyn. Syst. 3, No. 1, 83--91 (2002; Zbl 1043.34049) Full Text: DOI
Ortega, R. Dynamics of a forced oscillator having an obstacle. (English) Zbl 1054.34057 Benci, V. (ed.) et al., Variational and topological methods in the study of nonlinear phenomena. Papers from the international conference, Pisa, Italy, January–February 2000. Basel: Birkhäuser (ISBN 0-8176-4278-1). Prog. Nonlinear Differ. Equ. Appl. 49, 75-87 (2002). Reviewer: Alessandro Fonda (Trieste) MSC: 34C11 34C15 PDFBibTeX XMLCite \textit{R. Ortega}, Prog. Nonlinear Differ. Equ. Appl. 49, 75--87 (2002; Zbl 1054.34057)
Ortega, Rafael; Sánchez, Luis A. Periodic solutions of forced oscillators with several degrees of freedom. (English) Zbl 1041.34003 Bull. Lond. Math. Soc. 34, No. 3, 308-318 (2002). Reviewer: Igor Gumowski (Thoiry) MSC: 34A34 34C15 PDFBibTeX XMLCite \textit{R. Ortega} and \textit{L. A. Sánchez}, Bull. Lond. Math. Soc. 34, No. 3, 308--318 (2002; Zbl 1041.34003) Full Text: DOI
Ortega, Rafael Twist mappings, invariant curves and periodic differential equations. (English) Zbl 1172.34326 Grossinho, M.R. (ed.) et al., Nonlinear analysis and its applications to differential equations. Papers from the autumn school on nonlinear analysis and differential equations, Lisbon, Portugal, September 14–October 23, 1998. Boston, MA: Birkhäuser (ISBN 0-8176-4188-2/hbk). Prog. Nonlinear Differ. Equ. Appl. 43, 85-112 (2001). Reviewer: Ivan Ginchev (Varese) MSC: 34C27 PDFBibTeX XMLCite \textit{R. Ortega}, Prog. Nonlinear Differ. Equ. Appl. 43, 85--112 (2001; Zbl 1172.34326)
Ortega, Rafael; Robles-Pérez, Aureliano M. A duality theorem for periodic solutions of a class of second order evolution equations. (English) Zbl 1010.34054 J. Differ. Equations 172, No. 2, 409-444 (2001). Reviewer: Yujun Dong (Nanjing) MSC: 34G20 34C25 PDFBibTeX XMLCite \textit{R. Ortega} and \textit{A. M. Robles-Pérez}, J. Differ. Equations 172, No. 2, 409--444 (2001; Zbl 1010.34054) Full Text: DOI
Núñez, Daniel; Ortega, Rafael Parabolic fixed points and stability criteria for nonlinear Hill’s equation. (English) Zbl 0973.34046 Z. Angew. Math. Phys. 51, No. 6, 890-911 (2000). Reviewer: Marian Ivanovici (Craiova) MSC: 34D20 34C05 34C60 PDFBibTeX XMLCite \textit{D. Núñez} and \textit{R. Ortega}, Z. Angew. Math. Phys. 51, No. 6, 890--911 (2000; Zbl 0973.34046) Full Text: DOI
Ortega, Rafael; Tarallo, Massimo Degenerate equations of pendulum-type. (English) Zbl 0958.34033 Commun. Contemp. Math. 2, No. 2, 127-149 (2000). Reviewer: Kenneth S.Miller (Rye Brook) MSC: 34C25 34A34 PDFBibTeX XMLCite \textit{R. Ortega} and \textit{M. Tarallo}, Commun. Contemp. Math. 2, No. 2, 127--149 (2000; Zbl 0958.34033) Full Text: DOI
Ortega, Rafael Counting periodic solutions of the forced pendulum equation. (English) Zbl 0967.34037 Nonlinear Anal., Theory Methods Appl., Ser. A, Theory Methods 42, No. 6, 1055-1062 (2000). Reviewer: Bojidar Cheshankov (Sofia) MSC: 34C25 PDFBibTeX XMLCite \textit{R. Ortega}, Nonlinear Anal., Theory Methods Appl., Ser. A, Theory Methods 42, No. 6, 1055--1062 (2000; Zbl 0967.34037) Full Text: DOI
