Nontrivial solutions for a second order periodic boundary value problem with the nonlinearity dependent on the derivative
The author uses some results in [\textit{P. J. Torres}, J. Differ. Equations 190, No. 2, 643--662 (2003; Zbl 1032.34040)] combined with some degree computations to prove the existence of a non-trivial solution for the problem \[u''(t)+a(t)u(t)=f(t,u(t),u'(t)), \quad t\in [0,\omega],\] \[u(0)=u(\omega), \quad u'(0)=u'(\omega).\] His results complements the ones given in [\textit{Z. Ming} et al., J. Fixed Point Theory Appl. 22, No. 3, Paper No. 59, 13 p. (2020; Zbl 1448.34053)].
scientific article; zbMATH DE number 7443309