@article {2021, title = {On Dini derivatives of real functions}, year = {2021}, author = {Giuliano Klun and Alessandro Fonda and Andrea Sfecci} } @article {2021, title = {Non-well-ordered lower and upper solutions for semilinear systems of PDEs}, journal = {Communications in Contemporary MathematicsCommunications in Contemporary Mathematics}, year = {2021}, month = {2021/08/27}, pages = {2150080}, abstract = {

We prove existence results for systems of boundary value problems involving elliptic second-order differential operators. The assumptions involve lower and upper solutions, which may be either well-ordered, or not at all. The results are stated in an abstract framework, and can be translated also for systems of parabolic type.We prove existence results for systems of boundary value problems involving elliptic second-order differential operators. The assumptions involve lower and upper solutions, which may be either well-ordered, or not at all. The results are stated in an abstract framework, and can be translated also for systems of parabolic type.

}, isbn = {0219-1997}, url = {https://doi.org/10.1142/S0219199721500802}, author = {Alessandro Fonda and Giuliano Klun and Andrea Sfecci} } @article {2021, title = {Periodic Solutions of Second-Order Differential Equations in Hilbert Spaces}, volume = {18}, year = {2021}, month = {2021/09/07}, pages = {223}, abstract = {

We prove the existence of periodic solutions of some infinite-dimensional systems by the use of the lower/upper solutions method. Both the well-ordered and non-well-ordered cases are treated, thus generalizing to systems some well-established results for scalar equations.

}, isbn = {1660-5454}, url = {https://doi.org/10.1007/s00009-021-01857-8}, author = {Alessandro Fonda and Giuliano Klun and Andrea Sfecci} } @article {2021, title = {Well-Ordered and Non-Well-Ordered Lower and Upper Solutions for Periodic Planar Systems}, journal = {Advanced Nonlinear Studies}, volume = {21}, year = {2021}, month = {2021}, pages = {397 - 419}, url = {https://doi.org/10.1515/ans-2021-2117}, author = {Alessandro Fonda and Giuliano Klun and Andrea Sfecci} } @article {2020, title = {Periodic solutions of nearly integrable Hamiltonian systems bifurcating from infinite-dimensional tori}, journal = {NONLINEAR ANALYSIS}, year = {2020}, abstract = {

We prove the existence of periodic solutions of some infinite-dimensional nearly integrable Hamiltonian systems, bifurcating from infinite-dimensional tori, by the use of a generalization of the Poincar{\'e}{\textendash}Birkhoff Theorem.

}, issn = {0362-546X}, doi = {10.1016/j.na.2019.111720}, url = {https://doi.org/10.1016/j.na.2019.111720}, author = {Alessandro Fonda and Giuliano Klun and Andrea Sfecci} } @article {fonda2013periodic, title = {Periodic bouncing solutions for nonlinear impact oscillators}, journal = {Advanced Nonlinear Studies}, volume = {13}, number = {1}, year = {2013}, pages = {179{\textendash}189}, publisher = {Advanced Nonlinear Studies, Inc.}, doi = {10.1515/ans-2013-0110}, author = {Alessandro Fonda and Andrea Sfecci} } @article {FONDA20121369, title = {A general method for the existence of periodic solutions of differential systems in the plane}, journal = {Journal of Differential Equations}, volume = {252}, number = {2}, year = {2012}, pages = {1369 - 1391}, abstract = {

We propose a general method to prove the existence of periodic solutions for planar systems of ordinary differential equations, which can be used in many different circumstances. Applications are given to some nonresonant cases, even for systems with superlinear growth in some direction, or with a singularity. Systems {\textquotedblleft}at resonance{\textquotedblright} are also considered, provided a Landesman{\textendash}Lazer type of condition is assumed.

}, keywords = {Nonlinear dynamics, Periodic solutions}, issn = {0022-0396}, doi = {https://doi.org/10.1016/j.jde.2011.08.005}, url = {http://www.sciencedirect.com/science/article/pii/S0022039611003196}, author = {Alessandro Fonda and Andrea Sfecci} } @article {SFECCI20126191, title = {A nonresonance condition for radial solutions of a nonlinear Neumann elliptic problem}, journal = {Nonlinear Analysis: Theory, Methods \& Applications}, volume = {75}, number = {16}, year = {2012}, pages = {6191 - 6202}, abstract = {

We prove an existence result for radial solutions of a Neumann elliptic problem whose nonlinearity asymptotically lies between the first two eigenvalues. To this aim, we introduce an alternative nonresonance condition with respect to the second eigenvalue which, in the scalar case, generalizes the classical one, in the spirit of Fonda et al. (1991) [2]. Our approach also applies for nonlinearities which do not necessarily satisfy a subcritical growth assumption.

}, keywords = {Neumann problem, Nonresonance, Radial solutions, Time-map}, issn = {0362-546X}, doi = {https://doi.org/10.1016/j.na.2012.06.023}, url = {http://www.sciencedirect.com/science/article/pii/S0362546X12002659}, author = {Andrea Sfecci} } @article {fonda2012, title = {Periodic solutions of a system of coupled oscillators with one-sided superlinear retraction forces}, journal = {Differential Integral Equations}, volume = {25}, number = {11/12}, year = {2012}, month = {11}, pages = {993{\textendash}1010}, publisher = {Khayyam Publishing, Inc.}, url = {https://projecteuclid.org:443/euclid.die/1356012248}, author = {Alessandro Fonda and Andrea Sfecci} }