Ortega, Rafael; Sánchez, Luis Ángel Abstract competitive systems and orbital stability in \(\mathbb R^3\). (English) Zbl 0951.34032 Proc. Am. Math. Soc. 128, No. 10, 2911-2919 (2000). MSC: 34D30 34C25 34D20 34C12 PDFBibTeX XMLCite \textit{R. Ortega} and \textit{L. Á. Sánchez}, Proc. Am. Math. Soc. 128, No. 10, 2911--2919 (2000; Zbl 0951.34032) Full Text: DOI
Fonda, Alessandro; Ortega, Rafael Positively homogeneous equations in the plane. (English) Zbl 1079.34011 Discrete Contin. Dyn. Syst. 6, No. 2, 475-482 (2000). Reviewer: Mickel Fečkan (MR 2000k:34033) MSC: 34B15 34C25 37C27 PDFBibTeX XMLCite \textit{A. Fonda} and \textit{R. Ortega}, Discrete Contin. Dyn. Syst. 6, No. 2, 475--482 (2000; Zbl 1079.34011) Full Text: DOI
Ortega, Rafael; Serra, Enrico; Tarallo, Massimo Non-continuation of the periodic oscillations of a forced pendulum in the presence of friction. (English) Zbl 0970.34037 Proc. Am. Math. Soc. 128, No. 9, 2659-2665 (2000). Reviewer: G.V.Khmelevskaja-Plotnikova (Namur) MSC: 34C25 70F40 PDFBibTeX XMLCite \textit{R. Ortega} et al., Proc. Am. Math. Soc. 128, No. 9, 2659--2665 (2000; Zbl 0970.34037) Full Text: DOI
Ortega, Rafael Boundedness in a piecewise linear oscillator and a variant of the small twist theorem. (English) Zbl 1030.34035 Proc. Lond. Math. Soc., III. Ser. 79, No. 2, 381-413 (1999). MSC: 34C11 37E40 37J10 34C15 PDFBibTeX XMLCite \textit{R. Ortega}, Proc. Lond. Math. Soc. (3) 79, No. 2, 381--413 (1999; Zbl 1030.34035) Full Text: DOI
Alonso, Jose Miguel; Mawhin, Jean; Ortega, Rafael Bounded solutions of second order semilinear evolution equations and applications to the telegraph equation. (English) Zbl 0927.34048 J. Math. Pures Appl., IX. Sér. 78, No. 1, 49-63 (1999). Reviewer: S.Burys (Kraków) MSC: 34G20 34L20 35L20 35L70 PDFBibTeX XMLCite \textit{J. M. Alonso} et al., J. Math. Pures Appl. (9) 78, No. 1, 49--63 (1999; Zbl 0927.34048) Full Text: DOI
Ortega, Rafael On Littlewood’s problem for the asymmetric oscillator. (English) Zbl 1020.34032 Rend. Semin. Mat. Fis. Milano 68, 153-164 (1998). Reviewer: Giuseppe Gaeta (Roma) MSC: 34C15 34C11 PDFBibTeX XMLCite \textit{R. Ortega}, Rend. Semin. Mat. Fis. Milano 68, 153--164 (1998; Zbl 1020.34032) Full Text: DOI
Ortega, Rafael Nonlinear resonance and invariant curves. (Spanish) Zbl 0947.34516 Proceedings of the 15th congress on differential equations and applications and congress on applied mathematics, Vigo, Spain, September 23-26, 1997. Vols. I and II. Vigo: Servicio de Publicacións da Universidade de Vigo. Colecc. Congr. 9, 63-68 (1998). MSC: 34C15 34C05 PDFBibTeX XMLCite \textit{R. Ortega}, in: XV Congreso de ecuaciones diferenciales y aplicaciones y congreso de matemática aplicada, Vigo, España, 23--26 Septiembre 1997. Volumen I e II. Vigo: Servicio de Publicacións da Universidade de Vigo. 63--68 (1998; Zbl 0947.34516)
Ortega, Rafael The number of stable periodic solutions of time-dependent Hamiltonian systems with one degree of freedom. (English) Zbl 0946.34036 Ergodic Theory Dyn. Syst. 18, No. 4, 1007-1018 (1998). Reviewer: Ana Nunes (Lisboa) MSC: 34C25 37C05 70H25 PDFBibTeX XMLCite \textit{R. Ortega}, Ergodic Theory Dyn. Syst. 18, No. 4, 1007--1018 (1998; Zbl 0946.34036) Full Text: DOI
Ortega, Rafael; Tineo, Antonio An exclusion principle for periodic competitive systems in three dimensions. (English) Zbl 0901.34049 Nonlinear Anal., Theory Methods Appl. 31, No. 7, 883-893 (1998). Reviewer: Chen Lan Sun (Beijing) MSC: 34C25 92D25 37-XX PDFBibTeX XMLCite \textit{R. Ortega} and \textit{A. Tineo}, Nonlinear Anal., Theory Methods Appl. 31, No. 7, 883--893 (1998; Zbl 0901.34049) Full Text: DOI
Alonso, José Miguel; Ortega, Rafael Roots of unity and unbounded motions of an asymmetric oscillator. (English) Zbl 0899.34023 J. Differ. Equations 143, No. 1, 201-220 (1998). Reviewer: S.G.Zhuravlev (Moskva) MSC: 34C15 PDFBibTeX XMLCite \textit{J. M. Alonso} and \textit{R. Ortega}, J. Differ. Equations 143, No. 1, 201--220 (1998; Zbl 0899.34023) Full Text: DOI
Ortega, Rafael A forced pendulum equation with many periodic solutions. (English) Zbl 0899.34031 Rocky Mt. J. Math. 27, No. 3, 861-876 (1997). Reviewer: O.Akinyele (Bowie) MSC: 34C25 PDFBibTeX XMLCite \textit{R. Ortega}, Rocky Mt. J. Math. 27, No. 3, 861--876 (1997; Zbl 0899.34031) Full Text: DOI Link
Campos, Juan; Ortega, Rafael; Tineo, Antonio Homeomorphisms of the disk with trivial dynamics and extinction of competitive systems. (English) Zbl 0886.34025 J. Differ. Equations 138, No. 1, 157-170 (1997). Reviewer: G.Osipenko (St.Peterburg) MSC: 34C05 37A99 60K35 28D05 82C99 PDFBibTeX XMLCite \textit{J. Campos} et al., J. Differ. Equations 138, No. 1, 157--170 (1997; Zbl 0886.34025) Full Text: DOI Link
Ortega, Rafael Asymmetric oscillators and twist mappings. (English) Zbl 0860.34017 J. Lond. Math. Soc., II. Ser. 53, No. 2, 325-342 (1996). Reviewer: S.Nocilla (Torino) MSC: 34C15 34C28 PDFBibTeX XMLCite \textit{R. Ortega}, J. Lond. Math. Soc., II. Ser. 53, No. 2, 325--342 (1996; Zbl 0860.34017) Full Text: DOI
Ortega, Rafael; Tineo, Antonio Resonance and non-resonance in a problem of boundedness. (English) Zbl 0858.34018 Proc. Am. Math. Soc. 124, No. 7, 2089-2096 (1996). Reviewer: A.Szulkin (Stockholm) MSC: 34B15 34C11 PDFBibTeX XMLCite \textit{R. Ortega} and \textit{A. Tineo}, Proc. Am. Math. Soc. 124, No. 7, 2089--2096 (1996; Zbl 0858.34018) Full Text: DOI
Ortega, Rafael Periodic solutions of a Newtonian equation: Stability by the third approximation. (English) Zbl 0855.34058 J. Differ. Equations 128, No. 2, 491-518 (1996). Reviewer: S.G.Zhuravlev (Moskva) MSC: 34D20 34C25 PDFBibTeX XMLCite \textit{R. Ortega}, J. Differ. Equations 128, No. 2, 491--518 (1996; Zbl 0855.34058) Full Text: DOI
López-Gómez, Julián; Ortega, Rafael; Tineo, Antonio The periodic predator-prey Lotka-Volterra model. (English) Zbl 0849.34026 Adv. Differ. Equ. 1, No. 3, 403-423 (1996). Reviewer: Chen Lan Sun (Beijing) MSC: 34C25 92D25 34D05 PDFBibTeX XMLCite \textit{J. López-Gómez} et al., Adv. Differ. Equ. 1, No. 3, 403--423 (1996; Zbl 0849.34026)
Ortega, Rafael A criterion for asymptotic stability based on topological degree. (English) Zbl 0846.34056 Lakshmikantham, V. (ed.), World congress of nonlinear analysts ’92. Proceedings of the first world congress, Tampa, FL, USA, August 19-26, 1992. 4 volumes. Berlin: de Gruyter. 383-394 (1996). MSC: 34D20 58D10 55M25 PDFBibTeX XMLCite \textit{R. Ortega}, in: World congress of nonlinear analysts '92. Proceedings of the first world congress, Tampa, FL, USA, August 19-26, 1992. 4 volumes. Berlin: de Gruyter. 383--394 (1996; Zbl 0846.34056)
Campos, Juan; Ortega, Rafael Nonexistence of periodic solutions of a complex Riccati equation. (English) Zbl 0842.34046 Differ. Integral Equ. 9, No. 2, 247-249 (1996). Reviewer: B.Rodriguez-Salinas (Madrid) MSC: 34C25 34M99 34B15 PDFBibTeX XMLCite \textit{J. Campos} and \textit{R. Ortega}, Differ. Integral Equ. 9, No. 2, 247--249 (1996; Zbl 0842.34046)
Alonso, José Miguel; Ortega, Rafael Unbounded solutions of semilinear equations at resonance. (English) Zbl 0896.34026 Nonlinearity 9, No. 5, 1099-1111 (1996). MSC: 34C11 34C15 PDFBibTeX XMLCite \textit{J. M. Alonso} and \textit{R. Ortega}, Nonlinearity 9, No. 5, 1099--1111 (1996; Zbl 0896.34026) Full Text: DOI Link
Alonso, José Miguel; Ortega, Rafael Global asymptotic stability of a forced Newtonian system with dissipation. (English) Zbl 0844.34047 J. Math. Anal. Appl. 196, No. 3, 965-986 (1995). Reviewer: W.Müller (Berlin) MSC: 34D20 34C25 34C11 PDFBibTeX XMLCite \textit{J. M. Alonso} and \textit{R. Ortega}, J. Math. Anal. Appl. 196, No. 3, 965--986 (1995; Zbl 0844.34047) Full Text: DOI
Ortega, Rafael Some applications of the topological degree to stability theory. (English) Zbl 0834.34058 Granas, Andrzej (ed.) et al., Topological methods in differential equations and inclusions. Proceedings of the NATO Advanced Study Institute and séminaire de mathématiques supérieures on topological methods in differential equations and inclusions, Montréal, Canada, July 11-22, 1994. Dordrecht: Kluwer Academic Publishers. NATO ASI Ser., Ser. C, Math. Phys. Sci. 472, 377-409 (1995). MSC: 34D20 47H11 PDFBibTeX XMLCite \textit{R. Ortega}, NATO ASI Ser., Ser. C, Math. Phys. Sci. 472, 377--409 (1995; Zbl 0834.34058)
Ortega, Rafael; Tineo, Antonio On the number of positive periodic solutions for planar competing Lotka-Volterra systems. (English) Zbl 0903.34037 J. Math. Anal. Appl. 193, No. 3, 975-978 (1995). Reviewer: Wang Duo (Beijing) MSC: 34C25 92B05 PDFBibTeX XMLCite \textit{R. Ortega} and \textit{A. Tineo}, J. Math. Anal. Appl. 193, No. 3, 975--978 (1995; Zbl 0903.34037) Full Text: DOI
Alonso, Jose Miguel; Ortega, Rafael Boundedness and global asymptotic stability of a forced oscillator. (English) Zbl 0826.34043 Nonlinear Anal., Theory Methods Appl. 25, No. 3, 297-309 (1995). Reviewer: W.Müller (Berlin) MSC: 34D20 34D40 34C11 PDFBibTeX XMLCite \textit{J. M. Alonso} and \textit{R. Ortega}, Nonlinear Anal., Theory Methods Appl. 25, No. 3, 297--309 (1995; Zbl 0826.34043) Full Text: DOI
Ortega, Rafael; Tineo, Antonio Global existence of positive solutions of Lotka-Volterra systems. (English) Zbl 0821.34007 Nonlinear World 2, No. 1, 1-12 (1995). Reviewer: A.Cishliev (Sofia) MSC: 34A12 34C11 PDFBibTeX XMLCite \textit{R. Ortega} and \textit{A. Tineo}, Nonlinear World 2, No. 1, 1--12 (1995; Zbl 0821.34007)
Ortega, Rafael A boundedness result of Landesman-Lazer type. (English) Zbl 0817.34017 Differ. Integral Equ. 8, No. 4, 729-734 (1995). Reviewer: P.N.Bajaj (Wichita) MSC: 34B15 34C11 PDFBibTeX XMLCite \textit{R. Ortega}, Differ. Integral Equ. 8, No. 4, 729--734 (1995; Zbl 0817.34017)
Dancer, E. N.; Ortega, R. The index of Lyapunov stable fixed points in two dimensions. (English) Zbl 0811.34018 J. Dyn. Differ. Equations 6, No. 4, 631-637 (1994). Reviewer: M.Bartušek (Brno) MSC: 34C05 34C25 47H11 34D20 PDFBibTeX XMLCite \textit{E. N. Dancer} and \textit{R. Ortega}, J. Dyn. Differ. Equations 6, No. 4, 631--637 (1994; Zbl 0811.34018) Full Text: DOI
Ortega, Rafael The stability of the equilibrium of a nonlinear Hill’s equation. (English) Zbl 0807.34065 SIAM J. Math. Anal. 25, No. 5, 1393-1401 (1994). Reviewer: E.Ershov (St.Peterburg) MSC: 34D20 37C75 PDFBibTeX XMLCite \textit{R. Ortega}, SIAM J. Math. Anal. 25, No. 5, 1393--1401 (1994; Zbl 0807.34065) Full Text: DOI
Amine, Zitan; Ortega, Rafael A periodic prey-predator system. (English) Zbl 0808.34043 J. Math. Anal. Appl. 185, No. 2, 477-489 (1994). Reviewer: R.Manthey (Jena) MSC: 34C25 92D25 PDFBibTeX XMLCite \textit{Z. Amine} and \textit{R. Ortega}, J. Math. Anal. Appl. 185, No. 2, 477--489 (1994; Zbl 0808.34043) Full Text: DOI
Zitan, Amine; Ortega, Rafael Existence of asymptotically stable periodic solutions of a forced equation of Liénard type. (English) Zbl 0802.34050 Nonlinear Anal., Theory Methods Appl. 22, No. 8, 993-1003 (1994). Reviewer: Á.Bosznay (Budapest) MSC: 34C25 34D20 PDFBibTeX XMLCite \textit{A. Zitan} and \textit{R. Ortega}, Nonlinear Anal., Theory Methods Appl. 22, No. 8, 993--1003 (1994; Zbl 0802.34050) Full Text: DOI
Ortega, Rafael The twist coefficient of periodic solutions of a time-dependent Newton’s equation. (English) Zbl 0761.34036 J. Dyn. Differ. Equations 4, No. 4, 651-665 (1992). Reviewer: P.F.Moson (Budapest) MSC: 34C25 34D20 PDFBibTeX XMLCite \textit{R. Ortega}, J. Dyn. Differ. Equations 4, No. 4, 651--665 (1992; Zbl 0761.34036) Full Text: DOI
Ortega, Rafael The first interval of stability of a periodic equation of Duffing type. (English) Zbl 0757.34035 Proc. Am. Math. Soc. 115, No. 4, 1061-1067 (1992). Reviewer: A.Hausrath (Boise) MSC: 34C25 34D20 PDFBibTeX XMLCite \textit{R. Ortega}, Proc. Am. Math. Soc. 115, No. 4, 1061--1067 (1992; Zbl 0757.34035) Full Text: DOI
Martinez-Amores, P.; Mawhin, J.; Ortega, R.; Willem, M. Generic results for the existence of nondegenerate periodic solutions of some differential systems with periodic nonlinearities. (English) Zbl 0742.34043 J. Differ. Equations 91, No. 1, 138-148 (1991). Reviewer: P.Smith (Keele) MSC: 34C25 34A34 PDFBibTeX XMLCite \textit{P. Martinez-Amores} et al., J. Differ. Equations 91, No. 1, 138--148 (1991; Zbl 0742.34043) Full Text: DOI
Ortega, Rafael Stability of a periodic problem of Ambrosetti-Prodi type. (English) Zbl 0724.34059 Differ. Integral Equ. 3, No. 2, 275-284 (1990). Reviewer: E.Chukwu (Raleigh) MSC: 34D20 34C25 34D05 PDFBibTeX XMLCite \textit{R. Ortega}, Differ. Integral Equ. 3, No. 2, 275--284 (1990; Zbl 0724.34059)
Ortega, Rafael Topological degree and stability of periodic solutions for certain differential equations. (English) Zbl 0677.34042 J. Lond. Math. Soc., II. Ser. 42, No. 3, 505-516 (1990). Reviewer: R.Ortega MSC: 34C25 34D20 70B99 PDFBibTeX XMLCite \textit{R. Ortega}, J. Lond. Math. Soc., II. Ser. 42, No. 3, 505--516 (1990; Zbl 0677.34042) Full Text: DOI
Ortega, Rafael Stability and index of periodic solutions of an equation of Duffing type. (English) Zbl 0686.34052 Boll. Unione Mat. Ital, VII. Ser., B 3, No. 3, 533-546 (1989). Reviewer: C.He MSC: 34D20 70K20 34C25 PDFBibTeX XMLCite \textit{R. Ortega}, Boll. Unione Mat. Ital., VII. Ser., B 3, No. 3, 533--546 (1989; Zbl 0686.34052)
Ortega, Rafael Stability of periodic solutions and topological degree. (Spanish) Zbl 0743.34048 Differential equations and applications, Proc. 11th Congr., CEDYA, Appl. Math., Fuengirola (Málaga)/Spain 1989, 405-408 (1989). MSC: 34C25 34D20 PDFBibTeX XMLCite \textit{R. Ortega}, in: Comparison of several resolution methods for the equation for the migration of radionuclids. . 405--408 (1989; Zbl 0743.34048)
Ortega, R. A nonlinear perturbation of \(d^ 2u/dx^ 2+\lambda u,u(- \infty)=u(+\infty)=0\). (English) Zbl 0673.34011 Ann. Mat. Pura Appl., IV. Ser. 152, 159-169 (1988). Reviewer: O.Akinyele MSC: 34A34 PDFBibTeX XMLCite \textit{R. Ortega}, Ann. Mat. Pura Appl. (4) 152, 159--169 (1988; Zbl 0673.34011) Full Text: DOI
Arias, M.; Ortega, R. A periodic problem with a nonlinearity growing linearly in one direction. (Spanish. English summary) Zbl 0651.34016 Proc. 11th Span.-Port. Conf Math., Badajoz/Spain 1986, Vol. 1, Publ. Dep. Mat. Univ. Extremadura 18, 56-63 (1987). MSC: 34B15 34C15 34C25 PDFBibTeX XML
Kannan, Rangachary; Ortega, Rafael An asymptotic result in forced oscillations of pendulum-type equations. (English) Zbl 0613.34028 Appl. Anal. 22, 45-53 (1986). Reviewer: J.Ohriska MSC: 34C15 34C25 PDFBibTeX XMLCite \textit{R. Kannan} and \textit{R. Ortega}, Appl. Anal. 22, 45--53 (1986; Zbl 0613.34028) Full Text: DOI Link
Kannan, Rangachary; Ortega, Rafael Existence of solutions of \(x''+x+g(x)=p(t)\), \(x(0)=0=x(\pi)\). (English) Zbl 0585.34001 Proc. Am. Math. Soc. 96, 67-70 (1986). MSC: 34A12 PDFBibTeX XMLCite \textit{R. Kannan} and \textit{R. Ortega}, Proc. Am. Math. Soc. 96, 67--70 (1986; Zbl 0585.34001) Full Text: DOI
Ortega, Rafael The existence of periodic solutions to the equation of the faced pendulum. (Spanish) Zbl 0627.70022 Differential equations and applications, Proc. 7th Congr., Granada/Spain 1984, 317-322 (1985). Reviewer: G.Brunk MSC: 70K40 34C15 34C25 PDFBibTeX XML
Kannan, Rangachary; Ortega, Rafael Periodic solutions of pendulum-type equations. (English) Zbl 0608.34047 J. Differ. Equations 59, 123-144 (1985). Reviewer: H.Hochstadt MSC: 34C25 34B15 34C15 PDFBibTeX XMLCite \textit{R. Kannan} and \textit{R. Ortega}, J. Differ. Equations 59, 123--144 (1985; Zbl 0608.34047) Full Text: DOI
Cañada, A.; Ortega, R. K-contractions and periodic solutions to nonlinear ordinary differential equations by resonance. (English) Zbl 0606.34028 Rev. R. Acad. Cienc. Exactas Fís. Nat. Madr. 79, 171-182 (1985). MSC: 34C25 PDFBibTeX XMLCite \textit{A. Cañada} and \textit{R. Ortega}, Rev. R. Acad. Cienc. Exactas Fís. Nat. Madr. 79, 171--182 (1985; Zbl 0606.34028) Full Text: EuDML
Cañada, A.; Ortega, R. Existence theorems for equations in normed spaces and boundary value problems for nonlinear vector ordinary differential equations. (English) Zbl 0558.47046 Proc. R. Soc. Edinb., Sect. A 98, 1-11 (1984). MSC: 47J05 34B15 34C25 PDFBibTeX XMLCite \textit{A. Cañada} and \textit{R. Ortega}, Proc. R. Soc. Edinb., Sect. A, Math. 98, 1--11 (1984; Zbl 0558.47046) Full Text: DOI